Volume 6, Issue 1

2011 Vol. 6 Iss.1

D DV !

IT de M nsi M ta I SU Da R est CDsh T 11 Cra 20 &

C

ollision C The International Compendium for Crash Research

Volume 6 Issue 1

Spring 2011

Collision: The International Compendium for Crash Research

VEHICLE & OCCUPANT MOTION in Far-Side Impacts

Volume 6, Issue 1 - Spring 2011

ESTIMATINGMAXIMUMMOTORCYCLE Acceleration Rates INSURANCEAPPLICATIONSFORCDR Part Two in a Series THEPERFORMANCEOFSEATBACKS in High Speed Rear Impacts

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Contents features 10

Spring 2011

Vehicle and Occupant Motion in Far-Side Impacts

By Sean H. Haight and Kennerly H. Digges

22

Extracting Collision Data from Damaged Ford Powertrain Control Modules

By David M. Little

30

Estimating Maximum Motorcycle Acceleration Rates

By Wade Bartlett

40

The Speed Triangle: Momentum, Energy and PCM Data

The cover shot was taken at the 2011 CDR User's Summit in Houston, TX. This was one in a series of five crash tests conducted.

Cover layout and design by Scott Baker, Collision Publishing LLC.© 2011 Collision Publishing LLC. All rights reserved.

By Charlie Greear, David Thornburg, and Lee DeChant

50

Applying Heavy Vehicle EDR Data in the Real World

By William Messerschmidt, Benjamin Smith, and Al Dunn

62

An Accident Reconstructionist's Primer on: Tire and Wheel Rim Marks at Crash Scenes

By Donald F. Tandy, Jr., Jason Colborn, Robert J. Pascarella, Todd D. Hoover

82

10 30

Using CDR System Data in Crash Reconstruction or What Does the Term “Complete Reconstruction” Really Mean?

By: W. R. “Rusty” Haight

96

GPS Navigation Units: Recorded Data for Use in Accident Reconstruction

By Timothy J. Reust

100

The Performance of Seat Backs in High Speed Rear Impacts and the Effect to the Occupant

By Martin Werz and David Bliss

114

62

Insurance Applications for Crash Data Retrieval: Legal Considerations in 2011

By Michael L. Merolli, David O. Brink, and Andrew T. Apjohn

120

Preserving Heavy Truck Event Data

By Gary M. Johnson

www.collisionpublishing.com

Collision Magazine 3

Letter from the editor It seems like only yesterday we were wrapping a record-breaking CDR User’s Summit in Houston and, as I write this, we’re on the verge of the opening day of the 2011 ARC-CSI Conference in Las Vegas. You’ve probably heard it, or said it yourself but “wow! This year’s just flying by!”

This issue of Collision is the first time we’ve included crash data on the DVD accompanying the Spring issue because this year was the first time we’ve conducted actual crash tests at the Summit. For 2011, we were able to get specifically selected '08 and '09 CDR downloadable cars to conduct a series of specially designed crash tests. At “low closing speed” and then at a high closing speed, we were able to collect CDR data from a total of 5 crashes conducted in and around the presentations on the first day of the conference and, less than 73 hours later, distribute the data to those in attendance. That data is included on the DVD accompanying this issue of Collision.

By the time this issue goes to press, we’ll be well into the planning stages if not the implementation stages of the 2011 ARC-CSI Conference in Las Vegas. This year marks our 10th Conference and with that milestone we have arranged an incredible speaker line-up, an extra-special evening networking reception, and secured a fleet of late model vehicles that will certainly become on of the best crash days ever! Going back to our roots, “Human Crash Test Dummy” Rusty Haight will be driving in several of the crash tests this year which will feature late model Chrysler, GM and Ford vehicles not to mention two newer Toyota mini-vans. That, of course, hints at future announcements of CDR coverage that were alluded to at the Summit.

You might think we’ll be able to take something of a breather after that but, with the volume of this year’s ARC-CSI crash tests and the incredible line up of speakers, we’ll have to start working immediately on Collision Volume 6, issue 2 and planning for the 2012 CDR Summit almost as soon as the dust settles in Las Vegas in May.

On February 5, the accident reconstruction community lost one of the pioneers of CDR data with the early and untimely passing of William, “Bill” Davies. At only 59, Bill had in recent years retired from General Motors Canada after 30 years with the company, the last many years as a Senior Product Investigator, Product and Warranty Litigation Manager responsible for the forensic investigation and inspection of vehicle product allegations for General Motors of Canada Field Performance Assessment and Legal Staff.

He served as the Vice Chair of the Transportation Emergency Rescue Committee of Canada and taught vehicle fire rescue throughout the US and Canada.

In addition to the many that knew and admired him in our community, Bill leaves behind his wife Darlene, his mother Mildred , daughter Lynda, son Ray and his wife Holly and grandchildren William, Boyd and Jersie.

All of us who knew him benefitted from his knowledge and experience and are confident he’s somewhere better trying to explain that "if you do something abnormal, and you get something abnormal, its probably normal." His legacy will outlast us all.

4

Collision Magazine

www.collisionpublishing.com

Managing Editor

BACK ISSUES

Collision Publishing LLC PO Box 3383 Kirkland, WA 98083-3383 Toll Free: 800-280-7940 Email: editor@collisionpublishing.com Web: www.collisionpublishing.com ISSN: 1934-8681

If you would like purchase back issues of Collision Magazine, please visit www.collisionpublishing.com/backissues.html or call us toll free 800-280-7940.

COLLISION STAFF Scott Baker Sean Haight Tonya Baker Carla McLeod

Owner, Managing Editor Senior Editor Advertising Manager Subscription Services

All rights reserved, © 2006-11 Collision Publishing LLC. The opinions and conclusions expressed in this publication and attached data disk and throughout the articles attributed to specific authors are the opinions and conclusions of the authors noted and not necessarily the editorial staff or anyone else for that matter. While some articles have been reviewed for content, the accuracy of reprinted models or equations cannot be fully guaranteed. It is the responsibility of the reader to apply critical thinking to an individual review of the content and make their own personal judgements as to its value to them, individually.

At the end of the day, facts belong to everybody, any other opinions to us.

The distinction is yours to draw...otherwise, the opinions expressed herein are not necessarily those of any employer, not necessarily ours and probably not necessary. Dissenting opinions, discussion or conclusions which may express an adverse position to those expressed herein by specifically cited authors can be addressed in writing by sending an email to the editor at editor@collisionpublishing.com or sending a “regular mail” letter to us at PO Box 3383, Kirkland, WA 98083-3383. By sending correspondence to either our email or snail mail addresses listed in this publication you are agreeing that: (1) we are by definition, “the intended recipient” (2) all information in the email is ours to do with as we see fit and make such financial profit, political mileage, or good joke as it lends itself to and, (3) this overrides any disclaimer or statement of confidentiality that may be included on your original message. The entire physical universe, including this publication and attached data disk, may one day collapse back into an infinitesimally small space. Should another universe subsequently reemerge, the existence of this publication and data disk in that universe cannot be guaranteed.

ADVERTISER INDEX

PAGE

4N6XPRT Systems Inside Back ARAS360 1 ARC-CSI Crash Conference 9 ARC Network 80 CDR User's Summit 9 Collision Publishing 38, 128 Collision Safety Institute 95 Crash Data Group (CDR) 49 CrashTest-Service.com 41 CSVPro 2011 21 EDR Analytics 28 Engineering Dynamics 28, Inside Front Eos Systems: Photomodeler 61 HVE-CSI 20 iWitness 43 MapScenes 2, 57-60 NAPARS 6 NCAC 113 Northwestern University 81 Vericom Computers 29 Visual Statement 39, 99, Back

Included with this issue of Collision

SUBMIT AN ARTICLE If you would like to submit an article to be published in Collision please email us your article for review or call us toll free 800-280-7940. Email: editor@collisionpublishing.com

ADVERTISING RATES & INFO If you would like to advertise your products or services in Collision Magazine, rates, availability and other information are available online at: www.collisionpublishing.com www.collisionpublishing.com

is the 2011 CDR User's Summit data DVD. The Summit DVD includes all the photos, video, instrumented crash testing data, scaled diagrams, speaker Powerpoints, and any other supporting data compiled in a easy to review, menu-driven data DVD.

Next CDR User's Summit January 2012 www.cdrsummit.com Collision Magazine 5

Premier Industry Partner Letter from the President

NAPARS recently teamed up with the University of Tulsa’s “Traffic Crash Reconstruction Research Consortium”, becoming a member of the consortium beginning this year. TU-CRCC is a non-profit cooperative industry-government-university research project focused on conducting basic and applied research for the advancement of crash reconstruction practices. They will be tasked to handle the live crash testing planned each year by the host organization at our annual October conferences for the next five years. In addition, NAPARS members will receive free access to ALL crash testing done for any of the consortium members.

NAPARS has also been busy putting the finishing touches on the new web site, which by now the membership has gotten used to. I also invite the nonmembers (or shall we call you “prospective” members?) to visit the site and take a look at the public information available. The “Members Only” section contains our database of publications, technical papers, and reference materials that we hope will assist our members in their daily work.

Before I attended this year’s CDR Summit in Houston I had been told that this was going to be even better than in the past. Not that there have been any complaints mind you, but due to the fact that the folks at ARC-CSI are always trying to outdo themselves. And they did so again this year, with the addition of live crash testing and CDR downloading.

There is nothing better for your CV than actually watching the crash tests that made up the presentation you watch the next day. And speaking of crash tests, a long slate of them are planned for this year’s ARC-CSI Crash Conference in Las Vegas. Make sure to stop by the NAPARS vendors table and say hello.

NAPARS is proud to be a supporter of the yearly ARC-CSI CDR and Crash training events.

Coming October 3 – 7th, 2011 is the Joint Annual Conference that will be held this year near Harrisburg, PA with a focus on Pedestrian Crash Reconstruction. The folks from NATARI have promised to put on a great show, so you don’t want to miss it.

And as always, remember that asking a question or making a suggestion to NAPARS is only an email away by contacting me at President@NAPARS.org.

I hope to see you at a NAPARS event very soon!

Chuck Veppert President, NAPARS

The National Association of Professional Accident Reconstruction Specialists is a non-profit organization whose members have joined together to share the challenge of dealing with the complex problems of accident reconstruction and to upgrade and ultimately professionalize the accident reconstruction field.

6

Collision Magazine

www.collisionpublishing.com

www.napars.org

Industry Partners IAARS is one of the oldest associations dedicated to

expanding the knowledge and training of accident reconstructionists. Formed in 1980, we have members from several different countries as well as many different states across the U.S. We have three levels of membership. Our highest level, Fellow, includes a peer review of a reconstruction project. This peer review feature can be very beneficial to a member seeking expert witness qualification in court. One of the criteria a judge can consider when deciding if a person qualifies as an expert is a peer review of his or her work. We offer opportunities for a member to publish work or research in the field of accident reconstruction. This, also, can be very important when qualifying as an expert witness in court proceedings.

Membership in IAARS has other advantages, including a discount (from IAARS) on a subscription to Collision Magazine, member discounts at our training seminars and others listed on our web page, www.iaars.org.

ASPACI is a non-profit society whose members have

joined to share in the challenge of analysing the complicated issues of road collision investigation.

ASPACI was formed in 1991 by a group of police and collision reconstructionists who felt there was a need for information sharing between police and associated institutions in the Australia, South East Asia, New Zealand and South Pacific area.

Its primary function is to assist in the spreading of knowledge and enhancing expertise in the science. The Association seeks to promote a professional approach to collision investigation and to encourage the highest standard of ethics, integrity and honesty among its members.

The ARC Network was founded in 1998 and

since has grown to be the largest and most respected organization for Accident Reconstruction and Traffic Investigation.

The ARC Network is more than just an organization it is a research and communications Internet portal for everything accident reconstruction. The ARC Network provides research tools, Expert directory, event calendar, industry news feeds, discussioin forum and a Member's Only area that gives members access to various online databases and information.

We have annual training opportunities at different locations across the country. We try to have some sort of actual vehicle testing at each seminar, including full scale vehicle crashes. As a member, you would have access to a vast archive of results from many different and sometimes quite unique tests.

The 31st annual IAARS training seminar will be held in collaboration with the South Carolina Association of Reconstruction Specialists and the Southeast Accident Reconstruction Society.

The training seminar will be July 25 29, 2011 at the Holiday Inn in Charleston - Mount Pleasant, SC. More information will be posted at scarsrecon.org and iaars.org, as it becomes available.

Sincerely, Dan Lofgren President, IAARS www.iaars.org The early days saw the number of members vary with the base of the association in Victoria, Australia. ASPACI became ASPACI Incorporated in 1993 in Victoria. Now we boast members from all over mainland Australia, New Zealand., United Kingdom, and the United States, as well as parts of Asia.

Membership to ASPACI is open to all persons engaged in collision investigation and its allied fields. The association members include Engineers, Police Officers, Independent Consultants, Scientists, Insurance Corporations, Manufacturers and Safety personnel. ASPACI is not a Trade Association or Political Lobby group, nor is it a Police organisation.

in the ARC Network (including a listing in the Expert Directory) you also receive a free copy of REC-TEC's Drive3 software ($250 value), $50 discount to the annual ARC-CSI Crash Conference and $50 discount to the CDR User's Summit. Also included is a free copy of Greg Russell's Excel Crush Stiffness spreadsheet program. Extend your savings and sign up as a Police Agency member or Platinum member and receive a complimentary subscription to Collision Magazine!

The ARC Network offers various membership levels to fit your needs and budget. Membership starts at just $79.00 per year.

However, that is where the value of the ARC Network starts.

With your membership you not only get access to everything

Scott Baker President The ARC Network (800) 280-7940 www.accidentreconstruction.com arc@accidentreconstruction.com

For information on becoming a Collision Industry Partner send an email - editor@collisionpublishing.com www.collisionpublishing.com

Collision Magazine 7

training calendar for Accident Reconstruction and Traffic Investigation Company

Date

Course

Location

COLLISION SAFETY INSTITUTE: www.collisionsafety.net 7/11-15/2011

CDR Data Analyst Certification

Evanston, IL

7/18-22/2011

CDR Data Analyst Certification

Lansing, MI

8/29-9/2/2011

CDR Data Analyst Certification

Irvine, CA

9/19-23/2011

CDR Data Analyst Certification

Seattle, WA

9/26-30/2011

CDR Data Analyst Certification

Chantilly, WA

10/10-14/2011

CDR Data Analyst Certification

Longmont, CO

ENGINEERING DYNAMICS CORP: www.edccorp.com 11/7-11/2011

EDC Simulations Course

Coral Gables, FL

1/23-27/2012

EDC Reconstruction Course

Burbank, CA

6/20-24/2011

Basic-Intermediate Diagramming w/CrashZone

Haven, CT

FACTUALDIAGRAMS.COM

NORTHWESTERN UNIVERSITY: nucps.northwestern.edu 7/6-8/2011

Advanced Skills for the CDR System Operator

Evanston, IL

8/15-26/2011

Traffic Crash Reconstruction 1

Springfield, IL

8/29-9/2/2011

Traffic Crash Reconstruction 2

Springfield, IL

9/12-23/2011

Crash Investigation 1

Evanston, IL

9/26-10/7/2011

Crash Investigation 2

Evanston, IL

10/10-14/2011

Vehicle Dynamics

Evanston, IL

10/17-28/2011

Traffic Crash Reconstruction 1

Evanston, IL

10/31-11/4/2011

Traffic Crash Reconstruction 2

Evanston, IL

11/16/2011

CDR Technician Level 1

Evanston, IL

11/17/2011

CDR Technician Level 2

Evanston, IL

3/5-9/2012

Advanced Crash Reconstruction - Utilizing Human Factors Research

Evanston, IL

3/12-23/2012

Crash Investigation 1

Evanston, IL

3/23-4/6/2012

Crash Investigation 2

Evanston, IL

4/9-13/2012

Math and Physics Workshop for Crash Reconstruction

Evanston, IL

4/16-20/2012

Vehicle Dynamics

Evanston, IL

6/13-17/2011

EdgeFX Diagramming w/Total Station

Little Rock, AK

6/27-7/1/2011

EdgeFX Diagramming w/Total Station

Raleigh, NC

VISUAL STATEMENT: www.visualstatement.com

If you would like to list an upcoming training event in Collision's Training Calendar please email editor@collisionpublishing.com or give us call (800) 280-7940

COMING JUNE 2012

The ARC-CSI Crash Conference has set the standard for excellence in live, fully instrumented practical crash testing anywhere. Each year for the past 10 years, the ARC-CSI Crash Team has conducted multiple, fully instrumented crash tests that have been the basis for valuable insight into how various crash scenarios occur and have become the basis for a wealth of information on vehicle systems and operations. Nothing compares to an opportunity to see live, full scale crash tests and then, hours later, get your hands on actual data, video, photos and other documentation of those tests to take back and improve your crash reconstruction job performance.

arccsi.com

Vehicle and Occupant Motion in

Far-Side Impacts Sean H. Haight

National Crash Analysis Center The George Washington University

10

Collision Magazine

Kennerly H. Digges

National Crash Analysis Center The George Washington University

www.collisionpublishing.com

A

bstract The Federal Motor Vehicle Safety Standards (FMVSS) 214 was established in 1990 as a minimum requirement to reduce the risk of serious injuries and fatalities to occupants in side impact crashes. The standard focused on protecting the vulnerable occupants in the near side (i.e. seated on the struck side of the vehicle) by requiring placement of two dummies at these locations. More recently, research studies have indicated that far-side occupants are also vulnerable

www.collisionpublishing.com

in side impacts. The research presented in this paper is an extension to one of these studies. Two full-scale crash tests were conducted to determine the occupant kinematics of a far-side occupant. In addition, the effects of impact positions, rotation, and seatbelt performance were analyzed with regard to the far-side occupant. Analyses of the rotation of the vehicles showed that the impact point affects the magnitude and direction of yaw during the collision. Additionally, the vehicle motion affects the occupant motion relative to the vehicle.

Collision Magazine 11

B

ackground A far-side impact can be described as a collision in which an occupant is seated on the side of the vehicle that is opposite the impact location. For example, one far side scenario could be an occupant sitting in the driver seat, while being struck on the passenger side of the vehicle.

This research is a continuation of an earlier project to develop the technology base for far-side protection. The project was managed jointly by Monash University in Australia and The George Washington University in the US. [Fildes and Digges 2009].

This earlier project determined the crash environment associated with serious injuries in far-side crashes and developed a technical basis for the crash dummies, injury criteria, and test procedures to be used in evaluating far-side countermeasures. The results of the project and the published literature it produced are contained in an ESV paper by Digges [2009].

An in-depth analysis of the crash environment for belted occupants in far-side crashes was presented in earlier papers [Digges, 2006, Gabler, SAE 2005 and ESV 2005]. The analysis indicated that for belted occupants with MAIS 3+ injuries, the 50% median crash severity was a lateral delta-V of 28 km/h and an extent of damage of 3.6 as measured by the CDC scale [SAE Standard J224, Collision Deformation Classification]. The most frequent damage area for seriously injured belted occupants was the front 2/3 of the vehicle (42%), followed by the rear 2/3 (21%). The most frequent principal direction of force (PDOF) was 60° (60%), followed by 90° (24%). The head and chest were the most frequently injured body regions, each at about 40% [Gabler 2008]. The injuring contacts that most frequently caused chest injury were the struck-side interior (23.6%), the belt or buckle (21.4%) and the seat back (20.9%) [Fildes, 2007]. A Harm analysis showed 30% of the Harm associated with side impact crashes occurred to the far side occupant and that this figure was reasonably consistent in both the US and Australia [Gabler, Firzharris, et al 2005].

Sled tests that compared the kinematics of dummies and cadavers were conducted by the Medical College of Wisconsin [Pintar 2006, 2007]. A conclusion of this research was: “The THOR and WorldSID dummies demonstrate adequate biofidelity to develop countermeasures in this (far-side) crash mode” [Pintar 2007].

The sled tests conducted by Pintar did not include any rotation of the sled during the impact. However, MADYMO computer simulations by Cuadrado found that vehicle rotation could influence the occupant kinematics in far-side crashes [Cuadrado 2008, 2010]. The simulations by Cuadradro were limited by the small number of crash tests that have been conducted under the most frequent far-side crash modes. Data from the crash tests are needed to provide the vehicle translation and rotation to the MADYMO model.

Limited crash tests are available to investigate near-side occupant vulnerability in side impacts and more research is needed to analyze the occupant response in this crash scenario. This study continues the research in this crash scenario. Two far-side crash tests were conducted at the Federal Highway Administration (FHWA) Federal Outdoor Impact Laboratory (FOIL) to analyze the kinematics of occupants seated in this configuration. Based on earlier research, an angular crash is most frequently involved in MAIS 3+ injuries for belted occupants exposed occupants in far-side crashes. However, the location of the impact along the side of the vehicle can produce different vehicle intrusion patterns and different linear and angular vehicle kinematics. The goals of the tests were to understand how two different impact locations affect the motion of the vehicle and the occupant. Some important factors to be studied include the vehicle rotation, the head impact location and the seatbelt performance. These two tests were further analyzed to achieve the goals of the study.

C

rash Tests Two crash tests were performed in 2010 at FOIL. The first test was numbered #10010 and the second test was numbered #10016. These numbers will be used throughout the study to refer to the specific test being analyzed.

Test 10010 – B- pillar impact point (figure 1) The first test was designed to be a passenger side impact at a speed of 62 Km/h (38.5 mph). The bullet vehicle for this crash test was a 1996 Ford Explorer (four door) and the target vehicle was a 1997 Ford Taurus. The occupant in the Taurus was a Hybrid II, non-instrumented anthropomorphic test device (ADT).

The occupant was placed on the driver side of the Taurus. Additionally, the Taurus was positioned at 60 degrees to the test track and the impact point was set so that the first point of contact with the Explorer would be at the Taurus B- pillar.

Instrumentation for test 10010 consisted of two sets of tri-axial accelerometers at the center of gravity as well as a set of rotation sensors that measured roll, pitch and yaw. Seven high speed video recorders were placed around the target vehicle as well as one placed on the hood of the Taurus to capture the motion of the occupant. Two real time videos were used as well.

Test 10016 – A- pillar impact point (figure 2) The second test was also designed to be a passenger side impact at a speed of 62 Km/h (38.5 mph). The bullet vehicle for this test was the same vehicle used in test 10010. However, the damaged components were replaced with new, undamaged parts. The tar-

A limited number of crash tests to support the understanding of far-side occupant kinematics have recently been reported [Smyth 2007 and Newland 2008]. The two tests reported in this paper are a continuation of the research in far-side testing.

Currently, the (FMVSS) 214 tests require specific side impact protection for occupants in near-side impacts; risk of injury for far-side occupants are not assesed. Opportunities for safety improvements exist because far-side occupants account for up 30% of injuries in real world side impact collisions [Fildes 2000]. In Australia, where belt use is over 90%, head injuries occurred in higher frequencies in far-side collisions when compared to nearside collisions [Fildes 1994].

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Figure 1: Test configuration for Test 10010, B- pillar impact point; 60 degree; Hybrid II ADT occupant (un-instrumented) Figure 2: Test configuration for Test 10016, A- pillar impact point; 60 degree; Hybrid III ADT occupant

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get vehicle for test 10016 was a 2002 Ford Taurus. The occupant in the Taurus was a Hybrid III, instrumented, anthropomorphic test device (ADT). The occupant was placed in the driver side of the Taurus and the vehicle was angled at 60 degrees. The bullet vehicle was aligned so that the center would impact the A-pillar of the Taurus.

Instrumentation for test 10016 consisted of two sets of tri-axial accelerometers at the center of gravity as well as two sets of rotation sensors that measured roll, pitch and yaw. In addition, 40 data channels recorded data from the ADT including head and pelvis accelerations. Seven high speed digital cameras were placed around the target vehicle.

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est Results Test 10010 - B-pillar impact point Figure 3 shows the recorded accelerometer data and the calculated change in velocity for the Taurus. The recorded data, filtered with a class SAE60 filter [SAE J211, 1988] shows a max acceleration of 11 g’s at 52 ms. The maximum change in velocity (delta-v) was calculated to be 18.9 kph (11.8 mph). The crash pulse duration was about 115 ms.

Test 10016 – A-pillar impact point Figure 4 shows the recorded accelerometer data and the calculated change in velocity for the Ford Taurus. The recorded data, filtered with a class SAE60 filter, shows a max acceleration of 21 g’s at 52ms. The delta-v was calculated to be 29.7 Km/h (18.5 mph). The crash pulse duration was about 80 ms.

Figure 3: Acceleration and velocity data for the Ford Taurus (Test 10010)

Figure 4: Acceleration and velocity data for the Ford Taurus (Test 10016) www.collisionpublishing.com

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Figure 5 shows the recorded Hybrid III ADT head resultant data filtered with a class SAE1000 filter. The maximum resultant head acceleration for the occupant is 20 g’s at 145 ms. The calculated Head Injury Criteria (HIC, 32 ms) is 58.8.

Figure 6 shows the recorded Hybrid III ADT pelvis resultant data (class SAE1000 filter). The maximum resultant acceleration for the pelvis was recorded as 38 g’s at 78 ms.

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ADYMO Modeling The use of Mathematical Dynamic Modeling (MADYMO) is frequently used as a tool to simulate impacts for occupant kinematics. For this study, a MADYMO system model was created using the interior of a Ford Taurus and a human model. Figure 7 shows the model configuration for the two tests in the study.

For these tests, the data from the tri-axial accelerometers was used in conjunction with the data from the yaw rate sensor as inputs for the MADYMO model.

Overhead pictures from Test 10010 (B-pillar crash) are shown at contact (in Figure 8) and at 200 ms (in Figure 9). The location of the occupant in the MADYMO model after 200 ms for Test 10010 can be seen in Figure 10. Overhead pictures from Test 10016 (A-pillar crash) are shown at contact (Figure 11) and at 200 ms (Figure 12) The location of the occupant in the MADYMO model after 200 ms for Test 10010 can be seen in Figure 13. Figures 14 and 15 show frontal views of the MADYMO simulations of the two tests.

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Figure 7: The configuration of the MADYMO model for simulation of the two tests in the study (above) Figure 5: Resultant head acceleration for the Hybrid III ADT occupant (Test 10016) (top) Figure 6: Resultant pelvis acceleration for the Hybrid III ADT occupant (Test 10016) (bottom)

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Figure 8: Overhead view of test at impact (Test 10010) B-pillar impact

Figure 11: Overhead view of test at impact (Test 10016) A-pillar impact

Figure 9: Overhead view of test 200 ms after impact (Test 10010) B-pillar impact

Figure 12: Overhead view of test 200 ms after impact (Test 10016) A-pillar impact

Figure 10: Graphic results from MADYMO model 200 ms after impact (Test 10010) B-pillar impact

Figure 13: Graphic results from MADYMO model 200 ms after impact (Test 10016) A-pillar impact

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Figure 14: Graphic results from MADYMO model 200 ms after impact (Test 10010) B-pillar impact

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otation Analysis Since both crash tests had different impact locations relative to the center of gravity, the rotation about the vertical axis differs. For Test 10010, the B-pillar impact point, the rotation was positive. Since the impact point of Test 10016 was in front of the center of gravity, it caused a negative rotation about the vertical axis.

