Analysis of the biofidelity of aPLI under low-speed collision conditions

OBJECTIVES: To evaluate the applicability and limitations of the advanced pedestrian legform impactor (aPLI) under reduced-speed pedestrian lower-limb impact conditions. METHODS: Finite element simulations were conducted to compare the kinematic and injury responses of the aPLI with two human body models, THUMS and GHBMC. Five impact speeds from 20 to 40 kph and six simplified car models representing sedan, SUV, and high-bumper SUV front-end configurations were considered. RESULTS: The aPLI maintained good kinematic consistency with the HBMs during the primary loading phase, whereas rebound-phase differences were more evident. MCL elongation showed relatively close agreement at the standard 40 kph condition but was more sensitive to speed reduction. Femur and tibia bending moments showed more stable speed-dependent trends, although differences in absolute peak values remained. Transfer-function analysis showed that the MCL slope increased as impact speed decreased, whereas the femur and tibia slopes remained comparatively stable. CONCLUSIONS: The aPLI can provide useful information for interpreting reduced-speed pedestrian lower-limb impacts. However, its injury metrics should be interpreted with consideration of metric-specific speed sensitivity, HBM-dependent differences, and the limitations of simplified vehicle loading models.