In order to investigate traffic accidents and determine their causes, first it is necessary to clarify the circumstances in which they occurred. The traveling trajectory of the vehicle(s) involved prior to the collision is an important part of such clarification. In this study, we conducted experiments on a vehicle with an event data recorder (EDR) and examined its pre-collision trajectory estimated from data recorded by EDR, aiming to obtain such trajectories based on quantitative data recorded by EDRs. In the experiment, the test vehicle with an EDR had also a high-precision measuring system onboard that determined the vehicle’s position by a global positioning system (GPS) and measured vehicle behavior. The vehicle was driven on a test course, with the EDR and the measuring system recording their data simultaneously. The vehicle speed and yaw rate data recorded by the EDR were integrated to get an estimated trajectory of the vehicle. The comparison of the EDR-based traveling trajectory with the GPS positioning results revealed generally similar results when the vehicle behavior changed slowly (rounding curves, etc.). When the vehicle behavior changed sharply (zipping through a slalom, etc.), the difference between the EDR-based traveling trajectory and the GPS positioning results was larger than when it changed slowly. When the vehicle behavior changed sharply, the EDR-based traveling trajectory could not be fully reproduced because the sampling frequency of the EDR-based vehicle speed and yaw rate was lower. The results of this experiment suggest that the traveling trajectory can be estimated from the EDR-based vehicle speed and yaw rate if the vehicle behavior changes slowly. The results also indicated that, to get the traveling trajectory while the vehicle behavior keeps changing rapidly, we need to make the EDR sampling frequency higher than the current ones.