Figure 16 shows the rotation of the target vehicles the two test.

At 200 ms, the target vehicle in Test 10010 rotates +30 degrees, while the target vehicle in Test 10016 rotates -13 degrees over the same period of time.

The maximum rotation at 2 seconds was +130 degrees in Test 10010 and -80 degrees in Test 10016.

Figure 15: Graphic results from MADYMO model 200 ms after impact (Test 10016) A-pillar impact

Since both crash tests had different impact points relative to the center of gravity, the rotation about the vertical axis differs.

Figure 16: Graph of the rotation of the target vehicles for tests 10010 and 10016. Test 10010 has positive rotation and test 10016 has negative rotation.

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rash Pulse Analysis The side-by-side comparison of the crash pulses (Figures 3 and 4) show the difference in magnitude and duration of the acceleration for the different impact locations.

For test 10010, the location of the impact was at the B-pillar of the target vehicle. This impact location yields a lower peak acceleration and longer crash pulse duration. In comparison, the impact location of Test 10016 was at the A-pillar of the target vehicle. This resulted in a higher peak acceleration and shorter crash pulse duration.

These results also show that different areas of the target vehicle have different stiffness. The area of the vehicle around the Bpillar has less stiffness than the area around the A-pillar.

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elt Contact Analysis The performance of the seatbelt in far-side impact tests was examined in this study. In both tests the lap belt maintained contact with the occupant and kept the occupant in the driver seat. The shoulder belt lost contact and the

occupant slid out of position. Figure 17 shows the occupant position in Test 10010 at time zero (initial contact) and at 170 ms.

In both tests, the shoulder of the occupant slides underneath the shoulder belt and the upper body continues to move towards the striking vehicle. In both tests, the occupant lost contact with the shoulder belt between 80 and 90 ms into the event. Test 10016 did not have a video camera on the hood due to its instability in the crash configuration. The video analysis of the Hybrid III head resultant data from Test 10016, shows a steep drop in acceleration around 80 ms (See Figure 18.) Since the vehicle is accelerating, and accelerating the occupant’s head via the contact with the shoulder belt, the loss in acceleration indicates that the shoulder belt lost contact with the occupant. Since the contact is lost, the force of the belt on the occupant is effectively zero, causing the occupant head acceleration to decrease.

Based on the analysis of video and acceleration data, the rotation of the vehicle at the instant the shoulder belt lost contact with the occupant can be determined. For Test 10010, the rotation

Figure 17: Two frames from test 10010 showing the occupant-seatbelt contact at vehicle impact (above) and after 170 ms.

Figure 18: Head resultant acceleration for Hybrid III occupant (Test 10016) www.collisionpublishing.com

Collision Magazine 17

at 80 ms was +4.4 degrees. For Test 10016, the rotation at 80 ms was -3.8 degrees. This difference is very important because it illustrates the direction of a free moving occupant in relation to the motion of the vehicle.

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ccupant Motion Earlier research on computer modeling by Alonso indicated that the existing dummies used in the frontal standards do not replicate the human motion in a farside impact [Alonso, 2007]. However, Alonso found that the MADYMO human facet model was a good surrogate for a human in far-side tests. For both tests, the occupant data was determined using the MADYMO models. The crash environment for the occupant was determined by calculating the angle of the acceleration components and using test results as input data. In addition, the direction of the vehicle can be determined with the same lateral and longitudinal components. Finally, the model predicts the angle of the occupant in relation to the vehicle.

The angle of motion of the occupant relative to the vehicle was calculated for each test. For Test 10010, the angle of the occupant was 35 degrees (averaged over 200ms) relative to the longitudinal axis of the vehicle. Visually, this can be seen in Figure 19.

occur and develop testing procedures of safety systems to reduce these types of injuries. From the test data and high speed videos, it was found that occupants seated in the far side are vulnerable to many types of injuries. Most of these injuries occur because shoulder belts are ineffective in these types of impacts.

Two crash tests were conducted and analyzed in this study. The tests focused on occupants seated on the far-side. Acceleration data was recorded for the target vehicle in both tests and for the occupant in one of the tests. The data was analyzed, and the kinematics of the occupant was calculated. The use of MADYMO modeling aided in the analysis of the occupant kinematics when data or video view angles were not available.

Analyses of the rotation of the vehicles showed the effect of impact points on the magnitude of yaw during the collision. For a passenger side impact point behind the center of gravity, the vehicle will rotate positively about the vertical axis, while a passenger side impact point in front of the center of gravity will cause the vehicle to rotate negatively about the vertical axis. This rotation causes the occupant to move in different directions relative to the vehicle motion.

The differences in angles show that the rotation and impact points of the vehicles change the direction of the occupant motion. In addition, since the shoulder belt was ineffective in both cases, any impact location/angle combination in between these would result in an ineffective shoulder seat belt. Thus, since the two tests in this study have different impact points; any location in between these impact points would result in a loss of seatbelt performance. However, these two impact points are not the upper and lower limits of the area for seatbelt performance loss.

Other tests at other impact locations beyond the A or B pillars could also result in an ineffective shoulder belt.

The MADYMO simulations showed that for positive rotation, as seen in Test 10010, the occupant will have a larger longitudinal (+X) component of motion. In other words, the occupant will move further forward towards the front of the vehicle. (See Figure 19.) Conversely, the simulations show that for negative vehicle rotation, as in Test 10016, the occupant will have more lateral acceleration (+Y) and will move towards the far-side door or interior. (See Figure 20). Understanding how the vehicle rotates is important because it can provide a correlation between motion and injury. For example, in a collision like Test 10016 where the occupant moves towards the passenger door, the interior of the target vehicle can be displaced towards the occupant.

This decreases the distance between the occupant’s head and stiff objects in the vehicle that would cause injury. In Test 10016, a 62 kph impact, the high speed video shows that the intrusion into the passenger compartment was almost enough to cause the occupant’s head to strike the passenger door.

onclusions Further research of far-side impacts is essential to investigate near-side occupant vulnerability in side impacts research studies, similar to the one presented in this paper, must be conducted to develop understanding of how injuries can

In comparison, a positive rotation as in Test 10010, the occupant will move forward towards the center dash or the passenger airbag. This places the occupant in a dangerous position, with their head close to a rapidly deploying airbag. While SRS systems are very effective at saving lives for frontal impacts, when

Figure 19: Top view of occupant in MADYMO model (Test 10010). The arrows show the general direction of the human's motion.

Figure 20: Top view of the occupant in MADYMO model (Test 10016). The arrows show the general direction of the human's motion.

The angle of motion of the occupant relative to the vehicle was also calculated for Test 10016. The angle of motion for the occupant in this test was 15 degrees (averaged over 200ms) relative to the vehicle. This can be seen in Figure 20.

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occupants are out of place, it can lead to more injury than benefit. High speed video shows the passenger airbag deployment in Test 10010 coming very close to the occupant’s head while in motion towards the near-side. Rotation analysis can lead to further understanding to why specific injuries occur.

In addition to head injuries, the high speed video and MADYMO simulations both indicated a possible upper extremity injury on the near-side. As seen in Figures 19 and 20, the right arm was highly extended towards the near-side. This causes high forces on the shoulders and possible injury. Gabler [2005] reported that Upper Extremity injuries were second to Head injuries as a source of injury Harm to belted occupants in far-side crashes.

Further research into the occupant motion in far-side impacts can be done. For example, more MADYMO simulations can be completed in conjunction with finite element analysis to examine how vehicle intrusion can affect occupant injury. Also, other impact points and impact angles can be simulated to find the upper and lower bounds of shoulder belt performance. This kind of research can fine tune the supplemental restraint systems and encourage the adoption of countermeasures..

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eferences Alonso, B., Digges, K., and Morgan, R. (2007) Far-side vehicle simulations with MADYMO. SAE 2007-010378, April 2007.

Cuadrado, J. (2008) Comparison of crash pulses and sled responses for far-side impacts. M.S. thesis, Civil & Environmental Engineering Department, The George Washington University, Washington, D. C., 2008.

Cuadrado, J., Smyth, B., Smith, J., and Digges, K., (2010) Validation of sled tests for far-side occupant kinematics using MADYMO. SAE 2010-01-1160, 2010.

Digges, K., Echemendia, C., Fildes, B., and Pintar, F. (2009) A safety rating for far-side crashes. Paper Number 09-0217, Proceedings ESV, June 2009.

Digges, K., Gabler, H., (2006) Opportunities for reducing casualties in far-side crashes. SAE 2006-01-0450, April 2006.

Fildes, B., and Digges, K., (2009), Occupant protection in far-side crashes. Report by George Washington University and Monash University, June 2009.

Fildes B., Gabler H.C., Fitzharris M. & Morris A.P. (2000). Determining side impact priorities using real-world crash data and harm, Pr IRCOBI, September 2000.

Fildes B., Lane J., Lenard J. & Vulcan, A.P., (1994), Passenger cars and occupant safety: side impact crashes. Report CR134, Australian Transport Safety Bureau (formerly the Federal Office of Road Safety), Canberra, Australia.

Gabler, H., Digges, K., Fildes, B., and Sparks, L. (2005) Side impact injury risk for belted far-side passenger vehicle occupants. SAE 2005-01-0287, April 2005.

Gabler, H., Fitzharris, M., Scully, J., Fildes, B., Digges, K., Sparke, L., (2005) Far-side impact risk for belted occupants in Australia and the United States. Paper 05-0420, ESV Conference, June 2005.

Newland, C., Belcher, T., Bostrom, O., Gabler, H., Cha., J., Wong, H., Tylko, S., and Dal Nevo, R. (2008) Occupant-to-occupant interaction and impact injury risk in side impact crashes.

Stapp Car Crash Conference, October 2008.

Pintar, F., Yoganandan , N., Stemper, B., Bostrom , O., Rouhana , S., Digges, K., Fildes, B. (2007) Far-side impact response and dummy biofidelity. Proceedings of the 2007 Stapp Car Crash Conference, October 2007.

Smyth, B and Smith J. (3007) Developing a sled test from crash test data. SAE. 2007-01-0711, 2007.

Society of Automotive Engineers (SAE): Standard J211-1 (1988). Instrumentation for Impact Test, October, 1988.

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cknowledgements The authors wish to thank the USDOT for supporting the outreach program under which these two carsh tests were conducted and for allowing the use of the FOIL. Special thanks to everyone involved in the testing and analyses used in this study including the students and staff of the National Crash Analysis Center at the George Washington University. Sincere appreciation to Shaun Kildare, Larry Wilson, Chris Story, and the rest of the FOIL technicians.

Disclaimer: The contents of this paper reflect the views of the authors who are solely responsible for the facts and accuracy of the data, and the opinions, findings and conclusions presented herein.

The contents do not necessarily reflect the official views or policies of the U.S. Department of Transportation, the George Washington University, or the National Crash Analysis Center.

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www.CSV-PRO.com CSV Pro uses the Bosch Crash Data Retrieval Software's CSV (comma separated value) function for certain data sets and allows the end user to view and arrange the recovered data into meaningful, clear and concise reports and graphs supplementing the original CDR report for supported Ford, Chrysler and GM vehicles. This program does not change or alter any data in the .cdr file gererated from the CDr download.

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Collision Magazine 21

Extracting Collision Data from Damaged Ford Powertrain Control Modules

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ollowing a severe collision, the vehicle’s powertrain control module (PCM) may be damaged to the extent that it can not be downloaded directly using the Bosch Crash Data Retrieval (CDR) system. Unlike the airbag control modules (ACM), the PCMs are typically located in the engine compartment, making them more susceptible to damage in a frontal crash. If the PCM circuit board is cracked in the collision, the CDR system may not be able to communicate with the appropriate location on the board.

If this has occurred, the integrated circuit (“IC”, or “chip”) with the collision data may need to be removed and placed in a surrogate module in order to access the data.

Two examples are noted below where extensive damage to the PCMs required the chips to be swapped into undam-

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Baker Materials Engineering Ltd.

CPH-b182 Collision

David M. Little P. Eng

aged PCMs in order to obtain downloads. Figures 1 and 2 depict a 2004 Ford F150 that struck its right front against a large tree. The PCM had been located against the firewall but the battery was crushed back into the PCM, deforming the PCM casing. A tow truck was used to gain access to the PCM (Figure 3). Initial attempts to download the PCM were unsuccessful. Once the case was opened, a crack was observed across the circuit board.

Another example of severe PCM damage is shown in Figures 4 to 7. This 2005 Ford Mustang sustained a head-on collision at highway speeds. The case for the PCM, which was originally located in the forward portion of the engine compartment, was shattered and part of the circuit board was missing. As well, battery acid had burned parts of the board,

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Collision Magazine 23

Figures 1 and 2: This 2004 Ford F150 struck a tree with its right front, crushing the PCM between the battery and the firewall (above and right)

Figure 3: A tow truck was required to access the PCM. while other parts of the board were cracked. Several components (capacitors, ICs, etc.) were missing and the connector for the CDR cable was badly damaged. This PCM was an obvious candidate for chip swapping.

Prior to attempting to switch the PCM chip, a download should be attempted on the damaged module to establish if a simpler fix is all that is required. If the connector pins are bent, as was the case with the Ford Mustang, the pins should first be straightened so that a download can be attempted (Figures 8 and 9). If the exterior of the PCM case is obviously dented, such as that incurred by the Ford F150 (Figures 10 and 11) this may have caused a short across the circuit board. This problem may be easily rectified by opening the PCM and separating the case from the board. However, in more severe cases, the PCM board itself may be broken or otherwise damaged (see Figure 12). This article details a method by which the data can be retrieved even after severe damage to the PCM. From a collision-investigation perspective, there are three main types of Ford PCMs. The difference is determined by the amount of data that can be stored in the module. Ford modules are capable of recording either 12.4, 25.6 or 409.2 seconds of information at 5 Hz. This information is stored on an electronically erasable programmable read-only memory (EEPROM) chip located on the board inside the PCM. The challenges involved in extracting data from these chips when the conventional method won’t work are a) identifying the chip with the collision data, b) swapping that chip into a surrogate

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Figures 4 and 5: This 2005 Ford Mustang sustained extensive front end damage following a head-on collision.

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Figures 6 and 7: The PCM, which had been located in the front of the engine compartment, was severely damaged.

Figure 9: A download was attempted once the pins were straightened. However, damage elsewhere on the circuit board still prevented a successful download.

Figure 8: The connector pins from the Mustang PCM had to be straightened before a download could be attempted.

Figures 10 and 11: The F150 PCM case was bent, possibly causing a short against the case. The case was opened, the inner brace was removed, and another download was attempted, albeit without success.

PCM without damaging the data inside it, and c) properly documenting the process so that the data will be accepted in court.

A method for extracting data from damaged General Motors airbag control modules (ACMs) has been addressed by Bartlett1.

In ACMs, the collision related information is stored in a large, square 52 pin IC. This chip is easy to identify given its size and because there is typically only one on the ACM board. However, in PCMs, the collision data are stored in a smaller, 8 pin chip.

There are typically half a dozen of these chips in the PCM and the first step is to identify the chip containing the relevant information. The automobile manufacturers view the layout of their circuit board as proprietary and will not reveal the location of the chip without a non-disclosure agreement. However, the chip of interest can be identified by other means.

With the aid of a low power microscope, the identification (part number and date of manufacture) on the top of each chip can

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Figure 12: The PCM board from the Mustang sustained extensive damage.

Figure 13: The identification on the tops of the 8 pin chips can be read in order to establish what chip contains the collision-related data.

Figure 14: The PCM part number (outlined) is located along the edge or face of the PCM.

Figure 15: With the aid of a soldering iron, the EEPROM chips in both the F150 and the Mustang PCMs were removed and soldered into surrogate PCMs for successful downloading.

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“”

be read, along with the symbol of the manufacturer (see Figure 13). The internet can then be used to identify which chips have EEPROMs. Typically, this will reduce the selection to only one or two chips. The location of the chip on the PCM board will vary based on the vehicle model.

For the most common type of PCM (with 25.6 seconds of data) the relevant chip will have 16k of memory. The modules with the larger collision memory (in the 2004 F150, 2003-2005 Ford Thunderbird and 2003-2006 Lincoln LS) store the collision data on a 256k chip. This appears to hold true for both suppliers of Ford PCMs (Motorola and Visteon) that can be downloaded using the CDR system2. The memory chip containing the collision data in the PCMs that store only 12.4 seconds of data (2005 2006 Ford 500/Ford Freestyle and Mercury Montego) has not yet been validated by testing. However, there is one 4k, 8 pin EEPROM chip in this module which may store the data.

Once the relevant chip has been identified, a surrogate PCM must be obtained. The part number of the damaged PCM is located on the edge or face of the PCM and will have a code such as “5R3A-12A650-ADD”, as shown in Figure 14. The first number refers to the model year of the vehicle for which the PCM was built (in this case – 2005), while the middle information – 12A650 – identifies the module as a PCM. Since this will always be the same for a PCM, some suppliers have dropped this portion of the part number from their identification. The final two or three letters need not be identical with the damaged PCM in order to provide a download. However, if one is concerned about explaining the difference in court, it may be best to find a surrogate PCM with the identical part number. Again, this can be easily done with the use of the internet. Used PCMs may be available for $100-200.

Once an exemplar PCM has been obtained, a download should be conducted on this module to a) ensure that the PCM is functional, and b) document the existing data in the buffer. This must be done in order to show that the information obtained once the chips are swapped is different from the original data on the surrogate chip.

When the Ford PCM was first installed in the vehicle, the PCM was programmed with the original VIN. The VIN is stored in a different chip from the one that contains the EEPROM data we are attempting to access. Unless this second chip is also swapped, the download will display the original VIN, not the one related to our collision. Investigators should be aware of this and be able to explain the difference.

With the EEPROM chip identified, a soldering iron or hot air gun can be used to remove the chip (see Figure 15). The chips are mounted on the surface of the board and only require the solder holding the 8 pins to be melted. During manufacture, the circuit boards are coated with a silicone-like material. This material will burn away during the desoldering process. It can be partially scraped away prior to applying heat, to reduce the fumes. Care should be taken not to overheat the chip, destroying the data, or to desolder other components on the surrogate board that may be required later for the download. This stage is best done by someone familiar with this type of rework.

Once the chip has been removed and soldered into the surrogate PCM, the download can be conducted using the normal method.

Don’t forget to compare the download with the download conducted earlier on the surrogate PCM to ensure that the data have changed. If the information has not changed, then the wrong chip was switched.

If the question arises regarding whether the EEPROM chip has been switched, there are two locations that can be examined.

First, one can check the grey caulking material that was applied at the factory to seal the PCM case. This material has to be broken in order to open the case. If this material has been compromised, then open the case and check the circuit board. If heat has been applied to remove a chip, the silicone coating on the board will have been melted, leaving an obvious indication that work has been done.

This chip-swapping method for extracting data from damaged PCMs should only be conducted after more conventional methods have been tried. Due to the obvious continuity issues, it should only be attempted if one is comfortable explaining in court the method and the reasons behind the method. Adequate documentation, both written and photographic, should be done at each step so the investigator can support his or her work. No protocol is provided here because there is more than one way to conduct this method. Sound judgment and the ability to justify one’s decisions are more important than following a set of rules.

References and footnotes: 1. Wade Bartlett, “Getting Data from Destroyed SDMs: Transferring EEPROMS Between Modules” Collision: The International Compendium for Crash Research, Volume 3 Issue 1.

2. At the time of writing, the Bosch PCMs can not be downloaded with the CDR system.

Once the chip has been removed and soldered into the surrogate PCM, the download can be conducted using the normal method. Ensure that the changes to the EEPROM chip are adequately documented in the “Comments” section of the CDR download or in the file name, so that it’s clear the data are related to the collision you are investigating. Also, mark on the case of the surrogate PCM that the EEPROM chips have been switched. www.collisionpublishing.com

Collision Magazine 27

DamageStudio is a graphical analysis tool that allows the user to visualize collision data, and to correlate collision damage with the kinetics (force magnitude and direction), delta-V, acceleration and other important collision parameters. There are many uses for the kind of detailed collision information provided by DamageStudio. One example is the ability to directly compare simulated crush dimensions with a measured damage profile. This technique can also be used to fine-tune stiffness coefficients from staged collision data. DamageStudio can also be used to identify the magnitude and direction of individual impulses, peak collision forces and deltaVs for vehicles undergoing multiple impacts, even if the impacts are simultaneous.

Introductory pricing is now available for DamageStudio. For more information and to add DamageStudio to your HVE software, contact EDC Sales at 503.644.4500 or sales@edccorp.com.

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Motorcycle Acceleration Rates

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Wade Bartlett, PE

Mechanical Forensics Engineering Services, LLC

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I

n reconstructing motorcycle crashes, the reconstructionist must often evaluate the possible acceleration capabilities of a motorcycle in evaluating time and distance relationships of the event. This is commonly accomplished by assuming some single acceleration value. Unfortunately, maximum motorcycle acceleration rates are highly nonlinear. Figure 1 shows an example of a maximum-effort acceleration run on a 2003 Honda VFR800, a typical late-model sportbike from a stop to approximately 108mph (data compliments of Damian Harty). The non-linearity in the acceleration profile means that some aspects of the time/distance/ speed relationship will not be well-modelled by condensing the acceleration rate to a single value.

This paper will discuss information available to the reconstructionist, and outline two techniques for improving the analysis of the time/distance/speed relationship given limited information.

As with essentially all motorcycles, Figure 1 shows peak acceleration occurring early as weight shifts onto the rear wheel, after the clutch is fully released and the engine has reached the higher end of its torque and horsepower range, but it hasn’t begun to be dragged down by aerodynamic drag or higher gear ratios. A sportbike with modern tires may briefly reach peak acceleration values approaching 1.3g during the early part of a full-effort launch.

In a perfect world, the investigator will have access to the accident motorcycle or an identical unit for testing with reliable and accurate measurement equipment. In the real world, though, this is often not the case. This leaves the investigator to review published data on their motorcycle’s capabilities. In years gone by, it was common for enthusiast magazines to publish charts showing a complete plot of a standingstart quarter mile best-effort run. Figure 2a shows

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Collision Magazine 31

Figure 1: Example of maximum-effort acceleration trace from a typical modern middleweight sportbike. The downward spikes represent gear changes.

Figure 2a: Example of the type of data formerly commonly available in enthusiast magazines. The cross represents the quartermile time and speed.

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Figure 2b: Acceleration and speed as functions of time, from data in Figure 2a.

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one such complete speed-time chart built from data contained in the July 1983 Cycle Guide report on the Kawasaki GPz750 Turbo. Figure 2b shows the approximate acceleration profile based on data drawn from that chart. The time-distance-speed relationship can be worked out from these charts by breaking the curve into small steps and evaluating each step one at a time for average speed and distance covered.

Older charts of this type often indicated the top speed at redline in each gear along the way. Complete practical datasets such as this have fallen out of favor in recent years, in the USA at least, perhaps for fear that it encouraged people to try to best them, or a sense that most readers didn’t care or couldn’t understand the information conveyed. This leads to a dilemma now faced by many reconstructionists: how to predict maximum acceleration rates when no published sources can be found? In this article, I will explore two possible techniques. The amount of data available for the motorcycle of interest will inform the choice of technique for a given case.

Technique 1: When there are some time/speed data points available for the motorcycle of interest. Many enthusiast magazines publish the time to cover a quarter-mile from a standing-start, along with the terminal speed (providing a single point tying time, speed and distance). Fewer magazines publish the time required from a standing start to reach one or more speeds, typically 30, 60, 90, and 100 miles per hour. In recent years, Cycle World has been a good source of such data. These intermediate data points do not include the distance travelled at each point.

STEP 1: Plot the datapoints available as speed vs. time. STEP 2: Overlay a best-fit line for the speed/time relationship. I find a third-order polynomial passing through the origin (0,0) usually works best. Critically consider if the curve behaves as it should: some point sets can generate a curve with inflection points, which is not a good description of how a motorcycle’s speed changes over time in these circumstances. STEP 3: Calculate the predicted speed (si, mph) or velocity (vi, feet/sec) for every 0.1 seconds using the best-fit line equation. Quarter mile times will usually be under 15 seconds, so this step creates fewer than 150 lines. Finer steps are possible, but are unlikely to result in an improved result. STEP 4: Calculate the distance covered in each 1/10th second using equation 1. STEP 5: Calculate the cumulative distance covered by adding the distance at each step to the sum of all previous steps. di-1 to i=(ti - ti-1)*vi Equation 1

This produces a complete maximum-effort time/distance/speed relationship based on actual testing, which was previously unavailable. This also allows the investigator to plot the instantaneous acceleration rate, rather than have to rely on an average acceleration value. Though the average acceleration values are commonly used, and can provide an accurate time/speed relationship at the end point, they will not necessarily generate accurate intermediate correlations.

Speed (mph) Time (seconds) 30

1.3

60

2.8

90

5.0

100

6.1

131.4

10.65

Table 1: ZX9R Data.

Example for Technique 1: The May 1994 issue of Cycle World magazine reported a top speed for the Kawasaki ZX-9R of 166 mph, but did not provide the time required to reach that speed.

The best quarter-mile run (1,320 feet) was 131.4 mph at 10.65 seconds, as shown in Table 1 with their other time/speed data.

These five points are shown graphically in Figure 3 (per STEP 1) with the best-fit third-order polynomial equation (per STEP 2).

Figure 4 shows the calculated speeds at 1-tenth-second intervals.

The next step is to evaluate the distance relationships. The only commonly available distance anchor is the quarter mile point, at which the motorcycle has covered 1,320 feet (402.4m). I have obtained the best results by using the instantaneous speed at the end of each 0.1-second step to calculate how far the motorcycle moved in that step. For the above example, for instance, Table 2 shows the results of the step-by-step analysis described using a spreadsheet. Interpolating between the 10.6 and 10.7 second values produces 131.3 mph at 10.65 seconds after starting, having covered a distance of 1,319.8 feet. This compares very well with the published result (10.65 seconds, 131.4mph, and 1,320 feet), and represents acceptable accuracy given the other uncertainties in the data. The data from Table 2 can be used to construct a chart of the relationship between time, speed,

Figure 3: Plotted ZX9R data showing third order polynomial best-fit line.

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Figure 4: Blue circles indicate calculated speeds at 0.1 second intervals based on the best fit line in Figure 3.

Collision Magazine 33

and distance for the motorcycle, as shown in Figure 5. Tables and charts such as these can be used to evaluate the possible acceleration event from a stop, or intermediate portions of the event. They can also be combined with braking analysis to evaluate total distances to ensure internal consistency of all parameters in a time/distance analysis.

