Abstract
Less-than-expected fatality reductions after seat belt legislation has been introduced in a jurisdiction may be explained in terms of selective recruitment and/or behavioural adaptation by beginning belt users. The present investigation has compared the relative merits of these two hypotheses in two separate steps. In the initial study the driving behaviour of groups of habitual wearers and non-wearers of the belt was compared. The main part of the experiment was a 105 km motorway trajectory. In the follow-up study the original groups of wearers and non-wearers were assigned to one of four experimental treatments.