Differential Analysis Of Brain Injury Between Two-wheeler Cyclist And Pedestrian Based On Accident Reconstruction

As the most vulnerable road users,pedestrians are the first to receive attention for their safety.To better protect pedestrians,countries have enacted pedestrian protection legislation and pedestrian protection test protocols.With the proliferation of two-wheeler accidents,academics are concerned about the safety of cyclists and are considering the establishment of corresponding test protocols to assess the protection capability of vehicles.The head model impactor impact test has become a widely accepted test method for pedestrian head protection as the current pedestrian protection test protocol.Scholars have assessed the applicability of this method to the protection of cyclists by analyzing the kinematic variability during crashes between motorists and pedestrians,and the key causal factor for traumatic brain injury in vulnerable road user(VRU)head injuries is the deformation of brain tissue by caused by the deformation of brain tissue.In this paper,a total of 38 accident cases with detailed injury information,19 pedestrian and 19 two-wheeler accidents each,were screened based on the Changsha In-depth Traffic Accident Investigation Database(IVAC).Accident reconstruction and head damage reproduction were completed by a coupled multi-rigid-body-finite element analysis method.Differential analyses were conducted on cyclists and pedestrians in terms of four aspects: head human-vehicle collision boundary conditions,head injury parameters based on the kinematic response,brain injury parameters based on brain tissue deformation response,and effective head mass.The results show that two-wheeled vehicle crashes occur mainly in the low-speed range compared to pedestrians.The head wrap-around distances of cyclists and pedestrians were the same,but the head collision locations of cyclists were mainly located in the middle area of the windscreen compared to pedestrians.The relative head impact speed and head impact angle of the cyclist were significantly lower than those of the pedestrian,and there was some variability compared to the values specified in the pedestrian head protection test protocol(40 km/h,65°).The impact speed of the head model impactor was set at 54.71 km/h and the impact angle was set at 40.02° to better reflect the head impact of the cyclist in the accident.A comparison of the head injury parameters based on the kinematic response shows that the overall risk of head injury is higher for pedestrians than for cyclists.During a human-vehicle collision,the risk of skull fracture and subdural hematoma(SDH)injury does not exceed 20%for cyclists and pedestrians,with pedestrians having a higher probability of suffering skull fracture and SDH injury risk.Comparative analysis of brain injury parameters based on the deformation response of brain tissue showed that: using the maximum principal strain(MPS)to assess the probability of suffering a brain contusion and diffuse axonal injury(DAI)injury did not exceed 20% for both cyclists and pedestrians,and cyclists had a higher probability of suffering a brain contusion and DAI injury compared to pedestrians;using the cumulative strain damage measurement criterion(CSDM)to predict,cyclists were found to have a higher probability of suffering a brain contusion and DAI injury compared to The opposite prediction of DAI injury risk by MPS and CSDM may imply that there is a difference in the predictive validity of the two injury assessment criteria for DAI injury risk.A comparative analysis based on effective head mass showed that the head model impactor in the current pedestrian protection test protocol is not suitable for cyclists.The mass of the head model impactor in the current test protocol should be reduced to meet the protection of cyclists.This study provides a theoretical basis for optimizing the current pedestrian protection test protocol by analyzing the differences in craniocerebral injury between cyclists and pedestrians,so that it can improve the protection of two-wheeler cyclists in vehicles and has some practical significance for the development of the automotive safety industry in China.