Traumatic Head and Brain Injuries in Helmeted Motorcycle Crashes

This study presents an analysis of 364 motorcycle helmet impact tests, including standard certified full-face, open-face, and half-helmets, as well as non-certified (novelty) helmet designs. Two advanced motorcycle helmet designs that incorporate technologies intended to mitigate the risk of rotational brain injuries (rTBI) were included in this study. Results were compared to 80 unprotected tests using an instrumented 50th percentile Hybrid III head form and neck at impact speeds ranging from 6 to 18 m/s (13 to 40 mph). Results show that, on average, the Head Injury Criterion (HIC) was reduced by 92 percent across certified helmets, compared to the unhelmeted condition, indicating substantial protection against focal head and brain injuries. However, findings indicate that standard motorcycle helmets increase the risk of AIS 2 to 5 rotational brain injuries (rTBI) by an average of 30 percent compared to the unprotected condition, due to the increased rotational inertia generated by the added size and weight of the helmet. Advanced helmets performed, on average, about 5 percent better than standard certified helmets. Non-certified or novelty helmets offer inadequate protection against focal head and brain injuries, though they may offer some insight into rTBI protection. The findings of this study also indicate a critical methodological deficiency in the oblique impact tests utilized in revised motorcycle helmet standards, including ECE 22.06, Snell M2025, and FRHPe-02, which fail to correctly assess rTBI risk. This paper provides recommendations for enhancing motorcycle helmet design to improve protection against rotational traumatic brain injuries.