Vehicle Black Box (EDR) Reports 101 Expert Article

The data readout from an automotive Event Data Recorder (EDR) or vehicle "black box" is often a topic of curiosity. This data was designed by engineers to be analyzed by engineers toward the purpose of understanding crash dynamics and improving vehicle safety; it is necessarily technical and can be confusing if you're not experienced in reading these reports.

In this article, we provide an introduction to EDR readouts with a focus on some of the data that is typically provided.

Vehicle Black Box Data Expert Witness

Understanding EDR Readouts

Data Variability

The data provided, as well as the formatting of the data provided by an EDR readout is going to vary substantially across vehicle makes and models. You may also notice significant differences in data readouts from vehicles of the same make and model, but of different production years.

As of 2012, the National Highway Traffic Safety Administration (NHTSA) has regulated EDR data regarding the content, accuracy, collection, storage, and retrievability. Part of this regulation mandated that a vehicle store EDR data if the airbag control system measures an impact of greater than 8kph (4.8 MPH) over 150 milliseconds, regardless of direction of the impact.

EDR readouts are designed by engineers in a format that is intended to be reviewed and analyzed by other engineers; for this reason, the data is necessarily technical. The information provided here may provide a foundation of understanding, but is not intended to replace a proper engineering analysis.

Pre-Crash Data

The data in these tables provides insight on the status of vehicle safety systems as well as vehicle speed, throttle application, and brake-use leading up to the crash.

The data in these tables can be utilized by engineers to back vehicles up from the point of impact to understand placement of the vehicles and what was occurring prior to impact. This data can be helpful confirming witness testimony or clarifying conflicting testimony.

Pre Crash Data Image

Pre Crash Data Image 2

Vehicle Forces

The output of crash data varies greatly across different vehicle makes and models, but will typically be presented in common engineering measurements. In this section we discuss some of the most common datasets that are used in CDR reports.

Pre Crash Data Image (Vehicle Force)

Steering Wheel Angle Image

Steering Wheel Angle - Steering wheel position, from 0 º if wheel is in the neutral position, to +/- 1080 º if wheel is turned 3 times to either direction.

Lateral Acceleration Image

Lateral Acceleration - A measure of how hard the vehicle is cornering. Lateral acceleration can also be impact induced.

Longitudinal Acceleration Image

Longitudinal Acceleration - A measure of how hard the vehicle is accelerating or decelerating. Longitudinal acceleration can also be impact induced.

Yaw Rate Image

Yaw Rate - A measure of the rate at which the vehicle is changing its degree of rotation.
It is important to note that this measurement is a rate.

Roll Rate - A measure of the rate at which the vehicle is changing its degree of roll.
It is important to note that this measurement is a rate. Positive/negative convention varies across vehicles and is defined in each report.

Roll Rate Image

Delta-V - The change in velocity is most commonly calculated from accelerometer data in the Airbag Control Module and presented for longitudinal and lateral directions. In order to determine the actual Delta-V for the crash, engineers utilize both datasets to determine the principal direction of force for the crash. The amount of time that the change of velocity takes, or Delta-T, can also be determined through review of this information and is frequently of importance for understanding the accident.

Vehicle Crash Investigations

Every expert in the Crash Reconstruction practice at Robson Forensic came to our firm after longstanding careers in the automotive industry. As automotive engineers they understand vehicle dynamics and how vehicles respond before, during, and after a crash. Our engineers, through their education and training, have a thorough understanding of physics and vehicle systems and how they affect the nuances of crash reconstruction.

To discuss your case with a subject matter expert, submit an inquiry or call us at 800.813.6736.

Featured Expert

Chase Nalls, Automotive Engineer & Crash Expert

Chase Nalls

Automotive Engineer & Crash Expert
Chase Nalls is an automotive engineer specializing in the design and performance of airbag and restraint systems. He applies his expertise to forensic casework involving crash reconstruction and… read more.


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