Pedestrian crashes are the most frequent cause of traffic-related fatalities worldwide. The high number of pedestrian accidents justifies more active research work on passive and active safety technology intended to mitigate pedestrian injuries. Post-impact pedestrian kinematics is complex and depends on various factors such as impact speed, height of the pedestrian, front-end profile of the striking vehicle and pedestrian posture, among others. The aim of this study is to investigate the main factors that determine post-crash pedestrian kinematics. The injury mechanism is also discussed.
A detailed study of NASS-PCDS (National Automotive Sampling System - Pedestrian Crash Data Study, US, 1994-1998), showed that the vehicle-pedestrian interaction in frontal crashes can be categorized into four types: “Thrown forward”, “Wrapped position”, “Slid to windshield” and “Passed over vehicle”. A Principal Component Analysis (PCA) was performed and 11 independent factors were identified for study from a set of 26 variables, as defined in NASS-PCDS. Pedestrian-vehicle size ratio and the impact speed are the two most influential factors that determine post crash pedestrian kinematics. However, the standing posture of a taller pedestrian can also cause rotational movement around the local Z axis, leading to a face-up/down mode of head-face impact before falling on the hood.
The findings from the NASS-PCDS study were also confirmed and verified with the help of numerical simulations performed using two modified JAMA human FE models. An adult model (male, 175cm and 72kg) and a properly scaled child model (6 years old, 120cm and 21kg) were effectively utilized to investigate the post-crash kinematics in different conditions.
