38 Trial Lawyer • Summer 2023 module has enough power, and is not severely damaged, it will then write its pre-determined data onto the EDR. Severe damage is relative ACMs have survived a vehicle involved in a high speed, head-on crash where the vehicle burned and was drenched by firefighters, and finally ripped out of the vehicle by the investigator, and that data was still readable. The ACM and EDR are not indestructible, but total loss is rare. Airbags need not deploy to collect data There are two types of recordings in EDRs. Generally, they are referred to as “deployment” and “non-deployment” events. As the name indicates, when the airbag reaches its deployment level, the airbags deploy, and the information is recorded onto the EDR as a “deployment” event. This type of event is generally “locked” and cannot be written over by subsequent events. If the vehicle gets into a crash, and the airbags do not deploy, there is a good chance the ACM woke-up to assess if the deployment threshold had been reached or not. If not, the airbags do not deploy, but by “waking-up” the ACM will often write the info onto the EDR as a “non-deployment” event. This type of event can be written over by subsequent crashes. Which EDR data is recovered depends on the year, make and model of the vehicle. Let’s consider a 2019 Jeep. In this example, after a crash, EDR data shows five seconds of pre-crash data, broken down to the tenth of a second — new reading every 0.10 second. At each .10 second, there is a reading for the speed, accelerator pedal, engine throttle, service brake, engine revolutions per minute (rpm’s), stability control, steering input, raw manifold pressure, powertrain control module, electronic stability control, yaw rate, wheel speed left front, wheel speed right front, wheel speed left rear, wheel speed right rear, electronic throttle control lamp, engine torque applied, PRND status (indicates gear to be displayed), cruise control active, and cruise control system. The report indicates if there were any diagnostic trouble codes on hand and if the passenger seat was occupied and if both occupants were seat belted. It also gives post-crash lateral and longitudinal pulse information. I’ll be honest, that last paragraph was intimidating the first time I encountered the information. If this sounds a little esoteric, I’ll give an example. The diagram at the bottom of this page is a portion of a downloaded EDR. It shows post-crash data, so you can see an average type of readout. In the chart, you’ll see pre-crash data and how the driver is stationary and the rpm’s idle. The driver then accelerated to about 15 mph and the rpm’s went up accordingly before the triggering event (TRG) or crash ocBlack Box Continued from p 37 Above is a portion of a downloaded EDR. It shows post-crash data, so you can see an average type of readout. In the chart, you’ll see pre-crash data and how the driver is stationary and the rpm’s idle. The driver then accelerated to about 15 mph and the rpm’s went up accordingly before the triggering event (TRG) occurred.
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