The Effectiveness of Proposed Pedestrian-Friendly Vehicle Front-End Shapes and the Feasibility of Controlled Braking in Protecting Pedestrian Ground Contact Injuries

Previous studies had obtained some pedestrian-friendly vehicle front-end shapes, which shown good pedestrian protection ability, but their effectiveness in protecting pedestrian ground contact injury is not evaluated yet. For this reason, a total of 6 vehicle front-end shapes, 3 each for G shapes (pedestrian-friendly vehicle or ‘Good’ front-end shapes) and P shapes (pedestrian-unfriendly or ‘Poor’ vehicle front-end shapes), and a simulation test sample (containing 3 vehicle speeds * 4 pedestrian models * 2 pedestrian gaits) were selected to design 72 groups of 144 simulations. The results show that compared with the P shapes, the G shapes have better protection against pedestrian-vehicle contact injuries but worse protection against pedestrian-ground contact injuries. The analysis found that the direct cause of the difference in the protection effect of pedestrian-ground contact injury between the G and P shapes is that the change of the pedestrian's ground impact mechanism led to the head hitting the ground earlier and at a greater speed, and also higher ground-related WICpelvic (Weighted Injury Cost of Pelvis), while the essential cause is most likely the change in the angle of rotation of the pedestrian after the contact due to the difference in the shape of the bumper of the two types of vehicle front-end shapes. In order to further reduce pedestrian-ground contact injuries for the G shapes, 7272 simulations were designed relying on the simulation test sample, and a simple vehicle braking control method for a specific vehicle model was proposed by combining optimization and regression. Experiments based on the simulation test sample showed that a maximum reduction of 84% of the ground-related WIC (Weighted Injury Cost) could be achieved, with a ‘safe’ mechanisms proportion up to 74%. Experiments based on the new simulation test sample showed a maximum reduction of 43% of ground-related HIC (Head Injury Criterion) and the proportion of safe mechanisms reached 78%, which verified the good effect and adaptability of the proposed method. These findings provide strong support for better understanding the mechanisms generating pedestrian-ground contact injury and for developing better protection methods to reduce the severity of pedestrian-ground contact injury.