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FX3 from Visual Statement is a state of the art reconstruction solution that allows you to perform accurate reconstructions ranging from simple sketches to detailed 3D Environments. FX3 was designed specifically for reconstructionists who benefit from a

software package that contains all the tools required for crash and crime reconstructions. Wether you do a linear momentum analysis, SMAC Simulation or create captivating 3D Animations; You never leave one application - FX3

;GDB I=: H8:C: Dc i]Z hXZcZ " LZ XVc ]Zae Ndj Use our B";M Pocket PC data collector with any total station – see your points recorded in 3D. Use 6XXZaZgZM on the same Pocket PC to measure deceleration ( drag factor ). Use our EdX`Zi 8gVh]BVi] – to do preliminary calculations of impact speeds etc. Use =Vl`:nZ our photogrammetry program to take accurate measurements with your camera.

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ID NDJG 9:H@IDE Dc ndjg E8 Ä LZ XVc ]Zae Ndj Use ;M( Reconstruction software to download your measurements points and auto plot your scene diagram. Use ;M( to generate a powerful 3D scene complete with textured surfaces and any models you need.

Collision: The International Compendium for Crash Research

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Use our 8gVh] ;M momentum tool right on the diagram to generate impact speeds.

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ID I=: 8DJGI GDDB >c i]Z 8djgi Gddb " LZ XVc ]Zae Ndj Use our ;M( GZVaBdi^dc (9 to instantly animate your reconstruction results on your 3D scene. Use our HB68 ;M to simulate or predict collision results. Present powerful time distance reports and persuasive graphical output.

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                                                                                                          

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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

       

  

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      

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&OR SERIOUS 2ECONSTRUCTIONISTS SEE HOW &8 CAN BE RIGHT FOR YOU

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Volume 2, Issue 2 - FALL 2007

Use our 8gVh]BVi] application with 720+ reconstruction formulae to get all the answers.

ollision C The International Compendium for Crash Research

Volume 2 Issue 2

Night-Time Pedestrian

Collision Reconstruction Factors

Average Ignition Cycles For GM Vehicles

Comparison Test:

Vehicle Speed vs Speed Recorded by an SDM

Validating Speed Analysis Calculations with Crash Test Data

e DVD c n e r e f n o c h s a r C www.CollisionPublishing.com PLUS: 2007 ARC-CSI

If you found this article useful, look into a subscription to Collision Magazine at www.CollisionMagazine.com

Find out more about the next EDR User’s Summit at EDRSummit.com

Contents Fall 07

4 8 10 12 15

of interest

Letter from the Editor Industy Partners Calendar of Events Organization News Errata Sheets

features

On the cover: Taken at the 2007 Annual Conference of the South Carolina Association of Accident Reconstruction Specialists, the photo shows the developing crash between a Chevy Suburban and Dodge Intrepid. This test was one of several the Collision Safety Institute coordinated for SCARS Conference held in Charleston, SC. Photo by Jon Northrup.

On The Cover

General Motors Data Recording: A Visual Approach to the Logic Functions

Detailed Comparison of Vehicle Speed and the Speed Recorded by an SDM

Average Daily Ignition Cycles in SDM Equipped, GM Vehicles

Application of Drag Coefficients to ABS related Sideslip

Use of the Combined Velocity Equation In Cases Involving Post-Collision Movement

Vehicle Crush Measuring: Helpful For Extracting Key Details Of Crash Scenes

104

Implications of Symmetric Sine-Based Collision Pulse Models on Force-Deflection Characteristics: (Part 1)

114

Using GPS based Data Acquisition in Forensic Accident Reconstruction

120

Quantifying the Aerodynamic Forces Acting on a Vehicle and Projectile

124

Reconstruction and Analysis of Steering-Induced, On-Road, Untripped SUV Rollover Tests (Part 2)

32 120

2007 ARC-CSI conference Effects of Sample Rates on Accelerometer Based Skid Testing and Unit Comparison

Validating Speed Analysis Calculations with Crash Test Data

Snowmobile Data

Night-Time Pedestrian Collision Reconstruction Factors

European Accident Reconstruction by the Visual Comparison with Crash Tests

2007 ARC-CSI Crash Test Summary

case study

Case Study Problem

150

Case Study Solution

82 Collision

bstract Since 2000, the Vetronix CDR system has allowed public access to collision data stored in motor vehicle airbag control modules. Currently General Motors (GM) and Ford vehicles are accessible. Neither manufacturer provides a time clock, but GM Sensing and Diagnostic Modules (SDMs) do report the number of times the ignition has been turned on (the ignition cycles), which can be used to approximate the time between the event that was recorded, and the date of the investigation. The average daily ignition cycles can also be used to determine if there is likely to be any data in a non-deployment event file (or if it may have been erased), given the time delay between the event and the start of an investigation.

