Robert T. Lynch, PE, Principal Collision Reconstruction Engineer ::::
All model year 2013 and newer vehicles equipped with an event data recorder (EDR) that are sold in the United States need to adhere to the requirements set forth in 49 CFR Part 563 of the federal standards.
Part 563 establishes minimum requirements for an EDR. In particular, an EDR must record an event if the vehicle experiences a Delta-V (change in velocity) above 5 mph from any direction: front, rear or side. When a vehicle sees a Delta-V greater than 5 mph, the EDR will record 5 seconds of pre-crash speed, braking, and acceleration data, as well as severity data for the impact itself.
If the vehicle does not experience a Delta-V above 5 mph, as with most low-speed impacts, then no event will be recorded. And, whenever no event data is recorded, an upper bound to the severity can be established. That is, for instances where no event data was recorded, it can be established that the subject incident was less severe than that of a 5 mph Delta-V.
Additionally, Part 563 compliant vehicles are required to store an event indefinitely, or for a non-deployment event, until another event occurs that may overwrite it. The data does not erase, even if the vehicle was repaired or has been in use since the incident. Therefore, if there is no data stored in the EDR, the vehicle never experienced an impact above a 5 mph Delta-V throughout the life of the vehicle.
Bottom line: If the severity of an impact is of interest for a 2013+ vehicle, one must not overlook the value of the event data to quantify the collision event, or at least set an upper limit to the severity of the impact.
Robert T. Lynch, PE, Principal Collision Reconstruction Engineer with DJS Associates, can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.