Occupant Kinematics During Chain-Collisions: Discrete vs Combined Collisions 2024-01-2489

There is little prior research into chain-collisions, despite their relatively large contribution to injury and harm in motor-vehicle collisions. This study conducted a series of rear-impact, front-impact, and chain-collision impacts using a bumper car ride at an active amusement park as a proxy for automobiles. The purpose was to begin to identify the threshold time range when separate, discrete collisions transition into a hybrid or combined chain-collision mode and provide bases for future analyses. The test series consisted of rear impacts into an occupied target vehicle from a driven bullet vehicle; frontal impacts into a perimeter barrier (wall); chain-collisions consisting of a driven bullet vehicle striking an occupied primary target vehicle, which then collided with a non-occupied secondary target vehicle; and chain-collisions consisting of a driven bullet vehicle striking an occupied primary target vehicle which then collided with a wall. Time between collisions was adjusted via spacing. Vehicle impact velocities, changes in velocity (delta-Vs), accelerations, and coefficients of restitution are reported. Head and extremity excursions of the restrained occupant of the primary target vehicle were also tracked using high-speed video recording. The results show that chain-collisions exhibited three phases: an early phase that occurs during the initial rearward occupant excursion, a middle phase that occurs during the forward rebound occupant excursion, and a late phase that occurs while the occupant is recovering back to the initial position. The first phase appears to last for approximately 150 ms, the middle phase for approximately 50 to 75 ms, and the late phase from thereafter until approximately 400 ms to 500 ms after the initial collision. The middle phase appears to be related to the timing of the occupant’s return to their original position and their maximum rebound velocity and the late phase to the remaining occupant displacement but not velocity. Overall, occupant and vehicle kinematics during a chain-collision were different from those of the individual component collisions and were different from a superposition of the component collisions. This is the first reporting of these phases in a chain-collision.