event data recorders

Event Data Recorders

Approximately 99% of new vehicles are equipped with one or more electronic modules that can be downloaded by an accident reconstruction expert. These modules are technically known as Event Data Recorders (EDRs), colloquially referred to as a "black box." EDRs are typically a secondary function of a vehicle's airbag control module, recording and capturing important vehicle parameters in the event of a vehicle collision.

In that way, a passenger vehicle EDR is not the same as the "black box" that continually records data on an aircraft. An EDR does not record any audio and only captures data when a collision occurs. An EDR will capture useful collision-related data, such as vehicle speed, brake pedal status (on/off), accelerator pedal status (%), driver and passenger seatbelt status, steering wheel angle, and engine speed (RPM). Most commonly, this data will be recorded at half-second intervals and include data from five seconds before the collision. However, certain manufacturers such as Ford and Fiat-Chrysler record additional data reported at a higher frequency. This pre-crash data can be used to analyze the locations, speeds, and heading angles of the vehicle in the seconds before impact.

When combined with EDR data from other involved vehicles, a reconstructionist will be able to determine when a driver began to perceive and react to the potential hazard of the other vehicle, how they reacted (e.g. brake or steer), and whether the drivers could have done anything differently to have avoided the collision entirely. EDR data has been studied in numerous technical papers and has been proven to be highly accurate.

Collision reconstructionists use EDR data as an unbiased source of technical information to increase the accuracy of their analyses. This data has been accepted as evidence in countless court trials, both civil and criminal. Envista has all the necessary hardware, software, and knowledge to download data from any passenger vehicle equipped with an EDR.

Heavy Vehicle Event Data Recorders

Heavy vehicles, such as tractor-trailers and buses (school or transit), typically have a "brain" that controls their power generation systems, emission systems, and engine performance. This computerized system is known as the Electronic Control Module (ECM) and often contains an EDR that can store collision-related data that can be downloaded for analyses.

Data captured by these EDRs is similar to what is captured in a passenger vehicle EDR, but usually includes a longer set of data (up to 90 seconds overall) and is reported at less frequent intervals (once per second). Heavy vehicle ECMs also provide a plethora of engine history data in addition to the EDR data, including diagnostic codes and driver log data.

The data in a heavy vehicle EDR is more volatile than a passenger vehicle EDR because it is much easier to overwrite and does not have any built-in protocols to retain the data for long periods of time. Thus, downloading a heavy vehicle EDR is typically more time-sensitive than a passenger vehicle EDR. Envista has the knowledge and capability to download heavy vehicle EDRs and apply the information to an accident reconstruction analysis.

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