A Study On Dynamic Responses And Protections Of Pedestrians In Bus-pedestrian Frontal Collisions

Research in prevention of pedestrian vehicle traffic injuries has focused ondesign of safer passenger cars. However, it is not neglected that pedestrian casualtiescaused by bus impact are also common.This thesis aims to studying dynamic responses and injury biomechanics of thepedestrian in bus-pedestrian collisions and the influence of impact speed, pedestrianinitial state and the frontal structure on pedestrians’ responses. Through the analysisof those results, this study aims to provide some improvement measures andreferences on the design of bus frontal structures for pedestrian safety protection.A real accident involved a pedestrian and a bus was reconstructed to understandthe pedestrian kinematics response. Besides, the injury parameters related withpedestrian head, thorax, pelvis and lower extremities were analyzed and comparedwith the research data.Simulation models of a flat-front bus and a bonnet-front passenger car weredeveloped by using a finite-element (FE) program and a multi-body (MB) dynamicsprogram. Simulations of bus-pedestrian collisions and car-pedestrian collisions werecarried out at different impact speeds. The dynamic responses and injurybiomechanics of the pedestrian were analyzed and the differences and similaritiesbetween the responses of two types of vehicle were indicated.The influence of initial state of pedestrians on dynamic responses and injurybiomechanics were analyzed by using the MB model. The results demonstrated thatthe initial state of pedestrians has significant influences on their kinematic responsesand affected their injury parameters in various degrees.The influence of geometric parameters and stiffness of the bus frontal structureswere analyzed by using the orthogonal experiment and the factorial experimentrespectly. Based on the former results, a front protection system (FPS) was designed,testified and improved by simulations.The results demonstrate that the head injury is the main reason that leads topedestrian fatalities and the thorax and pelvis could easily suffer severe injuriesduring the collision with bus. The pedestrian initial state affects the rotationorientation and the thrown patterns of pedestrians significantly. The geometricparameters of the frontal structures of the bus have great influences on head and lower extremities injuries. Reducing bus front structure stiffness evenly can reduce theinjury risks for pedestrian remarkably. However, when the local stiffness is reduced,the local injuries of pedestrian will decrease but other regions of the body will sufferseverer injuries. Adding the FPS to the bus front is able to diminish the injury risk forpedestrians effectively.