Pedestrian dynamic response and injury risk in high speed vehicle crashes.

Purpose: The purpose of the current study is to understand pedestrian kinematics, biomechanical response and injury risk in high speed vehicle crashes.

Methods: Vehicle-to-pedestrian crashes at the impact speeds of 40 km/h (reference set) and 70 km/h (analysis set) were simulated employing FE models of a sedan front and an SUV front together with a pedestrian FE model developed using hollow structures. The predictions from crash simulations of different vehicle types and impact speeds were compared and analyzed.

Results: In crashes at 70 km/h, pedestrian head-vehicle contact velocity is by about 20-30% higher than the vehicle impact speed, the peak head angular velocity exceeds 100 rad/s and is close to the instant of head-vehicle contact, brain strain appears two peaks and the second peak (after head contact) is obviously higher than the first (before head contact), and AIS4+ head injury risk is above 50%, excessive thorax compression induces rib fractures and lung compression, both sedan and SUV cases show a high risk (>70%) of AIS3 + thorax injury, and the risk of AIS4 + thorax injury is lower than 40% in the sedan case and higher than 50% for the SUV case.

Conclusions: Pedestrians in vehicle crashes at 70 km/h have a higher AIS3 + /AIS4 + head and thorax injury risk, high vehicle impact speed is more easily to induce a high head angular velocity at the instant of head-vehicle contact, brain strain is strongly associated with the combined effect of head rotational velocity and acceleration, and pedestrian thorax injury risk is more sensitive to vehicle impact speed than the head.