Accident Reconstruction with Data Recorded by Electronic Control Units in Vehicles with a Pre-crash Safety System

Data recorded by vehicle-mounted electronic control units (ECUs) are highly useful in traffic accident reconstruction. In this context, event data recorders (EDRs) are airbag ECU components used to log information from crash events, typically providing data on speed, accelerator operation, RPMs and brake lamp activation for a period of around 5 s before a collision. Information on accelerator/brake lamp operation is very useful in understanding pre-crash driver actions, but the accuracy of EDR speed data must be checked in this regard. Such data are unlikely to reflect actual speed during brake-related skidding, for example, as they are determined from the rotational speed of the drive train. Thus, it is important to check the accuracy of EDR speed data in accident reconstruction. Meanwhile, pre-crash safety systems (PCSs) are also becoming more widespread in automobile usage today. Such systems automatically apply braking in hazardous situations, and the relevant data recorded in the ECU are promising in the field of accident reconstruction. This study involved physical tests in the form of simulated rear-end collisions and the collection of recorded PCS data at the post-test stage. A Subaru Levorg was used as the test vehicle equipped an EyeSight version 3 unit, which incorporates dual color stereo cameras near the rear-view mirror. A PCS provides single-frame data from the point at which system braking is applied, with information including vehicle speed and driver actions. The speed data produced were highly accurate, having been collected before hard braking was applied. Checking to determine the influence of PCS automatic braking on EDR speed data showed that high accuracy was maintained. This is attributable to the PCS limiting deceleration from automatic braking to less than 8.0 m/s² (0.82 G) in order to prevent skidding.