Time Speed Velocity Velocity Dist. This Dist. This (seconds) (mph) (feet/sec) (m/s) Step (feet) Step (m)

Distance Total (ft)

Distance Total (m)

0

0

0

0

0

0

0

0

0.1

2.6

3.8

1.2

0.4

0.12

0.4

0.12

0.2

5.2

7.6

2.3

0.8

0.23

1.1

0.35

0.3

7.7

11.3

3.5

1.1

0.35

2.3

0.69

0.4

10.2

15.0

4.6

1.5

0.46

3.8

1.15

0.5

12.7

18.6

5.7

1.9

0.57

5.6

1.72

Technique 2: When no time-tospeed data can be found. Even when no time-to-speed test data can be found, one can generally still find horsepower ratings and vehicle weights. The weight-tohorsepower ratio is one characteristic descriptor which may then assist in our time/distance analysis.

0.6

15.1

22.2

6.8

2.2

0.68

7.9

2.40

10

127.5

187.0

57.0

18.7

5.70

1196

364.7

10.1

128.1

187.9

57.3

18.8

5.73

1214

370.4

10.2

128.7

188.7

57.5

18.9

5.75

1233

376.1

10.3

129.3

189.6

57.8

19.0

5.78

1252

381.9

10.4

129.8

190.4

58.1

19.0

5.81

1271

387.7

10.5

130.4

191.3

58.3

19.1

5.83

1290

393.6

10.6

131.0

192.2

58.6

19.2

5.86

1310

399.4

10.7

131.6

193.0

58.8

19.3

5.88

1329

405.3

10.8

132.2

193.9

59.1

19.4

5.91

1348

411.2

Enthusiast magazines commonly list either a motorcycle’s weight with fluids and fuel (wet weight) or without (dry weight). When a weight is provided without any clarification it is usually the “dry”

Table 2: Spreadsheet analysis of time and distance for ZX9R example.

Figure 5: Time, speed, and distance relationship for ZX9R example.

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weight, as provided by the manufacturer. Published pairs of “wet” and “dry” weights for 163 motorcycles were collected, and the extra weight due to fuel/fluids was found to vary with the type of motorcycle and the “dry” weight. To estimate the wet weight, the following three equations can be used: Sport/standard: Wet Weight (lb) = (Dry Weight)*1.03 + 13.2 Equation 2 Cruisers: Wet Weight (lb) for = (Dry Weight)*1.03 + 6.9 Equation 3 Dual Purpose/Offroad: Wet Weight (lb) for = (Dry Weight)*1.11 - 13.4 Figure 7a: Quarter mile speed, mph.

Equation 4 The average weight differential for streetbikes was found to be approximately 28.4 pounds, with a standard deviation of 4.4 pounds. Since all motorcycles used in actual testing were, in fact, carrying a human, I will add 200 pounds for the rider, and for the motorcycle I will use the known wet weight where possible, and the calculated wet weight where only the dry weight is known.

Figure 7b: Quarter mile time, seconds.

The horsepower measured at the rear wheel using the most common type of dynamometer is commonly expected to be about 85% of that reported at the crankshaft due to losses in the driveline.

In the current analysis, comparing 30 such pairs of claimed/measured data from published sources reveals the average loss from the claimed value to be approximately 13%, which matches the expectation quite well. If only published “crankshaft” or “claimed” horsepower values are available, they should be degraded by 15% to approximate rear wheel horsepower. See this website for more detail on dynamometer readings: http://www.factorypro.com/dyno/true1.html. The following analysis is based on data sets that included measured rearwheel horsepower values.

As groups, sportbikes and cruisers can generally be differentiated by their weight-to-power ratios, with sportbikes typically ranging from 4 to 12 lb/hp and cruisers ranging from 10 to 20 lb/hp.

Despite this differentiation, the time and speed data appeared well suited to common analysis.

Figures 7a and 7b show the quarter mile speed and time data for all two-wheelers. The best-fit equations for those relationships, shown in Table 3, are very similar to equations long used by dragracers to predict quarter-mile elapsed times and speeds [http://www.stealth316.com/2-calc-hp-etmph.htm].

Figure 8: Time-to-speed for all two-wheelers, using rear wheel horsepower and wet weight (including 200lb rider). www.collisionpublishing.com

Figure 8 shows collected time-to-speed data for the four data points commonly published (zero to 30, 60, 90, and 100 mph) for a variety of street bikes based on their weight-to-power ratio. Twowheelers with more than 30 pounds per rearCollision Magazine 35

wheel-horsepower were rarely, if ever, capable of speeds in excess of 75mph. Scooters with more than 45 pounds per horsepower were excluded, as their performance was highly model specific, and clearly different from other two-wheelers.

With the equations in Table 3, one can construct a chart comparable to Figure 3 for any motorcycle, given the weight and

horsepower. For motorcycles and scooters carrying more than 25 pounds per horsepower (including operator), one should be cautious of using these equations at speeds over 60mph, as acceleration rates drop precipitously as one approaches a vehicle’s top speed. These equations should not be used to evaluate time to reach speeds approaching a motorcycle’s maximum speed.

“ ”

Using the equations in Table 3, the time to each speed was calculated for all datasets currently available. Since many magazines only publish values for zero-to-60 and the quarter mile, there are many more data points for those values. The average absolute errors and their percentage of the nominal value are shown in Table 4. The quarter mile speed and time were more accurate than the intermediate values, but the average absolute error in all cases was less than 8%.

With these equations in hand, one could now assess the complete time/ distance/speed relationships as discussed earlier in this paper.

Parameter

Example of Technique 2: Two motorcycles for which test data was available were selected for their dissimilarities to each other for comparison with predicted time-to-speed values from Technique 2. The 1994 ZX-9R described earlier had a wet weight of 533 lb, and 124.9 horsepower at the rear wheel, giving 5.75 lb/hp (including a 200-pound test rider). The October 1988 Cycle World reported that the 1987 Harley Davidson FLTC, a big-twin cruiser with a wet weight of 788 lb, had a claimed 70 horsepower. This would correspond to approximately 59.5 rear-wheel-horsepower, and a weight-to-power ratio of 16.6 lb/ hp with a rider. Figure 9 shows the predicted versus actual timeto-speed test results. In this example, the Kawasaki’s predicted points are well described by the earlier-suggested third-order polynomial, which exhibits the desired monotonically decreasing slope. However, applying a third-order polynomial equation to the Harley Davidson data reveals obvious problems. The acceleration curve should not reverse slope midway. By coincidence, the calculated quarter mile speed was 89.5 mph at 14.4 seconds, which is almost identical to the calculated time required to reach 90mph (14.6 seconds), somewhat degrading the fidelity

Equation

R2

Quarter mile time (lb/hp<30)

time = 6.5729 x0.278

0.97

Figure 7a

Quarter mile speed (lb/hp<30)

speed = 239.90 x-0.351

0.97

Figure 7b

Quarter mile time (lb/hp>30)

time = 5.9504 x0.322

0.90

Figure 7a

Quarter mile speed (lb/hp>30)

speed = 172.78 x

0.70

Figure 7b

0-30mph

time = 0.0023x -0.01x+1.23

0.78

Figure 8

0-60mph

time = 0.0067x +0.1x+2.13

0.97

Figure 8

0-90mph

time = 0.0342x2+0.1x+3.47

0.89

Figure 8

0-100mph

time = 0.0312x +0.45x+2.55

0.92

Figure 8

-0.267

2 2

2

Location

Table 3: Equations for best-fit lines to evaluate maximum-effort acceleration.

0-30 mph time (sec.)

0-60 mph time (sec.)

mi.

0-90 mph 0-100 mph 1/4 mph time (sec.) time (sec.) (sec.) time

1/4 mi. speed

Average Absolute Error

0.090

0.239

0.810

0.704.

0.296.

2.49

Average Absolute Error Percentage of Nominal

6.1%

5.2%

7.4%

6.7%

2.5%

2.2%

(mph)

Error Std. Dev.

4.8%

4.0%

7.2%

5.3%

1.8%

1.6%

Count

110

387

111

114

316

316

Table 4: Errors between predictions and reported values for time-to-speed.

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“ ”

of the data and affecting the quality of the curve-fit.

For this case, I would suggest using a simple slope/intercept model between each of the calculated 5 points, as indicated by the dotted line in Figure 9. With these equations in hand, one could now assess the complete time/distance/speed relationships as discussed earlier in this paper. The predicted elapsed times are in each case very close to the test results. This success for two very different motorcycles speaks to the utility and accuracy of the technique described.

C

onclusion This paper described a technique to evaluate the non-linear maximum acceleration profile for a motorcycle given various available types of publicly available data, in order to more accurately assess time-speed-distance relationships. When no test data can be found, a technique for estimating performance given just the motorcycle’s weight and horsepower was described. This estimation technique was shown to predict with relative accuracy quarter-mile elapsed times and trap speeds, as well as the time-to-speed for four intermediate speeds commonly reported in the literature.

When no test data can be found, a technique for estimating performance given just the motorcycle's weight and horsepower was described.

Figure 9: Predicted v. actual test results for two very different motorcycles. www.collisionpublishing.com

Collision Magazine 37

Crash Poster Full Color 22" x 34"

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This beautiful, full-color crash poster was inserted as a free poster to everyone who received Collision Volume 5, Issue 2. Because of the feedback we have received regarding this poster, we are now making it available in a non-folded version. Order your Crash poster today and receive it, rolled and shipped in a durable mailing tube.

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The Speed Triangle Momentum, Energy and PCM Data Charlie Greear, David Thornburg, and Lee DeChant

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P

olice officers and accident reconstruction practitioners often use digital photography as a means of determining the root cause of an incident. In order to extend the use of such photography, investigators have recently turned to Close-Range Photogrammetry (CRP) techniques to derive accurate three-dimensional (3D) measurements from photos taken shortly after a crash or crime scene event. CRP is a proven measurement technique that extracts 3D information from multiple overlapping 2D photographic images. This article reports on the use of photogrammetry in an investigation of a fatality resulting from a three-car traffic incident. During a street race between two cars driven by teenagers, one of the drivers hit a third vehicle in which a passenger was killed. In the subsequent accident reconstruction investigation, which utilized the “Speed Triangle” (Momentum, Energy and the Power Train Control Module (PCM)) concept, CRP proved to be a valuable integral component in the calculations of vehicle speed, as well as providing a fast and accurate means to map the crash scene.

T

he crash Kathleen Avenue is a residential street in down-town Coeur d'Alene, Idaho. It has two lanes in each direction and a dedicated center-turn lane. The street travels east-west, with an elementary school at the west end and a “charter” school at the east. Two teenage drivers entered Kathleen Avenue from the west end. Driver 1, in a 2005 Subaru Impreza WRX STi, was adjacent to the elementary school when a 2006 Mustang with Driver 2 at wheel pulled up alongside and revved his engine. Driver 1 revved his engine in response and the race was on. The two cars sped eastbound along Kathleen Avenue, fast approaching the intersection with Howard Street.

At that same time moment, a 1987 Chevrolet Caprice under the control of Driver 3 was entering Kathleen Ave from Howard St. The Mustang slammed into the Caprice near the driver’s side ‘B’ pillar, shattering Driver 3’s pelvis and killing her 14-year old son who was seated in the right rear of the Caprice. The Impreza swerved to avoid the collision and Driver 1 lost control, going into a yaw and quickly transitioning into a broad slide, leaving the roadway and rolling to the vehicle’s final rest position more than 100 yards beyond the point of impact between the Mustang and Caprice.

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Collision Magazine 41

Figure 1: The scene

T

he police investigation The iWitness™ photogrammetry software system, combined with a Nikon DSLR camera, was used to map the crash scene, which extended over 403 feet. (see figure 2) Due to the length of the scene, it proved easier to perform two separate “image-based measurement networks” that were later ‘stitched’ together within the iWitness software to form a unified reference coordinate framework to produce an accurate scaled diagram in which the crash evidence was recorded. The total

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Collision Magazine

time to process this scene using photogrammetry, or the ‘digital camera approach’, was approximately 40 minutes. The iWitness software was employed to generate a 3D model and measure the scene, with the scaled 3D model in DXF format being subsequently exported to the Crash Zone diagramming software (see figure 3).

It took approximately 3 hours of PC work at the office to fully accomplish the photogrammetric mapping and diagramming using iWitness, which was also employed to develop damage profiles for both the Caprice and Mustang.

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Figure 2: iWitness™ photogrammetry software system, combined with a Nikon DSLR camera, was used to map the crash scene.

Figure 3: Map of the crash scene.

Through use of a Vericom VC2000 accelerometer, the drag factor at the scene was determined as being 0.77.

From the iWitness image-based measurement data, and the subsequent diagramming, the following was determined: • The Mustang left 73.8 feet of visible pre-collision skid before it struck the Caprice and it then traveled a further 60.6 feet, while rotating through 70 degrees, before coming to rest.

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• The Caprice was struck behind its center of gravity and was spun rapidly through 242 degrees, coming to rest 41.0 feet beyond the point of impact.

• The Impreza started its critical speed yaw just east of the intersection, first sliding into the oncoming travel lanes and then re-entering the eastbound lanes and leaving the roadway. By plotting the Impreza’s center of mass path of travel over the first 68 feet of its yaw, the course of its center of mass was shown to have inscribed an arc with a radius of 572 feet.

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Concerning the Subaru, its speed was calculated using the relationship:

These expressions are used in determining the applied drag factor,

“ ” Here, since the roadway was level, this became:

Since there were impact and departure angles as well as crush data, a two-pronged approach to speed calculations were used.

Since there were impact and departure angles as well as crush data, a two-pronged approach to speed calculations were used.

David Thornburg’s Excel Spreadsheet “Equation Calculator” was first employed to determine post collision speeds for both cars.

The effective drag factor for each vehicle was determined based upon the Regression Equations presented by Dr. Gordon Bigg P.E. at the 2003 IPTM Special Problems event, this approach having been confirmed in research by John Daily . The investigative was based upon evidence that the Caprice had two wheels locked, while the Mustang had no wheels locked. From the work of Bigg and Daily, we have:

(where θ= the total heading change in degrees and d = the total distance traveled by the center of mass).

For a vehicle with engine braking only (the Mustang) we have:

and for a vehicle with two locked wheels (the Caprice) we have:

Hence, the two applied drag factors would be: and

����������� Application of these rotational drag factors to the post collision distances, along with utilization of the slide-to-stop formula:

yielded post collision speeds of approximately 24 mph for the Mustang and 26 mph for the Caprice. The scale scene diagram and crush profiles for the Mustang and the Caprice (all generated from the CRP projects; both at the scene and afterwards) were then used to determine approach and departure angles for both vehicles. The Mustang was set up as the “bullet” car with approach and departure angles of 0°. The Caprice then had an approach angle of 104° and a departure angle of 12°. The vehicles were weighted after collision, yielding weights of 3555 lbs. for the Mustang and 3950 lbs. for the Caprice. Through use of a momentum solution, this yielded an impact speed of 54 mph for the Mustang and 5 mph for the Caprice. It also indicated a Δv of 29.8mph for the Mustang and 26.8 mph for the Caprice.

In evaluating this crash from an energy perspective, it was discovered that there were no stiffness coefficient values available for a side impact on a 1987 Chevrolet Caprice. Here, impact forces were balanced upon the principles espoused in Nathan Shigemura and Andrew Rich’s paper, Balancing Collision Forces in Crush/Energy Analyses (2007). Through use of the CRP measurements of each vehicle, the crush profiles were plotted against exemplar vehicles (see figures 4 and 5).

The calculated stiffness coefficients for the Chevrolet and stiffness values from NHTSA testing of the Mustang were then applied to calculate a collision speed of 57 mph for the Mustang and 5 mph for the Caprice. This analysis yielded a Δv of 33.2mph for the Mustang and 29.9mph for the Caprice.

The Mustang was equipped with ABS brakes and all four wheels were actively braking before collision. Resulting marking on the road was very faint; but it could be established that the Mustang left 73.8 feet of visible pre-collision skid. Application of slide-tostop analysis to this braking maneuver indicated that the Mustang lost at least 41.3 mph. This pre-collision speed loss, along with the impact speeds calculated from the Momentum analysis and Energy analysis above, was used to determine pre-braking speeds for the Mustang of:

and

The airbag control modules from the Subaru and the Mustang, as well as the Mustang’s Powertrain Control Module, were also analyzed. No imaging data was available for the Subaru (either then or now). In 2006, there was no support for any of the Ford modules; however Bosch released the software and hardware for the Mustang in late 2007. David Thornburg analyzed the data

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Collision Magazine 45

Figure 4: Photos of the vehicles after the crash 46

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Figure 5: Through use of the CRP measurements of each vehicle, the crush profiles were plotted against exemplar vehicles.

Pre-braking Speed ~ 82 mph Collision Speed ~ 65 mph

Separation Speed ~ 25 mph

Figure 6: PCM Data viewed in CSVPro Purple = Brake Switch -- RPM (x100) = Yellow Percent Accelerator = Green -- Percent Throttle = Blue www.collisionpublishing.com

Collision Magazine 47

from the PCM and used C. Gregory Russell’s CSV Pro spreadsheet to graphically represent the image (see image 6).

The Mustang was not using “stock” wheels/tires and there was no evidence the speedometer had been re-calibrated to the aftermarket equipment. Since the actual wheels and tires were slightly smaller in diameter, it was determined that the actual speeds would be approximately 4.8% lower than what was represented here. Hence, the following speeds from the PCM data were established: Mustang pre-braking

78 mph

Mustang impact

62 mph

Mustang separation

24 mph

C

Now the “Triangle” is complete. Looking at the calculated speeds from the momentum and energy analyses and comparing them to the PCM data, we have: MUSTANG SOURCE

PRE-BRAKING SPEED IMPACT SPEED

Momentum 68 mph

54 mph

Energy

70 mph

57 mph

PCM

78 mph

62 mph

Average σ

72 mph

58 mph

± 4.29 mph

± 3.74 mph

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Collision Magazine

The higher pre-braking speed is easily explained, since the faint nature of the ABS marks would lead to an under-reporting of the skid distance and hence a lower calculated speed. Given the PCM data is reported every 0.2 seconds, the reported speeds were integrated to calculate the approximate distance the Ford Mustang traveled before impact. This total distance was around 1,700 feet or nearly one-third of a mile. This helped placed the Mustang along the roadway as it traveled and was consistent with several of the witness statements. onclusion: Different technologies were used to determine the root cause of a vehicular homicide in this case. CRP allowed accurate and rapid 3D measurement of both the crash scene and vehicle profiles, providing the needed distances to complete the “Speed Triangle”. The close correlation between the calculated collision speeds using momentum, energy and the PCM image is inescapable. Additionally, the PCM data clearly showed the “racing” trend in acceleration and throttle, which mirrored witness testimonies at trial. Furthermore, comparing the regression analysis for post-collision rotational speeds against the recorded speed for the Mustang showed a negligible difference (24 mph for both). Also, the Subaru’s speed was calculated at 81 mph from CRP measurements and the applied “critical speed” calculation. This correlates well with the Mustang’s corrected PCM speed of 78 mph at the beginning of braking. Finally, by applying and evaluating all of today’s available techniques and technologies in this crash, an accurate reconstruction was obtained and the three analyses formed a strong “Speed Triangle”.

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Collision Magazine 49

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applying

heavy vehicle edr data in the real world william messerschmidt MPA, ACTAR Messerschmidt Safety Consultants

benjamin smith ACTAR Messerschmidt Safety Consultants

al dunn PhD, PE SEA, Ltd.

a

bstract The accuracy of Heavy Vehicle Event Data Recorder (HVEDR) data has been repeatedly tested and validated in various studies over the last decade (see Reust 2004; Reust & Morgan 2006; van Nooten & Hrycay 2005; Bayan & Dunn et al. 2009; Rogers & Hrycay et al. 2009; Messerschmidt et al. 2009, 2010). Most major engine types have been studied extensively, and at this point, much is known about each engine’s specific characteristics. However, all of these studies have been done in controlled environments with very well maintained or pristine test vehicles. In addition, test drivers are typically primed with pre-determined behavior action plans. These studies do provide a solid baseline for HVEDR performance and accuracy statistics, but are they ecologically valid?

Do these studies create accurate models for analyzing real world crashes?

This article is a study of HVEDR data and physical evidence from a real world crash.

It is comprised of work performed by experts for the plaintiff and defense. The study attempts to correlate data from controlled research with data from the real world, physical evidence, and human factors research.

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Collision Magazine 51

t

he Crash The crash that is the subject of this article occurred in Central Mississippi at the intersection of a city street and a divided four-lane highway. A 2001 Freightliner FLD-120 pulling a 53-foot refrigerated trailer was traveling in the right northbound lane of the highway when it collided with a 1993 Chevrolet Corsica, travelling eastbound and crossing the highway. Two of the Chevrolet’s three passengers were killed as a result of this crash.

Figure 1 shows the Freightliner, and Figure 2 shows the Chevrolet.

Figure 3 shows the general layout of the crash site, the vehicles at final rest, and some of the physical evidence present on the

roadway. The crash occurred in clear and dry daylight conditions. The physical evidence included gouge marks at the area of impact and 145 feet (95 feet pre-impact and 50 feet postimpact) of dual-wheel skid marks in the right northbound lane of the highway. In total, the Freightliner traveled 213 feet from the beginning of the skids to final rest.

The 2001 Freightliner was equipped with a Detroit Diesel Series 60 engine and Detroit Diesel Electronic Control (DDEC) IV electronic control module (ECM). The ECM was downloaded using the Detroit Diesel Electronic Suite software package. In addition to calibration and historical data, this download provided the authors with two hard brake reports and one last stop record. In this case, the last stop record and the first hard brake report corresponded to this crash. It is important to

Figure 1: 2001 Freightliner FLD-120

Figure 2: 1993 Chevrolet Corsica 52

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Figure 3: General layout of the crash site, the vehicles at final rest, and some of the physical evidence present on the roadway note that the tractor had deficiencies with its air brake system.

Two brakes were out of adjustment, and there were notable issues with the air delivery system’s balance and function.

e

By adding together the reported speeds per second in column two of the DDEC Reports data shown in Table 1, we see the hard brake report appears to show a minimum braking distance of 242 feet. This is 29 feet longer than the 213 feet of braking evidence measured at the crash site. The hard brake report also shows that the brake circuit was not on until time -0:01, even though there was a 4.5 mph speed loss between time -0:02 and -0:01. These are obvious discrepancies that must be resolved in order to prove that this hard brake report corresponds to the crash in question. In order to resolve these problems, we must consider plausible reasons for why the discrepancies exist.

Based on the overall dimensions of the tractor-trailer and based on the physical evidence, it was determined that the unit braked for 33 feet before the collision (95 feet pre-area-of-impact skid distance – 62 feet from the front of the tractor to the #4 axle = 33 feet pre-impact trailer skid distance).

One explanation might be the asynchronous data sampling processes. For example, this explanation would suggest that the ECM sampled the brake circuit status before the actual brake application, within the second between -0:02 and -0.01.

This is a common occurrence with many EDRs and explains why the vehicle’s wheel speed declined even though the hard brake report said the brake was off.

valuating the ECM Data, Physical Evidence, and Driver Response Characteristics One of the main goals of the ECM data analysis was to determine whether the hard brake and last stop data matched the physical evidence. The first step was to compare the braking distance reported in the hard brake report and the braking distance evident from tire marks. Table 1 is an excerpt from the first hard brake report.

Table 1: Excerpt from the first hard brake report www.collisionpublishing.com

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Another possible explanation for the speed loss could be rolling friction. The hard brake report shows that engine speed, percent throttle, and percent engine load all decline between time -0:02 and time -0:01. The idea that rolling friction is fully responsible for speed loss is unlikely because a 4.5 mph speed loss in one second constitutes a 0.20 g negative acceleration factor. However, rolling friction and the loss of engine speed must have played some role in the speed loss.

These explanations help us explain the speed loss with no reported braking, but they do not address the larger problems with correlating the event data in DDEC reports and the physical evidence. Furthermore, we still have to explain why we are missing at least 29 feet of dual wheel skid marks. The fact that our distance appears to be underreported contradicts a substantial portion of the accuracy research testing that has been done with commercial vehicle ECMs. Recent research has revealed that ground speed can be underreported by an average of 18% in commercial vehicles that are braking heavily (van Nooten & Hrycay 2005). Two-hundred-twenty-five research tests performed for SAE 2010-01-1004 all showed similar reporting discrepancies. This apparent difference between multiple research studies and the ECM data requires further analysis.

One very simple explanation for the lack of skid distance is that the full distance of the skid marks could not be measured due to the intensity or darkness of the mark. If we examine Figure 4, we can see that the tire mark does appear to extend beyond the orange paint marks laid down by the investigating officer.

This photo was taken with a circular polarizing filter. However, this skid mark extension is very faint and easily could have been missed if viewed only with the naked eye.

Air pressure rise time in the braking system is one possible reason we might see differences in braking distances derived from ECM data and braking distances derived from physical evidence measurements. This hypothesis suggests that the tractor-trailer was actually braking before time -0:01, but the air pressure had not risen to a level that was sufficient to actually leave skid marks.

There are several explanations for why we might see delayed air pressure rise time. The first explanation is equipment related.

We know from multiple examinations of the Freightliner and its trailer that there were definite problems with the air brake system. An air brake system with performance deficiencies is also a departure from most current ECM accuracy testing.

Research test vehicles are typically well maintained and thoroughly inspected prior to testing, which is necessary for the safety of the test driver and onboard crew. However, this does widen the gap between data associated with controlled tests and real world crashes.

Driver behavior is also an area that must be considered when correlating physical evidence with ECM event data. Drivers in research tests usually have a plan for how they will accelerate and brake.

Figure 4: Skid mark from the scene 54

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“ ”

They face no uncertainty, and their decision to brake is purely mechanical: when the test vehicle reaches a certain speed, which they can easily anticipate, they plan to apply full braking. Therefore, we would expect to see full braking occur very rapidly in such a test.

the first step in creating a crash timeline is establishing when the first brake application actually occurred.

When actual drivers respond to real-world scenarios, or when research respondents are confronted with multiple response options, full braking almost never occurs immediately. This phenomenon has been called “response inertia.” Essentially, response inertia is a gap between the driver’s first pedal touch and when they achieve full braking that is greater than what can be explained by the mechanical time required to fully depress the brake pedal. Notable studies that have demonstrated this driver behavior include McGehee et al. (2000) and Muttart et al. (2006).

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reating a Crash Timeline To carefully analyze the time and distance relationships shown in the ECM data in conjunction with both physical evidence and independent research in the area of Human Factors, it is helpful to construct a timeline of the events in the crash.

