Objective: This study aimed at investigating the effects of vehicle impact velocity, vehicle front-end shape, and pedestrian size on injury risk to pedestrians in collisions with passenger vehicles with various frontal shapes. Method: A series of parametric studies was carried out using 2 total human model for safety (THUMS) pedestrian models (177 and 165 cm) and 4 vehicle finite element (FE) models with different front-end shapes (medium-size sedan, minicar, one-box vehicle, and sport utility vehicle [SUV]). The effects of the impact velocity on pedestrian injury risk were analyzed at velocities of 20, 30, 40, and 50 km/h. The dynamic response of the pedestrian was investigated, and the injury risk to the head, chest, pelvis, and lower extremities was compared in terms of the injury parameters head injury criteria (HIC), chest deflection, and von Mises stress distribution of the rib cage, pelvis force, and bending moment diagram of the lower extremities. Result: Vehicle impact velocity has the most significant influence on injury severity for adult pedestrians. All injury parameters can be reduced in severity by decreasing vehicle impact velocities. The head and lower extremities are at greater risk of injury in medium-size sedan and SUV collisions. The chest injury risk was particularly high in one-box vehicle impacts. The fracture risk of the pelvis was also high in one-box vehicle and SUV collisions. In minicar collisions, the injury risk was the smallest if the head did not make contact with the A-pillar. Conclusion: The vehicle impact velocity and vehicle front-end shape are 2 dominant factors that influence the pedestrian kinematics and injury severity. A significant reduction of all injuries can be achieved for all vehicle types when the vehicle impact velocity is less than 30 km/h. Vehicle designs consisting of a short front-end and a wide windshield area can protect pedestrians from fatalities. The results also could be valuable in the design of a pedestrian-friendly vehicle front-end shape. [Supplementary materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention for the following free supplemental resource: Head impact conditions and injury parameters in four-type vehicle collisions and validation result of the finite element model of one-box vehicle and minicar. ]

Pedestrians are exposed to the traffic environment without protection and thereby easily suffer serious traffic injuries when involved in a motor vehicle collision. The aims of this study were to investigate the pedestrian kinematics and ground impact in 200 real-world accident cases with video recordings. The impact velocities, pedestrian kinematics and ground impact were analysed by utilising the video information. The highest frequency of the vehicle impact velocity was estimated to be between 30 and 50 km/h. Sedan impacts led to high rotation angles of pedestrians, and the rotation angles increased as the impact velocities increased. The highest occurring frequency of kinematics involved somersaults which accounted for 39% in sedan accidents. The pedestrian rotation angle and kinematics depends on a vehicle's front shape and impact velocity. Also, the pedestrian rotation angle and kinematics can influence the pedestrian landing mechanisms including the order of the body region landing to the ground and the pedestrians’ landing posture. The findings of the accident analysis will be helpful for future studies on pedestrian protection.

Compared with the young, the elderly (age greater than or equal to 60 years old) vulnerable road users (VRUs) face a greater risk of injury or death in a traffic accident. A contributing vulnerability is the aging processes that affect their brain structure. The purpose of this study was to investigate the injury mechanisms and establish head AIS 4+ injury tolerances for the elderly VRUs based on various head injury criteria. A total of 30 elderly VRUs accidents with detailed injury records and video information were selected and the VRUs’ kinematics and head injuries were reconstructed by combining a multi-body system model (PC-Crash and MADYMO) and the THUMS (Ver. 4.0.2) FE models. Four head kinematic-based injury predictors (linear acceleration, angular velocity, angular acceleration, and head injury criteria) and three brain tissue injury criteria (coup pressure, maximum principal strain, and cumulative strain damage measure) were studied. The correlation between injury predictors and injury risk was developed using logistical regression models for each criterion. The results show that the calculated thresholds for head injury for the kinematic criteria were lower than those reported in previous literature studies. For the brain tissue level criteria, the thresholds calculated in this study were generally similar to those of previous studies except for the coup pressure. The models had higher (>0.8) area under curve values for receiver operator characteristics, indicating good predictive power. This study could provide additional support for understanding brain injury thresholds in elderly people.