Occupant Dynamics During Low, Moderate, and High Speed Rear-End Collisions 2020-01-0516
Numerous studies have evaluated occupant kinematics and dynamics in “low-speed” rear-end impacts. Occupant biomechanics during “moderate-to-high” speed rear impacts (delta-V ≥ 15 mph), however, has not been thoroughly examined. This study characterized the motions and forces experienced by the occupant head, neck, torso, hip, and left/right femur during these collisions. The publicly available NHTSA rear-end crash test data were examined. More specifically, the FMVSS 301 Fuel System Integrity tests were used. The test procedure involved a 30 mph moving barrier impacting the rear of the vehicles. Instrumented 50th percentile male Hybrid III ATDs were positioned in the left front driver seat. Occupant data including head accelerations, upper/lower neck shear and axial forces, upper/lower neck moments, lower neck acceleration, torso accelerations, torso deflection, hip accelerations, and left/right femur axial forces were measured and compared to published IARV tolerance data. The vehicle accelerations, vehicle delta-Vs, occupant position data, seat angular velocity, seat rotation and seatbelt forces were also evaluated during these crash tests. The occupant data for the “low-speed” rear-end impacts were extracted from the literature. The results indicated a strong correlation between “head resultant acceleration vs. head x-acceleration”, “upper neck resultant force vs. upper neck z-force”, “upper neck resultant moment vs. upper neck flexion moment”, “lower neck resultant force vs. lower neck z-force”, “torso resultant acceleration vs. torso x-acceleration” and “hip resultant acceleration vs. hip x-acceleration”. A linear relationship was also detected between peak “head rotation vs. vehicle delta-V” and “lower neck flexion moment vs. vehicle delta-V”. The lower neck and torso accelerations were also correlated with vehicle longitudinal accelerations. No correlations between femoral forces and hip accelerations were observed. The data from this study is essential in the development of new injury criteria and countermeasures for occupant protection in “moderate-to-high” speed rear-end collisions.