Coefficient of Restitution and Collision Pulse Duration in Low-Speed Vehicle-to-Barrier Impacts

The coefficient of restitution is utilized in various methods for determining the change in velocity (delta-V) associated with a vehicle collision event. Additionally, for a given delta-V, the magnitude of vehicle acceleration varies with different collision pulse durations. Collision restitution and duration parameters are thus considered by both accident reconstructionists and biomechanists in the investigation of vehicle collision severity and occupant injury potential. Because of the uniqueness of individual vehicle designs, it is difficult to determine a collision’s specific coefficient of restitution and crash pulse duration. Accident reconstructionists often estimate the values of these parameters based on staged crash tests. Prior studies involving low-speed collisions have sought to determine correlations between restitution and collision characteristics and have established equations to assist in estimating restitution. Most of these equations are based around the correlation between restitution and vehicle closing speed. Furthermore, the previous work is largely based on pre-2000 model year vehicles. This study seeks to expand the restitution data for vehicle-to-barrier collisions to a more modern vehicle fleet and examine potential vehicle and collision characteristics that influence restitution and crash pulse duration. The Insurance Institute for Highway Safety (IIHS) conducted a series of low-speed vehicle-to-barrier and vehicle-to-vehicle crash tests. The IIHS test series includes both front and rear collisions with a fixed bumper-like barrier in full-overlap and corner (offset) configurations. For this study, over 100 vehicle-to-barrier front and rear full-overlap collision videos were analyzed to compute the coefficient of restitution and crash pulse duration for each test. The relationships between vehicle weight, vehicle wheelbase, bumper engagement, and bumper construction with the coefficient of restitution and pulse duration were evaluated.