Article: "EDRs and restraint systems," Davies, B.

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2010 Vol. 5 Iss.2

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The International Compendium for Crash Research

Volume 5 Issue 2

Volume 5, Issue 2 - Fall 2010

Time Development of Delta-V & PDOF

during a collision

Crash Data Collection Guide for GM Airbag Electronic Control Units

Beyond the Drag Factor Accident Reconstruction Testing

Speedometers

Post-Collision Readings & Vehicle Impact Speeds

Filament Analysis of Light Bulbs

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Collision: The International Compendium for Crash Research

Fall 2010

www.collisionpublishing.com

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 features 10

Fall 2010

Model For Analyzing Single Vehicle Rollover Accidents

By Juan M. Herrera And Anselmo Najera G.

22

Devices For Accident Reconstruction Testing Beyond The Drag Factor

By Brad Muir And Jon Northrup

32

Post-Collision Speedometer Readings And Vehicle Impact Speeds

By Robert D. Anderson

42

Determining A “Best Effort” Heavy Truck Acceleration Rate Based On Time, Weight & Distance

The cover shot was taken at the 2010 ARC-CSI Crash Conference by Sam Morris, Las Vegas Sun. This image is used with permission from Library Services Specialist, Las Vegas Sun, Greenspun Newsroom. Cover layout and design by Scott Baker, Collision Publishing, LLC. © 2010 Collision Publishing, LLC. All rights reserved.

By David A. Stopper, Phillip D. Darnell And Christopher C. Voeglie

48

Light Bulb Filament Analysis From The 2010 ARC-CSI Crash Conference

By Christopher J. Brignola

58

Crash Data Collection Guide For GM Airbag Electronic Control Units

By Donald Floyd

76

10

Time Development Of Delta-V Recording And PDOF During A Collision

By Bruno Schmidt

86

Vehicle Navigation GPS Units Could Be The Overlooked EDR

By Timothy J. Reust

92

The Butterfly Effect Of Crash Investigations

By Robert Miller

98

58

EDRs And Restraint Systems

By Bill Davies

102

86

Reading Data From International Medium And Heavy Duty Truck Electronic Control Modules

By Dustin Nolen and Gary Johnson

108

Cone Of Departure: A Good Idea, But Not A Law

By Wade Bartlett and Bruno Schmidt

www.collisionpublishing.com

Collision Magazine 3

EDRs and

Restraint Systems

Bill Davies

Collision Safety Institute Canada, Ltd. www.collisionpublishing.com

Collision Magazine 99

sion that perhaps the pretensioners fired at the time of the non deployment, so that there would be a different seat belt situation in the subsequent frontal deployment. This would only be true if we knew the ability of the module configuration with the restraint system we are looking at. Some ACM’s might fire a pretentioner on a non deploy, but as an example, GM systems will not deploy pretensioners until involved in a full frontal deployment. Some pretensioners may be deployed in rollover situations, or impending side impact situations. Remember that all these systems are predictive in nature, and want to be up and running before the big event.

"

For example, the ACM may be configured for frontal bags and side bags that are an option in the vehicle. If someone were to use an ACM for a vehicle without the side airbag option, then it would be impossible for the ACM to deploy the side airbags in a vehicle collision if the ACM was not configured for it. Hence Bill’s first law of reconstruction: “If you do something abnormal, (install an ACM configured for no side impact bags) and you get something abnormal, (non deployment of side impact bags when we would have expected them), then it’s probably normal” (outcome being the impossibility of a deployment signal to the side airbag.)

If you do something abnormal , and you get something abnormal , then it’s probably normal

If you have a passenger side seatbelt with a pretensioner deployed, you will have a seatbelt as tight as a guitar string, if the seat belt was not worn during the collision, or the passenger seat was not in use. ( depending upon PPS or not)(above) You have to look at this against the event data. In our example here, the front passenger bag fired, and the seat belt pretensioner fired. If there was a passenger presence system in this car, it would mean the passenger space was occupied, and that the passenger was not belted. If there was no PPS, then you would not know that the passenger was unbelted until you confirmed that there was a passenger in the car.

Most belts that have a fired pretensioner will lock in that position, and never spool back into their retractors. This will tell you the length of the belt in use, (and perhaps identify who was driving) and let you see the web loading. This may tell you whether the belt was worn properly, or whether previous belt damage affected the load on the webbing.

"

“Seat Belt Buckled” in a report will indicate what the ACM saw the last time it looked at the data. There may be some occasions when the event data write is not complete, from a power interrupt or failure, so the information would be incorrect from an unwritten value. The physical evidence will always prevail. You can sometimes verify the buckle switch with a diagnostic tool, if the vehicle is still electrically viable. If you get a change of buckle status, this means that at some time in the key cycle, the buckle changed status. This could mean that you buckled the seat belt up after you put the vehicle in gear, or that the belt was unbuckled to reach around to get something in the back seat. Again, the physical evidence will help you unravel the sequence of events.

Remember that when looking at passenger airbag suppression systems that when the airbag switch is turn off, the suppression system is turned on. Semantics within the report are important. Terminology of late indicates that the passenger bag is “suppressed”.

One of the other things that we try and verify during our research, is that the ACM from the wrecked vehicle is the original ACM for that vehicle, or, that it is the proper replacement part for that vehicle.

We know that in some ACM families, the connectors are the same, and that it is physically possible to attach an ACM that is generic, but not the specific part for that vehicle. There are two aspects when we talk about specific replacement part for the vehicle, and this may require a trip to the dealer to verify. You might be able to ascertain that the ACM is for the year and model of vehicle that you are concerned about. But is it the proper ACM for the year, model and option content of the vehicle in question? Some ACM’s are configured for the vehicle options that they are installed within.

100 Collision Magazine

You may also see ACM’s that are self-configuring. This means when they are installed at the assembly facility, on first wakeup they do a sweep around the car to see what restraint systems are in the car, (frontal bags, passenger suppression system, thorax airbags, side impact airbags, either roof or side mounted, or rollover airbags) and then configure for these systems. Once set however, if these ACM’s are subsequently put into a vehicle without some of these options, you would have some MIL or airbag light on, and specific airbag codes for the airbag systems that were not on the subsequent vehicle, but being looked for by the self configured ACM.

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Passenger seat belt buckle status is usually valid, and not a default value, if the vehicle is equipped with PPS. Vehicles with forward seat position sensors will also turn off “suppress” airbag deployments.

These can be physically located during a vehicle inspection on the seat track.

A word of warning here would be appropriate. This is one of the main reasons that we discourage the practice of VIN “spoofing”, or trying to get an image out of a car by using another VIN. While initially this may prove helpful in an investigation, it sometimes will raise questions you can’t answer, or present fault codes you don’t understand. Such would be the situation in this scenario of ACM’s configured specifically for a particular set of restraints within a vehicle.

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Collision Magazine 101