C
2015 Vol.10 Iss.2
ollision C The International Compendium for Crash Research
Volume 10 Issue 2
FAll 2015
Collision: The International Compendium for Crash Research
Reviews of Crash Testing
Occupant Kinematics in Low-Speed Bumper-to-Bumper Rear Impacts
collisionmagazine.com
Volume 10, Issue 2 - FALL 2015
Traffic Camera Video Analysis Digital Forensics in Accident Reconstruction
New format. More data. More ARC-CSI. The flash drive included with this issue of Collision is from the 2015 ARC-CSI Crash Conference. The flash drive contains over 7 GB of crash data including crash test videos, digital photos, CDR data, drawing files, and more.
Flas h Drive
Contents
Fall 2015
Volume 10 Issue 2
inside
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06
Letter From the Editor
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Crash and Learn 2015
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A Team Approach to Crash Investigation
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The Rest of the Story
features
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Kinematics of Braced, Un-braced, and Out-of-position Occupants in Lowspeed Bumper-to-bumper Rear Impacts by: Lawrence A. Wilson and Sean Haight
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My Turn at the Wheel: Don't Look Too Closely by: Erik Carlsson
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A Review of the Development and Validation of Simulation Technology for Vehicular Accident Reconstruction by: Brian G McHenry
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Traffic Camera Video Analysis Validation by: Adam Cybanski
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case study
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Case Problem: Who Hit Whom First? by: W. R. Rusty Haight
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Case Problem Solution
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Collision Magazine - Volume 10 Issue 2 3
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n October, 2015, the leadership of New the England Association of Insurance Fraud Investigators (NEAIFI) spearheaded a truly landmark Joint Conference in Mendon, Massachusetts bringing together insurance companies and law enforcement agencies from around New England. The two day conference featured more than 12 fully documented and instrumented crash tests from simple guard rail, pole or Jersey berm impacts to high closing speed, multiple car tests, snow plow sideswipes of parked cars and much more. Dubbed "Crash & Learn" this 2015 conference was successor to the NEAIFI "Crash and Burn" conference in 2011 and was, again, a success because of the efforts of a number of people and organizations involved in the planning for months. A truly meaningful conference can't be thrown together 45 days out and the NEAIFI planning group clearly understood that having met for months ahead of time securing the training venues, cars for testing, recruiting and involving public and private sector groups, companies and agencies alike resulting in a memorable and valuable training opportunity. The NEAIFI conference planning committee was headed by Mike Merolli, MAPFRE Insurance & NEAIFI President; Kerri Sugrue, Geico Insurance & NEAIFI Vice President, Suzette Cavanaugh, Pilgrim Insurance & NEAIFI Secretary; Tim Sweeney, Allstate & NEAIFI Treasurer NAIFI Board of Directors: Rick McMaster of Liberty Mutual Insurance, Derek Byron of Plymouth Rock Assurance, Mike Petrillo of Norfolk & Dedham Insurance, Jonathan Almos of Electric Insurance, Sergeant Tim Dowd of The Massachusetts State Police, Chief Ernest Horn of Mendon, MA Police; and NEAIFI Council, Attorney David O. Brink. Even with a group that large and diverse, things got done. That could even be the theme of "Crash and Learn:" things got done. The two day conference started with more than 70 people from both the public and private sector attending an 8 hour program offered by the Collision Safety Insti-
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tute on incorporating EDR/CDR data into a momentum based crash analysis. Using crash test data from conferences such as the annual ARC-CSI Crash Conference and others, those in attendance were exposed to a review of vector analysis and how graphically how that relates to some of the data elements in crash data retrievable using the Bosch CDR Tool. The second day was dedicated primarily to crash tests and track side demonstrations. Starting and ending the day on schedule and on time, the more than 255 who attended the field day saw more than a dozen crash tests ranging in severity to someone backing into a pole to a three car in-line crash with the "striking vehicle" coming in at over 30mph. While much of the focus of the testing was on damage analysis in general, the design of the tests gave those in law enforcement and those in the insurance industry or private practice something they could come away with and apply back at their regular jobs. For example, one series of tests were conducted with guardrails, Jersey berms and poles installed specifically by Liddell Brothers, Inc., and National Grid for this event. In one series, the test vehicle was driven into the Jersey berm (and another into the guard rail) at various speeds and angles. Acceleration and EDR data was recovered and damage photographed. Down the road, those in attendance will have seen the damage first hand and whether it's a "hit while parked/unoccupied" in the "insurance world" or a hit and run in law enforcement, seeing the dame and the dynamics, seeing the tire marks on the berm or the paint transfer to the car is an invaluable bit of experience. With NEAIFI and the allied organizations combining their efforts, focusing on what's important to the members, member organizations and agencies and developing a solid plan in advance and then implementing that plan, we can say that, for "Crash and Learn" 2015, THINGS GOT DONE.
