Car Accidents and Black Box Data


In airplane accidents, investigators and experts often refer to “black box data”, and that terminology has carried over and is sometimes used in the context of car accidents too.  However, in car and truck accidents, the more accurate description of black box data is Event Data Recorders (EDR).  Of course, nothing is ever quite that simple because some experts and manufacturers refer to an Event Data Recorder more specifically as an Airbag Control Module (ACM), Restraint Control Module (RCM) and System Diagnostic Module (SDM), etc.  But regardless of what you call it, these devices can be invaluable in determining what happened in a car or truck accident.  Read on to find out how EDRs came into existence, how they work, what information they record and why it is important to know what to do immediately after an accident so that this valuable information is not lost.

Event Data Recorders have been around since 1974 when General Motors introduced them.   Ford, Toyota and Chrysler eventually followed suit, and now almost all vehicles have an EDR. Initially, manufacturers installed EDRs so they could gain technical information about their vehicle’s performance in a crash and, as a result, the data could only be retrieved by the car’s manufacturer, some of whom jealously guarded the information. Eventually, as EDRs became more prevalent, law enforcement, accident reconstructionist experts and others could access the data instead of it being reserved solely for the use of the vehicle manufacturer.

Just as their name implies, Event Data Recorders can record data from an event i.e, the moments before, during and after a car or truck accident. The amount of data recorded depends upon the type of EDR installed in the vehicle but can include the speed of the vehicle, engine RPM, braking inputs, steering inputs, change in velocity (longitudinal and lateral) seatbelt usage, seat occupancy, engine trouble codes, ignition cycles, traction control, cruise control and more.  All of this information can help law enforcement, investigators and attorneys piece together what really transpired in a car or truck accident.

The last thing you want to do is lose this valuable evidence, but it is possible.   Some vehicles have EDRs that lock after an event and others have unlocked systems.  If you are involved in a car or truck accident and your EDR is an unlocked system, then certain activities can cause the data to be overwritten and lost.  The two most common ways for overwriting to occur is the occurrence of a more severe event or after the ignition has been cycled a set number of times (as determined by the manufacturer).  For example, the manufacturer may have designed the EDR to overwrite after 5 ignition cycles.  Even if the vehicle is not drive-able because of the severity of the accident, it can be relatively easy to reach 5 ignition cycles.  For example: after the accident, a bystander or law enforcement turns the vehicle off for safety.  The ignition may be cycled back on for a variety of reasons: (1) a law enforcement officer needs to complete an accident report and wants to check the mileage of the vehicle or if taillights or some other feature of the vehicle is operational; (2) the tow truck driver needs to turn the ignition on to gather mileage information or to shift the vehicle into neutral and he may do this both picking up the vehicle and off-loading it; (3) an insurance appraiser or investigators cycle the ignition to check mileage information and other data. If you wait to get a lawyer involved, all these folks may cycle the ignition so many times that the crash data is irretrievably lost.   Of course, the information from EDRs is not needed in every crash but it can make a critical difference in some cases.

If you or a loved one has been injured in a car or truck accident, we urge you to hire an experienced attorney, even if it is not us.  We feel so strongly about it that we have developed this checklist of questions you should ask when hiring an injury lawyer.  In the meantime, the award-winning attorneys at the Law Offices of John Day are here to help if you decide to hire us.  We offer a free initial consultation and we handle all accident cases on a contingency basis so we only get paid if we recover money for you and your family.  Give us a call at any of our Middle Tennessee locations and, as always, we will come to you (wearing a mask) if you can’t come to us for any reason.

Nashville: 615-669-3993

Murfreesboro: 615-867-9900

Brentwood: 615-742-4880

Toll-Free: 866-812-8787


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