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 most typically provided.
Understanding EDR Readouts
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.
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 in this brochure may provide a foundation of understanding, but is not intended to replace a proper engineering analysis.
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 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.
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 - A measure of how hard the vehicle is cornering. Lateral acceleration can also be impact induced.
Longitudinal Acceleration - A measure of how hard the vehicle is accelerating or decelerating. Longitudinal acceleration can also be impact induced.
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.
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 actual Delta-V for the crash, engineers utilize both datasets to determine the principle direction of force for the crash.
Vehicle Crash Investigations
Every expert in the Crash 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 through our website.
Peter occupied a variety of engineering positions with vehicle manufacturers. His expertise includes vehicle structures and safety equipment, suspension and dynamics, and driver aids such as ABS and Electronic Stability Control systems. He was involved in nearly every phase of design and manufacturing; from early design, to full vehicle development. He has qualified as an expert in vehicle design, repair, and crash reconstruction in various State and Federal courts.
As the head of our Vehicle Crash practice, Mr. Leiss can help identify the most appropriate expert to assist on your case.