Browse Publications Technical Papers 2005-01-1705

Lap-Shoulder Belt Performance as a Function of Occupant Size 2005-01-1705

The Federal Motor Vehicle Safety Standards (FMVSS) require rear seat, lap/shoulder belts to “fit” Hybrid III dummies ranging in size from a 6 year old child (H3-6C) to a 95th-percentile-male (H3-95M). No dynamic performance FMVSS, however, exist for rear seat belt systems. Variations in the three-dimensional “fit” of the same lap-shoulder belt positioned around these extreme dummy sizes suggest a possible difference in performance.
The purpose of this study was to assess the performance of two production lap-shoulder belt designs in a large SUV buck on a rebound sled using instrumented H3-6C, 5th-percentile-female (H3-5F) and H3-95M dummies. Sled velocities were approximately 35 kph.
Test instrumentation included: lap and shoulder belt load transducers, triaxial accelerometers at the center of gravity of the head, triaxial accelerometers and a deflection gauge in the chest, and six-axis force (and moment) transducers in the neck of the dummy. Tests were photographed using high-speed digital photography in the oblique and lateral views at rates of approximately 1,000 frames per second. In addition, pre- and post test images were taken using still digital photography. Sensor signals were filtered according to SAE specifications. Physical evidence on the lap-shoulder belts and retractor housings were carefully documented.
A relationship exists between belt loads to the restraint as a function of occupant mass and sled velocity. Physical damage to the belt systems provides forensic evidence that varies with occupant mass, crash severity and principal direction of force.


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