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.
