A Study On The Biomechanical Mechanism Of Pedestrian Lower-extremity Injuries In Pedestrian-M1 Category Vehicle Collisions

Vehicles have become indispensable tools in modern society, which have brought enormous impetus to economic growth and social development; however, the number of traffic accidents also has surged forward, resulting in increasingly serious traffic problems. The pedestrian-car collision, one of the highest incidents of vehicles accidents, has drawn more and more attention. The injuries probability of lower extremity among those accidents was more than 1/4. Better investigation on injury mechanism of lower extremity has become a hot researching field, so that more accurate judicial identification of such accidents can be done. Moreover, for the purpose of reducing the degree of lower extremity injuries of pedestrians, further improvement in vehicle design has become a central issue in this field.This paper studied the injuries of lower limbs which are the most vulnerable parts of person, in a pedestrian-car collision. To further illustrate the mechanism and dynamic response of lower extremity injuries in pedestrian-M1 category vehicle accidents, firstly, human lower extremity anatomy was introduced to lay the foundation for mechanisms of lower extremities injury. Then, the pedestrian-vehicle traffic accident site survey, environmental information collection, verification of vehicle damage and pedestrian casualties were detailedly introduced. Typical cases of collisions between cars/mini-buses in M1 category vehicles and pedestrians were selected, and large number of accident data was collected with methods mentioned before. Afterward, the damage processes of those cases were reconstructed with the Total Human Model for Safety(THUMS) and vehicle model. At last, the dynamic response of a pedestrian collision and the kinematics response of lower extremity injuries were analyzed.In this study, Toyota’s THUMS human body FE(Finite Element) model and effectively verified mini-bus/car model were applied to execute the finite element simulation of typical pedestrian-car collision. When setting the initial conditions of vehicle speed in the simulation, a new speed detecting technology called Event Data Recorders(EDR) was employed to determine the exactly speed of the accident vehicle. Application of this technology can provide reliable and accurate data for our study as well as a new identification method to disclose the vehicle speed for accidents judicial identification institution. The simulation indicated not only the pedestrian trajectory in a pedestrian-car collision but also the process of dynamic response for pedestrian lower extremity injuries quite well. Simulating results showed that when the speed of car was 40Km/h in a side collision, the equivalent von Mises force of femur, tibia and fibula were 121.7Mpa, 198 MPa,243Mpa, respectively. As for mini-buses, the value were 122.4 Mpa, 156.4 Mpa and 215 Mpa respectively. The analysis suggests that the dynamic responses of the pedestrian lower extremities in finite element simulation are consist with the real condition of autopsy reports or image data.This study, which relies on Chongqing Bayi Judicial Identification Center for Traffic Accident and is funded by the depth accident investigation project NAIS(National Vehicle Accident Investigation System) of National Administration of Quality Supervision Organization, summarizes the methods of information collection for road traffic accidents in Chongqing. Our methods include information collections of accident site, vehicles and road environment, data collection of vehicle damages and acquisition of pedestrian casualties. Effective use of those methods will not only assist traffic management to better analyze the causes of accidents and further confirm the responsibility, but also provide a large number of basic real data for other related studies(vehicle protection, pedestrian traffic injury protecting measures, etc.). With their significant promoting and advising effects, those methods and simulating results will play an important role in the biomechanical study of lower extremity injury in traffic accident, in the Judicial Identification for traffic accidents and in the study of pedestrian protection measures.