The Hybrid III dummy as a discriminator of injurious and non-injurious restraint loading

This study evaluates the ability of the Hybrid III dummy and its associated injury criteria to discriminate sled tests with injurious conditions from those without. Ninety-three matched human cadaver and Hybrid III frontal sled tests over a range of impact speeds and restraint conditions are considered. Chest acceleration, deflection, and CTI are used as predictors of rib fracture outcome in the matched cadaver tests. Univariate and multivariate models are developed to evaluate the importance of the dummy measures relative to three experimental parameters (test speed, restraint condition, seating position) and three cadaver characteristics (age, gender, mass). The primary findings are, first, that chest acceleration has no utility for injury discrimination (Kruskal's Gamma = 0.0319, area under the receiver-operator characteristic = 0.500). Second, the functional relationship between any Hybrid III injury measure and injury risk is sensitive to all three experimental factors. Injury risk models with consideration of this dependence are presented. It is shown that the Hybrid-III chest deflection corresponding to a given level of injury risk is greatest for air bag loading, lowest for belt loading, and intermediate for combined loading. This is shown to be non-biofidelic, since chest deflection as measured directly on the cadaver does not exhibit this sensitivity.