The first step in creating a crash timeline is establishing when the first brake application actually occurred. Using the calculations presented in Reust and Morgan’s publication (SAE 200601-1129), we can calculate a more specific brake application time. This calculation is based on research test data trend lines and speed loss. Reust and Morgan’s findings tell us the first brake application, or brake touch, occurred 0.27 seconds before the first ECM time frame where the brake was reported as “on.” These initial calculations result in a time of -0:01.27 for the first brake touch. Now that we have the first brake touch time, we can attempt to establish the time period for impact.

At this point, we must consider appropriate time lapses from first brake touch to full braking. McGehee, Mazzae, & Baldwin (2000) found in their research that the average time from first touch to full braking for drivers responding to a hazard was approximately 0.60 seconds. If we add this time to our time for first brake touch (-0:01.27 seconds), we find that the Freightliner and trailer should be braking at full capacity

at -0:00.7 seconds. Table 2 shows the new timeline for the Freightliner’s speed and braking before and after the crash.

As shown in Table 2, our original estimate for total braking distance has been extended from 242 feet to 266 feet. If the 0.60 seconds from first brake touch to full braking is considered, we find that the Freightliner would have traveled 50 feet in that time period. If we subtract that time from our new total of 266 feet, we arrive at 218 feet for total skid distance. This is only five feet from the measured distance (213 feet) from the beginning of the skid marks to final rest. Now we must determine where impact actually occurs in relation to the timeline presented in Table 2.

Table 2: The new timeline for the Freightliner’s speed and braking before and after the crash www.collisionpublishing.com

Collision Magazine 55

As discussed above, physical evidence indicated that the trailer skidded approximately 33 feet before impact. If we calculate the time that it would have taken the unit to travel this distance, we can determine a more precise time for impact. Referring to Table 2, we see that it would have taken the Freightliner approximately 0.40 seconds to brake over that 33-foot distance. Subtracting this time (0.40 seconds) from the time where skidding began (-0:00.7 seconds) yields an impact time of -0:00.3 seconds. With a timeframe for impact, now we can see how our calculations compare with statistical research regarding ECM data and speed loss. Using the data in Table 2, a 1 hertz speed loss table can be constructed (see Table 3).

The largest one-second change in speed is 33.1 feet per second (fps). Evaluating these figures with the results of Messerschmidt and Muttart’s work on the statistical analysis of ECM data (SAE 2001-01-0880), we see that a speed loss of 33 fps corresponds to a 99% likelihood that our impact time determination is correct.

c

onclusions There is a growing body of HVEDR data that are available to accident investigators, and much of it is directly applicable to the analysis of a crash. However, it is important to understand that these data are not “plug and play.”

Each case where ECM data must be correlated to a crash event should be handled in respect to case-specific factors like vehicle condition, driver response behavior, and physical evidence. In addition to case-specific factors, the limits of applied research findings must be carefully considered and accounted for.

This study of HVEDR data and physical evidence from a real world crash shows how seemingly problematic real world ECM data can be associated with physical evidence using current research and basic mathematical operations. The analysis presented here allowed the authors to correlate the physical evidence with ECM data, determine pre-impact and impact speeds, and validate these hypotheses by associating them with statistical models of HVEDR data from crashes.

r

eferences Bortolin, R., van Nooten, S. A. B., Scodeller, M., Alvar, D., Gervais, J., & Hrycay, J. (2009). Validating Speed Data from Cummins Engine Sudden Deceleration Data Reports (Technical Publication No. SAE 2009-010876). Warrendale, PA: Society of Automotive Engineers.

Drew, K., van Nooten, S.A.B., Bortolin, R., Gervais, J., & Hrycay, J. R. (2008). The Reliability of Snapshot Data from Caterpillar Engines for Accident Investigation and Analysis (Technical Publication No. 2008-01-2708). Warrendale, PA: Society of Automotive Engineers.

McGehee, D. V., Mazzae, E. N., & Baldwin, G. H. S. (2000).

Driver Reaction Time in Crash Avoidance Research: Validation of a Driving Simulator Study on a Test Track, Proceedings of the International Ergonomics Association 2000 Conference.

Messerschmidt W., Austin, T., Smith, B., Cheek, T., Plant, D., & Voeglie, C. (2010). Simulating the Effect of Collision-Related Power Loss on the Event Data Recorders of Heavy Trucks (Technical Publication No. SAE 2010-01-1004). Warrendale, PA: Society of Automotive Engineers.

Messerschmidt, W., Muttart, J. (2009). A Statistical Analysis of Data from Heavy Vehicle Event Data Recorders. (Technical Publication No. SAE 2009-01-0880). SAE International – Journal of Commercial Vehicles, Vol. 2:1. Warrendale, Pennsylvania.

Muttart. J., Vandenburg, G., Yosko, M., Messerschmidt, W. (2006). Proceedings of the 2006 Canadian Association of Technical Accident Investigators Annual Conference. London, Ontario.

Reust, T. J., & Morgan, J. M. (2006). Commercial Vehicle Event Data Recorders and the Effect of ABS Brakes During Maximum Brake Application (Technical Paper No. 2006-011129). Warrendale, PA: Society of Automotive Engineers.

Reust, T. J. (2004). The Accuracy of Speed Captured by Commercial Vehicle Event Data Recorders (Technical Publication No. 2004-01-1199). Warrendale, PA: Society of Automotive Engineers. van Nooten, S. A. B., & Hrycay, J. R. (2005). The Application and Reliability of Commercial Vehicle Event Data Recorders for Accident Investigation and Analysis (Technical Publication No. SAE 2005-01-1177). Warrendale, PA: Society of Automotive Engineers.

Table 3: 1 hertz speed loss table 56

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An accident reconstructionist's

primer on d n a e m i r r i t el t a e h ks h w r as a m cr es n e c s Donald F. Tandy, Jr. P.E. Jason Colborn

Robert J. Pascarella Todd D. Hoover

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I

n the field of accident reconstruction, it is sometimes important to determine how certain tire mark or rim mark evidence was created during a crash. Tire marks can take many forms, but proper analysis techniques can be used to determine if the vehicle’s brakes were applied, if the vehicle was placed in a yaw, and if a tire became deflated or experienced a tire tread belt separation or other type of tire disablement. There have been numerous papers and books written concerning the differences between skid marks, yaw marks, and deflated tire marks 1-22. Many of these studies, however, were performed years ago and were published with black and white photographs and did not address vehicles with advanced electronic systems such as anti-lock brakes, traction control, or electronic stability control systems.

Also, in terms of tire disablements, emphasis in these studies has been placed on deflated tires rather than the marks on the roadway left while a tire was undergoing a tread belt separation. Other studies have addressed wheel marks on the pavement but one in particular did not consider all available evidence as to what forces could be created when rims gouge the pavement 23.

Roadway and test surfaces are commonly constructed using one of two different materials, either asphaltic concrete or Portland cement concrete. An effort has been made in this study to document tire marks on both surfaces in crashscene and testing photographs. For the sake of simplicity, more familiar terms for these surfaces will be used throughout this paper. Asphaltic concrete surfaces will simply be called “asphalt,” and Portland cement concrete will be referred to as “concrete.”

This article summarizes a thorough study of tire marks on and off the roadway in order to show what various tire marks may look like and how they were created. The paper also addresses rim gouges and scrape marks and explains how they are created and what effect such marks have on the dynamics of the vehicle. On-track testing as well as evidence from actual crash scenes is used to help assist the accident reconstructionist in determining how tire and wheel rim marks were created during a crash.

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arks made by tires on roadways Tires can make marks on dry roadways when there is relative sliding between the rubber of the tire and the surface of the road. This sliding action causes the rough surface of the pavement to grind or sand away rubber particles which are then deposited on the road.

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kid marks Skid marks are defined as tire marks created by a locked tire, i.e., when the tire/wheel assembly has stopped rotating, but the vehicle itself continues with some velocity. Since locked tires cannot develop lateral turning forces, skid marks are generally straight (unless other external forces are acting on a vehicle such as in a collision). These marks are becoming rare in modern day crashes due to the increased use of anti-lock braking systems (ABS).

ABS, now standard equipment on vehicles equipped with electronic stability control and most other vehicles, modulates the brake pressure to keep the brakes from locking with hard brake applications where longitudinal tire forces exceed the grip capacity on a particular surface. However, it is possible for ABS to make marks on pavement during panic braking situations (see next section).

Figures 1 and 2 are examples of locked-wheel skid marks on asphalt and concrete created in a test environment using a non-instrumented 2002 mid-size SUV with the ABS disabled. Panic brake stops were made from sixty-five kilometers per hour. Note the straight appearance of the tire marks and the spaces created within the mark indicating the separation of tread blocks. Figure 3 is an example of skid marks found at an actual crash scene of a compact SUV. The dual marks in Figure 4 were created by a trailer of a semitruck (note the constant distance between the left and right side tires). The intermittent nature of these marks is due to the axle of the truck hopping under full braking, a trait that is not common in passenger cars or light trucks.

Figure 1: Testing locked skid marks on asphalt

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Figure 2: Testing locked skid marks on concrete

Figure 3: Crash scene locked skid marks

Figure 4: Crash scene dual-wheel locked skid marks

BS braking marks When drivers apply very hard braking with vehicles equipped with ABS, there is some relative sliding between the tire patch and the ground that can allow tire marks to be generated on the pavement surface. Figure 5 shows how intermittent tire marks can be made due to the application and release of brake pressure sent to the service brakes using a non-instrumented 2002 mid-size SUV with four-wheel ABS at sixty-five kilometers per hour on concrete. The tire marks shown in Figure 6 were created by applying hard braking from one hundred kilometers per hour in an instrumented 1993 compact SUV equipped with three-channel ABS (i.e., one sensor at each front wheel and a single sensor on the rear differential for both rear wheels) on an asphalt test track. The videotape and data in this test confirmed that the wheels never locked but distinct

marks which resembled intermittent skid marks were made.

Therefore, if tire marks such as these are found at a crash site with a vehicle with ABS brakes, it cannot be assumed that the ABS was not working properly.

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Some motorcycles are equipped with ABS systems. The tire marks shown in Figures 7 and 8 were generated using a noninstrumented 2007 1800cc motorcycle with front and rear ABS. The tire mark in Figure 7 was created by braking hard by applying the front and rear brake enough to cycle the front and rear ABS from sixty-five kilometers per hour on a concrete surface.

Figure 8 was created by applying only the rear brake such that the rear ABS activated. In both tests, the driver made sure the ABS was activating (i.e., pulsing of the brake system).

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Figure 5: Testing ABS tire marks

Figure 6: Testing ABS tire marks

Figure 7: Motorcycle with ABS (front and rear braking)

cceleration marks Tire marks can also be created by applying enough throttle to cause the rear tires to lose traction and spin.

These marks tend to be made at low speeds where enough engine torque can be generated to overcome the frictional capacity of the tires. The marks look similar in nature to locked-wheel braking marks but sometimes have some curvature to them, indicating the vehicle was slipping as the speed increased, possibly due to steering input, road slope, and/or a split between left to right torque delivery to the drive tires. Acceleration marks also tend to be darker at the beginning of the marks and taper off as the tires develop enough traction to eventually stop spinning. Figure 9 is an example of an acceleration mark created purposely by these authors with a non-instrumented

1999 rear wheel drive sports car on a concrete surface. This mark is mostly rubber dust and disappeared after several weeks. Note that both rear tires made marks.

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When a vehicle is not equipped with a limited-slip differential, the acceleration tire mark may only be created from one tire. An example of this type of mark on asphalt can be found in Figure 10. Also of note is that in a rear wheel drive vehicle with a solid axle, the driveshaft torque reacted through the axle will create a differential loading on the rear tires, thus making one tire lose traction before the other. With today’s rear wheel drive configurations, these vehicles will almost universally spin the passenger side tire.

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Figure 8: Motorcycle with ABS (rear braking only)

Figure 9: Acceleration tire marks without TCS

Figure 10: Single acceleration tire mark

Figure 11: Acceleration marks with TCS on asphalt

Figure 12: Acceleration marks with TCS on concrete

Figure 13: Step steer (50 mph, 90 degree, drop throttle)

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Figure 14: Step steer (50 mph, 90 degree, drop throttle)

Figure 15: Crash scene yaw marks

Figure 16: Crash scene yaw marks

Figure 17: Yaw mark prior to barrier collision

cceleration marks with traction control Vehicles equipped with traction control systems (TCS) can leave intermittent marks when a driver chooses to apply more throttle than the available traction of the drive tires. As the tires begin to break loose and spin, the TCS will reduce the engine power and/or begin to apply some braking to the drive wheels. When this occurs, tire marks can be made which appear to be straight and intermittent. The intermittent nature of these marks can be due to many factors, including the application and releasing of the brakes, oscillatory suspension dynamics or power hop, as well as undulations in the roadway surface. Figure 11 is an example of such marks created on asphalt in a test environment using a 1993 rear wheel drive sports car without instrumentation. The driver stomped on the accelerator while at a complete stop. Figure 12 depicts marks made by the same vehicle on a concrete test surface.

Yaw marks are not created during normal driving and only occur in high lateral acceleration events. These marks will travel in an arc, at least initially, since lateral forces are being created on the vehicle which will force it to turn. On some road surfaces, yaw marks can have an alternating pattern of light and dark stripes called striations. These are created by the tread blocks which rotate through the tire patch and slide along the surface during the yawing 10. One difficulty in determining whether a tire mark is a pure yaw mark (i.e., free rolling with no braking or accelerating involved) or one in which braking is also being applied is that light to moderate braking will not generally create evidence in the tire marks since the tire continues to rotate through the turn.

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aw marks Yaw marks are defined as tire marks generated by a tire while the tire/wheel assembly is rotating and at a significant slip angle relative to the vehicle velocity vector.

Figures 13 and 14 are examples of yaw marks created during testing of an instrumented 1992 two-door compact SUV on an asphalt test track. Lateral accelerations in excess of 0.7 g’s were generated during these maneuvers. Figures 15 and 16 are examples of yaw marks found and documented by police officers at crash scenes. Note that yaw marks can sometimes be darker on asphalt roadways than on concrete. The shape of yaw marks can sometimes be an indicator of a vehicle's interaction with outside forces during the yaw. Figure 17 shows a yaw mark that changed

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Figure 18: Yaw marks on concrete at crash scene

Figure 19: Yaw marks on concrete at crash scene

Figure 20: Yaw mark on concrete and asphalt

Figure 21: Yaw marks on concrete at crash scene

direction abruptly when the vehicle impacted a barrier. Figures 18 and 19 illustrate how yaw marks can be difficult to see on a light concrete surface, contrary to what one might expect. Figure 20 shows how a single yaw mark can change in appearance as the tire travels over concrete, road paint, and asphalt.

Figure 24 shows an intermittent tire mark created by testing a non-instrumented 2010 passenger car on an asphalt test track during violent maneuvers at one hundred kilometers per hour.

However, this one was created in a test track environment when a tire slid across a tar filled seam as the vehicle was in a yaw. The darker portion of the yaw mark is due to the tar being deposited on the tire and these patches are approximately one tire circumference from one another.

Sometimes when a vehicle yaws across a roadway that has gravel or small stones on it, these rocks will be crushed and slide between the tire and the roadway surface. An example of this can be found in the yaw mark on the right side of Figure 21. Note the white lines that show up in the tire mark to the right. A final note should be made concerning striations since these are not always present in a yaw mark as shown in Figure 22. The presence or absence of striations is related to the type of tire, the maneuver, whether braking is applied, and the surface of the road.

Yaw marks can be intermittent in nature as well. This can be due to change in load on a tire as is slides across a surface. Such load changes can be due to road irregularities which excite a suspension or vehicle body mode such as bounce, pitch, or roll.

Figure 23 is an example of a yaw mark created during a crash where the vehicle was bouncing and rocking as it traveled across the road due to roadway undulations and impact with a curb.

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eflated tire marks Deflated tire marks are created when a vehicle is traveling on a roadway with a tire that has no air pressure. A deflated tire mark tends to have a “waffle” pattern. This is created by the flexing of the tire carcass under the wheel as it rotates (see Figures 25 and 26 which were generated by deflating a tire during a test using a special device that sends projectiles into the tire on an instrumented vehicle at over one hundred kilometers per hour). Sometimes a pair of solid dark lines can also be found on the outboard side of the mark. These marks are created by the rim pushing down, pinching the sidewall to the ground (see Figures 27 and 28 which were created in a con-

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Figure 22: Yaw marks on asphalt

Figure 23: Intermittent yaw marks

Figure 24: Intermittent yaw mark created in testing

Figure 25: Deflated tire mark created in testing

Figure 26: Deflated tire mark created in testing

Figure 27: Deflated tire mark on test track

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Figure 28: Deflated tire mark on test track

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Figure 29: Deflated tire mark at crash scene

Figure 30: Deflated tire from Figure 29

Figure 31: Deflated tire mark at crash scene

Figure 32: Intermittent mark from vehicle interaction

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Figure 33: Deflated/delaminated tire mark on test track

Figure 34: Locked delaminated tire mark at crash scene

Figure 35: Deflated and delaminated tire

Figure 36: Deflated/delaminated mark at crash scene

trolled test environment). Testing by these authors found that even when tires are run at pressures of five to ten psi, no such tire marks were generated on a test track. Therefore the existence of such marks would likely indicate that the tire is completely deflated.

SUV being driven at approximately one hundred ten kilometers per hour on an asphalt test track. The tire marks on the roadway were intermittent braking-type skid marks and were created when the tire tread interfered with the rear axle and caused a braking action (see Figure 32). The details of this event are covered in Reference 12. It is possible for some small, light patches of tire marks can be created during a tread belt separation event but that is if there is some slippage between the tire carcass that is separating and the ground.

Figure 29 documents an example of a deflated tire mark which was photographed at a crash scene. Note the waffling of the tread and the two darker border lines. Figure 30 shows the tire that created that mark. Due to the extended driving on this deflated tire, the tread had completely detached from the inner sidewall.

Figure 31 is another example of a deflated tire mark found at a crash scene.

T

ire tread belt separation marks with inflated tires Absent special circumstances, when a tire experiences a tread belt separation and does not deflate, it is rare to locate tire marks on the road surface. In the more than one hundred tire tread belt separation tests that these authors have participated in, only once were tire marks created on the ground. It was a test involving an instrumented 1997 compact

T

ire tread belt separation marks with a deflated tire Sometimes when a tire tread belt separates from the carcass of a tire, it will tear the inner liner and allow the air to escape from the tire. In this situation, a tire mark will resemble that of a deflated tire mark. Figure 33 shows an example of this type of mark created in a test environment on an instrumented 2004 midsize SUV at one hundred kilometers per hour.

Figure 34 shows a deflated separated tire mark documented at a crash site where the brakes were locked or the tire had stopped rotating for some other reason. Figure 35 is a photograph of a deflated and delaminated tire that experienced a tire tread belt

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Figure 37: Deflated and delaminated tire

Figure 38: Deflated/delaminated tire mark at crash scene

Figure 39: Yaw marks with ESC (beginning)

Figure 40: Yaw marks with ESC (end)

separation on the front axle of a pickup truck. Figure 36 shows the tire mark that was created. Figure 37 is a photograph of a left rear deflated tire that experienced a tire tread belt separation. Figure 38 shows the tire mark. Note that the vehicle is in a clockwise yaw and the rim is engaging the road surface, creating gouges in the roadway which will be discussed in a later section.

front tires when the brakes are applied to the outside front tire.

Figure 42 is another example of ESC engagement during severe turning. Note again the darker outside front tire mark and how the curvature straightens somewhat as the ESC system engages and applies the outside front brake. Figure 43 shows another example of a yaw mark showing ESC activation and Figure 44 is a close up view of that mark. Figure 45 shows a photograph at a crash scene of tire marks created by a van equipped with ESC. Figure 46 is a close up view of those marks. In this case, there is no clear evidence of ESC engagement. Therefore, it cannot be concluded that a vehicle’s ESC system is not working or not working properly by only looking at tire marks in a crash or test environment.

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ire marks created by electronic control systems (ESC) During some situations where drivers have driven their ESC equipped vehicles to the limit of tire adhesion, the ESC system will engage and begin to brake one or more tires. Careful observation of yaw marks created by vehicles equipped with ESC systems sometimes, but not always, show where a yaw mark changes in character and transitions into a more linear skid-type mark as the ESC system engages. Figures 39 and 40 show the progression of a yaw sequence made on a test track by a test driver in a non-instrumented 2010 four-door sedan equipped with ESC. ESC engagement was confirmed by the driver and the right front passenger during the testing. Note how the outside front tire mark is darker than the others which signifies ESC engagement. Figure 41 is a close-up photograph of a portion of the inside tire marks documenting how the yaw mark gets straighter due to the reduction in cornering capacity of the 72

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arks made by tires off the roadway When vehicles enter into slides off the roadway, the tires can carve into the soil, grass, or gravel surfaces.

When this occurs, it is routinely referred to as “furrowing” and the forces generated on the vehicle can be very large. This is due to the two mechanisms which are at play during furrowing. The first is the basic friction between the underside tire and the surface it is sliding over. The second mechanism is the force created by the tire having to expel the dirt or gravel

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Figure 41: Curvature change in ESC yaw marks

Figure 42: Yaw marks with ESC engagement

Figure 43: Tire marks with ESC engagement

Figure 44: Close-up of Figure 43

Figure 45: Crash scene tire marks with ESC

Figure 46: Close-up of Figure 45

out from in front of the tire. The tire is essentially doing work (force times distance) on the surface material, which was initially at rest, that it is pushing away. The work is proportional to the kinetic energy of the dirt which is now flying out in front of the tire:

A study by The Ohio State University on furrowing found that sliding even at low speeds into dirt can cause a full-size utility vehicle and a passenger car to roll over (see Figures 47 and 48).

The furrows created where on the order of one to two inches deep. Contrary to the belief of some researchers, a pile of dirt is not always found at the end of the furrows (see Figure 49).

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Figure 47: Furrow tripped passenger car

Figure 48: Furrow tripped full size SUV

Figure 49: Furrow marks in Ohio State study

Figure 50: Furrow marks at crash scene

Figure 51: Furrow marks at crash scene

Figure 52: Furrow marks at crash scene

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Figure 53: Rim scrape created during testing

Figure 55: Rim scrape at crash scene

Figure 54: Rim scrape created during testing

“

Furrows are frequently found in off-road rollovers of vehicles.

Some examples of furrows that were found at the crash sites are presented here (an SUV in Figure 50, a pickup truck in Figure 51, and a passenger van in Figure 52).

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arks made by wheel rims Wheel rims typically do not contact the roadway unless a tire deflates or is underinflated or if a vehicle is placed in a very severe turn or spin such that the lateral forces on the tire can cause it to deflect sufficiently to expose the rim flange. When rims contact a surface, the metal can scrape or gouge the surface. There are also instances that can occur where a tire debeads or unseats from the rim during severe maneuvers.

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im scrapes If rims lightly contact a roadway or if the surface is hard concrete, they may make only a shallow mark on the roadway surface. These marks can be pronounced and appear white in nature since the rim can cut away at the surface, grinding up rock and concrete and creating dust. Figures 53 and 54 show examples of rim scrapes created during testing of an instrumented 1997 compact four wheel drive pickup truck at the very end of an 85 kilometer-per-hour J-turn maneuver. Figures 55 and 56 are examples of some rim scrapes documented at actual crashes.

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Figure 56: Rim scrape at crash scene

If rims lightly

contact a roadway or if the surface is hard concrete, they may make only a shallow mark on the roadway surface.

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Figure 57: Rim stamp with accompanying tire marks

Figure 58: Rim stamp in asphalt surface

Figure 59: Rim Stamp with hub on asphalt surface

Figure 60: Rim gouges created during testing

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im stamps During a rollover crash, there are generally moments when the vehicle's translational and rotational velocities are such that there is little sliding relative to the earth. When a wheel makes contact with the roadway under these circumstances, it will often create a circular or crescent shaped “stamp” in the surface of the roadway, depending on orientation. These stamps are often excellent indicators of vehicle orientation at the time the stamp occurred. Figure 57 shows an example of semicircular rim stamps from the front and rear rims of one side of a vehicle during a rollover crash. Figure 58 shows a good example of a rim stamp with the tire making marks as well.

Figure 59 is a round rim stamp with the center hub of the wheel also crashing into the surface.

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im gouges Wheel rims can also gouge into a roadway surface and carve out significant amounts of asphalt. This sometimes occurs when a tire deflects enough while the vehicle is in a yaw and it can occur when a vehicle is beginning to overturn and the vertical forces and the tire inclination angle both increase. Figure 60 shows a rim gouge created during a very severe handling maneuver conducted on a test track of an instrumented 1997 compact four wheel drive pickup truck in an 85 kilometer-per-hour J-turn maneuver. Figures 61 through 64 are examples of rim gouges photographed by investigating officers at crash scenes. A rim gouge can also be made by a tire unseating while the vehicle is in a severe turn. When this occurs, the evidence on the roadway typically shows the tire mark disappearing as the rim mark continues, as can be seen in the left most gouge in Figure 61. At this point, the vertical forces at that corner of the vehicle are only supported by the rim. Figure 64 shows rim gouges created during a yaw of a small passenger car. The vehicle was overturned on road.

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Figure 61: Rim gouges at crash scene

Figure 62: Rim gouges at crash scene

Figure 63: Rim gouges at crash scene

Figure 64: Rim gouges at crash scene www.collisionpublishing.com

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orces created by rim gouges When rims dig into a roadway surface, the resultant forces transferred into the vehicle can be very high. During some testing conducted by the National Highway Traffic Safety Administration (NHTSA), (Reference 13) tires were debeading and generating extremely high lateral accelerations on the vehicle. An excerpt from page 124 of the 2002 NHTSA Light Vehicle Rollover Research Program Phase IV Testing Summary, stated “…the maximum lateral acceleration during the test producing the left rear debead was 1.79g.” This is a very large lateral acceleration, well in excess of that which could have been created by the tires alone. In order to study this phenomenon, the NHTSA instrumented a vehicle with six-axis wheel force transducers and on-board accelerometers. Figure 65 is a photo of the wheel force transducer mounted on the vehicle whose purpose was to measure the forces created when a rim gouges into the pavement. Figure 66 is the test data recorded during a maneuver where the rim engaged the asphalt test track surface. In this run the peak lateral acceleration recorded was approximately 1.6 g’s and the measured lateral forces were also extremely high and in excess of 6000 pounds. This is well beyond what the tire could generate in a maneuver on an asphalt skid pad. It is important to note that even though the transducer clipped (i.e., forces were created beyond the range of the transducer), it measured 6,027

pounds of lateral force. Clearly this event confirms rim gouges can create much higher forces than the friction of modern-day tires.

