Investigation of Restraint Function on Male and Female Occupants in Rollover Events

Factors influencing neck loading in rollover events were identified in a series of spit tests where vehicles were inverted. Drivers included both male and female human volunteers, as well as seated standard and standing pedestrian 50^th percentile anthropomorphic dummies. The passenger sides of the vehicles were rotated down first, simulating the most dangerous rotation for the driver, a far-side roll. The variables investigated during the spit tests included body shape, pre-roll body position and vertical seat velocity. Conditions causing shoulder belt webbing to pass through to the lap belt were investigated together with the corresponding body kinematics. Early in the far-side rolls, the belt tended to slip off the shoulder and the slack was immediately passed through to the lap belt, increasing body excursion toward the roof. An alert position (i.e. sitting more upright prior to the roll) increased the body excursion in the roll and, correspondingly, the risk of neck injury. Chest geometry and compressibility caused some women to experience excessive motion toward the roof, increasing their risk of neck injury. Neither dummy adequately simulated the excursions experienced by the volunteers. Latch plates that restricted webbing pass-through to the lap belt reduced the body excursion and thus, provided better neck protection. Computer simulations using the MADYMO occupant simulator program were also performed to study the dynamic interaction of the head, torso, and roof during contact with the ground, a study which was not possible using volunteers.