User centred design customisation of bicycle helmets liner for improved dynamic stability and fit

In order for bicycle helmets to maintain sufficient coverage and protection of riders, the helmets must be adequately positioned and secured on the head. This research investigates helmet's dynamic stability parameters in order to determine whether a customised liner can improve the retention and therefore safety. A specialist 3D scanner was used to scan a total of 17 male participants who volunteered for this study. Through 3D scanning the shape and depth of each section of a participant's head and facial structure was captured. All the heads scanned were orientated with respect to the same coordinates based on the Australian and New Zealand Standards in order to customize the liner design to fit the user's heads. The dynamic stability of the commercially available helmets and the customized helmet were assessed using relevant video and goniometer techniques. The results indicate that for frontal roll-off, the customised helmet liner passed in all simulations of the 160mm drop height. It consistently performed better in the lateral roll-off at height of 40mm and 80mm compared with the commercially available helmets. While the dynamic stability measurements and the design strategies offer the potential to improve fit for different user's head, further studies should take into consideration a larger population size to draw more accurate conclusions.