Figure 65: NHTSA wheel force transducer

Figure 66: NHTSA data from run with rim gouging

Figure 67: Rim gouge terminating at fractured axle

Figure 68: Axle fracture at end of rim gouge

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In the investigation of a crash involving a sport utility vehicle, the evidence at the scene confirmed that the left rear rim gouged into the asphalt road surface until enough force was created to overload fracture the left rear axle shaft. Figure 67 is a photograph of the rim gouge (note the disappearance of a tire mark, indicating a debeaded tire) and Figure 68 is a photograph documenting that the wheel slammed down on the roadway making an oval mark when the axle shaft fractured. Figure 69 is a photograph of the wheel and tire at the crash scene which shows the axle shaft fracture and Figure 70 shows the axle itself on the crash involved vehicle.

A test on an exemplar vehicle was performed to determine what amount of lateral force could fracture the axle (see Figure 71).

It was found that it took over 12,000 pounds to duplicate the axle damage (see Figure 72). This is clearly a significant amount of force and on the order of over four times what the tire would typically generate by sliding on the surface with high vertical forces.

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Figure 69: Broken wheel and axle shaft

Figure 70: Broken axle shaft on crash vehicle

Figure 71: Axle break test fixture

Figure 72: Axle broken in test environment

The findings above are in contrast to a paper by Bilek, et al (Reference 23), who studied such marks and concluded that rim gouges do not create high lateral forces unless the rims gouge through several inches of asphalt and into the dirt substrate. They based the results of this study on some limited on-track experiments performed by Robert Hooker and the National Highway Traffic Safety Administration. This study ignored several other experiments. The first was the finding of the NHTSA cited above where very high forces were created during rim gouging. The second was a test by a co-author on the paper, Micky Gilbert, where he measured 1.46 g’s of lateral acceleration during a rim engagement in a test of a 2002 Ford Explorer (Figure 73 is the lateral acceleration data from that run compared to a purported similar run where the rim did not engage the surface). The lateral accelerations were clearly higher for the run with rim gouging.

Figure 73: Lateral acceleration comparing runs with and without rim gouging www.collisionpublishing.com

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eferences Brown L.C., Grimm L., and Hansen C., “Relationship Between Anti-Lock Tire Mark Length and Speed Change”, SAE 2007-01-0723.

2. Fricke L.B., “Traffic Accident Reconstruction Vol 2”.

Evanston, IL1990.

3. Baumann, F.W., Schreier, H.H., and Simmermacher, D., “ Tire Mark Analysis of a Modern Passenger Vehicle with Respect to Tire Variation, Tire Pressure and Chassis Control Systems”, SAE 2009-01-0100.

4. DIEKEL, T.: Unfallspuren auf der Fahrbahn, in (Accident Tire Marks on the Road Surface): Hugemann, Wolfgang: Unfallrekonstruktion (Accident Reconstruction), Verlag Autorenteam, Muenster, 2007.

5. Reyeley, M.S., Brown, D.R., and Guenther, D.A., “A Comparison Study of Skid and Yaw Marks”, SAE 890635.

6. Baker, J.S., Traffic Accident Investigation Manual, pp.

213-221, 1975.

7. Baker, J.S., Fricke, L. B., The Traffic-Accident Investigator's Manual, pp. 17.1-18.7, 1985.

8. Barzelay, Lacy. Scientific Automobile Accident Reconstruction, pp. 3.1-9.97, 1988.

9. Beauchamp, G., Hessel, D., Rose, N.A., Fenton, S.J., Voitel, T., “Determining Vehicle Steering and Braking from Yaw Mark Striations”, SAE 2009-01-0092.

10. Gardner, J. A. and Moffatt, E. A., “Controlled Skid Studies Illustrating Tiremarks Generated by Radial Tires,” Highway Collision Reconstruction, ASME, 1980.

11. Brach, R.M., Brach, M.R., “Vehicle Accident Analysis and Reconstruction Methods”, SAE International, 2005.

12. Tandy, D.F., Tandy, K.T., Durisek, N.J., Granat, K.J., Pascarella, R.J., Carr, L., Liebbe, R., “An Analysis of Yaw Inducing Drag Forces Imparted During Tire Tread Belt Detachments”, SAE 2007-01-0836.

13. NHTSA, “A Comprehensive Experimental Evaluation of Test Maneuvers that May Induce On-Road, Untripped, Light Vehicle Rollover – Phase IV of NHTSA’s Light Vehicle Rollover Research Program.” DOT HS 809 513. October 2002 14. Given, Nehrich, Shields, Obtaining motor vehicle evidence fromtire track and read marks: a complete reference for collecting, recording, and analyzing track and tread evidence, Gulf Publishing Company, Houston, TX, 1977 15. White, A.J., Tire dynamics: Tire marks and their relationship to vehicle velocity prior to brake application, Motor Vehicle Research, 1956 16. Garrott, W.R., Guenther, D., et al, ”Improvement of Methods for Determining Pre-Crash Parameters from Skid Marks” National Highway Traffic Safety Administration Technical Report, DOT HS-806-063, May 1981 17. Neil, A.H., A comparison of tire traction test methods: mobile traction dynamometer vs. instrumented passenger car, NTIS, 1977 18. White, A.J., Dynamics of tire failure, Motor Vehicle Research of New Hampshire, 1967 19. White, A.J., The role of tires in vehicle accidents, Motor Vehicle Research of New Hampshire, 1972 20. Moyer, R.A., Tire wear and tire failures on various road surfaces, University of Michigan Library, 1943 21. Dahir, S.H., Henry, J.J., and Meyer, W.E., Seasonal Skid Resistance Variations, Pennsylvania Department of Transportation, 1979 22. Baker, J.S., Tire examination following accident (Advanced accident investigation series), Traffic Institute, Northwestern University, 1977 23. Gilbert, M., Kaplan, M., Bilek, D., Kaplan, S. Vellos, D., “An Examination of Rim Gouging and Its Relation to On-Road Vehicle Rollover”, The SOARcs, Spring 2004 1.

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Using CDR System Data in Crash Reconstruction ...

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fter Vetronix introduced the Crash Data Retrieval (CDR) System for sale to the public 1,2, they sponsored the first CDR system “Training Seminar” in Santa Barbara, CA3. At the time, the most frequently heard refrain in the crash reconstruction community - public or private - was: “this ‘black box’ stuff is going to put reconstructionists out of business!”

Later, some would go on to ignorantly suggest that CDR (System) reports would be “the next generation of police report;” to one degree or another, further fueling the misguided notion that the data imaged/ downloaded using the CDR system would “replace”crash reconstructionists.

The obvious comparison there to the longer standing aviation Flight Data Recorders (“FDR”) and the ongoing work by investigators from, for example, the US NTSB who are still doing the human-based hands on work they do despite the far greater complexity of the data available from the “FDR” should have been sufficient comparison to quell that concern.

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or what does the term “complete reconstruction” really mean?

W. R. “Rusty” Haight Collision Safety Institute www.collisionpublishing.com

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While Chidester, et al 4 mainly addressed the broader safety, research and regulatory advantages of collecting objective crash data following the “FDR” example, it became more and more clear that crash reconstructionists would find - while not being “replaced”- that some of their traditional methods of analysis would be supplemented and/or enhanced in one way or another by the otherwise objective data while, in some cases, their analysis would be subjected to further review or scrutiny as a function of conflict - whether real or interpretative - with crash data recovered from light vehicles. Still, the fear that traditional crash analysis would become a thing of the past became the frequently heard refrain.

In the earliest training on the CDR System, Floyd and Haight attempted to address this concern, writing: “Benefits of data collection - Assists collision reconstructionist to be more accurate, reliable and better understand the collision event” 5 and then writing to highlight the general application(s) of surface vehicle crash data with, for example: “Reconstructionist Replacement? - EDR data doesn’t stand alone in many “real world” events ... Supplements good investigative and analytical procedures ...The EDR data is a tool to be used by the reconstructionist not a replacement ... Limitations of the system necessitate analysis ... Stresses need for continued reliance on analysis and understanding of collision dynamics ...” 6,7 The passage took on an interpretative life of its own and some translations became inexplicably limiting and unnecessarily restrictive with assertions such as: “Nothing about this course suggests that the data obtained from an EDR or ECM should replace the collection of the physical evidence, application of valid mathematical principles, evaluation of human factors, or the development of investigator skills and understanding of collision analysis. The data provided by these instruments should always supplement, and verify, a properly conducted collision reconstruction.”

(Emphasis, the original author(s)) 8 As will be demonstrated more clearly later in this narrative, the latter (underscored by the original authors) portion of that passage is, by any measure, simply wrong in its blanket limitation of CDR data application. While it’s true that data from an “event data recorder” subsystem 9 should not be used independent of sufficient information to connect it with an event under study, the notion that it should be relegated to a role where may only “(always) supplement, and verify, a properly conducted collision reconstruction” would presuppose (1) that crash reconstructionists would be incapable of undertaking the independent steps necessary to connect such data with a collision event and (2) that the volumes of research, crash tests and documentation of the relevant and related systems compiled over the last many years is to be blindly discounted. 1 But even documentation within the system itself can be, at least, misinterpreted, or be seen as so badly constructed as to be, again, overly, even unnecessarily restrictive. For example: “Ford Motor Company RCM's were not designed for the purpose of assisting accident reconstructionists. ...

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tations of the data recorded in Ford's control modules and should compare the recorded data with the physical evidence at the accident scene using professional accident reconstruction techniques (i.e. vehicle crush characteristics, momentum analysis, etc.) before making any assumptions about the import and validity of the data recorded in the module with respect to the crash event being analyzed.” 10 In Lesser v Collier County 11, during cross examination of the defense expert on a case involving data from a Ford vehicle, there is a line of questioning suggesting that at least the first portion of that passage suggests against if not outright eliminates using CDR imaged data in crash reconstruction (“So, you’re using some sort of data that was not intended for use by crash reconstructionists, is that what you’re saying?”) In rebuttal, the follow-up line of questioning highlighted the second portion of the passage as that which would enable the reconstructionists - having applied “some (certain) technique(s)” - to use the data. While it was argued that the passages are almost mutually exclusive, this ultimately revisits the flawed notion that “... data provided by these instruments should always supplement, and verify, a properly conducted collision reconstruction...” 8 That position is also often advanced in the overly broad and over simplified: “you have to do ‘a reconstruction’ to use ‘CDR data’;” however, that proposition ignores the independent nature of various types of data imaged using the CDR system and their potential for various applications of that data as an integral part of an analysis just as much as a supplemental tool to corroborate an analysis given the documented reliability of various elements and lacking conditions which might effect the data.

At the same time some were suggesting restrictions on the use of CDR imaged data 8, a more holistic approach adopted that: “Analysts apply the data to/with a situationally complete crash analysis/reconstruction” 12 and advanced in the idea that training on the system should be/ was structured such that: “CDR general course objectives - Provide CDR Toolkit Data Analysts with ... The ability to read and understand stored crash data then apply that data properly to a situationally complete crash analysis.” 13

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ituationally Complete?

The simplistic and restrictive, at least on the surface, notion that “you have to do ‘a reconstruction’ to use ‘CDR data’” assumes there is a commonly or widely accepted definition of what constitutes “a reconstruction.” As far back as 1994, Day 14 posed that question to the co-author/ panelists “(Question 1:) Describe the ‘product’ called accident reconstruction. ... Are all reconstructions basically the same?”

The panelists gave various answers but none were so specific or restrictive to presume to lay out any sort of set or list of particular requirements or “checkpoints” which would somehow define a “reconstruction.” Most were sufficiently general including: “...Reconstructionists take bits and pieces of information from the collision, like pieces of a puzzle, and compare, analyze and evaluate those pieces and finally fit them together to discover the ‘how’ of a traffic collision.” 14

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None of the answers were so specific as to offer a check list and the panelists recognized that such a list was overly and unreasonably restrictive and doomed, from its inception, to be incomplete. Referenced there 14, and written well before the release of the CDR system, Baker offered: “.... the thinking required (to ‘do a reconstruction’) is essentially disciplined and purposeful study of available data, always keeping in mind two quite different ideas: 1) the issues to be resolved; and 2) applicable principles of basic sciences...” 15 Which brings us back to the suggestion that if one were to include “CDR data” in the category of “available data” and simultaneously apply principles of basic sciences during the assembly of “the puzzle” that is reconstruction, that would run afoul of the idea that “(CDR data) should always supplement, and verify, a properly conducted collision reconstruction.” 8 As found in the Bosch preferred training offered by the Collision Safety Institute as an extension of Floyd, et al 5, 6, 7 , we find: “(the situationally complete) Analysis takes into account the available information toward an analysis including ... Information about the humans, the vehicles and the environment ... Will normally require at least an analysis of the vehicle dynamics and many times an evaluation of the physical evidence supporting the analysis of those dynamics ..."

“A ‘situationally complete’ crash analysis may be based on ... Policy and procedure, existing or available crash facts/evidence, little or no visible roadway evidence, practice (i.e.: suicide, solo vehicle/driver) ... Individual analyst’s training and experience ... The limits of the available data and data limits ... “A man’s got to know his (data) limitations..” - H. Calahan, 1973.” 16 What is not said there is “you have to do (insert some sort of specific list here) which constitutes a reconstruction and THEN one may 'supplement or verify' that work with the CDR imaged data.” Rather, as the reliability of individual parameters found in CDR imaged data has been documented in crash tests and other research, a pattern which fits Baker 15 and Day 14 is one which, once sufficiently informed care is taken, may include the CDR imaged data in the underlying analysis rather than subjugating it to a “supplemental’ role.

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ufficiently informed care?

Something else that is not being said 16 is that one should blindly adopt CDR imaged data, instead there is instruction 17 that, given the demonstrated reliability of CDR data in general, one should take certain steps to evaluate whether or not and then how that data - in whole or in part - might be applied as part of an analysis/reconstruction rather than being relegated to a supplemental or verification step.

The underlying idea is that the crash analyst may, perhaps should, as Baker 15 suggested, apply “all available data” - which would today include CDR imaged data - together with appropriate reconstruction training and experience in the initial, underlying analysis of a crash. To that end, one should apply certain steps to first evaluate the CDR imaged data; apply sufficiently informed care.

Perhaps the key word in that statement is “informed.” Moving blindly, without a thorough or proper understanding is to be UNinformed. In the context of CDR technology, being informed starts with consistent, current training on the CDR System and a solid background in crash reconstruction techniques. After that, the trained data analyst should be further informed, as Baker put it, regarding “the issues to be resolved and the applicable principles of basic sciences.”

Assuming one who would attempt to use CDR imaged data has sufficient training to apply the principles of basic sciences, this brings us to “what has to be done with that CDR data to use it properly, in an informed way?”

It all starts with an understanding of the collision under study.

At the very least, one has to have an idea of the basic facts of the collision as they might relate to the CDR data, the involved vehicles, a general sense of the dynamics of the collision and, as Baker noted, the issues to be resolved. 15 This means, at a minimum, understanding the collision event and vehicle dynamics in a broad, general sense: Is the crash an in-line, “rearender?” Is it an offset head-on crash? Is it a broad side crash? What would be the directionality of the force applied on the involved cars, in particular the one that may contain CDR system retrievable data? Were both cars moving?

Was one stopped? What was the roadway surface like? Wet, dry? Was there a deployment? Was there pre-crash braking evidenced at the scene?

After that, one should contemplate, as Baker wrote, “the issues to be resolved.” This step may; however, be interpreted in too narrow a fashion; so narrow as to become again overly restrictive. Meaning the questions “how did the crash happen?” and “what is most important in this case?” are two entirely different things and the latter is not something an investigator can answer in the field and may not be able to address ever particularly as lawyers begin to shape the issues - what’s ‘most important” - later as the case moves to trial, for example.

A question like “what’s most important in this case,” particularly at the stage of the investigation where an investigator is just trying to figure out what happened, is, at least premature.

For example, what starts out as an otherwise “simple crash” where the “issues” seem to be focused on the speeds of the vehicles could later, because of other information uncovered, become a “who was driving?” or “which car was on what side of the road?” case.

So, again deferring to Baker, we need to be looking at starting with a “study of available data” and then applying it all appropriately toward a comprehensive analysis, not one narrowly focused on what one might think, at the time is (was) “most important.” That misguided approach begs the question later, “so, Mr. Expert, at the outset of your investigation, you indicated that what was ‘most important’ in the case was vehicle speed, right? So, what you’re saying is you were so guided by that preconceived notion, so focused on the speeds of the involved vehicles you failed to consider the PDOF which, together with the delta-V you could have calculated using your so-called ‘angular momentum analysis,’ would have suggested the speeds you were so focused on calculating are simply wrong, isn’t that correct?”

Having then taken the “bigger picture” approach, having developed at least an understanding of the dynamics of the crash at hand, the analyst can then work toward a “traditional” approach, one which might exclude data gathered using the CDR

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system altogether or work on an approach which is inclusive of the CDR gathered data, a more holistic approach: “emphasizing the functional relationship between parts and the whole.”

Meaning, essentially, we’re now more than ten years into the application of this technology to crash reconstruction and the concern that it’s “going to replace reconstructionists” is no longer, moreover, by now, reconstructionists should be able to recognize the relevance and reliability of the data and its application to crash analysis, as part of an analysis, not a supplement, afterthought or verification. After all, if no one can clearly define what a “complete reconstruction” is, how can one “of those” be required to then somehow “permit” the use of CDR data as a “supplement... (to that which can’t be simply defined)?”

This is where (1) proper training in evaluating the CDR system, (2) a review of the Data Limitations portion of the CDR Report for the involved vehicle, together with (3) an understanding of the involved human, vehicle and environment become important and, in this case, guide us to use the CDR report/data as a functional part of the underlying analysis not a supporting, after-the-fact “aside” information or “verification.”

After all, in this example, the CDR report shows a quantifiably different vehicle speed than might be calculated and would, therefore, neither supplement nor verify the reconstruction based striking speed if taken at “face value” and highlights why that approach, at “face value,” would be in error.

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Further review of Figure 1 suggests something “strange” about the brake switch status versus the percent throttle versus the reported speed of the car. Notably, it appears the car is “slowing” significantly over the last three time increments reported (times “-3s”, “-2s” and “-1s”) while the brake switch is reported as “off” (where the brake switch status as “off” suggests there was “no braking”).

“Example #1"

So, one has to wonder why the brake switch would be “off” in light of how the car would appear to be slowing so dramatically. So, during the analysis and while wanting to use CDR data as part of the underlying analysis, the reconstructionist looks at the scene of the crash. There, leading up to and through the area where the impact was believed to have occurred, we find tire marks made by the striking vehicle (leading to the vehicle at rest).

Let’s start with a relatively simple example of where data might be included in an analysis. Imagine a car-to-pedestrian crash.

For the sake of the example, the car is a 2001 Pontiac Sunfire (approximate weight 2765lbs/1257kg) and the pedestrian weighs about 200lbs/91kg. The investigator sees, at the scene of the crash, the car at rest, the pedestrian at rest, deduces, from an examination of the scene, pedestrian and car, that the pedestrian’s trajectory might be described as “wrap” 18 but, for the sake of the example, is unable to find a “good” area of impact. Say the data available from the road makes it such that the investigator is unable (immediately) to narrow down the area of impact more than to, say, within a range of 15 or 20 ft from a central point.

At some point in the analysis, not after, the reconstructionist appreciates that: (1) a pedestrian “wrap trajectory” is common when the striking vehicle is braking pre-crash, (2) there are tire marks on the roadway pre-crash and through the area where the collision is believed to have occurred which are demonstrably left by the striking vehicle, (3) given the uncertainty of the area of impact, the “traditionally” calculated striking speed is between 33 and 43 mph while (4) the CDR report suggests the vehicle speed is about 26 mph near the time of the collision but (5) the CDR report also suggests the brake switch was “off” near the collision (suggesting “no braking” leading into the event) but (6) there are tire marks from braking in that same area on the roadway.

Using normal pedestrian motion models, the investigator might calculate the impact speed of the car, given the uncertainty of the area of impact, at 33 to 43 mph but, for the purposes of a time-and-position analysis, that range leaves to large a gap to draw conclusions (to, as Baker put it, resolve the issues in the collision, for example here: where was the driver when the pedestrian entered the road?).

On its face, then, there is a conflict in the CDR report data both respect to speed at or near impact and whether or not there was braking. But, the trained data analyst remembers to read the Data Limitations as found in the CDR report produced using the latest version of the CDR program for the involved vehicle and finds:

art of an analysis It’s easy to say “you can use CDR based data in an analysis,” but what about an example? Under what circumstances can one use CDR data as part of an analysis? Assuming the reconstructionist understands the techniques available to them (i.e.: concepts of linear momentum, damage/crush relative to delta-V, PDOF and so on) and is familiar with the reliability of the of the various data parameters and, perhaps most importantly, appreciates the importance of reading the “Data Limitations” portion of a CDR System report, the next step really isn’t as daunting as one might imagine.

If we are to stop there and say “well, that’s a ‘complete reconstruction’ now we can examine CDR retrievable data from the striking vehicle...” are we any closer to conclusions in the analysis? Have we done a “purposeful study of (all) the available data?” No, we really haven’t.

If we review the CDR report for the striking vehicle, we see (as found in Figure 1), the speed of the striking vehicle within the last second before what might be described as “impact” (time “-1s”) is reported as 26 mph/42 km/h. On its face, then, the data suggests that the car was going slower than the analyst has calculated which, if this is to be taken at face value, suggests either the analyst made a calculation error or there’s “something wrong” with the data.

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“If the vehicle is a 2000 - 2002 Chevrolet Cavalier Z24 or a Pontiac Sunfire GT, with a manual transmission (RPO MM5) and a 2.4L engine (RPO LD9), the Brake Switch Circuit Status data will be reported in the opposite state than what actually occurred, e.g. an actual brake switch status of ‘ON’ will be reported as ‘OFF’.” 19 To address this issue (which begs the question: would that be identified at the outset as something that would make the cut as “what’s most important in this case?”), the investigator needs to know more about the involved vehicle. It turns out that we are dealing with a Sunfire GT with the transmission and engine regular production options (RPOs) identified in the Data Limitations text as those which, together with the specified year, make and model vehicle would be associated with a condition where the brake switch data is reported opposite the

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Figure 1: The CDR report for the striking vehicle in Example 1. actual state. So, what we know is: the brake switch data we see in Figure 1 (“on” versus “off”) is “backwards” - where it reports “on” it’s actually “off” and the other way around.

That observation is consistent then with what we know from the scene: the tire marks in the area of the collision leading to the vehicle at rest and what we see in the report showing the vehicle speed dropping significantly, almost artificially over the “last three samples” before “impact.” We have used scene observations with what we know about the vehicle and what we glean from the CDR report data and conclude, as part of the analysis, that the car was braking immediately pre-impact and that would, given the published work in the area, suggest the speed, as reported, would be less than the speed of the center of mass of the involved vehicle - the 26 mph reported speed versus the calculated 33-43 mph range.

If we were to adopt the traditional analysis using the broad range for the area of impact and resulting broad range for “throw distance,” to the exclusion of the CDR data, we would conclude that the best we can do in this case is to assert that the speed at impact was about 38 mph, plus or minus 5 mph. However; if we blindly adopt the CDR report speed last sampled before impact at the reported 26 mph, we might conclude that the

(traditionally) calculated speed range is artificially high. Some might be inclined then to adopt a shorter throw distance to artificially adjust the analysis to meet the data which is just as wrong headed an approach as adopting the data blindly.

Once we consider “all available data;” however, it becomes clear that the striking vehicle was actually traveling about 38 mph before an application of brakes and that the wheels being slowed approaching impact produced a reported speed artificially lower than the speed of the center of mass of the striking vehicle when it hit the pedestrian explaining, generally, the “difference” between the reported 26 mph at “-1s” and the calculated range of 33-43 mph.

What this should suggest to the analyst is that the lower end of the calculated speed range is probably actually “pretty good” as representative of the actual striking speed of the involved vehicle particularly taking into account the range of time between reported samples and friction potential for that car and road in the roughly 4 seconds between the time it was reported as traveling at 38 mph and then impact.

As part of the analysis, as a way of narrowing the reconstructionists’s opinion as to the impact speed for the striking vehicle,

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we see where an evaluation of the CDR data, an understanding of the scene and vehicle data come together in the analysis and work toward refining the analysis, not supplementing it after the fact.

The example illustrates how the “disciplined and purposeful study of available data” 15 can lead to the inclusion of CDR imaged data in the analysis of a collision rather than after the fact review of the data. In this instance, it helps to narrow the analyst’s opinion of an impact speed from what, only about 10 or 12 years ago, would have been an overestimation (on the high end) of the striking speed of the involved vehicle. The application is consistent with the use of the data as part of analysis as found in several of the references previously noted.

5, 6, 7, 12, 13, 16, 17

“Example #2” In Example #1, we can make the case for a situation where CDR data can be used to narrow a range of calculated speeds and better evaluate the dynamics in a crash. But let’s contemplate a scenario where there might not be any definitive calculations for an “impact speed” given the available scene data and where then the CDR data becomes all the more important.

Such a situation might be found on one similar to crash test #5 conducted at the CDR User’s Summit in Houston, TX in January, 2011. In that test, two vehicles with CDR accessible data were used in a head-on, two car moving crash test. The complete details of that crash test and the actual CDR reports from the test are part of the CDR User’s Summit proceedings which accompany Collision Magazine, Volume 6, Issue 1. For the sake of this discussion, let’s assume the data is from a crash under investigation.

For this example, let’s adopt that all the reconstruction has to work with is that the two vehicles - a 2009 Chevy Impala and a 2008 Ford Focus - collided head-on. There are no appreciable tire marks from pre-crash braking and nothing on the roadway

to really tell us where the impact took place other than debris and a lack of redirection marks which suggests that, after impact, the two vehicles basically came to an almost immediate stop “right there.” The 08 Focus weighed about 3300 lbs/1497 kg. The 09 Impala weighed about 3800 lbs/1723 kg.

If we were to attempt to turn to the question: “what’s most important in the case?” we realize that answering that becomes really a virtual impossibility. Before one can figure out what’s “important,” this analysis becomes one of “what can I do with what’s available?” part of what’s available in this instance is the CDR data.

We have (1) the weights of the vehicles, (2) a lack of marks on the roadway in the area of the collision which might suggest redirection of either vehicle or a very specific “point of impact” although there is sufficient material in and around the cars at rest to suggest (3) the vehicles basically at rest at or about the area of impact as seen in Figure 2 and (4) no tire marks coming into (or out of ) the collision. The problem is an in-line, headon crash with little to work from.

One “traditional” approach would be to evaluate the crush damage to the involved vehicles as seen in Figures 3 and 4 for delta-V. The delta-V for each might then be used to calculate a closing velocity for the collision using first the delta-V for the Impala then the Focus but that still doesn’t get us to an “impact speed.”

While we still see, from time-to-time a misapplication of the damage and energy model adopting the idea that once can calculate “speed from crush,” damage assessment to one vehicle relates to delta-V, not impact speed. Another concept misapplication is the notion that closing velocity and impact velocity are the same. That isn’t necessarily true...unless one of the two vehicles is stopped at impact.

