Effects of pre-impact pedestrian position and motion on kinematics and injuries from vehicle and ground contact

Abstract

Pedestrian injuries from vehicle collisions arise from both the vehicle and the ground contact. Early work showed that above 7 m/s collision speed, the vehicle impact is responsible for higher severity injuries. There has now been considerable development of car design to reduce pedestrian injury severity and thus the role of the ground impact in causing severe head injury should be reexamined. A Madymo model is used to examine the relative severity of the road and vehicle impacts and the effect of pedestrian motion before impact. Results show head impact locations on the vehicle are predictable but their severity varies with pre-impact stance by up to 30%. In contrast, impacts between the body region and the ground are highly variable. The stiff ground results in high contact forces, but the ΔV for ground impact is less severe than the vehicle impacts, showing a higher momentum change in the latter. Evaluation of the HIC₃₆ and 3 millisecond (ms) acceleration criteria for the head and the 3 ms for pelvis and chest also shows that the ground impact results in far more unpredictable injuries compared to the vehicle impact. However, at all speeds head 3 ms scores from the vehicle impact are higher than for the ground contact. Both the HIC₃₆ and the 3 ms acceleration criteria for the head show that the relative importance of the ground impact compared to the vehicle impact reduces with vehicle impact speed. At low to medium speeds, the predicted chest 3 ms responses from the vehicle and ground impacts are similar on average, but at high speeds the vehicle impact is more severe. At low speeds, pelvis 3 ms accelerations from the ground impact are higher than for the vehicle impact, but this trend is reversed at higher speeds.

Keywords:

• Pedestrians
• impact variability
• vehicle and ground impact
• injury criteria