Abstract
In Japan, the number of car models equipped with Event Data Recorder (EDR) has increased in recent year. The EDR is an additional function installed in airbag control module (ACM) to record vehicle and occupant information for a brief period of time before, during, and after a crash event. EDRs record delta-V, indicated vehicle speed, engine speed, seat position, safety belt status, percentage of engine throttle or acceleration pedal, on/off of service brake, and so on. Accordingly, EDR recorded data are promising for accident investigation. However, if the read out data from the EDRs are to be utilized for accident investigation, it is first necessary to examine their reliability and accuracy. The aim of this study is to evaluate the characteristics of EDRs and to understand the performance of EDRs for the improvement of accident reconstruction with more reliable and accurate information.
The analysis is based on two types of crash tests. The first type is the J-NCAP crash tests conducted in 2006–2008 by National Agency for Automotive Safety and Victim’s Aid (NASVA). The analysis of the J-NCAP data is for understanding the EDR characteristics under standardized crash test conditions. The second type is the real-world accident reconstruction tests conducted by National Research Institute of Police Science (NRIPS) in 2007-2009 for evaluating the performance of the EDRs under complex and/or severe crash conditions. The accident reconstruction tests consist of thirteen cases which are frontal barrier impacts (2 cases), frontal pole impacts (3 cases) and a side pole impact, car-to-car impacts (5 cases) and multiple rear-end collisions (2 cases). The pre-crash velocity, maximum delta-V, and delta-V time history recorded in the EDRs are compared with the results obtained from instrumented sensors, an optical speed sensor and high-speed video cameras in those tests.
The conclusions are summarized as follows:
(1) The pre-crash velocities recorded by the EDR were highly accurate and reliable when cars proceeded without braking prior to the collision. However, the braking conditions and the EDR time zero information affected the accuracy and reliability of the EDR impact velocity.
(2) The accuracy and reliability of the maximum delta-V recorded by the EDR decreased under complex or severe crash conditions, as compared to the results obtained from the standardized crash tests. The factors responsible for this result were attributable to the characteristics of the accelerometers used in EDR, the large deformation at the location of the airbag control module, vehicle body rotation in a collision, etc.
(3) The result of car to concrete pole crash test shows that EDR’s recording time for delta-V may not be enough for accident with long duration of crash phase.
Keywords: event data recorder (EDR), accident reconstruction, crash test, delta-V, new car assessment program