A biomechanical modelling study of pedestrian skull and brain injury risk in vehicle collisions affected by head rotational speed

The purpose of the current study is to investigate the influence of head rotational speed on pedestrian skull and brain injury risk while considering the variation of head linear impact speed and contact location. Methods: Pedestrian head-to-vehicle collision simulations are defined by the distributions of pedestrian head–vehicle impact boundary conditions extracted from reconstructions of real-world accidents, where finite element (FE) models of a human body head and vehicle front-end are applied. Results: In general, a higher rotational speed at the instant of contacting with vehicle structures leads to a higher skull and brain injury risk: an increase of 30 rad/s in head rotational speed increases the skull fracture risk on average by 2.1–2.6 times and the AIS2+ (Abbreviated Injury Scale) brain injury risk by 1.7–2.7 times in head-hood impacts; for the contacts on the windscreen, the AIS2+ brain injury risk is below 15%, the effect of head rotational speed could be ignored, though an increase of 30 rad/s in head rotational speed leads to 1.6–2.9 times increase in AIS2+ brain injury risk. Conclusions: Head rotational speed has significant influences on both skull and brain injury risk. The effect of head rotational speed is always adverse for the risk of brain injuries and hood contact induced skull fractures. However, head rotational speed has no apparent effect on the skull injury risk for head-vehicle contacts at the windscreen.