Relation between vehicle travel velocity and pedestrian injury risk in different age groups for the design of a pedestrian detection system

The vehicle travel velocity at the moment of pedestrian contact is considered to be an important parameter that affects the accident outcome. To reduce the vehicle-to-pedestrian travel velocity, a pedestrian detection system using a sensor in a vehicle could be an effective countermeasure. The specifications of the pedestrian detection system will need to be designed properly based on real-world accident situations. Then, the purpose of this study is to clarify the relation between vehicle travel velocity and pedestrian injury severity or fatality risk in traffic accident analyses in order to propose specifications of a pedestrian detection system. We analyzed the relation using the Institute for Traffic Accident Research and Data Analysis (ITARDA) database for 2009 in Japan, considering different factors including a vehicle type and pedestrian age in actual traffic accidents. The results indicate that the percentage risk of fatality was consistent between sedans and light passenger cars at every vehicle travel velocity, rising sharply at a vehicle travel velocity of 40 km/h. Meanwhile, in car-to-pedestrian accidents involving sedans and light passenger cars, pedestrians aged 60 and over faced the higher risk of fatality, which increased rapidly at the vehicle travel velocity of 40 km/h. Therefore, the present study proposes that the specifications of the pedestrian detection system should be designed so that the vehicle travel velocity in traffic accidents could be reduced to 30 km/h or lower, when we consider the decrease of fatality.