Closing velocity is a system based property 20 and defines the difference between the velocity of one car and that of the other

Figure 2: Photo of vehicles after impact in Example 2.

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Figure 3: Photo of 2008 Ford Focus after impact in Example 2.

Figure 4: Photo of 2009 Chevrolet Impala after impact in Example 2.

as Vc = V1 - V2 . For example, if V1 were 20 km/h and V2 were zero, then both the impact speed for V1 and the closing speed for the system would be 20 km/h. If, however, V1 were moving at 30 mph overtaking V2 moving the same direction at 10 mph, then, when they collided, the impact velocity (V1) would be 30 mph; however, the closing velocity would be 20 mph.

Turn V2 around moving toward V1 head on at the same speeds and the closing velocity becomes 40 mph. Once the action is off a single axis, the analyst must account for the relative angle between the two working from an assumed baseline for the system. In any event, knowing the delta-V for one vehicle or both will still only get us to a closing velocity not “impact speed.”

Equation 1

In the example before us, we might work a damage and energy approach and calculate the delta-V for each vehicle and find that, for the Impala, the delta-V is about -18.2 mph/-29 km/h (on the X axis) and about -23.3 mph/-37.5 km/h (on the X axis) for the Focus. 21

Equation 2

We can then turn to the CDR report for each and find that the reported X axis delta-V for the Impala is about -19 to -20 mph (Figure 5). The CDR report for the Focus shows an X axis delta-V of about -23-24 mph (Figures 6 and 7).

At this point, we should see a pretty good fit between what would be the “traditional approach” (that being “crush”) and the CDR data and if we stop at that point, we might conclude that the CDR data was being used to “verify” the traditional analysis (the “complete reconstruction,” “complete” in this case because that’s all that we seem to be able to do). But, having made the connection between the data in the CDR report for these cars and the cars themselves (the comparison of the crush based delta-V and CDR reported delta-V), we can turn to a calculation for closing speed using both the “crush” based and CDR report based delta-V values.

Using either equation 1 and equation 2 seen here, we can calculate the closing speed based on either the delta-V for the Impala or the Focus from both the CDR reported delta-V and the “crush” based delta-V 20. (Assigning one car or the other “V1” or “V2” is unimportant so long as the weights match the chosen designation.) If we use the delta-V for the Focus from the CDR report (-23 mph), we find that the closing speed for the crash would be about 42-43 mph and then, using a version of equation 3 which calculates the delta-V for one car or the other from closing velocity, we’d calculate the delta-V for the Impala as -19-20 mph.

Equation 3 If, instead, we use the CDR reported delta-V for the Impala as -20 mph, we find that the closing speed for the crash would be about 42-43 mph and the delta-V for the Focus should be about -23 mph.

Both approaches - the “crush damage” approach and using the CDR reported delta-V data - used in parallel during the analysis thus far only calculate closing velocity and still don’t get us to the speeds of the involved vehicles at impact. If we adopt the idea we have to “do a compete reconstruction” and relegate the CDR data to a “supplemental role,” we’re essentially “done,” the best we can do is report closing speed.

In this example, reporting the closing velocity of 42-43 mph alone, on its face, means that the Impala could be going 40 mph and the Focus 3 mph, vice versa or any combination of that makes it such that, moving head on to each other, the closing speed for the cars in this system make up about 43 mph.

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Figure 5: Exerpt from the Chevrolet Impala CDR Report in Example 2.

But there remains data available to us: the CDR reported vehicle speed for these cars coming into the crash. Have we done a “complete reconstruction?” Can we turn to the CDR reported speeds near impact although we don’t have a way of independently calculating them (in the problem presented)?

We’re back now to the notion that CDR data can and should be included in an analysis where appropriate informed evaluation is completed. Meaning, we would have, by this point, read and understood restrictions to the data 6,7 as found in the Data Limitations and have applied the data thus far to a situationally complete reconstruction. 13,16 What is identified as “pre crash data” in the CDR reports for both of these vehicles is suitable (having been evaluated for constraints found in the data limitations text and taking into 90

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account demonstrated reliability based on testing) for use in a crash analysis, that is based on an emphasis on the functional relationship between parts and the whole rather than taking the parts in a vacuum.

To that end, we find figures 8 and 9, the pre-crash data sections of the CDR Reports for the Impala and Focus respectively.

In figure 8, from the Impala, we see the “vehicle speed” reported as 23 mph over the last two half second samples collected by the airbag control module before impact and the module experienced “algorithm enable.” We also see that there was an indication of brake switch “on” during this time. The last sample before the module woke up was within about the last half second (0.5s) before that wake up.

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Figure 6: Exerpt from the Ford Focus CDR Report in Example 2.

In figure 9, we see the vehicle speed for the Focus in the period leading to the impact/wake up in one second increments where the vehicle - having been under 100% open throttle acceleration - has moved to a speed of about 26 mph in about the last second before the crash/module wake up (where the speed and other parameters are captured about every second).

If we take the last vehicle speed values observed by each of these modules at face value, that is, if we adopt that the Impala was at about 23 mph at impact and the Focus at 26 mph at impact, then the closing speed for the crash is about 49 mph. The previously calculated closing speed for the crash is somewhat lower: 42-43 mph. Now, the analyst has to evaluate that “difference.” Surely it’s a quantitative “difference,” on its face, but is it qualitative?

Meaning, 49 mph is obviously not the same as 42-43 mph.

They are quantifiably different numbers; however, in light of what the analyst should know about the data and taking into account things like, for the Impala, an indication of brake switch coming “on” somewhere near the last half second of data before the crash and there being potentially a full second after the last observed sample in the Focus data to “impact” where the speed of the Focus isn’t known with any precision not to mention the knowledge that there is some rounding and truncating in the Impala’s vehicle speed reported as a whole number which could mean that, for example, both the Impala and the Focus could be moving slower at impact meaning the closing speed calculated using the pre-crash data - if it were known

closer to impact - could be more “in line’ with the calculated closing velocity.

Another way of contemplating this is to evaluate what the delta-Vs would be if we adopt the last reported impact speeds and closing speed of about 49 mph. Using the relative weights to check the ratio each should share of that 49 mph closing velocity, the Impala should have a delta-V of about -23 mph and the Focus should have a delta-V of about -26 mph. Clearly somewhat higher than the delta-Vs captured by the airbag control modules in these vehicles and suggesting, in light of the recorded delta-Vs, that there likely was some sort of slowing in the half second to something akin to about a whole second before impact and the modules “waking up.” 22 All of which begs the question then: is there anything “wrong” with, “using (all) the available data”, 15 such that the reconstructionist could reasonably report the closing velocity for the crash as between 42 and 49 mph and then opine, given the totality of the data available, that it was actually likely closer to the lower end of that range?

The answer might be found in the remaining speeds for this crash test where, using the remaining instrumentation since the actual impact point on the test location didn’t exactly end up being where it was planned. That additional instrumentation suggests 21 that, closer to impact, the actual speeds of the involved vehicles were closer to 22 mph for the Impala and 25 mph for the Focus ... a closing speed of 47 mph. Perhaps

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Figure 7: Exerpt from the Ford Focus CDR Report in Example 2.

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Figure 8: Exerpt from the Chevrolet Impala CDR Report in Example 2.

Figure 9: Exerpt from the Ford Focus CDR Report in Example 2. www.collisionpublishing.com

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another way of reporting the closing speed then might be to say it was about 46 mph plus or minus about 3 mph. Easily a defensible application of CDR data as part of the analysis rather than an after thought.

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onclusions Inasmuch as there is no single, universally accepted definition of what “a reconstruction” is, there’s no reasonable way to direct that “CDR data can ‘only’ be used/applied after some sort of “complete reconstruction.”

Rather, as identified herein, a situationally complete analysis may include, where the CDR data has been fully vetted and evaluated, one or more parameters from the CDR report as an affirmative part of the underlying analysis in more than an after-the-fact supplemental or verifying role.

CDR Data has now a relatively long history of testing and the general reliability - taking into account the appropriate and applicable Data Limitations - has been proven out to a point where the application of the data in the analytical process should become more commonplace while still not being a replacement for the reconstructionist undertaking that analysis.

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eferences and endnotes 1. Haight, W. R. “Rusty”, “An Abbreviated History of CDR Technology,” Collision Magazine, Volume 5 Issue 1

2. Vetronix Corp, “Vetronix Corp. Launches the Automotive Crash Data Retrieval System,” press release through Business Wire and Automotive Wire, March 13, 2000 3. Floyd, Don, Haight, W. R. “Rusty”, Turner, Bruce and Kerr, James, “Vetronix Crash Data Retrieval (CDR) Training Seminar,” Vetronix Corp, General Motors and the Collision Safety Institute, June 2001 4. Chidester, Augustus "Chip," et al, “Recording Automotive Crash Event Data,” International Symposium on Transportation Recorders, 1999 5. Floyd, Don, and Haight, W. R. “Rusty,” for the presentation “The EDR- Technology and Application” dated 12/3/2000 at “Part 2" slide 40 in the presentation “CDR Training Seminar.”

6. Floyd, Don, and Haight, W. R. “Rusty,” for the Training Seminar sponsored by the Vetronix Corp, Santa Barbara, CA dated 6/29/2001 at slides 8-9 in the presentation “CDR Training Seminar.”

7. Floyd, Don, and Haight, W. R. “Rusty,” for the presentation “The Event Data Recorder, Evolution, Data and Reliability” for the IAARS Annual Conference dated 7/19/2001 at slides 20-21

11. Lesser v. Collier County, 20th Judicial Circuit, Collier County, 2005 Case No. 04-CA-004905 12. Haight, W. R. “Rusty” from the “Crash Data Retrieval Analyst Certification Course,” Collision Safety Institute, course materials dated 3/12/2008 at slide 17 13. Haight, W. R. “Rusty” from “Crash Data Retrieval Analyst Certification Course,” Collision Safety Institute, course materials dated 3/12/2008 at slide 9 14. Day, Terry, et al; “Qualifications of the Reconstructionist: Differing Points of View”, Society of Automotive Engineers #941053 15. Baker, J. Stannard; “Traffic Accident Investigation Manual,” The Traffic Institute, Northwestern University, 1975 16. Collision Safety Institute, from “Standardized CDR Data Analyst Course,” Collision Safety Institute course materials dated 3/21/2011 at slides 70 and 73 17. Collision Safety Institute, from “Standardized CDR Data Analyst Course,” Collision Safety Institute course materials dated 3/21/2011 at slide 72 18. Eubanks, J., Haight, W. R. “Rusty”, “Trajectory Analysis for Collisions Involving Bicycles and Automobiles” 1990, Society Of Automotive Engineers 900368 19. From the “Data Limitations” as found in “ 01023_SDMG99JXZ01-07_r002 ”, Bosch Crash Data Retrieval (CDR) System version 3.7, Robert Bosch, GmbH. 20. Schmidt, B. F., Haight, W. R. “Rusty”, Szabo, T. J., and Welcher, J. B., “System-Based Energy & Momentum Analysis of Collisions”, 1998, Society of Automotive Engineers 980026 21. Haight, W. R. “Rusty” “Crash Data Review, CDR User’s Summit 2011, Houston, TX”; rather than complicate the example with a divergence into a discussion of stiffness coefficients and “crush” based programs, for the sake of this example, the in-car control instrumentation based delta-V is adopted as what would be the damage/crush based delta-V for the involved cars in the test (both the Impala and Focus).

22. Ed note: Remembering that this was in fact a fully documented crash test, we can look at the accelerometer data distributed as part of the data from the 2011 CDR User’s Summit and we find that, in fact there was pre-crash braking documented for both vehicles. After the fact in roadway crash investigation, there would be little way of knowing that in the field, but in support of the conclusions, the accelerometer data for both cars shows significant braking for at least a half second pre-crash/impact.

8. The “EDR Working Group” in course materials for “Methodology and Technology of Crash Data Retrieval,” IPTM, dated 8/27/08 at Page 10, slide 20 9. 49CFR563.5, “Part 563 - Event Data Recorders, Definitions;” see also the glossary found in the“Crash Data Retrieval System Help File,” ver 3.7, Robert Bosch, GmbH. 10. From the “Data Limitations” as found in “ 02004_RCMTakata2_r001 ”, Bosch Crash Data Retrieval (CDR) System version 3.7, Robert Bosch, GmbH.

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GPS Navigation Units

Recorded Data for Use in Accident Reconstruction Timothy J. Reust Accident Science, Inc

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ntroduction The consumer GPS navigation units commonly used in vehicles often record and store information that can be downloaded and used to evaluate accident events. For this research article the Garmin StreetPilot and nuvi units have been tested. The available information from these units include date, time, GPS coordinate, elevation, compass heading angle, travel distance and vehicle speed. This article is written as a follow-up to the one published in the Collision magazine Fall 2010, volume 5, issue 2. Since that article, additional research and testing has been completed.

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ummary The cable used to connect to most of the Garmin nuvi and StreetPilot units is the standard USB mini cable.

There are some units that require the USB sub-mini cable, such as the nuvi 37XX series.

Most units will power up by itself at the beginning of the download procedure, however some of the large screen StreetPilots will require external power to power up, such as the model 7200.

Most of the units that have been tested do record and provide useful information, however an exception is the nuvi model

200 which does not record. However, the nuvi model 200w (w designates wide screen) will record useful data.

Testing was conducted with different price range and age of units to evaluate their sampling rates. It was found that the cost of the unit did not affect the sample rate as they are very similar. The older units, such as the StreetPilot models were found to sample less often than the more modern nuvi units.

Archive files are stored in some units. An archive file contains old log files that can go back many months but depends on how often the unit is used and the trip durations during use. The active log files become archive files when the active memory space becomes full. Generally when the active files reach approximately one meg in size, the file is sent to the archives. A one meg file size contains approximately 10,000 data points (one data point contains a single set of date, time, GPS coordinate, elevation, compass heading angle and vehicle speed). The archive files can be accessed by downloading the internal memory of the unit.

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ata Use After the data from an event is obtained and deemed related to the event of interest then the speed of the vehicle, location of the vehicle on the road or heading Collision Magazine 97

angle of the vehicle can be analyzed. The location of the vehicle on the road can be established by visiting the scene using a handheld GPS unit to re-establish the downloaded GPS coordinates.

It is recommended that the handheld GPS unit be used with an external antenna to provide better satellite reception as the body of the operator can interfere with the reception.

A pole can be used to elevate the external antenna above the operators head (recommended a height of at least six feet). This author uses a Garmin handheld model 60CSx, RAM mount RAM-B-108U-GP1, a Titan III external antenna (GPS Outfitters), a Seco 5001-20 clamp-on bubble sight and a section of ¾ inch PVC pipe approximately seven feet long.

tation). The layout of the roadway can be used as a guide to the direction of the translational shift if needed. As an example, a shift in one direction or another may place the vehicle off the road in an unexpected area so this may be a reason not to shift in that direction.

The procedure to re-establish the GPS coordinate is to walk on the roadway (safely) and observe the reading of the handheld unit. The first step of the procedure is to determine the direction of true north (using the handheld GPS or a magnetic compass and the known magnetic declination in the area). The next step is to continue walking in the north direction until the desired north coordinate is first seen (then place a mark for that position on the road at right a right angle to the direction of travel). The next step is to continue walking in the north direction until the desired coordinate changes and placing a second mark on the road. This will form the bounds of that coordinate. The same procedure is repeated in the east direction. The four marks placed on the road will form the sides of a box or rectangle.

This procedure is repeated for all the desired coordinates to form points along the path of the vehicle.

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ccuracy of the data Testing was conducted to evaluate the accuracy of the distance between data points. The downloaded data will provide a “leg length” which is the distance between two successive data points. After running a test with a GPS unit in a vehicle and re-establishing the coordinate positions on the road, a Total Station was used to measure the straight line distance from the center of each rectangle marked on the roadway.

The results of this testing indicated that “leg length” distances between 20 to 30 feet have an accuracy of approximately 3.3 to 10%. Distances between 100 feet and less than 0.1 mile have an accuracy of approximately 1.7% or better. Distances given in tenths of a mile have an accuracy of approximately 2.3%.

Additional testing was conducted to test the accuracy of both single point GPS coordinates and continuous strings of coordinates. This was done by documenting the position of the vehicle at the beginning or end of a test and documenting the path position of the vehicle on the roadway.

Based upon this testing it has been found that the coordinate’s positions may vary over time by as much as eight feet. A continuous string of coordinates may vary by eight feet but can be corrected by a translational shift (i.e., move the entire string by as much as eight feet without ro-

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The Performance of

Seat Backs in High Speed Rear Impacts and the Effect to the Occupant Martin Werz

National Crash Analysis Center The George Washington University

David J. Biss

Automotive Safety Analysis Corporation

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bstract Three rear impact tests were performed and the seat backs which deformed and reclined due to the crash forces were analyzed. The setup of these tests was geometrically similar to the updated FMVSS 301 standard, but the closing speeds were up to 112 Km/h (70 mph). The analyses were focused on the failure mechanics of the seats and data analysis included high speed videos, acceleration data, and the tear-down analysis of the seats. Applicable FMVSS standards regarding seats-back strength requirements were reviewed and De Haven’s basic occupant protection principles were interpreted for seats in rear-impacts. It was found that while the seats meet the minimum FMVSS standards, there reason to be concerned about seat safety in rear impacts.

Comparison with other research, and with a different class of seat, showed the possibility of designing safer seats using existing technologies.

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ntroduction In the summer of 2010 the National Crash Analysis Center (NCAC) of The George Washington University (GWU) ran three high speed car-to-car rear impact crash tests at the Federal Highway Administration (FHWA) Federal Outdoor Impact Laboratory (FOIL) facility. The test conditions were geometrically similar to the new test procedure for FMVSS 301 [12] covering rear impacts, but two of the tests used high impact speeds (67.95 mph and 69.6 mph) while one of the tests demonstrated full-overlap. Table 1 shows the test matrix and conditions for these three tests. In all three of these tests the driver’s seats were found to be considerably reclined post-test as compared to the pre-test positioning. The following research was performed to identify the failure modes for each of these seats, and to observe how production seats perform from a crashworthiness standpoint. Also, investigations were performed regarding improvements to rear impact crashworthiness performance that would be required in order to meet basic occupant protection principles and survivability limits for rear impact tests at speeds up to 112 Km/hr (70 mph) [12].

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MVSS as Related to Rear Impact Protection While Federal Motor Vehicle Safety Standards (FMVSS) address the fundamental concepts of occupant protection such as dummy accelerations and post-crash occupant survival space. In a variety of tests for front and side impacts, like the FMVSS 208 [13] which have been updated more recently, these concepts are not evaluated in rear impacts. FMVSS 301, which was developed as fuel-system-integrity test, is the only regulation leading to dynamic rear impact tests. In this test, “dummies as specified in part 572” of the FMVSS are to be seated in the positions as required by FMVSS 208. In other words, the dummies are placed in the front seats as ballast weight and instrumentation is not required. Additionally, the original seating system is not required for this rear impact test and it has been reported that there are car manufacturers who use modified seats in which the recliner or seat tracks were reinforced by welding them into fixed positions. Consequently, limited tests are available to investigate seat integrity in rear impacts. FMVSS 207 is currently the only test dealing with the seat strength Test Number

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10011

10014

To pass this test, an unoccupied seat may not fail with a forward acceleration (or load) of 20 G (applied to the weight of the seat only) and has to withstand a static moment which is defined for hinged seats (S4.3.2.2), as used in today’s automobiles, as follows: The moment is produced by a force, equal to 20 times the gravitational force of the seat back which is applied at the center of gravity of the seat back, but generating at least 373Nm (3300 inch-pounds) about the seating reference point which is equivalent to the so called H-point in with a seat in its rearmost position. This torque of 373Nm is the approximate torque produced by a large man bracing his feet on the floor-boards and his back braced on the seat back, for instance, to reach for his wallet [14]. Thus, the initial FMVSS 207 was only meant to prevent the seat from spontaneous collapsing during driving or during parking lot maneuvers. Indeed, there are many office and lawn chairs that will easily pass the minimum FMVSS 207 standards.

The FMVSS 202 and 202a [11], which are the regulations for the head restraints, repeats the requirements of FMVSS 207 regarding the moment of 372 Nm about the seating reference point. However, in addition, it requires that the moment generating force has to be applied 64 mm below the top of the head restraint at a level which causes the seat or seat back to fail before the head restraint fails. In cases that the seat is not failing the maximum sustainable force has to be 890 N.

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ow Does FMVSS 207 Relate To Real World Auto Safety?

A section of the United States Code [USC-15 … ] states that: “Because collisions between automobiles are so frequent and common that they must be considered an unavoidable incident of the normal and proper use of automobiles, an automobile manufacturer may be held strictly liable for a defective design which produced injuries ...”

Bullet Vehicle

Test Conditions

Seat Details

01/07/10

1995 Jeep Grand Cherokee Limited Rear Platform '93-'98

Ford Taurus 80.26 Km/h (49.87 mph)

0 degree 30% offset to left-rear corner of target

Power Seat Track Adjusters Manual RECL Mechanism Leather hi-line Upholstery

06/08/10

'96 2 Dr. Explorer Rear Platform '95-'01

Ford Taurus 109.35km/h (67.95 mph)

0 degree 30% offset to left-rear Corner of target

Manual Seat Track Adjusters Manual RECL Mechanism Velour lo-line Upholstery

09/28/10

'98 4 Dr. Explorer Rear Platform '95-'01

Ford Taurus 112.0km/h (69.6 mph)

Power Seat Track 0 degree Adjusters 0% offset Manual RECL Mechato full rear of nism target Velour hi-line Upholstery

Test Date

Target Vehicle

Table 1: Test matrix and conditions for all three rear impact tests 102 Collision Magazine

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This paragraph from the USC can be summarized as a “foreseeability” standard, and it is foreseeable that vehicles will travel down the roads at 80 – 110 Kph (50 – 70 mph), and it is also foreseeable that, at times, those vehicles will inadvertently run into stopped vehicles in front of them. Thus, while proponents of minimum standard requirements might exclaim regarding the extreme severity of a 110 kph (70 mph) closing speed, such a closing speed is not unrealistic. As such, this present research investigates the feasibility of improving rear impact occupant protection up to these foreseeable closing impact speeds.

The FMVSS are minimum safety standards for which an auto manufacturer can sell a vehicle in the United States. Claybrook [1980] has stated that the FMVSS were never meant to be ceilings to limit the degree of safety the automotive manufacturers provide their customers. In fact, the NHTSA expects the auto manufacturers to use “due-care” and the best available technology to provide reasonable state-of-the-art safety to passenger vehicle users [see Martinez below].

April 19, 1999, Statements from Public Meeting, by Dr. Ricardo Martinez, NHTSA Administrator: “The agency commends industry actions to go well beyond the minimum requirements of our standards. These standards were never meant to be maximums.”

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“The Government can never check every technology that … the industry may choose to introduce into their automotive products as to its safety potential and attendant risks … [The industry] has the responsibility to test … technologies under real world conditions and make sure that they produce the purported benefits.”

hat The Standards Cover and Why Crash Tests Should Go Above Those Standards As described above, the FMVSS 207 requires that unoccupied seats may not fail at accelerations of 20 G, or withstand at least a moment about the seat reference point of 373 Nm (3300 in-lb). So, it might be expected that heavy seats could fail from their own inertia at above 20 G without an occupant while very light seats have only to withstand 373 Nm. But, what does this requirement mean to today’s automobiles and today’s speeds? With the conservative assumption that the mass of head, neck, upper and lower torso and the arms is 70% of the Hybrid-III dummy’s mass, or about 52.5 Kg and the center of mass of this assembly is about 0.33 meters above the H-point, the corresponding acceleration on the occupant that can generate these magnitude of loads can then be calculated. The acceleration to meet the minimum sustainable moment of 373 Nm would then be 21.5 m/s² or 2.19 G. Referring to Husted, Biss and Heverly [6] it is not universally possible to relate accelerations with “Delta V's.” However, it is possible to extrapolate the data from a series of low speed rear crash tests [7] even lower because of the reasonable limits that an acceleration of zero would relate to a Delta-V of zero.

Taking this relationship into account we obtain Delta-V’s between about 5.3 kph (3.3 mph) and 10 kph (6.2 mph). Knowing that Linder et. al [7] used the values of mean accelerations, it is very likely that peak accelerations of 2.19 G will occur in today’s rear impact car crashes at even much lower speeds (see figure 1).

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Figure 1: Mean acceleration vs. Delta-V, Data from [7] In contrast to these small forces and velocities, speeds limits on today’s freeways are typically 65 mph (104 kph), with traveling speeds over 70 mph (112 kph), and in certain U.S. states velocities up to 80 mph (130 kph) are allowed.

One moment of distraction or confusion coming upon a traffic jam, or an unclear intersection, and a high speed rear impact can easily happen. While delta-V's of 56 kph (35 mph) are required by FMVSS 208 for the bullet vehicle, the safety of the occupant in the target vehicle in a rear impact crash is largely left to the discretion of the manufacturer. These examples indicate that the minimum requirements for seat strength are below realistic values and improved seats are needed to protect occupants in real-world crashes and contribute to the prevention of serious injuries.

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imitations to the Human Body In the widely known “Daisy Track“ tests it was found that “+Gx [forwardly directed acceleration] is the most tolerated direction for the human body to avoid injury, if head and body are fully sported” [3]. Furthermore it was ascertained that exposures to accelerations of 30 G in these sled tests “were well below human tolerance levels.” The maximum acceleration of the sled was 42G and the occupant incurred only minor injuries to his chest, although accelerations of 83 G were measured on his chest. Consequently, it is remarkable why, in today's rear impact crashes, injuries occur at all even though the accelerations therein are much lower than the limitations found in the Daisy Track tests. As will be discussed below, the key to effective rear impact restraint is the balanced restraint support and ride-down of the head, neck and upper torso complex.

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bjectives For the purposes of this analysis and discussion, it is essential to distinguish the term “failure” with at least two meanings. First there may be a failure due to overloading that cannot be prevented in any practical manner. Second, there are failures due to defects in which a component “fails” due to under-design and/or just not performing in an environment that is foreseeable, such as a moderate rear impact. An example of overloading would be a seat back which deforms into the rear occupant survival space because the impact speed is un-survivably high. In contrast, a failure results from poor design that does not anticipate a foreseeable closing speed, or can be a simple as an inadequate design and/or defective manufacturing. In the tests analyzed in this study, we did not see conditions that were un-survivably high, and indeed, we have Collision Magazine 103

identified alternative design concepts in this study that would have made survivability for both the front and rear occupants feasible.

Methods known as “fail-save-principles” and “Failure Mode and Effects Analysis” should be applied, which can be stated for seat crash performances as follows: There is no reasonable demand that after a severe crash, vehicle seats be unaffected and function normally while the whole vehicle is damaged to an un-repairable, (insurance totaled), state.

