PMHS Sled Testing of Reclined Small Female Occupants: Pelvic Dynamics and Injury Evaluation.

As automated vehicle technologies enable increased seat recline angles during travel, understanding the biomechanics of injury under these novel occupant postures becomes imperative. This study evaluated the pelvis injury response and associated kinematics of reclined small female post-mortem human surrogates (PMHS) subjected to frontal sled tests across three restraint configurations. Each configuration varied in seat stiffness and the presence of a knee bolster to assess their influence on pelvic dynamics and submarining risk. Nine PMHS tests were conducted using a consistent reclined posture (38° thorax, 75-80° pelvis angle) and production restraint systems. Submarining probability was estimated using a validated logistic regression referenced from previous study. Distinct pelvic kinematics, fracture patterns, and associated injury mechanisms emerged across the test configurations in the current dataset. Configuration 1, featuring a stiffer seat without a knee bolster, exhibited complex pelvic fractures-most notably iliac wing fractures resulting from inward bending of the ilium-and a higher probability of submarining primarily due to rearward pelvic rotation. In contrast, Configuration 2, with a compliant seat and no knee bolster, produced comminuted iliac wing fractures, dominated by shear component and a moderate probability of submarining driven primarily by downward pelvic displacement. Configuration 3, which included a knee bolster, showed injury propagation to the posterior pelvis, and none of the subjects submarined. Each configuration included three specimens; therefore, results should be interpreted with caution. Despite the small sample size, the findings highlight the critical influence of seat stiffness and restraint design on pelvic kinematics and injury mechanisms under reclined conditions. The data provided could serve in validating computational models and anthropomorphic test devices (ATDs) in reclined seating configurations.