A Study Of Risk Prediction And Protective Measures For Pedestrian Injuries Based On Accident Reconstructions

Pedestrians in a public transport environment are the most vulnerable road users, and the rate of injury and death is very high in the reported traffic casualties. In China, nearly 100,000 people died in traffic accidents every year, in which pedestrians accounted for about one-quarter. The head and neck juries in vehicle-pedestrian collisions accounted for around 30% of all injuries on the different body regions, and at the same time the head injury often resulted in a fatal consequence. It is therefore significant for safety community to conduct the researches on causation of vehicle-pedestrian accident and injury mechanism of the head-neck for improving safety of traffic environment and vehicle to prevent pedestrian accident and injuries.The purpose of the current paper is for study of the law of injury and prediction of risk of head-neck injuries. For the purpose, multi-body model and finite element model were used for accident reconstructions and analysis of the real world accident. The calculated injury parameters were compared with the observed injuries in real world accidents. Furthermore the protective effect of airbag and pop-up hood are analyzed and proposed. The paper selected 14 cases of real world accidents for reconstruction analysis. A multi-body pedestrian model developed by Chalmers University was used to analyze the dynamic responses of pedestrian, and the injury parameters such as head acceleration, HIC, force of neck were calculated.Regression method was used to build up a regression model of head-neck injury parameter and velocity of vehicle. The results indicated that velocity of vehicle is the main factor related to the severeity of the pedestrian injury. The multi-body model and the finite element model were used to simulate pedestrian collides with vehicle at 40km/h and predict the injury risk of head-neck. The results show that the two models can predict the AIS3+ injury risk of head-neck well, but it is better to use finite element model to study the injury caused by stress and strain of brain impact to the car front.Two real world accidents were used to study the protective effect of pedestrian airbags and pop-up hood. The results showed that the protective effect is good when the head impact on the area of airbags, and HIC value decreased by 55.7%. The protective effect is not obvious when the head impact area is out of the region of airbags, but HIC value still decreased by 6.3%. Optimazation was carried out by using the genetic algorithm in terms of the design parameters of the two protective devices such as the stiffness of pop-up hood, the mass flow rate, the permeability coefficient of the fabric and the ignition time under the condition which the pedestrian and vehicle collided at 40km/h. The optimization results showed that by adopting these optimized design parameters we can reduce the injury risk greatly and meet the requirement of the regulations.This study provided a useful reference for prediction of pedestrian head-neck injury in the accident and evaluation of protective effect of pedestrian airbags and pop-up hood. The simulation conclusions can be used as a reference to vehicle safety design.