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A conference of this magnitude couldn't have just come together on its own, a number of entities big and small contributed time, manpower and physical resources to make "Crash and Learn" happen. Among those organizations directly participating in the conference success are: • • • • • • • • • • • • • • • •
MAPFRE Insurance Geico Insurance Plymouth Rock Assurance Lieutenant Andrew Klane, Sergeant Timothy Dowd, and The Massachusetts State Police Collision Analysis Section Detective Sergeant Marcus Eddings and the Boston, MA Police Department Officer Roger Wiseman and the Worcester, MA Police Department Mendon, MA Public Safety Director Ernest Horn Sgt. Matt Hoar and the Central Massachusetts Law Enforcement Council Crash Reconstruction Team Sergeant Jeff L'Heureux and the Rhode Island State Police Deputy Chief Mark Bucchino and The Mendon, MA Fire Department Craig Bernard and Liddell Brothers, Inc. Paul Larson and National Grid Alan Tetreault and the Mendon, MA Highway Department Alan Davey and Karcraft of Uxbridge, MA The Collision Safety Institute Collision Publishing
Editor's Note: For better or worse, fall seems to have traditionally been the time of year for a number of the professional association annual conferences and while especially this year it seems like there was "organizational inattention" relative to some of the annual meetings and conferences compared to years past, other groups have stepped up to provide relevant and timely regional training opportunities. In this issue of Collision, we'll highlight two such training opportunities, one offered in Massachusetts in fall 2015 and the other in Illinois in fall 2014 and the Case Problem in this issue uses data directly from one of the crash tests from the NEAIFI Crash and Learn Conference. www.collisionpublishing.com
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A Team Approach to Crash Investigation Lake County, Illinois Adam Hyde and Joseph Manges Major Crash Assistance Team (MCAT) Deputy Commanders and Crash Test Team
Michael DiTallo Crash Consultant and Crash Test Team
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he "Team Concept" Overview In 2003, the Lake County (Illinois) Chiefs of Police Association identified the need for a team of specially trained police officers with expertise in crash investigation to be organized and available to assist allied regional police agencies with serious traffic crashes. The result was a formalized team of well trained crash investigators which became known as the Major Crash Assistance Team of Lake County, or MCAT. The team is governed by a board of directors and operationally consists of a commander, four deputy commanders and sixty crash investigators that cover thirty six police jurisdictions covering mainly Lake County, Illinois – mainly the area north of Chicago, east to Lake Michigan and north to the Wisconsin border - as well as some jurisdictions in three adjacent Illinois counties.
