Lateral Restraint: Comparison of Lap/Shoulder Belt vs. Lap/Shoulder Plus Supplemental Shoulder Belt Restraint Systems

This paper reports the findings of research conducted to study the lateral crash protection for occupants of ground vehicles. The tests conducted as part of the research compared a seat mounted, continuous loop, lap and shoulder belt restraint system to a seat-mounted, continuous loop, lap and shoulder belt with a supplemental shoulder belt system. Analysis of Army ground vehicle crashes and DYNAMAN computer crash simulations indicate that crashes with lateral force vectors may cause occupants restrained by the standard vehicle-mounted lap/shoulder belt to impact the interior of the vehicle due to insufficient lateral restraint. A seat-mounted, continuous loop, lap and shoulder belt (similar to production vehicles) and a prototype seat-mounted, continuous loop, lap and shoulder belt with a supplemental shoulder belt were modeled in DYNAMAN computer simulations under a variety of crash conditions. Following this, Horizontal Accelerator (HA) and vehicle rollover testing was conducted on each system. The simulations and testing confirmed that conventional three-point lap/shoulder belts fail to provide adequate lateral upper torso restraint during crashes with a direction of force that causes the occupant to move away from the shoulder belt. In Army vehicles, this results in the occupant displacing toward the center of the vehicle where various structures or installed equipment introduce strike hazards. Results of the research and testing indicate that the prototype system effectively restrained the occupant in crashes with significant lateral force vectors, including side and frontal oblique crashes and rollovers, eliminating head strikes permitted by the standard lap/shoulder belt restraint. These findings, and the prototype system developed, have application in both ground and air vehicles.