Linear and Rota,onal Brain Injury Protec,on of Air-Filled and Foam-Liner Bicycle Helmets Under Oblique Impacts

Abstract

Air-filled chambers can be used to design portable helmets. A few air-filled helmets have been publicised, but they have not yet reached market readiness. As such, there is no knowledge of their performance under oblique impacts, which represent most real-world cycle incidents. Here, for the first time, we evaluated the performance of a commercially available air-filled helmet under oblique impacts, determined its brain injury mi?ga?on performance and compared it with three conventional cycle helmets, ranking high, middle and low in a recent study of 30 cycle helmets. We used a new headform, which beDer represents physical properties of the human head than other available headforms. The helmeted headform was dropped onto a 45° anvil at 6.5 m/s at four different locations, front, back, side and front-side. The risk of linear and rotational injuries, using risk functions based on PLA (peak linear acceleration) and BrIC (brain injury criterion) and exposure weighting, were calculated. The PLA and linear risk were lower for the air-filled helmet than the EPS helmets in all impact locations, showing a 44% reduction in the overall linear risk compared with the best-performing EPS helmet. This was attributed to the nearly twice as long impact duration of the air-filled helmet. The air-filled helmet's rotational performance compared to the EPS helmets was dependent on the impact location, with its overall rotational risk being slightly lower than the EPS helmet ranked middle. This study shows the great promise of air-filled helmets for mi?ga?ng both linear and rotational brain injury risks in cycle incidents, while addressing the portability user requirement.