The team's function is quite simple, but its success hinges on close cooperation and a solid working relationship between the member police departments, State's Attorney's office and coroner's office. Since 2004, MCAT has responded to well over 250 fatal and serious injury investigations. A successful prosecution rate demonstrates the sheer cooperation between all entities of the justice system. Made up of members of the various allied agencies, an MCAT team is available to respond to requests from one of the regional agencies looking for assistance handling serious injury or fatal crashes where MCAT member expertise can be effectively employed. Each scene is handled by a commander and six to eight crash investigators. At each incident, the team completes all at-scene investigative duties (i.e.: forensic measurements, CDR Tool downloads, photographs, scene video, diagrams, vehicle examinations, electronic device examinations, and more) and all investigative findings are returned to the agency responsible for the original investigation upon completion of the investigation team's workup. Special request reconstructions are also completed by team skilled reconstructionists from the team. 10 Collision Magazine - Volume 10 Issue 2
Success of the Regional Team Approach MCAT was formed with the idea that agencies within a defined geographic region could pool both human and physical resources in a larger effort to improve public safety generally and, more specifically, traffic safety. When the creation of MCAT was first proposed for Lake County, there wasn't much information available from the larger law enforcement crash investigation community related to a multi-agency team such as was being proposed. Much of what was learned by the leadership of MCAT was a function of previous individual experience, trial-and-error, and an unprecedented collaborative effort cutting across a variety of agency lines. There were examples of Multidisciplinary Accident Investigation Teams (MAIT) being formed from coast-to-coast from the California Highway Patrol MAIT to the South Carolina Highway Patrol MAIT but those, as with so many others, were teams built within a single agency. Surely, some had members from various sections or specialties within that agency but they were still one agency units. MCAT was proposed as a multi-agency entity which, from the start, presented a new and different set of obstacles. Where a single agency team has one internal set of policies and procedures to incorporate into the operational structure of the unit, from the start, MCAT was designed as a multi-agency organization and, from that outset, there had to be at least an awareness of the policy variations between agencies such that members of a variety of agencies could work together within MCAT. MCAT was designed as a "call out" type of unit, where teams from MCAT each composed of members from a multiple agencies, would respond when team activation occurs. The initial proposal was such that all "on duty" investigators would respond to the crash scenes, but the team management quickly learned that additional assistance was needed by off-duty personnel. Currently, team responses are generally covered with a 60/40 on-duty, off-duty response split.
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Members of Peter Ahern's MCAT Investigative team hard at work on the aftermath of "their" crash test
Investigators forensically measuring and documenting a motorcycle crash scene
The first crash test of the training day, a Chevrolet rearending a stopped motorcycle with rider
An angled crash involving a station wagon and a Chevrolet
The final of four tests, a Pontiac rear-ending a car and pickup stopped at an intersection www.collisionpublishing.com
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Kinematics of braced, un-braced, & outof-position occupants in low-speed bumper-to-bumper rear impacts Lawrence A. Wilson P.E. Wilson Consulting, LLC
Sean Haight collision safety institute
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bstract Five low-speed rear crash tests involving instrumented human test subjects were conducted at the testing and proving grounds of the Las Vegas Motor Speedway as part of the 2014 ARC-CSI Crash Conference. These crash tests were front-to-rear bumper-to-bumper crash tests involving a Chevrolet Cobalt and a Toyota Prius. Two of these tests involved analysis of belted occupant kinematics when the test subject was braced and fully expecting the rear impact and when the test subject did not anticipate the rear impact. The impact speeds for the bullet vehicle were approximately 12 mph and the resulting delta-Vs for the target vehicle were approximately 6-7 mph. Even though the seatbelts locked up in both tests, there were appreciable differences in occupant kinematics when comparing these two tests. When the occupant anticipated the impact, he was able to maintain his grip on the steering wheel and brace his back against the seat back, thereby limiting the amount of lower extremity, upper extremity, and torso movement. However, neck flexion was increased.
