Injury Risk Assessment at the Timing of a Pedestrian Impact with a Road Surface in a Car-Pedestrian Accident

In a car-pedestrian accident, there are two major phases that exist when a pedestrian injury occurs. One is the timing of a pedestrian colliding with a car body (denoted initial collision hereafter). The other is the timing of a pedestrian colliding with a road surface (denoted secondary collision hereafter) which occurs after the initial collision. Up until now, pedestrian protection has been considered mainly for the initial collision, and several countermeasures have been developed by automobile manufacturers. On the other hand, pedestrian protection issues in a secondary collision have not been considered in depth, therefore, collision phenomenon and pedestrian protection methods in a secondary collision have not been investigated deeply. The purpose of this study is to clarify the risk to a pedestrian in a secondary collision using traffic accident data as well as a computer simulation analysis method. First, the reality of accidents relevant to a secondary collision was investigated by using car-pedestrian accident data. As a result, it was found that the rate of road surface causing pedestrian injury is twice the rate of injuries caused by a bonnet and fender of a car, both of which are targeted by regulations of pedestrian head protection worldwide. Next, the phenomenon of car to pedestrian collisions was analyzed by using JARI pedestrian models which are calculated by MADYMO (Tass) and these base models’ biofidelity was validated by using Post Mortem Human Subject test data. Computer simulation analyses were carried out in a total of 45 conditions which consisted of combinations of three kinds of vehicle models (sedan type, sports utility type, van type), five kinds of pedestrian models (six-year old child, fifty-year old male and female, seventy-year old male and female, because such ages are frequently involved in car-pedestrian accidents) and three collision velocities of car to pedestrian (20, 30, 40km/h).The results showed that the Head Injury Criterion (HIC)15 value in a secondary collision was higher than that of the initial collision in 38 of the 45 conditions. In addition, the HIC15 value in 30 of those 38 conditions was over 2000. Based on this analysis, it became clear that it is necessary to not only focus on the initial collision but also focus on a secondary collision in car-pedestrian traffic accidents. For their future plans, the authors are going to conduct additional analysis by using additional sizes of human models and additional analysis conditions, and also have a plan to develop more effective countermeasures for pedestrian protection in secondary collisions to reduce pedestrian injuries which are generated by secondary collisions in the real-world.