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.