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Two low-speed rear crash tests were conducted to analyze the occupant kinematics related to seat back rebound. In one of the tests, the occupant was belted in a normal seated position. In the other tests the occupant was in a normal seated position, but unbelted. The impact speeds for the bullet vehicle were 10-11 mph and the resulting delta-Vs for the target vehicle were 6 to 7 mph. For the belted occupant, the seatbelt locked after the occupant rebounded off the seat back resulting in a maximum forward head excursion of approximately 10 inches. The corresponding maximum resultant head velocity relative to the vehicle was approximately 11 ft/s. For the unbelted occupant, the maximum forward head excursion was approximately 16 inches and the maximum resultant head velocity relative to the vehicle was approximately 10 ft/s. An additional low-speed rear crash test was conducted to analyze the occupant kinematics of an out-of-position occupant who was belted and leaning forward. The impact speed of the bullet vehicle was approximately 6 mph and the resulting delta-V of the target vehicle was approximately 4.75 mph. Following the occupant's initial rearward movement into the seatback, he rebounded forward, but not far enough to return to his original location.
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The testing described in this paper was conducted at and was part of the ARCCSI Crash Conference which is held annually in Clark County, Nevada at the Las Vegas Motor Speedway. During the Crash Conference, one day is dedicated to a series of fully instrumented and documented crash tests. Each year for the last 14 years, the ARC-CSI Crash Conference has featured 8 to as many as 14 crash tests conducted live where those attending the conference can not only watch the tests live but, at the end of the conference, will leave with - as found with this issue of Collision Magazine - a flash drive full of photos, videos and data collected during the testing series. Human subjects involved in the testing, as described in this article, are often monitored by 15 channels of data or more including accelerometers placed on their bodies and load cells on their seat belts. www.collisionpublishing.com
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at n tur eel y M wh e h t
DON'T LOOK TOO CLOSELY! Erik Carlsson
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his article is about a legal case that has some similarity with the case described in "A Dirty Trick By A Law Of Physics, Or What?" from the Spring 2015 issue of Collision. Even in this case, a defendant carmaker retained a testing laboratory that had a reputation for its ability to conduct tests that show the desired results, and also this full scale test ended up showing what the carmaker no doubt did not want the test to show. The case concerned the severe spinal injuries the driver of a small car sustained when the front section of the roof of her car was pushed down by a wheel that a moment earlier had come off a car traveling in the opposite direction. The accident happened on a straight four-lane two-way road. The driver of the car that lost a wheel stated at the subsequent police investigation that he was traveling at about 40 mph when suddenly the left rear wheel came off. He immediately pulled over onto the shoulder 36
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and stopped, he stated. His passenger told the investigating police officer that she stepped out of the car as soon as the driver stopped, and saw the wheel continuing down the road, bouncing up and down, and crossing over into the oncoming lanes. A driver of an oncoming car in the left lane managed to avoid the wheel, but the driver of a car farther back in the right lane did not. The bouncing wheel came down on the front part of the roof of that car. The roof collapsed onto the head of the driver, compressing her spine. She survived the accident, but sustained severe injuries. (A passenger in the car brought it to a safe stop after the impact.) The dislodged wheel came to rest on the edge of the road, close to where the eyewitness pointed out where the car was at the time of the impact. www.collisionpublishing.com
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Who hit whom first?