Thus, a retrospective study was conducted to determine the average daily ignition cycles for GM vehicles over the life of the vehicle. The study of 135 vehicles revealed that the average ignition cycles for vehicles that were not used commercially were between 6 and 7 per day. Commercial vehicles, such as taxis, had considerably more ignition cycles, in the range of 20 to 30 per day. iterature Review

The author is aware of only two previous studies of average ignition cycles. These were both conducted through the CDRtool group – a web based group of police officers, engineers and investigators who share experiences with, and knowledge about event data recorders. The CDRtool studies involved a relatively small sample size and occurred over one month. The current study involved a larger sample size and extended 42 Collision

across the life of the vehicle, from assembly to the collision under investigation. ethod The database that was utilized encompassed GM airbag control modules previously downloaded by engineers at Baker Materials Engineering Ltd. in the course of other collision investigations. This encompassed collisions throughout the province of British Columbia, Canada from 2000 to 2006.

In order to calculate the average ignition cycles over the life of the vehicle, start and end times were required. The end time was readily established from the collision date, but the start time was not so apparent. The vehicle was not being driven by the consumer from the moment the vehicle was first made. During the early stages of its life, the vehicle would have spent some time sitting idle on a dealer’s lot. Thus, any calculation of daily ignition cycles had to account for this early time when the vehicle was not being driven by the consumer. Two start dates were located on the vehicle and two start dates were obtained from the General Motors Vehicle Inquiry System (VIS), for a total of four start dates for each vehicle. The following dates were obtained from examination of the vehicles:  

Date of vehicle manufacture (located on the driver’s door or B-pillar) Date of manufacture of the module (located on the top of the module)

The manufacture date of the SDM was obtained from the “AS” code www.collisionpublishing.com

on the top of the module. A typical code is shown below:

 

Warranty start date (when the vehicle was purchased by the consumer) SDM scan date (when the SDM was installed in the vehicle, which is also when the vehicle was built)1

The number of ignition cycles at the time of the collision and the investigation were obtained for the study from the SDM download, using the Vetronix CDR kit.

In this example, the build year is shown by the 9th digit – a 9, signifying 1999, and the 10th to 12th digits indicate it was built on the 334th day of that year. Thus, this SDM was built on 29 November 1999. Three different exceptions to this rule were noted: 1 - 2006 Chevrolet Trailblazer: There was no shift code recorded after the plant location (K). The year is the 8th digit (6, for 2006) and the day is shown in the 9th through 11th digits (048, for 16 February).

2 - 2006 Malibu Maxx (all SDM-Epsilon modules): This module was made in Mexico and had completely different coding. The coding sequence is currently unknown to the author.

3 – GM Replacement SDM. These modules can be identified because the Part number and the Service number are the same. This indicates that the SDM was replaced at a GM dealership as a result of a prior airbag deployment. The date on this module will not correspond with the date of manufacture of the vehicle. The ignition cycles will start from zero after the repair. The GM VIS was then accessed to determine the following:

It was expected that the first three start dates noted above would underestimate the actual daily ignition cycles because those dates included time before the vehicle was purchased by the consumer. The last start date was expected to overestimate the cycle count because it did not consider any time when the vehicle was driven between the date of manufacture and the date of sale to the consumer. esults A. Earlier CDRtool Surveys: Two online surveys were conducted: one in April 2003 and one in March 2005. Participants were asked to track their ignition cycles daily for one month. There were 28 participants in the first study and 40 participants in the second study. Some respondents participated in both surveys, so the two surveys are not entirely independent. The results have not been previously published. They were as follows:

Daily Average Standard Deviation Median Maximum Minimum N

First Study

Second Study

4.9 1.9 4.7 10.1 1.7 28

4.0 1.3 3.9 7.3 0.9 40

There were certain limitations noted with these studies, including the following:  The results were dependant on the participants remembering to record each ignition cycle. As a participant in the first study, the author noted it was possible to forget to record each ignition cycle.  The participants were a select group of people, and were not necessarily representative of the general motoring public.  Each study covered only one month of driving habits. B. Current Retrospective Study: The database was obtained from all SDMs downloaded by Baker Materials Engineering between 2000 and 2006. It included vehicles built from 1995 to 2006 that were involved in collisions in the province of British Columbia, Canada. In all, 135 SDMequipped GM vehicles were examined. Complete data on each vehicle were not always obtained, for various reasons. The average daily ignition cycles were calculated based on the four different start times:

If the SDM was not accessed on the vehicle, the SDM date of manufacture was obtained from the GM VIS.

Collision