Kinematics of two-wheeler cyclists toward head-ground contact after vehicle collisions

Ground contact is the main source for head injuries of two-wheeler (TW) cyclists in vehicle collision accidents, and there is still a lack of understanding of TW cyclist ground impact kinematics. The purpose of the current study is therefore to investigate the kinematics of TW cyclists toward head-ground contact after vehicle collisions via multi-body modeling of vehicle-to-TW crashes under different scenarios. The results indicate that: a lower relative height of pelvis to vehicle bonnet leading edge and vehicle impact speed are more likely to induce a forward landing kinematics to TW cyclists, while higher values of these parameters are generally associated with the backward rolling or soaring movement; TW cyclists are more likely to drop to the side of the vehicle when the TW is moving or with a large offset distance from the center line of the struck vehicle; the head-first ground contact configuration is generally associated with shorter bicyclists in sedan impacts, bicyclists in MPV crashes and all TW cyclists in the crashes with a high vehicle impact speed (>30 km/h); the head-ground contact velocity of TW cyclists is significantly higher in the rear-end dropping cases, and shows relatively high correlation to vehicle impact speed but low correlation to TW moving speed; the head-ground contact velocity of TW cyclists is strongly affected by the body motion before head-ground impact, and head-first contacts could have an either low or high ground contact velocity. The findings may provide preliminary reference for future strategies of TW cyclist ground injury prevention.