w. R. Rusty Haight
Collision Safety Institute
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he "who hit whom first?" multiple car in-line collision is one crash investigators see virtually every day. We may be interested in the order of the impacts or we may be interested in the impact speeds of the involved vehicles or the severity of each impact as it may relate to the occupants of the vehicles; there may be a number of areas of interest in this type of collision. This case problem comes from a crash test involving three cars and creates just that scenario such that the potential solutions offer ways some of CDR Tool retrieved data may be useful in an analysis. With the ever increasing availability of Event Data Recorder (EDR) data, this case problem includes Airbag Control Module (ACM) data as well as Powertrain Control Module (PCM) data from one of the involved vehicles as a focal area of the problem statement and exercise: a 2006 Ford Crown Vic. There is also a limited amount of data from one of the other vehicles - a 2000 Chevy Malibu - for use in this analysis. The data from the Malibu has been intentionally presented in such a way in the case problem statement as to add an additional area of focus to the case problem and later suggested solution(s). Data from both has been edited to fit the format of Collision Magazine. The involved vehicles are, from "front to rear" in the line of cars: 1999 Nissan Maxima, 2000 Chevy Malibu, and a 2006 Ford Crown Vic. Photos of the involved vehicles at rest, after the collision, accompany this narrative. The case problem will focus, in part, on evaluating the data from the Crown Vic and the Malibu to see if we can sort out whether or not the Malibu was stopped when hit by the Crown Vic. For this problem, you may assume that the cars have been weighed and the weights presented are accurate at: 1999 Nissan Maxima: 3100lbs (1406kg), 2000 Chevy Malibu 3150lbs (1428kg), and a 2006 Ford Crown Vic 4600lb (2086kg). There was no pre-existing front or rear damage on the Malibu, no rear damage on the Maxima and no front damage to the Crown Vic. As seen in the photos accompanying this problem statement, the rear of the Maxima has relatively minor visible damage. Similarly, the front of the Malibu has rela-
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tively minor damage and there is, outwardly, moderate damage to the rear of the Malibu. You may assume that all damage front or rear on the involved vehicles is/was associated with this crash test/case problem. The cars, at rest as seen in the photos accompanying the problem statement, are essentially lined up as described from "front-to-rear" with the Maxima at a slight angle to the other two. There is a slight "downhill" grade to the road relative to the apparent direction of travel of the involved vehicles. We are lead to believe, and will agree for this problem, that the Maxima was stopped prior to this event and we have no reason to believe that any of the other vehicles might have been "backing," yawing or coming into the crash in any other way that essentially "straight ahead." We are provided with the data from an imaging/download of the Crown Vic's ACM as well as its PCM as found with this problem statement. The data is presented here, translated/reported in the latest version of the CDR program (at this writing, CDR version 16.2.1). We are also provided with a imaging report from the Malibu; however, for the initial discussion/problem statement, it is provided in CDR version 11.0. Given what we are provided with, for this exercise, one should want to know: 1. Is there sufficient information available here to evaluate whether or not the Malibu hit the stopped Maxima first or did the Crown Vic hit the Malibu and push it into the Maxima? 2. Assuming the answer to question #1 is "yes," describe the order of the impact(s); who hit whom first? 3. Given the order of impact(s) you have decided on, what are the speeds of the various vehicles at impact(s) (again, assuming the Maxima is stopped as the events unfold)? 4. We find the equivalent of "pre-crash" data in the Ford PCM data set. Does the speed shown at "time zero" in the Ford PCM data set represent the speed of the Crown Vic at impact?
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The cars involved in this case problem/crash test as they were immediately post-impact
On the left, the rear of the Maxima, on the right, the front of the Malibu as they were immediately post-impact
On the right the rear of the Malibu, on the left the front of the Crown Vic as they were immediately post-impact
The front of the Crown Vic as it was immediately post-impact www.collisionpublishing.com
On the left, the rear of the Malibu, on the right the front of the Crown Vic as they were immediately post-impact Collision Magazine - Volume 10 Issue 2 45
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A Review of the Development and Valida tion of Technology for Vehicular Accident Reco Simulation nstruction Brian G McHenry
McHenry Software, Inc.
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bstract The principals at McHenry Software, Inc. (MSI), Raymond & Brian McHenry, have been active in the field of highway safety research for a combined period of over 90 years. In that time we have performed research for NHTSA, FHWA, NTSB, public and private research organizations and MSI internal development through which we have invented, developed and enhanced the state-of-the art of collision and rollover simulation programs and other reconstruction tools. The programs include CRASH, SMAC and HVOSM which are acronyms for accident simulation and collision reconstruction programs invented by Ray McHenry while at Calspan and on which Ray and I have extensively researched, developed and published. These programs form the foundation for many of the 62
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accident reconstruction and simulation tools in widespread use today. This paper includes a background on these programs including some of their unique validations and enhancements as well as more recent validation and correlation tests of the three-dimensional next generation combination of these programs: msmac3D. A discussion is included of what constitutes a proper demonstration of the validity of simulation and other reconstruction programs used for motor vehicle collisions, rollovers and other types of highway accidents.
