Production BMW
Pre-Tensioner

Seat Belt Pre-Tensioning in Rollovers

3-point safety belts are designed and provided with a primary objective being to control and limit occupant motions within the vehicle. These systems function differently in different accident modes. In frontal impacts, the safety belts primarily limit forward occupant motion towards interior vehicle components. In rollover crashes, the belts should provide both restraint from vertical motion towards dangerous upper interior contacts as well as prevent ejection. Controlling the severity of the occupant's "second collision" within the vehicle is critical to injury reduction. These projects study the effect of simple belt pre-tensioning on occupant vertical motion in a simulated roll environment. Inversion tests comparing production belt designs to those same designs with the addition of simple pre-tensioning show 30% to 40% reduction in occupant motion toward the upper interior of the vehicle, and, with increasing retractor sensitivity as well, from 40% to 75% reduction is demonstrated.