Simulation of occupant kinematics and injury risk assessment in a passenger bus rollover

Although rollover do not occur as frequently as other types of accidents in passenger bus, the number of occupant killed or seriously injured is five times higher than other fatal crashes. The ECE-R66 regulation is widely employed to guarantee a proper design of passenger bus superstructure regarding rollover crashworthiness. Nonetheless, considerations on occupant injury severity are not implemented to the regulation criteria. This work aims to investigate the kinematics and injury risks of hybrid III 50th percentile adult male occupants during passenger bus rollover test according to the ECE regulation. Explicit dynamic finite element analyses were performed via Hypercrash and RADIOSS solver under several cases of different bus structural rigidity, occupant seating positions and design conditions. The injury measures were analyzed based on Abbreviated Injury Scale concerning the head acceleration curves during impact as well as the forces and moments at the occupant's upper necks. Simulation results demonstrate that occupants at rollover-window position are likely to be seriously injured than the gangway-positioned occupants owing to direct head collision during rollover. Although the probability of skull fracture is not high, the risks of neck injuries are fatal from the extreme axial neck force. Despite the fact that the bus designed according to ECE regulation can essentially decrease the passenger's injury severity, the probabilities of serious neck injuries (AIS3) is up to 88% and the probability for critical neck injuries (AIS5) is as high as 34%.