Furthermore it is not even expected that the seat remain adjustable or in the same geometric shape as before. However, whatever transformation the seat undergoes in a crash, it should to be in a manner which absorbs energy in a controlled manner and protects the occupants to the extent possible.

The present investigation of the FOIL rear impact tests provides information about how well the subject seat designs met the basic occupant protection principles defined by Hugh De Haven and other crashworthiness pioneers. It is also discussed herein that while the speeds of these tests are challenging, they are definitely foreseeable and are to be expected due to actual speeds on the highway and in real world collisions.

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ugh De Haven's Principles For Rear Impacts.

The four basic occupant protection principles published

by Hugh De Haven in 1952 are often discussed only in the form of short summarizations or applied to certain limited forms of impact. Therefore, we will now apply De Haven's original principles specifically for the behavior of seats in rear impacts.

In his first principle De Haven “states that the package should not open up and spill its contents and should not collapse under reasonable or expected conditions”. Without becoming enmeshed in a discussion about what is “reasonable,” his first principle then can be interpreted that seats should not collapse and should sustain the forces produced by the inertia of the occupant without excessive deformation such that the occupant shall not be ejected from their original seating position or even the car. Indeed, De Haven’s first principle can also cover the fact that the necessary survival space must be maintained, for both the front and rear seat occupants.

In the second principle, De Haven claims that no “brittle or fragile materials” should be used around the occupant. Moreover, the restraint system “should resist forces by yielding and absorbing energy”. But first, we must state another basic occupant protection principle expounded by Viano and others that the seat surfaces are a fundamental part of the occupant restraint system. So, DeHaven’s second principle is equal to the requirement that seats should not break free to move rearward without absorbing energy. In addition, elastic seats are also undesirable because they release all the accumulated energy to the human after the collision and can therefore likely cause higher accelerations with even longer exposure durations.

The third principle of De Haven deals with the movement and dynamics of the occupant and the “resultant damage from the impact against the inside of the package itself.” More broadly, not only is the interaction of the occupant with the seat relevant, but also the impact of the seat into another structure can be interpreted as a negative event. This is because a sudden change in stiffness of the entire occupant packaging assembly can cause high spikes in accelerations, and thus, forces on the occupant, as seen in these subject tests.

104 Collision Magazine

Finally, De Haven states that the restraint system “must transmit forces to the strongest parts of the contained” occupant.

In simple terms this means applying forces to parts of the body that can tolerate the restraint loads. As already discussed, +Gx [forwardly directed acceleration] is the direction in which humans can survive the highest loads when fully supported by a well designed and balanced seating system.

Generally the interface of the occupant’s back and the seat back during rear loading has a much larger surface area than that between the occupant’s torso and the thin straps of a seat belt in a frontal impact. In the real-world, occupants tend to sit with a posture with the head “slouched” forward which curves the neck backward. This slouching posture is called lordosis. This posture increases the distance between the head and headrest and as such, this head-neck relationship remains one of the main challenges for today's seat design for rear crashes.

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ethods For Evaluating The Results Of The Three Rear Impact Tests The methods applied for the evaluation of the crash tests are divided into the following steps:

First, all the available data about the crash test were reviewed, this included photos, high speed videos and the evaluation of the acceleration data.

In a second step, exemplar seats were procured and torn down, in a manner that potential failure modes could be categorized.

Third, the seats of the crash target vehicles were disassembled in a layered fashion to verify which failure modes indeed occurred Finally, to be able to compare the structure of the test seats to other, stronger, seat structures a high strength ABTS (allbelts-toseat) seat from a Chrysler Sebring convertible of the same model year period was also torn down and comparatively analyzed.

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esults Table 1: NCAC/FOIL rear impact crash test matrix As shown in Table 1, the basic setup was the same for all three crash tests. In each test a Ford Taurus with a total weight of 1510 (+/-10) Kg was used as bullet vehicle. In the tests 10008 and 10011 the off-set was 30% which is equivalent to an overlap of 70% because of the same breadth of the vehicles, whereas in test 10014 an overlap of 100% was chosen.

As mentioned before, these tests were primarily performed and studied as benchmarks to show the behavior regarding to the heightened requirements of the new FMVSS 301 procedure.

Also, due to resource limitations, some data which would otherwise have been enlightening were not acquired.

TEST 10008 – Jeep Grand Cherokee Target Vehicle Contrary to expectations, the permanent reclining deformation was not caused by just one single failure mode. The total post-test recline position was the accumulation of a number of deformations. Specifically, the seat track was deformed downward at the left rear corner; the screw connections between recliner and the seat back structure were twisted; and, the overall seat structure was deformed into a more reclined position, but again, all seemingly without a single large failure point. The plastic post-crash deformation of the seat back of the Jeep was only slight. However, it is very likely that the seat back structure which was designed with a tubular construction seemed to elastically bend much more during the crash, and possibly contacted the rear seat bottom during maximum impulse transfer.

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Figures 2 and 3: Photos from test 10008 A further indication of this elastic deformation of the Jeep seat was the vigorous rebound forward motion of the dummy's torso after the actual event which vigorously loaded the belts see figures 2 and 3).

TEST 10011- Ford Explorer 2 Door Target Vehicle Figure 4 shows the reclined seat inclusive of the dummy, the reason for the reclined position of the seat back can be seen in Figure 5; the seat bottom was distorted at the anchor points were the recliner was bolted down.

This movement was possible by the local but heavy plastic deformations in the seat bottom structure and a crack that surrounded the welding point which holds the nut of the recliner mechanism.

Figure 4: The reclined seat from test 10011

This crack lead to decreasing the stiffness of the seat; nevertheless the crack shows some amount of plastic deformation and may have absorbed some amount of energy before it broke.

Figure 6 shows the asymmetric bending of the seat back. The recliner adjuster/locking mechanism is only on the one (the out-side), pivot of the seat back while the in-side pivot is a freely rotating joint that transmits no torque.

It is curious that the side with recliner mechanism is deformed back further than the unlocked, right side. A likely explanation is that the forward bending of the seat on the right side was caused by the intrusion of, and contact with, the rear seat.

The analysis of the high speed videos showed that the seat first began to recline, and then the seat tracks released and moved backwards on the tracks, and finally the seat back was forced more vertical again by the collision with the back seat.

The high speed video furthermore showed, that the dummy ramped up the seat back via a combination of the extreme recline angle generated through the reclining deformation motions and a lack of belt tension. As a result, the head restraint did not support the head, but hit into the dummies neck.

Finally, the dummy was not excessively accelerated by the seat after the impact as it was the case in the test 10008 with the Jeep Cherokee. The explanation therefore may be that the plastic fractures and/or potential damping was caused by the rear seat upholstery. However, it is certain, that the seat tracks locking mechanisms failed during this test, and the seat ran back to the rear limits of the tracks, but otherwise no excessive deformation or breakage could be found on the tracks other than the breakage to the locking dog mechanisms on the seat tracks. www.collisionpublishing.com

Figure 5: The seat bottom was distorted at the anchor points

Figure 6: Asymmetric bending of the seat back Collision Magazine 105

TEST 10014 – Ford Explorer 4 door Target Vehicle Figure 7 shows the pre-test condition and Figure 8 the posttest condition of the seat and the seat position for Test 10014 with the 4 door Explorer. The analysis of the Test 10014 video shows the dummy and seat moving backwards without being noticeably decelerated, until the front seat reached the rear seat where it stopped.

Of note during this test was the breakage of both the left and right seat track load transfer tabs that position the power seat tracks between the upper and lower seat tracks. Once these tabs break the upper seat tracks, they are free to slide completely out of the lower tracks. During this test, the only thing that stopped the driver’s seat from completely becoming detached from the vehicle floor was that the rear seat bottom stopping the rearward motion of the driver’s seat.

Due to the fact that this vehicle was a 4 door configuration with a larger rear seat area, and also that the impact area had 100% overlap, the car body structure in the area of the rear seats was in comparatively better condition post-test such that the rear seats did not move as far forward despite a Delta-V of 51.5 kph (32 mph). While the maximum peak of the vehicle acceleration was only 26G, the head acceleration reached more than 100 G when the head hit the upper edge of the back seat (see figure 9) Figure 10 shows the position of the seat tracks. For reference, the right exemplar seat track is adjusted to its rearmost position. In contrast, the left seat track tab broke from its original

locked middle position allowing the left track to move backwards without absorbing energy or transmitting restraint loads.

The seat track positioning tabs were only mounted by two rivets on each side, and so the resulting and relatively brittle fracture experienced was directly at the mounting point (Figure 11).

An approximate calculation of the mounting rivets was performed using the following geometrical data for the mounting tab: thickness: 3.7 mm, width: 32.9 mm, cantilevered length of 54 mm; and, with the diameter of the rivets of about 9 mm.

Together with the assumption of Rm=250 N/mm² a total withstandable force of about 4300 N was estimated. Taking into account the total weight of dummy and seat of about 95 Kg, a maximum tolerable acceleration of 4.6 G can be calculated when the locating tabs break. This leads to the presumption, that the seat track was broken already after 0.05 sec. However, the sliding in the track was measured to be 29 cm (11.5 in).

In contrast to test 10011 the seat bottom structure in test 10014 (Figure 12) did not show significant fractures, but was perceptibly bent. Obviously, the significantly different behavior of the otherwise identical seat bottom structures was caused by the different seat tracks they were mounted on. Opposed to the relatively rigid tracks of the Explorer 2 door the aluminum power seat tracks of the 4 door allowed a more global deformation.

The test seats were weighed, to be able to compare the mass of the different parts. It is remarkable that the difference between the manual and power seat tracks of the Ford Explorer is only 0.13 Kg, despite the additional parts such as lead screws, electric motors and gears.

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omparison Between the Failures and to the ABTS Seat An investigational analysis of a 1997 Chrysler Sebring convertible All-Belts-to-Seat (ABTS) seat showed a totally different and impressively strong seat structure.

While the seats in the FOIL tests described above used recliner mechanisms used a gear sector which followed a circular motion about the pivot and lock, the Sebring seat uses a length adjustable truss component (Figure 13), which resulted in a much stronger and stable seat back.

Figure 7: Condition of the seat before test 10014

Figure 8: Condition of the seat after test 10014 106 Collision Magazine

Figure 9: X- Accelerations of Head, Chest and Vehicle, Test 10014 www.collisionpublishing.com

Figure 10: The position of the seat tracks after (left) and before (right) test 10014

Figure 11: Seat track after test 10014

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Figure 12: The seat bottom structure after test 10014

Collision Magazine 107

Figure 13: Configuration of Chrysler Sebring seat back

Figure 14: Diagonal truss feature in Chrysler Sebring

Explorer Explorer Jeep Chrysler 2dr.

4dr.

Cherokee Sebring

the loading better. This issue should be investigated further to determine if there is a real problem, and if so, what solutions are available?

Total seat with upholstery

21.39

21.74

20.22

26.16

Total Seat structure, Bare (without upholstery)

To conclude, with an additional mass of less than 5 Kg, the Sebring ABTS can withstand multiples of forces as compared to the Explorer seats before breaking free.

17.06

17.41

15.81

22.14

Upholstery

4.33

4.33

4.41

4.02

Seatback frame inclusive recliner

5.5

5.46

3.94

6.24

Seat tracks

6.25

6.38

iscussion Compared to the number of high speed front impacts, rear impacts with the similar impact speeds are not so common, because in front impacts the speeds of the vehicles are typically added, whereas in rear impacts the same direction differential in travel speeds causes the resultant closing speed many times to be less. High speed rear impacts do occur, however, because of the relative tolerance advantage of the human body to the +Gx acceleration direction [3], these forces should not cause as much harm as they often do.

Table 2: Weights of the seat structures in Kg Further essential differences were seen in the arraignment of seat back and seat bottom to the tracks of the analysis seats.

While the seat backs of the Explorer and Cherokee seats are adjusted to the seat tracks through the seat bottom, the ABTS seat back is directly adjusted to a reinforced seat track. Therefore, the seat bottom has to hold only gravitational forces of the occupant. A further advantage of this arrangement is in the different resulting seat-occupant-iteration concerning the height position. If the seat bottom is lifted up for small occupants, the resulting head position relative to the head restraint is nearly the same as if the seat bottom is lowered for taller people.

A potential disadvantage of this particular seat is the diagonal truss (Figure 14) in the seat back which could load the occupant selectively and might cause harm to the mid or lower spine. The thickness of the foam between the occupant’s back and the steel truss is only 5.6 cm (2.2 in), whereas the tested seats show a more padded structure which seems to distribute 108 Collision Magazine

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Two different schools of thought were evident during the research for this project. On the one hand there are researchers like Prasad, Kim and Weerapuli [4] associated with the Ford Motor Company, along with a number of smaller research companies, which argue for yielding seats. However their use of the term “yielding” comes under a very large tent. They do not differentiate with validation testing or other analyses, the difference in crash performance between truly yielding and energy absorbing seats that control occupant motions versus those that break and fly freely without absorbing any significant amounts of energy, and without regard to rear occupant survival space. On the other hand there is research done by independent groups (e.g. Muzzy [3] and Saczalski [2]) which argue either for stronger or at least more energy absorbing seats in order to exert more control over occupant kinematics /dynamics and also to preserve both the rear as well as the front seat survival spaces.

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Test No.

Delta-V

Target Vehicle

Seat behavior

Dummy motion

10011

52.0 Km/h (32.3Mph)

'96 2 Dr. Explorer

Fracture in the seat bottom, seat tracks moved to its end

Ramping, rearward bending of the neck through loose of head restraint

10014

53.0 Km/h (32.9Mph)

'98 4 Dr. Explorer

Bending in the seat bottom, mounting of seat tracks broke

Ramping, neck compression when impacted into rear seat

Table 3: Overview - seat behavior and dummy motion

In comparing these competing approaches one can use the basic principles of mechanics which state that accelerations applied over a greater distance should result in overall lower accelerations for the same change in velocity. The argument for yielding vs. rigid seats is a bit of a red-herring and needs to be placed into the context of the “Daisy Track” experiments where accelerations up to 30 G's were endured by occupants without signs of harm. Whereas, in the FOIL crash tests even the peak accelerations of the center of gravity of the target vehicle were well below these values.

Research done by Pinkel et al. [8] shows the possibility using controlled seat deformation in order to prevent somewhat higher frequency peaks from the overall crash pulse being transmitted to the occupant. This mechanical filtering reduces the overall peak accelerations on the occupant even further.

In any event, valid arguments which advocate yielding seats in order to “filter” out higher peak accelerations; lower the mean acceleration; and, absorb energy assume that the seat is always deforming in a controlled manner and is able to transmit the crash pulse in a compatible manner to the occupant. Whereas the FOIL rear impact tests results show that for the given sample of 1990’s vehicles, this “ideal” concept of large yielding deformation of seats did not satisfy basic occupant protection principles in many different ways, even though some incidental accelerations may have met the injury criteria. However, from other examples of passenger vehicles in the 1990’s marketplace, it is obvious that this dual requirement of absorbing energy, controlling excessive deformations; and , balancing the loading of the head, neck and upper torso, can all be achieved, thus satisfying the DeHaven and other pioneer’s basic occupant protection principles.

Some observations of poor occupant protection principles from the FOIL tests were: 1. The Jeep seat stored the energy by elastic deformation and caused additional harm by catapulting the occupant forward into the belt, after the actual rear impact.

2. The Explorer 2 door seat slid back to the end of its tracks; and/or, until it slammed into the intruding rear seat, causing the dummy to ramp up and very possibly causing neck injuries because the dummy over-rode and hyper-extended over the head restraint.

3. The Explorer 4 door seat slid 29 cm back without absorbing energy and was stopped only by the rear seat. The relative backward moving of the dummy stopped only when its head impacted into the rear www.collisionpublishing.com

seat, and with an impact direction that could cause quadriplegia.

Furthermore, in all the FOIL tests the survival space for a rearoccupant was not maintained. It is particularly very likely that the backward movement of the Explorer seat would have caused not only serious leg injuries to a rear occupant but would have resulted in serious injuries to both the front and rear occupants if their heads had collided. This is a very likely scenario if there had been a rear seat occupant.

These listed problems could be avoided by employing more controlled yielding, or at least by not permitting totally uncontrolled and collapsing seats. This shows that even today the basic principles developed by De Haven 60 years ago, are violated for rear impacts in some vehicles on the US roads. To avoid ramping up the seat back with the likelihood of resulting head and neck injuries, or even total ejection, the seat should yield only to lesser recline angles. Also the use of seat belt pretensioners that deploy in rear impacts should also be studied further.

As the weight analysis of the seats showed, multiple times stronger seats can be manufactured by less than 5Kg (11lb) of additional material.

To summarize, the seats tested during this FOIL rear impact test series all meet the minimum requirements of the applicable FMVSS standards, but evaluation of their response during the impact lead to the conclusion that there is reason to be concerned about occupant safety in these types of impacts.

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imitations The subject tests were run under the significant limitations of resources and without total knowledge of all possible outcomes which might be manifested and studied afterwards. As such, dummy data was available for only one of the three tests, and not all pre- and post-test measurements were taken.

Despite these limitations, much useful information became available from the subject tests in order to provide guidance in the direction of identifying design improvements for occupant protection in higher speed rear impacts. To obtain more repeatable and comparable results, sled tests with a variety of different seats could be done.

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onclusion The FOIL tests showed that a sample of today's car-seats meet the minimum FMVSS standards but may not be adequate for protecting occupants in rear impacts. The results showed that a number of injuries for front and rear oc Collision Magazine 109

cupants could be solved just through non-collapsing, stronger (albeit more controlled energy absorbing) seats. More robust seats are possible with less than 5 Kg of additional weight per seat. Even with today’s knowledge it should be technically and practically feasible to design and produce much safer seats which protect both the front and rear occupants in rear end collisions.

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knowledgements I first want to thank Professor Kennerly Digges for suggesting such an interesting and encompassing project.

Next, I especially want to thank my technical advisor for this project, Mr. David J. Biss of the Automotive Safety Analysis Corporation, who brought his 40 years of experience and insights in automotive safety to provide a comprehensive perspective of the regulatory and technical history of seat performance in rear impacts.

My appreciation also goes out to all the NCAC/FOIL management and staff who helped me in innumerable ways with this very satisfying project, including Larry Wilson and Shaun Kildare who made the tests possible, and particularly, Mr. Kildare who also processed the test data. Special thanks to the USDOT for sponsoring the outreach program under which the crash tests were conducted and for allowing the use of the FOIL.

8. Pinkel I. Irving, Edmund G. Rosenberg, “Seat Design for Crash Worthiness”, NACA Report 1332 9. Carl L. Ragland, “Research Tests to Develop Improved FMVSS 301 Rear Impact Test Procedure”, Paper Number 98-S4P-16, National Highway Traffic Safety Admin US 10. U.S. Department of Transportation, National Highway Traffic Safety Administration (NHTSA), and Federal Motor Vehicle Safety Standard (FMVSS), FMVSS 207, 49 CFR Ch. V (10–1–08 Edition) § 571.207 11. U.S. Department of Transportation, National Highway Traffic Safety Administration (NHTSA), and Federal Motor Vehicle Safety Standard (FMVSS), FMVSS 202, 49 CFR Ch. V (10–1–01 Edition) § 571.202 12. U.S. Department of Transportation, National Highway Traffic Safety Administration (NHTSA), and Federal Motor Vehicle Safety Standard (FMVSS), FMVSS 301, 49 CFR Ch. V (10–1–08 Edition) § 571.301 13. U.S. Department of Transportation, National Highway Traffic Safety Administration (NHTSA), and Federal Motor Vehicle Safety Standard (FMVSS), FMVSS 301, 49 CFR Ch. V (10–1–08 Edition) § 571.30149 CFR Ch. V (10–1–01 Edition) § 571.208

Disclaimer: The contents of this paper reflect the views of the authors who are solely responsible for the facts and accuracy of the data, and the opinions, findings and conclusions presented herein. The contents do not necessarily reflect the official views or policies of the U.S. Department of Transportation, the George Washington University, or the National Crash Analysis Center.

14. Ellison v. General Motors, Deposition of Lloyd Heck, State of Michigan, Circuit Court for the County of Wayne, Case No. 98 809973 NP, January 7, 2000.

eferences 1. Anthony Sances, Jr.* Keith Friedman, Fiona Gaston and Jack Bish. ”Serious Injury in Rear Vehicular Impacts,” Proceedings of The First Joint BMES/EMBS Conference Serving Humanity, Advancing Technology Oct 1516, 99, Atlanta, GA, USA

16. RERPORT ON THE DEVELOPMENT OF THE INITIAL FEDERAL MOTOR VEHICLE SAFETY STANDARDS ISSUED JANUARY 31, 1967, United States Department of Commerce, National Traffic Safety Agency, Washington, D.C., March 17, 1967

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2. Saczalski, KJ, Syson, SR, Hille RA, and Pod MC , “Field Accident Evaluations and Experimental Study of Seat -Back Performance Relative to Rear-Impact Occupant Protection”, SAE 930346 3. Muzzy WH III, Cantor AE, Eisentraut DK and D'Aulerio LA “Seat-back Yielding and Collapse: A Danger to Occupants During Real- World Collisions”, 1996.

4. Prasad P, Kim A, Weerappuli DPV, Roberts V and Schneider D, “Relationships Between Passenger Car Seat Back Strength and Occupant Injury Severity in Rear End Collisions: Field and Laboratory Studies”, Society of Automotive Engineering, Paper # 973343.

15. Federal Register / Vol. 69, No. 220 / Page 67068, Tuesday, November 16, 2004 / Rules and Regulations, FMVSS 207, NHTSA Docket 2004-19216, November 16, 2004

Additional Sources Interview with Louis A. D'Aulerio, October 4, 2010: Seat and belt-integrated-to-seat design engineer at The Naval Air Warfare Center [formerly the Naval Air development Center] Warminster, PA, now at ARCCA in Penns Park, PA. Mr. D'Aulerio holds patents regarding seat and belt-integrated-to-seat designs and has conducted extensive testing in both the dynamic and the static strength of seats and seat back structures.

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ppendices (following pages) Appendix I: – Evolution Of Seat Back Strength Due To Various Events Appendix II: – History Of Seat Back Strength And Protection

5. De Haven Hugh, “Accident Survival -Airplane and Passenger Automobile” Society of Automotive Engineers, January 1952 6. Husted C. Daniel, David J. Biss, David E. Heverly, “The Appropriate Use of “Delta-V” in Describing Accident Severity”, 1999-01-1295, SAE TECHNICAL PAPER SERIES, 1999 7. Linder Astrid, Avery Matthew, Krafft Maria, Kullgren Anders, “Change of Velocity and Pulse Characteristics in Rear Impacts: Real World and Vehicle Tests Data”, Paper No.285, Folksam Research, Sweden, 110 Collision Magazine

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 



1990’s

2000’s

2009 FMVSS 301 upgrade

Volvo expands WHIPS

Voluntary upgrades in seat back strength



By 2009, all PV’s will be covered by the new FMVSS 301 Rear Impact Fuel System test:  50 mph @ 30% offset.  Peak accelerations will be about the same as the old test, but the duration of the crash pulse and Delta-V’s will be longer.  Regardless of the upgrade to FMVSS 301, it is not a seat test or standard, and any and all occupant data is voluntary and non-binding.

Volvo extends WHIPS to its full-line of vehicles.





CFR -- FMVSS

Volvo

General references

The initial FMVSS do not reflect dynamic rear impact loading.

General references

Viano in the ‘90’s conducted the first systematic study of seat back strength in American cars.

Volvo voluntarily introduced the WHIPS concept.

20 x e m p ty wt. of seat and/or 3,300 in-lb above H-pt.

GM depositions(1) document that the 3,300 in-lb in the initial FMVSS are not any type of realistic dynamic loading and that a large man, bracing from the floor to the seat back, reaching for his wallet, can generate 3,300 in-lb on the seat back.

As-built using manufacturer’s discretion.

SOURCE

FMVSS 301

1967 – the Initial FMVSS

 FMVSS 301 -- Rear Impact Fuel System Test

The Initial FMVSS were taken from SAE Recommended Practices, among other sources, and there were, and still are, no dynamic crash requirements for rear impact protection.

1970’s – 1990’s

 

No objective crash criteria for seat back strength



Pre – 1967 -- No FMVSS

HISTORICAL BACKGROUND COMMENTS

 In the absence of a dynamic rear impact test requirement, the FMVSS 301 Rear-Impact Fuel System test became, and remains, a de facto indicator of seat back strength for rear impacts.  Dummies basically are used only as ballast and are not even required to be instrumented.  Any data collected on seat strength was on a “ride-along” and optional basis.  The Delta-V’s for the 301 Rear Impact tests were typically 15-22 mph.  Volvo, Mercedes, and a few others voluntarily increased seat back strength and occupant containability.



NOTES/ COMMENTS

Deposition of Lloyd Heck, January 7, 2000, Ellison v. General Motors, Pages 21—34.

TIME PERIOD

(1)

APPENDIX II: HISTORY OF SEAT BACK STRENGTH AND OCCUPANT PROTECTION

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Michael L. Merolli MAPFRE USA

David O. Brink, Esq. Andrew T. Apjohn Smith & Brink PC

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Insurance Applications for Crash Data Retrieval:

Legal Considerations in 2011

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ntroduction On January 26, 2010 Mike Merolli and Attorney David Brink gave a presentation at the CDR Summit entitled “Insurance Applications for Crash Data Retrieval: Legal Considerations”. The core of this presentation was later published in the Spring 2010, Volume 5, Issue 1 Edition of Collision Magazine. This article will provide an update as to how the law is evolving with respect to Event Data Recorder information. The authors suggest the reader review the previous Collision Magazine Article to provide a basis for these supplementary materials.

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tatus of Proposed Federal Regulations From 1998 to 2001, the National Highway Traffic Safety Administration (hereinafter “NHTSA”) sponsored two working groups specifically tasked with the study of event data recorders (hereinafter “EDRs”). The two groups, comprised of members from the automobile industry, academia, and other government organizations, were given the task of facilitating the collection and analysis of collision avoidance and crashworthiness data from on-board EDRs.

the vehicle is equipped with an EDR and describing its purpose. The original compliance date for this rule was set as September 1, 2010, with multi-stage vehicle manufacturers having until September 1, 2011. Due to the costs, research, and development associated with meeting these requirements, the NHTSA released an update to 49 CFR Part 563, extending the time to comply with the new uniform standards to September 1, 2012 for passenger and light duty vehicles, and September 1, 2013 for multi-stage vehicles.

In August of 2001 and May of 2002, the two working groups published their results, leading the NHTSA to publish in the Federal Register a request for comments concerning EDRs and suggestions as to what role the NHTSA should take in the study, development, and installation of the devices. Based on the reports of the two working groups and the general response to the Federal Register request for comments that the NHTSA become more involved in the research and development of EDR standards, the NHTSA released a formal Notice of Proposed Rulemaking in 2004. In August of 2006, the NHTSA published a final rule, specifying uniform requirements for the accuracy, collection, storage, survivability, and retrievability of onboard EDRs voluntarily installed in passenger cars and other light vehicles.

