Seat Belt Restraint Evidence Generated by Unrestrained Occupant Interaction in a Rollover 2022-01-0846

Assessment of the physical evidence on a seat belt restraint system provides one source of data for determining an occupant’s seat belt use or non-use during a motor vehicle crash. The evidence typically associated with loading from a restrained occupant has been extensively researched and documented in the literature. However, evidence of loading to the restraint system can also be generated by other means, including the interaction of an unrestrained occupant with a stowed restraint system. The present study evaluates physical evidence on multiple stowed restraint systems generated via interaction with unrestrained occupants during a full-scale dolly rollover crash test of a large multiple passenger van. Unbelted anthropomorphic test devices (ATDs) were positioned in the driver and right front passenger seats and in all designated seating positions in the third, fourth, and fifth rows. Occupant kinematics during the dolly rollover were evaluated through on-board and off-board real-time and high-speed video, and physical evidence on the restraint systems was documented. Analysis of the occupant kinematics demonstrated multiple ATD interactions with stowed restraint systems in the vehicle, which generated corresponding physical evidence on those restraint systems. The findings of the present study demonstrate that the presence of physical evidence on the restraint system alone is insufficient for determination of occupant seat belt usage. A methodology for assessing restraint webbing and hardware evidence in the context of occupant seat belt use versus non-use is detailed. Thorough documentation of the restraint system physical evidence, evaluation of the occupant kinematics and injury patterns, and evaluation of the restraint system evidence as it relates to the body habitus of the occupant of interest can provide an objective scientific basis for the determination of occupant restraint status.