Effects Of Pedestrian Age And Collision Speed On Pedestrian Lower Limb Injury

In complex pedestrian-car-road traffic environments,traffic accidents occur frequently as motor vehicle ownership increases rapidly.Pedestrians are the most vulnerable road users.Among them,Pedestrian lower limbs are one of the most vulnerable parts,accounting for 32.8%of the total number of injuries.Although lower extremity injuries are rarely fatal,they require long periods of recovery and can even cause permanent disability,requiring more social resources.Therefore,improving pedestrian protection and identifying relevant parameters that affect the risk of pedestrian lower limb injury will help reduce the risk of pedestrian injury in traffic accidents,and at the same time provide reference for the formulation of laws and regulations and the setting of lower limb injury assessment indicators.Therefore,studying the mechanism of pedestrian lower limb injury has practieal significance at present.This paper sorts out the pedestrian cases that occurred in 2012-2017 from the CIDAS database,and screened the samples according to the selection criteria.The relationship between collision speed,pedestrian age and risk of long bone fracture and severe injury was analyzed,and the distribution of femoral fracture and tibial fracture at different speeds in different age groups was discussed.Based on the logistic regression model,the speed and age risk curves were established,and the interaction between speed and age and the risk of lower limb injuries was discussed.Finally,the risk curves of femur fracture,fibula and tibia fracture were discussed.The results showed that when the speed was greater than 44.3 km/h,the risk of AIS3+ severe injury increased.As the age of pedestrians became larger,the risk of serious injury increased.When the risk of injury to lower limbs was 50%,the age of pedestrians was 33 years.Through the damage risk prediction,it is found that at the same collision speed,the older the age,the more likely the fracture occurs.Therefore,age and speed are two important parameters that affect the risk of long bone fractures and serious injuries in lower limbs.In order to understand more about the pedestrian damage mechanism and to develop more targeted pedestrian protection measures,this paper uses LS-DYNA software to establish a finite element simulation model of vehicle and pedestrian lower limb collision,and deeply studies the pedestrian lower limb models of different ages in different collisions.Biomechanical response,damage mechanism and tolerance limits in speed.Firstly,according to the accident selection criteria,232 pedestrian cases were selected from 569 cases of CIDAS database,and the accident was reconstructed using PC-Crash software to determine the relative collision speed of the accident and the boundary and loading of the relative collision position of the lower limbs and the vehicle.Conditions and verify the accuracy of the simulation.The boundary and loading conditions were imported into the collision finite element simulation model for simulation.The bending parameters,shear force and Von Mises stress of the lower limbs,bending moment,shear displacement and bending angle of the knee joint were compared and analyzed.Logistic regression models between injury parameters and AIS3+ severe injury groups were established,and the effects of age differences on pedestrian lower limb injury were analyzed.The results of this study ean provide a reference for the setting of age-related pedestrian lower limb injury assessment indicators.