Although 49 CFR Part 563 did not go into effect in 2010 as originally planned, multiple bills were introduced in both the Senate and House this year in an attempt to establish EDR requirements and make EDRs required in vehicles within the next few years. These bills include:

The final rule, 49 CFR Part 563, requires voluntarily installed EDRs in vehicles with a gross weight rating (GVWR) of 8,500 pounds or less to: (a) record 15 essential data elements, (b) record up to 30 additional elements if the vehicle is equipped to record these elements, (c) record these data elements in a standardized format, with specifications for range, accuracy, resolution, sampling rate, recording duration, and filter class, (d) function after full-scale vehicle crash tests specified in the Federal Motor Vehicle Safety Standards and Regulations Number 208 and 214, and (e) have the capacity to record two events in a multi-event crash. In addition to these specifications, the final rule requires manufacturers to make a retrieval tool commercially available to access the information contained in the EDR, while also requiring the manufacturers to include a standardized statement in the owner’s manual that indicates that

“

Multiple bills were introduced in both the Senate and House this year in an attempt to establish EDR requirements.

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S. 3271.IS – Vehicle Safety Improvements Act of 2010: Introduced by Senator Tom Udall (D-NM) on April 28, 2010, this Act would amend section 30166 of Title 49 USC, to require the installation of event data recorders in all motor vehicles manufactured for sale in the United States. EDRs would be mandatory in light passenger vehicles within 18 months after the date of the enactment of this Act, and required in all medium and heavy duty motor vehicles within three years after the date of enactment. In addition to making EDRs mandatory, the Vehicle Safety Improvement Act would establish a national EDR database for research and analysis of accident data.

S. 3302 – Motor Vehicle Safety Act of 2010: In response to the Toyota Sudden Unintended Acceleration issues faced in 2010, Senator John Rockefeller (D-WV) introduced this Act on May 4, 2010. The Act, if passed, would compel the NHTSA to establish four new standards regarding pedal placement, electron systems performance, keyless ignition, and transmission configuration while also strengthening the current EDR standards. Under this Act, the NHTSA would be required to promulgate a rule requiring manufacturers to install EDRs in all passenger vehicles sold in the United States beginning in the model year 2015 and in all medium/heavy duty vehicles by the model year 2017. The Act would also require the NHTSA to promulgate a second rule, requiring that all EDR recorders be temperature, water, crash, and tamper resistant, to increase the amount and type of data recorded, to make the data more accessible to investigators, and to establish ownership, privacy, and disclosure requirements.

H.R. 5381: Motor Vehicle Safety Act of 2010: Sponsored by Representative Henry Waxman (D-CA30), this resolution would require the NHTSA to promulgate a rule requiring that all vehicles be equipped with an EDR that meets the requirements of the existing voluntary standard issued by the NHTSA by 2015.

In addition to equipping every vehicle with an EDR, this resolution would require a second rule establishing that all EDRs be temperature, water, crash, and tamper resistant, while increasing the amount and type of data that must be recorded. This resolution, while making the data more accessible to investigators, would establish ownership, privacy, and disclosure requirements regarding data collected by the recorders.

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“ ”

H.R. 5169: Event Data Recorder Enhancement Act: Sponsored by Representative Raymond Green (D-Tex29), this proposed resolution would amend Title 49 USC to require the Secretary of Transportation to promulgate rules requiring all motor vehicles be equipped with EDRs by 2015. It would further amend Subchapter II of chapter 301 by adding section 30129. This addition would require manufacturers to install EDRs in not less than 25% of their vehicles in 2013, not less than 65% of their fleet in 2014, and 100% of their vehicles in 2015. In promoting consumer privacy, this resolution would ensure that the information contained in the recorder would not be retrievable by a person other than the owner of the vehicle without the owner’s consent or a court order.

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H.R. 5345: Consumer Auto Safety Enforcement (CASE) Act of 2010: Sponsored by Representative Jackie Speier (D-San Mateo/San Franscisco), this bill would require every new car sold in the United States to be equipped with an EDR in two years, beginning with all 2012 models. The bill would further require that all EDRs be readily accessible to regulators and require each EDR to meet a rigorous set of new guidelines to promote safer vehicles.

tate Statutes Entering into 2010, only twelve states had enacted laws addressing EDR technology in vehicles. With the passage of Substitute Senate Bill 5574, Washington became the thirteenth state to enact such legislation. The bill, which had been introduced by Senator Claudia Kauffman in 2009 and went into effect in July of 2010, amended Title 46 of the Revised Code of Washington to provide protection for consumer data. The consumer protection requires owner approval or a court order to gain access to information stored on EDRs. The bill further requires car makers to disclose whether the vehicle is equipped with a recording system and if so, what information is being recorded.

The consumer protection requires owner approval or a court order to gain access to information stored on EDRs. New York A.B. 690 would require that motor vehicles manufactured after December 31, 2004 and operated in New York be equipped with an EDR.

New York A.B. 3059 would require the use of EDR data to reconstruct accident scenes; require the vehicle salesperson to disclose to purchasers orally and in writing that the vehicle contains an EDR; makes the tampering, disabling or removal of the device a misdemeanor; and allows for the use of the data in criminal actions or court proceedings involving motor vehicle crashes.

While Washington was the only new state to enact laws addressing EDR technology, multiple bills were introduced across the nation in 2010 to make EDRs mandatory, alert owners that their vehicle is equipped with an EDR, or to provide further consumer protection and privacy. These bills include:

Pennsylvania H.B. 1112 would require purchasers of a motor vehicle to be notified of the EDR contained in the vehicle and its use while also requiring mandatory disclosure of EDRs installed as part of a subscription service agreement.

Massachusetts H.B. 3348 would amend Chapter 90 of the Massachusetts General Laws by inserting a new section, 9E, after Section 9D. Section 9E would require the manufacturer to clearly disclose the presence, capacity and capabilities of the recording device.

It would additionally serve to define the “owner” of the vehicle as: (1) a person having all the incidents of ownership, including legal title regardless of whether the person lends, rents, or creates a security interest in the vehicle, (2) a person entitled to the possession of a vehicle as the purchaser under a security agreement, (3) the person entitled to possession of the vehicle as lessee under a written lease agreement if the agreement at inception is for a period of more than 3 months.

Pennsylvania S.B. 1412 would require purchasers of a motor vehicle to be notified of the EDR contained in the vehicle and its uses; would impose penalties for failing to notify purchasers of the device; and provides that the data contained in the EDR may be used in legal proceedings.

Missouri H.B. 1558 would require rental car companies to disclose to a renter of a vehicle or motorcycle of the use of recording systems for the purpose of tracking and imposing fines or surcharges.

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South Carolina H.B. 3081 would require manufacturers of new motor vehicles equipped with EDRs or a sensing and diagnostic module sold or leased in the state to disclose the information in the owner’s manual and window sticker.

Washington H.B. 1500 would require that manufacturers of motor vehicles sold or leased in the state and that are equipped with EDRs disclose that information in the owner’s manual, including the data that is being recorded and whether the device is capable of transmitting the information to a central communication system or other device.

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“ ” 2010 saw the passing and proposal of legislation that will greatly enhance the function and use of EDRs.

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ew Case Law From Around the United States The Toyota Unintended Acceleration Issue was arguably one of the most important motor vehicle stories of 2010, as it resulted in Toyota facing approximately 400 lawsuits alleging lost vehicle value, injury, or death as a result of sudden acceleration. An examination of the EDR data in these accidents, however, revealed that driver error, and not sudden acceleration, may have been an alternative cause of the accidents. In 2007, Toyota began installing EDRs into select models and as a result, the manufacturer was able to analyze the data from the EDRs of the vehicles involved in accidents where the alleged cause of the accident was sudden acceleration. Of the 58 vehicles that Toyota and the NHTSA were able to review, 35 showed that at the time of the accident, the brake pedal had not been depressed at all. Fourteen additional results demonstrated only partial braking, while the remaining 9 showed evidence of braking just before the accident occurred. Relying on this data and the NHTSA findings, Toyota has attempted to concentrate on the two known issues, sticking gas pedals and pedals that could become stuck in nonstandard floor mats, while moving away from the theory of sudden acceleration.

Toyota’s reliance on the EDR data to suggest alternative causes, such as driver’s error for these accidents rather than sudden acceleration, shows not only a complete reversal of their previous stance, but also the general use of EDR data at trial. In order to use the EDR data at trial, the data must be used in the right setting and be found to be scientifically reliable. Unlike the case Commonwealth v. Zimmerman, 70 Mass. App. Ct. 357, which determined that the expert was qualified and that there was a “general acceptance in the scientific community of the validity of such data”, the recent 2010 decisions in the McAlonan and Malith cases show that Toyota’s EDR data and retrieval tools are not yet fully accepted in the scientific community and that proper foundation must be shown to use the EDR data at trial.

In the case, McAlonan v. Tracy, 2010 N.J. Super. Unpub.

LEXIS 588 (App. Div. Mar. 16, 2010), Toyota’s attorneys ques-

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tioned the reliability of the EDR found in Toyota vehicles, the EDR use as a reconstruction tool in the field, and the validity of the EDR as a reconstruction tool or crash data recorder.

Prior to the trial, the trial judge granted Toyota’s motion to preclude the Plaintiff from offering evidence or testimony regarding the EDR data. In granting the motion, the Court held that the EDR data had limited significance and relevance, that the EDR data was not critical as each side had retained an accident reconstruction expert, and that the time required to put all of the information on the EDR before the jury was not warranted. The judge further ruled that Toyota’s EDR readout tool had not been validated as a reliable device and could not be seen to be scientifically reliable to allow for the data contained in the EDR to be offered as evidence.

In a decision from the Court of Appeals of Minnesota, the Court in Isaac Malith v. Brian Thomas Soller, et al., 2010 Minn. LEXIS 479 (Minn. 2010) affirmed the trial court’s decision to grant summary judgment and dismiss the Appellant’s negligence claim based on the Appellant’s expert’s reliance on EDR data. The case centered on the issue of whether the Appellant sustained his traumatic injuries as a result of losing control of his vehicle and rolling over several times through the divided highway median, or whether the injuries were caused by the subsequent accident in which the Respondent’s truck collided with the Appellant’s vehicle. The Appellant engaged David Daubert, a professional engineer, to evaluate the accident and serve as an expert witness. Daubert analyzed the data derived from the EDR and used this data to base his conclusion that the injuries that the Appellant suffered were a result of being struck by the Respondent’s truck and not as a result of the vehicle rolling over. The Respondent presented the affidavit testimony of Dr. Gerald Harris, a biochemical engineer, who testified that Daubert’s use of the EDR data was not generally accepted in the field of biomechanical engineering for determining injury causation. Harris further testified that the expert’s use of the EDR data was no more than a preliminary step in determining causation, and that the report of a neuropsychologist and orthopedic surgeon demonstrated that the degree of the injury from the Respondent’s vehicle striking the Appellant could not be determined.

The Court ruled that the testimony of the Appellant’s expert, David Daubert, was inadmissible on the ground that it lacked foundational reliability and that Daubert’s analysis of the EDR data to reach his conclusion was not a practice that was generally accepted in the biochemical community. Reaching the conclusion that the Appellant was unable to establish injury causation without the expert testimony, the Court determined that there remained no material fact issue for trial and granted summary judgment. On appeal, the Court’s holding was affirmed, as the Appellate Court concluded that an ordinary lay person does not have the requisite medical and biomechanical knowledge to determine what injuries would be caused by multiple rollovers. Without an expert to analyze the data and establish a cause of injury, such causation cannot be established. The Appellate Court ultimately affirmed the trial court’s decision and limited the use of EDR data at trial.

While the McAlonan and Malith cases demonstrate issues in introducing and using EDR data during trial in 2010, the case State v. Abbey, 28 So. 3d 208 (Fla. Dist. Ct. App. 4th Dist.

2010) exemplifies how EDR data is sufficient evidence to support a search warrant and establishing probable cause as evidence of a crime. In this case, the Defendant was driving his car when he struck another vehicle, killing the driver. The detective investigating the scene of the accident obtained a search warrant for the Defendant’s vehicle “black box”. The Appel-

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late Court found that the detective presented enough facts in the affidavit to allow for the magistrate to make a practical, common sense decision based on the circumstances set forth in the affidavit that the Defendant committed the alleged crime and that the evidence relevant to the probable crime of vehicular homicide was likely to be located in the car’s “black box”.

The facts showing excessive speed supported the finding that there was a probability, though not necessarily a prima facie showing of a criminal activity of operating a motor vehicle in a reckless manner likely to cause the death of, or great bodily harm to, another. Because the affidavit and application of the search warrant contained sufficient facts to establish probable cause, and the evidence of the crime would be found in the Defendant’s vehicle, the Appellate Court held that the magistrate properly issued the search warrant, and reversed the trial court’s ruling to suppress evidence seized after the execution of the search warrant.

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onclusion Despite the fact that the National Highway Traffic Safety Administration’s rule requiring increased standards for EDRs was extended to 2012, 2010 saw the passing and proposal of legislation that will greatly enhance the function and use of EDRs. This legislation will continue to increase the use of EDRs in motor vehicles and will continue to evolve as technology and the laws regarding EDR data use develop. With many pieces of legislation still under review, it appears as though the next development in this field will deal with an increase in data recording and tracking. Insurance companies and the U.S. Federal Highway Administration, for example, are looking to record more than just the data at the time of an accident through the use of telematics. Telematics would allow insurance companies to gather data on speed, braking, location, and other information pertaining to the use of the motor vehicle to not only reduce risky behavior, but also offer lower prices as an incentive to policy holders. In a similar manner, by offering incentives to drive less and reduce fuel use, the U.S. Federal Highway Administration hopes to use telematics in an effort to reduce congestion on the nation’s highways. While still in the development and test marketing stages, the use of telematics and the increase in data collected could continue to greatly change the way EDR technology and laws evolve.

Obviously, the statutory and decisional law relating to EDR technology continues to move forward. There is no question that this technology will continue to gain significance in the future in both civil and criminal litigation.

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eferences: 1. National Highway Traffic Safety Administration, Final Regulatory Evaluation: Event Data Records (EDRs), July 2006 at I-2.

2. Id at I-2.

3. Id at I-5.

4. Id at I-6.

5. National Highway Traffic Safety Administration, 49 CFR Part 563 [Docket No. NHTSA-2006-25666].

6. Id. at 11.

7. Id. at 21.

8. Id. at 2.

9. National Highway Traffic Safety Administration, 49 CFR Part 563 [Docket No. NHTSA-2008-0004].

10. Vehicle Safety Improvements Act of 2010, S.3271, 111th Cong., 2d Sess. (2010).

11. Motor Vehicle Safety Act of 2010, S.3302, 111th Cong.

(2010). www.collisionpublishing.com

12. H. Rep. No. 5381, 111th Cong. (2010).

13. H. Rep. No. 5169, 111th Cong. (2010).

14. H. Rep. No. 5345, 111th Cong. (2010).

15. Washington Substitute Senate Bill 5574, 61st Legislature, 2009 Regular Session.

16. Id at 1.

17. Id at 3.

18. Id at 2.

19. Massachusetts House Bill 3348, 187th General Court of the Commonwealth of Massachusetts, 2010.

20. Missouri House Bill 1558, 95th General Assembly, 2010.

21. New York State Assembly Bill 690, 2010 Session.

22. New York State Assembly Bill 3059, 2010 Session.

23. Pennsylvania House Bill 1112, Session of 2009.

24. Pennsylvania House Bill 1412, Session of 2009.

25. South Carolina House Bill 3081, 118th General Assembly, 2010.

26. Washington House Bill 1500, 61st Legislature, 2010 1st Special Session.

27. Petterson, Edvard. "Toyota Disappointed $10 Million Crash Deal Disclosed by Dealer's Lawyer." Bloomberg 23 December 2010: 3. Web. 28. Voelcker, John. "NHTSA: Toyota Electronics Have No 'Sudden Acceleration' Fault." Car Connection 11 August 2010: Web. 29. Valdes-Dapena, Peter. "Toytoa probe: Drivers May Have Botched the Braking." CNN Money 11 August 2010: Web. 30. Id. 31. McAlonan v. Tracy, 2010 N.J. Super. Unpub. LEXIS 588 (App. Div. Mar. 16, 2010) 32. Commonwealth v. Zimmerman, 70 Mass. App. Ct. 357 (1994) 33. McAlonan v. Tracy, 2010 N.J. Super. Unpub. LEXIS 588 (App. Div. Mar. 16, 2010) 34. Id. at *20.

35. Id. at *21.

36. Id. at *22.

37. Isaac Malith v. Brian Thomas Soller, et al., 2010 Minn.

LEXIS 479 (Minn. 2010) 38. Id. 39. Id. 40. Id. 41. Id. 42. Id. 43. Id. 44. Id. 45. Id. 46. Id. 47. Id. 48. State v. Abbey, 28 So. 3d 208 (Fla. Dist. Ct. App. 4th Dist. 2010) 49. Id. at 210.

50. Id. at 210.

51. Id. at 212.

52. Id. at 212.

53. Costlow, Terry. "Traffic Congestion Gets U.S. Attention."

SAE International 22 November 2010: Web. 54. Costlow, Terry. "Systems Could Help Improve Driver Behavior." SAE International 22 November 2010: Web. 55. Costlow, Terry. "Traffic Congestion Gets U.S. Attention."

SAE International 22 November 2010: Web.

Collision Magazine 119

Preserving Heavy Truck

Event Data GaryMSME, M. Johnson ACTAR VEAR, Inc.

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n heavy truck ECU downloads with potential or pending litigation, there are files that need to be retrieved and preserved depending on the engine manufacturer.

There has already been one instance in the United States where passenger car data was suppressed by the court because the original file was not available. There are several different files and file types stored in different locations. The default file names, types and locations will be discussed for Caterpillar, Detroit Diesel/ Mercedes-Benz, Cummins and Volvo engines. Some of these files are automatically downloaded and saved with cryptic names such as “042265AD.XTR.” Often, “shop” personnel are unaware of the locations or even existence of these files. There are additional reports such as

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“Warranty Reports” (Caterpillar), “Work Orders” (Cummins), and “Job Cards” (Volvo) that can be created to assist with crash reconstruction analysis. Also, a true “image” of a Cummins ECU can be created and saved allowing future reading of data without having to reconnect to the ECU.

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ommon Abbreviations Electronic Control Unit (ECU): refers to the module or modules that control vehicle functions and may store data relevant to crash reconstruction.

Personal Computer (PC): laptop or desktop used to connect to the ECU. Portable Document Format (PDF): an open standard for document exchange.

The purpose of this article is to assist a basic user or person receiving heavy truck event data or to assist them while having a non-reconstruction facility retrieve event data. This article is not intended to replace appropriate study and training that is associated with classroom activities.

One of the main principles of the scientific method is reproducibility. This refers to the ability of a test or experiment to be accurately reproduced or replicated by another party working independently to repeat an operation and obtain the same results. If care is not taken, important data may be reset or updated inadvertently during an ECU download. Ideally, the only difference between two downloads should be the time on the PC and the serial number of the software used.

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eneral Rules There are certain rules for downloading that should always be followed. These include:

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• Ensure the clock and time zone are correct on the downloading PC. • Expand trees that do not do so automatically.

• Extract trips and incidents.

• Don’t change, add or reset anything.

• Save the proprietary files.

• Print what you can to a pdf.

• Otherwise take screen shots.

ummins To retrieve data from a Cummins ECU, two software suites are required. The first is InSite. This is commercially available software that allows the user to obtain calibration, fault codes, trip information and the audit trail. The second software suite is PowerSpec. This was originally marketed as a free sales tool that owners could download. PowerSpec is required to retrieve Sudden Deceleration events and data from Road Relay units. Most Cummins dealers do not have PowerSpec installed simply because they don’t need it to service an engine.

Safety – Steps to prevent corruption of the ECU during download In PowerSpec, ensure that Auto-Edit Dataplate is set to Never, and Read Disabled Features is checked under Engine Read Options (see figure 1).

In InSite Tools > Options, under Inquire Data Extraction, ensure no extraction resets are selected (see figure 2).

“Work Orders” should be created when retrieving data from a Cummins ECU. The work order can be exported to a comma file and transferred to another PC with InSite installed. The work order can then be opened as if the PC was physically connected to the ECU. Do not move the original work order, it will corrupt the file (see figures 3, 4 and 5).

Figure 1: PowerSpec>Configuration Options.

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Figure 2: InSite Inquire Data Extraction

Figure 3: Enable Work Order Mode

Figure 4: Right click and export the image to a comma delimited (csv) file.

Figure 5: Ensure that all “+” fields are expanded.

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etroit Diesel/Mercedes-Benz The software required is Detroit Diesel Diagnostic Link (DDDL). Detroit Diesel Electronic Controls (DDEC) Reports is part of the tool suite. DDDL works with Detroit Diesel and Mercedes-Benz engines. There are small differences between the engines. Most notably, Mercedes-Benz ECUs do not include an Audit Trail.

When DDEC Reports is run and connected to an ECU, it will automatically save an extraction (xtr) file to the specified directory. Typically this is C:\Detroit Diesel\Diagnostic\Data Pages.

The name of the file will be a function of the date on the attached PC. For example, if the download was conducted on 1210-2010, the file name would be 121001AA.XTR. 11-12-2009 would be 111291AA.XTR (see figure 10).

Safety – Steps to prevent corruption of the ECU during download

If printing the extraction file on site, ensure that “Print All” is selected under the File menu. Also, get a copy of the extraction file and preserve it. When printed, the file should be approximately 35 pages long. Due to its size, it is difficult to maintain and transmit physically. Having the original xtr file will allow reprinting by anyone with the DDDL software. Another proprietary file that should be saved and preserved is the Calibration Data File (cdf ). This file is created in DDDL and can be saved in any location.

DDDL default settings are to reset trips and the clock. This will happen automatically on connection with DDEC Reports. Trip information will be 0’s on next download. In the case of a Detroit Diesel engine, the time change can be seen in the audit trail, but not on a Mercedes-Benz engine. These settings must be changed PRIOR to connecting to the ECU. They should also be checked after every upgrade or reinstallation of the DDDL program (see figures 6-9).

Figure 6: Tools>Vehicle Registry>Double Click DEFAULT

Figure 8: Another location to automatically reset the clock.

Figure 7: Ensure any resets under each tab are not checked. Also extract trips with incidents.

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Figure 9: 4 Extracted but not reset.

Figure 10: On a printed extraction file, the file name will be in the lower, left corner.

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olvo The software needed is Premium Tech Tool (PTT) which contains Volvo’s Vehicle Computer Aided Diagnostic Software (VCADS) Pro. Create a “Job Card.”

Open the desired parameters; mainly fault codes (look for associated “Freeze Frames”), parameter programming and sensor value history. They will automatically be added to the job card except for parameter programming – it must be added manually. Finalize the job card, save and export it to HTML. The HTML can then be printed.

Safety – Steps to prevent corruption of the ECU during download To page through the parameters, a right arrow button with a tool tip that says “Open” is used. Once opened, a right triangle (“Start”) is used to view the data.

Caution should be used, some start buttons reset data. Generally, use the start button on the tool bar (see figure 11).

Figure 11: VCADS Pro multiple start buttons

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aterpillar The software required to read data from Caterpillar ECUs is Caterpillar Electronic Technician (CatET).

Caterpillar stopped producing on-highway engines in June 2009. Create and save a warranty report. After the calibration is retrieved, click expand all. Incidents in a Caterpillar are called Snapshots. The Snapshots have to be selected individually, saved and should be exported to Excel (see figures 12 and 13).

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nternational The software required to retrieve data from International ECUs is ServiceMAXX Fleet Pro. The data remains very limited although there appear to be placeholders for event data. Vehicle information and parameters can be exported or printed. Under “Sessions,” there are “Vehicle Events,” and “Vehicle Trip Report.”

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ack Mack ECUs should only be downloaded by Mack designated affiliates. Currently this is limited to Delta[v] and Keva Engineering. InfoMax is older Mack diagnostic software that can retrieve event data from some VMAC III ECUs. This software is no longer supported and also resets the data thereby violating the reproducibility part of the scientific method. On some Mack trucks, the Instrument Cluster ECU, Vehicle Electronic Control Unit (VECU) and Engine Electronic Control Unit (EECU) are required to properly retrieve event data. Contact one of the affiliates for assistance as soon as it is known that a Mack ECU is involved.

Figure 12: Caterpillar Snapshot Viewer

Figure 13: Exporting snapshots in CatET. 126 Collision Magazine

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Figure 13: International hard brake placeholder in vehicle events

raining Every one of the discussed ECUs record event data differently, and under different sets of circumstances. Performance characteristics of one manufacturer should not be expected to apply to an ECU from a different manufacturer. Anyone attempting to analyze this data should be thoroughly familiar with the nuances of the ECU that is at issue. Fortunately, there are two different classes currently available for those wishing to access and interpret heavy truck EDR data. The first is from the Society of Automotive Engineers (SAE), “Accessing and Interpreting Heavy Vehicle Event Data Recorders.” The second is from the University of Tulsa Continuing Engineering & Science Education, “How to Interpret Commercial Vehicle Event Data Recorders (EDRs).” The author is not affiliated with either organization conducting the classes but has attended the SAE class. There are also numerous technical papers written about heavy vehicle ECUs covering topics such as wheel slip, sampling, power failures and the effects of downloading the data directly from the ECU versus through a diagnostic port.

About the author: Mr. Johnson is a former police officer holding a Master’s Degree in Mechanical Engineering. He has been downloading passenger car event data since 2000 and heavy truck event data since 2004. He has attended or presented at 22 classes and conferences on the topic of event data recording.

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efereneces: 1: State of Oklahoma v. Janet Ingram, Case No. CF-2006-403, http://www.harristechnical. com/downloads/OK1.pdf retrieved 3-28-2011.

2: http://www.powerspec.cummins.com/site/home/ download.htm retrieved 3-28-2011.

3: www.hvedr.com 4: http://www.sae.org/pdevent/C1022 5: http://www.cese.utulsa.edu/programdetail. php?FLAG=EngP&ID=169 www.collisionpublishing.com

Collision Magazine 127

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2011 Vol. 6 Iss.1

D DV !

IT de M nsi M ta I SU Da R est CDsh T 11 Cra 20 &

C

ollision C The International Compendium for Crash Research

Volume 6 Issue 1

Spring 2011

Collision: The International Compendium for Crash Research

VEHICLE & OCCUPANT MOTION in Far-Side Impacts

Volume 6, Issue 1 - Spring 2011

ESTIMATINGMAXIMUMMOTORCYCLE Acceleration Rates INSURANCEAPPLICATIONSFORCDR Part Two in a Series THEPERFORMANCEOFSEATBACKS in High Speed Rear Impacts

Plus Articles from the