Some of the environmental, vehicular and behavioural aspects of belt use under voluntary conditions are presented. It is shown that belt use varies by type of environment, time of day and vehicle type. Interactions between driver and passenger presence and sex are shown to affect belt use. Risk taking in a turning gap-acceptance task shows that voluntary belt users accept longer gaps than do non-belt users. The introduction of the mandatory use of seat belts in Britain has produced usage rates in excess of 90% regardless of environment.