Mechanism of Abdominal Injury by Steering Wheel Loading

The introduction of energy absorbing steering systems has provided a substantial reduction of occupant injury in car crashes. However, the steering system remains the most important source of occupant injury. Injury associated with steering assembly contact is due to high exposure; energy absorbing steering systems reduce the risk of injury for drivers when compared to the injury risk of right front passengers. Our investigation addressed loading of the upper abdominal region by the steering wheel rim using a physiological model for study of soft tissue injury.

Injury to the liver was related to the abdominal compression response associated with rim loading. Although liver injury correlated somewhat with peak abdominal compression, a better correlation was found when the rate of compression was also considered. Force limiting by the steering wheel, not by column compression, most strongly influenced the outcome of abdominal injury. The force generated by wheel-rim compression of the abdomen was insufficient to cause either column compression or significant whole-body motions. Subjects loaded by “stiff” steering wheels (having rim deformation forces greater than the abdominal compression force) exhibited greater abdominal compression, rate of compression and resulting extent of injury than did subjects loaded by “softer” wheels which deformed more and thus reduced abdominal compression.