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 Technical bulletins
June 2015

A Crash Course on Electronic Crash Data

By Jean-François Goulet Eng., P. Eng., M.A.Sc.,

Technology is everywhere at home, in your office and in your car. In your car the technology is used for entertainment but also for safety reasons. For example, all cars equipped with airbags have a computer, often referred to as a "black box" whose purpose is to sense a collision and then quickly decide whether the collision is severe enough to warrant deploying the airbags. As a bonus feature, it may also record some electronic crash data. Some crash data may have been recorded in the seconds leading to the crash and contain information about what the driver and the car were doing. The crash data may also include information about the severity of the collision, the use or non-use of the seat belt, the seat position and even the approximate size of an occupant. That data can be useful for your cases as it may shed some light on what happened.

The forensic engineer specializing in accident reconstruction will take that data into consideration, but whenever possible he will also do an independent reconstruction of the collision using the physical evidence available such as vehicle damage and tire marks on the road.

Interpreting the Data

The electronic crash data must be carefully analyzed. For example, the data may suggest that a car was travelling very fast before impact, but it may be that its wheels were simply spinning on ice. The data may indicate that a car was not moving at impact, but it may be that it was skidding with its wheels locked. The engineer must also make sure the electronic crash data is related to the incident being investigated as some "black boxes" can record several events. If the collision compromised the electrical system and resulted in a power interruption while the crash data was being recorded, some of the data may simply be default values that were set at the factory.

Black box
Black box data retrieval

Going, Going, Gone!

The electronic crash data may be volatile. Depending on the system, it may be overwritten by subsequent collisions, or it may be erased after a number of engine ignition cycles, or it may be overwritten if the engine is left running after a collision.

The Airbags did not deploy? Some crash data might still have been recorded

Electronic crash data may be recorded even if the airbags were not deployed. This can be very useful in a typical rear-ender case in which the vehicles were not damaged and the issue is collision severity. Without the electronic crash data, the engineer can only say that the collision severity was below damage threshold, but how much less might not be possible to say.

The electronic crash data may also be useful in cases of suspected airbag malfunction. For example, if a collision appears to have been severe enough to warrant the deployment of the airbags but that they were not, the crash data may indicate whether a deployment was commanded or not, whether the airbag malfunction light on the instrument panel was turned on, or whether some trouble codes were present before the collision.

With ABS-equipped vehicles, the electronic crash data may be the only way to know whether the driver braked or not.

Commercial vehicles such as tractor-trailers and buses may also have the capability of recording crash data. Companies managing a fleet of commercial vehicles may have GPS logs that can contain useful information. You have a bicycle case? The rider might have been using a bike computer that recorded some useful data or perhaps one of those wearable body movement recording devices.

If you are unsure whether the vehicles involved in one of your claims have some electronic crash data, give your accident reconstruction expert a phone call and he should be able to help.

To learn more on Electronic Crash Data or to organize a training seminar at your office, please contact Mr. Jean-François Goulet, Eng., P. Eng., M.A.Sc.