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ntroduction Today, on a PC or MAC laptop or desktop, anyone can easily and affordably make 3 Dimensional animations which can rival Hollywood's best. With these phenomenal capabilities
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pert, with impeccable and impressive academic credentials, counters that argument and supplements it with a realistic looking movie of a pig flying, how will the jury avoid being swayed to believe something that we all know is obviously not true. For a sample of proof that 'pigs fly' take a look at an example from a Time Warner Cable Commercial "Pigs", animated by la maison, directed by Bruno Aveillan [1] In consideration of this extreme example you might begin to understand the possible problems which can occur with improper application of simulation and/or animation. The field of accident reconstruction has an increasing use (and abuse) of animation techniques for demonstrative evidence purposes. at your fingertips, it can be very easy to make anything imagined look very realistic. For example, a sample application which is included with some animation software is how to make a cow fly! By following the example, anyone can create an animation of a cow flying. And very quickly and easily someone could create a very realistic animation such that upon viewing the animation you might believe that cows do indeed fly! So let us take this a bit further: Let's substitute a pig for the cow. And let's say there is a court hearing to determine whether pigs fly. And at the court, an expert with an advanced degree from an esteemed university and years of experience testifies that 'pigs can fly!' and as part of the testimony the expert offers a video to prove it! Well everyone knows that pigs don't fly, yet, when the exwww.collisionpublishing.com
So you may find yourself, either as an expert or attorney or defendant, being faced with an accident reconstruction supplemented with a very realistic looking 3-dimensional animation. This paper includes an overview of the origins and capabilities of some of the more widely used computer simulation programs for the reconstruction of collision and rollover accidents in highway safety and litigation. There is also a discussion of some of the comprehensive validations and correlations of these programs and a presentation of some of the updates and enhancements by McHenry which have evolved over the years. This information is then used to provide a baseline to assist in understanding and Collision Magazine - Volume 10 Issue 2 63
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Traffic Camera
Video Analysis Validation Adam Cybanski, BSc, IIC3 Gyro Flight & Safety Analysis
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ideo cameras are everywhere in the modern world. Every year there are more traffic accidents caught on video because of the proliferation of dash cameras, red light and security cameras, and cell phones. Most modern cities employ cameras at major intersections and on highways in order to monitor traffic conditions and document accidents. Until recently, this recorded witness video has been employed qualitatively rather than quantitatively in traffic accident reconstruction. New technologies have made it possible to extract motion data from video of a traffic accident. With identifiable features, a video analyst can determine the speed,
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location, heading, acceleration/deceleration, and rate of turn of a vehicle at up to 29 times a second. In addition, the same data can be obtained on other vehicles within the field of view of the camera. Whether captured from a camera mounted in a car, a traffic camera overhead, or a pedestrian holding a cell phone, analysis of video can produce detailed and useful information. There have not been, as of yet, any published velocity comparisons between video analysis and other technologies such as GPS and radar. This test will provide quantitative insight and serve as a starting point in determining the accuracy and utility of video analysis for accident reconstruction.
