An analysis of head impact severity in simulations of collisions between pedestrians and SUVs/work utility vehicles, and sedans.

Objective: To describe the determinants of the severity of the head kinematics of a pedestrian when struck by common sport utility vehicles (SUV) and work utility vehicles (WUVs) to assess how effective assessment protocols are in assessing injury risk for SUVs and work utilities.

Methods: Three hundred twenty-four simulations of pedestrian collisions with SUVs, work utility vehicles, and sedans were performed using several vehicle geometries, pedestrian orientations, speeds, and braking levels. Contact stiffnesses in the models were based on impact test results with exemplar vehicle structures. A single contact characteristic was used for all head-to-hood contacts to allow the effects of other factors on head injury risk to be compared. Simulations of standard headform tests on the same hood characterized the structure from a subsystem test perspective.

Results: Head injury criterion values were higher in SUV/WUV simulations than sedan simulations because of high neck tension rather than through higher contact forces with the hood. In fact, the severity of the impact between the head and hood was slightly less in SUV/WUV simulations. Sedan and SUV/WUV simulations produced lower head injury criterion (HIC) values than did the subsystem tests.

Conclusions: High bonnet leading edges led to increased neck loads in these simulations of pedestrian collisions. Neck loads were influential on head injury risk in the SUV/work utility simulations but not in sedan simulations. Subsystem impact tests may overestimate head impact risk from the hood itself but fail to capture a potentially important injury mechanism in collisions with vehicles with high leading edges and thus fail to differentiate completely risks posed by such vehicles. These results may have implications for the interpretation of pedestrian subsystem test results: a given HIC value in an SUV/WUV test may represent a relatively higher risk of injury than the same results recorded in a sedan test.