Effectiveness of wearing a bicycle helmet for impacts against the front of a vehicle and the road surface.

OBJECTIVE

To assess the effect of wearing a bicycle helmet using an adult headform in terms of the head injury criterion (HIC) when the frontal and lateral parts of the helmet impact a vehicle body and also when the frontal part of the helmet impacts the road surface.

METHODS

The adult headform was made to impact the hood, windscreen, roof top, and roof side rail of a vehicle body at an impact velocity of 35 km/h, which is a common head-to-vehicle impact velocity in real-world cyclist-vehicle collisions, in which the vehicle impacts the cyclist at 40 km/h. For the road surface impact experiments, we set a drop height of 1.5 m (impact velocity of 20 km/h).

RESULTS

Helmet usage helped to reduce the HIC when the frontal and lateral parts of the helmet impacted vehicle parts other than the hood. The HIC reduction for the frontal impact was greater than that for the lateral impact. Moreover, the higher the stiffness index of the vehicle structure, the greater was the HIC reduction. However, helmet usage was ineffective for reducing skull fracture risk (HIC 2558) when the lateral part of the helmet impacted stiffer parts of the vehicle, such as the roof side rail close to the B-pillar. Helmet usage helped to reduce the HIC by 91% when the frontal part of the helmet impacted the road surface.

CONCLUSIONS

Wearing a helmet reduces skull fracture risk when the frontal and lateral parts of the helmet impact vehicle parts (excluding the hood) at 35 km/h and the road surface at 20 km/h. However, when the lateral part of the helmet impacts the B-pillar, the helmet cannot effectively reduce the skull fracture risk at these real-world velocities.