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Test Plan The aim of the testing was to determine the utility of vehicle motion data extracted from witness video for crash reconstruction. Objectives The aim will be met through the following objectives:
including vehicles, motorcycles, bicycles, pedestrians as well as the surrounding physical environment 4. Video analysis provides sufficient quantitative data on entities involved in a collision, including position, velocities, acceleration/ deceleration, orientation, rate of turn and ground track 5. Video analysis provides sufficient accuracy for motion data 6. Onsite video data collection and subsequent analysis can be conducted quickly with a reasonable amount of effort 7. Additional video analysis capability development is required
1. Assess the relevance and usefulness of video analysis as investigation tool to provide traffic accident investigation evidence 2. Validate the accuracy of velocity extraction from a traffic camera video for crash reconstruction 3. Make recommendations on future video anal- Test Site ysis testing The testing was conducted on a 250m stretch Scope of divided highway on Greenbank road at Fallowfield road, Ottawa, ON. The test runs were Testing was to determine if: conducted on a northerly track, in the right lane. 1. Video analysis sufficiently covers the physical The radar gun was employed on the northeastarea surrounding a collision ern median of the intersection, directly below the 2. Video analysis provides sufficient temporal traffic camera. resolution and endurance on motion data 3. All entities in the vicinity of the collision are captured,
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udy t S Case
n o i t Solu
Who hit whom first?
w. R. Rusty Haight
Collision Safety Institute
Solution:
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s simple as it sounds, the best place to start an analysis is by asking yourself the question: what do I have to work with? Instead of a guide ("guide" which may come from an old word meaning "crutch"), one should really start with the basics: a blank piece of paper on which you can make lists and even maybe sketches. This is usually a much better way to start if for no other reason than to push you into really evaluating the information before you and carefully reading things like CDR Tool reports as though each one is unique because ultimately, they are. So, for this case problem, we might make a list of some of the things we know from the problem statement. We'll be focused here on addressing the questions posed so the information in our list will be a little more narrowly focused than a list you might want to make in another situation. You may well find other information in the CDR report(s) or information you gather separately from the human, vehicle and/or environment in a given case to add to a list specific to that scenario. What we know about the Nissan Maxima We know that the 1999 Nissan Maxima weighed 3100lbs (1406kg). We have adopted/accepted that it was stopped before any other collision(s) took place. There is relatively minor damage to the rear of the Maxima particularly in the area where we see the Malibu at rest against the Maxima post impact. What we know about the Chevy Malibu We know that the 2000 Chevy Malibu weighed 3150lbs (1428kg). We are trying to find out if the Malibu hit the Nissan first or it if was pushed into the Nissan by the Crown Vic. We find damage on the front of the Malibu consistent with the damage to the rear of the Nissan. On the rear of the Malibu, we see that the rear bumper is displaced "inward and downward" relative to a rear-to-front viewpoint of the car frame of reference. This is also evidenced by the inward and downward twisting of the Malibu's exhaust assembly. The
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damage to the rear of the Malibu is more significant than that on the front. The twisting of the rear bumper cover and damage appearance suggests the rearending Crown Vic "under rode" the rear of the Malibu, at least to some degree. Based on the CDR report for the Malibu, as provided in the problem statement, we know that the airbag control module (ACM) has recorded a single Non-Deployment (ND) event. Reading the Data Limitations text in that report, we know that this module "... (SDM) can store up to one Non-Deployment Event. This event may be overwritten by another Non-Deployment Event. ..." Reading that, we notice there's no mention of the later occurring, potentially overwriting event having to be of greater severity. We see that there is a mention of "... the Time Between Events (being) displayed in seconds. If the time between the two events is greater than five seconds, "N/A" is displayed in place of the time. ..." but notice there is no data parameter displayed in the report for "time between events." We also see, in the Data Limitations text, as we see in most, that the "precrash data is asynchronous" and we see the source of the pre-crash data parameters identified. In the CDR Report "System Status at Non-Deployment" data table, we learn that the driver's belt was unbuckled and if there was a passenger airbag suppression switch on the Malibu, the passenger airbag was not suppressed (and after looking in the car, we find there is no such switch). We find that the ignition cycle count for the Malibu at the time of the ND was 26,346. Notably, there is no ignition cycle count for the time of the imaging/download which, based on our training and experience, we know is normal for this type of system. Together with other observations regarding the data, that there's a number for the ignition cycle count at the time of the event which both makes sense to the vintage of the vehicle and is not reported as "0 (cycles)" we may conclude that there was no apparent power interruption which lead to a power depletion during the data recording process; the data which the ACM held
