Head protection with cyclist helmet in impact against vehicle A-pillar

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Head protection with cyclist helmet in impact against vehicle A-pillar

Mizuno, Koji / Ito, Daisuke / Oida, Keiji / Kobayashi, Goichi / Han, Yong

In vehicle–cyclist collisions, the head of cyclists impacts frequently against the windshield and the A-pillar of the vehicle. Accident analyses show that the head injury risk is high in impacts with stiff A-pillars. In this research, the head protection with cyclist helmets in impacts against the A-pillar was investigated from experiments and finite element (FE) analyses. The headform impact tests were conducted using the pedestrian headform with and without a cyclist helmet. In the A-pillar impact at 35 km/h, the HIC reduced substantially from without helmet (4815) to with helmet (3000) though it was far above the injury acceptance level (1000). The head protection by helmets in impacts against A-pillars might be limited because of high impact velocities of the head and A-pillar stiffness. The FE simulations of the headform impacts indicated that the helmet liner deformed locally and bottomed-out in the A-pillar impacts, whereas the A-pillar deformation was small. In the FE analysis of a human head model with a capping helmet, the skull fracture did not occur but the brain strain was large. From a simple model of the head acceleration in the A-pillar impact, it was shown that the helmet liner has little effect on the HIC, whereas a deforming A-pillar with a force level of 5–7 kN could reduce the HIC of the head with helmets less than 1500.