An argument raised against mandatory motorcycle helmet legislation is interference with the abilities to see and hear. This study assessed the effectsof helmets upon seeing and hearing by having 50 riders operate over a test route, changing lanes in response to an audible signal under three helmet conditions:​ none, partial coverage, and full coverage. Half of the subjects were assessed for the degree of head rotation during the lane changes, while he other half were assessed for hearing threshold (decibel level at which they first responded to the signal). Subjects in the vision study increased the degree of head rotation in proportion to the vision restriction imposed by the helmets, though not to the full extent of the restriction. However, individual differences in head rotation far exceed the effects of helmets. Subjects in the hearing study evidenced no differences in hearing threshold across the three helmet conditions. The authors conclude that the effects of helmets upon the ability to see and hear are, at most, extremely small and do not compete with the safety benefits offered by head protection.