The effects of impact energy, impact partner shape and compound impacts (where a single location is impacted multiple times) on cycle helmet safety performance during linear impacts are not well characterised by the literature.
Establish the influence of impact energy and compound impacts on injury risk during flat and kerbstone anvil impacts.
Linear wire-guided drop tests were implemented by mounting helmets to a hemispherical headform, before impacting the left/right temporal regions of the helmet against flat and kerbstone anvils. Two consecutive drops of each helmet were performed against each location. The first drop was performed from heights ranging between 1-3 m (in 0.5 m increments), whilst the second drop was performed from a 1m drop height. Peak linear headform accelerations were recorded.
For the first impact, higher impact energies resulted in greater peak headform accelerations, regardless of anvil shape. Anvil shape affected outcomes at higher impact energies, as the kerbstone anvil resulted in greater peak accelerations at drop heights of >2.0 m. When observing the effects of the initial impact on the second impact, two variables affected safety performance. Firstly, the greater the energy of the first impact, thegreater the peak accelerations during the lower energy compound impact. Secondly, the greater the overlap in impact partner shape, the greater the accelerations during the compound impact.
Conclusions: Impact energies, impact partner shapes and compound impacts all affect helmet safety performance during linear impacts. Advanced testing protocols should consider assessing helmet safety performance against these variables.