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in RAM when it came time to record that data was apparently completely recorded. In the CDR Report pre-crash data table we see what appears to suggest the Malibu was slowing from the "-5sec" sample frame at about 12mph to about 2mph at the "-2sec" sample frame. After that, the vehicle speed shows as "0mph" up until the recorded ND occurred "freezing" the pre-crash data buffer at "algorithm enable" for potential recording. The brake switch shows "ON" from the "-6sec" to "-3sec" data frames consistent with the vehicle slowing as suggested by the pre-crash speed data. Looking back to the System Status at Non-Deployment data table, we find that the "Maximum SDM Algorithm Longitudinal Velocity Change (MPH)" is reported as "0.00mph." Based on our training and experience with other similar GM ACMs of this type, we know that these systems will only report a negative longitudinal "Velocity Change" (delta-V). So we can conclude that the ND was a function of a very, very minor frontal collision - one which somehow woke up the ACM but failed to reach a reportable value greater than 0.00mph for the longitudinal deltaV - or there was another reason for this event. At this point then we're left to attempt to deduce the cause of the ND. Was it because the Malibu hit the Nissan "very gently," below the threshold where a number (other than 0.00mph) could be recorded for the "Maximum SDM Algorithm Longitudinal Velocity Change (MPH)?" If that's the case, we're left to explain how it would be that the speed, for the last two second's worth of pre-crash data samples, would be "0mph." One might speculate, given there was braking observed ("ON") in the "Brake Switch Circuit State" portion of the pre-crash data that the Malibu was in full locked wheel braking; however, that switch status changes for the last two samples leading to the ND when the speed is reported as "0mph." Moreover, for that to be true, we'd have to evaluate the car and find it was possible to have locked wheels during braking meaning: does the car have ABS and, if so, was it working properly? Still, that doesn't take us away from the observation that the brake switch status is "OFF" for the last two samples of data before the ND. That observation would seeming run counter to the idea that the "0mph" is a function of locked wheel skidding. The other possibility is that the Malibu was rearended by the Crown Vic, which would result in a positive longitudinal delta-V, with a magnitude not reportable by this ACM and that would then be the cause/source of the ND. Since the accelerometers in the ACM respond to both inertial motion and vibration, and given our training and expewww.collisionpublishing.com
Editor's Note: Regular readers of Collision will recognize that the Case Problem found in the last issue (Volume 10, Issue 1, "Case Study: Three Car In-line Crash Analysis with CDR Data") was also a "who hit whom?" type of crash; however, one should also recognize that the CDR data we're working with here comes from different manufacturers and, as we'll see in this solution, the analytical sequence - and the answer(s) to the question of who hit whom first - is approached somewhat differently with these cars and this data. While the type of crash is basically the same, key concepts from both this three car example and the one in the last issue can be applied in a number of scenarios. It should quickly become clear that this isn't simply some "plug and chug" approach to "testing one's skills," rather these case problems are offered to challenge the reader to look at the crashes and retrieved data in, perhaps, a new light. Too often, we see one engaged in reconstructing a crash has the propensity to look at the problem and want to go immediately to a calculator or, worse, a formula sheet. The truth is, trying to simply throw a "formula" at a problem is always the wrong way to start a real, solid analysis. Rather than trying to oversimplify or even dumb down the analysis with "one size fits all guides," "formula sheets" and the like, one should approach each crash analysis as though it's unique - because it is. So, in Volume 10, we've offered two 3 car in-line crashes; however, they are very different in many ways. Just like there's no "one size fits all" definition to what "a reconstruction" is, there's no quick and easy, all-encompassing approach to analyzing a crash particularly when using CDR Tool retrieved data, or at least when using it properly. This Case Problem then, the second in a series of case problems illustrating the use of Event Data Recorder data as part of an analysis, together with the first one, should serve to reinforce that point.
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