Seat belt use under voluntary and mandatory conditions and its effect on casualties.

Seat belt usage rates in Britain in the decade prior to the introduction of a mandatory usage law in January 1983 are reviewed to show a stable rate of around 30% in the 1970s. Various risk compensation theories are mentioned briefly, and then some observational data collected in 1982 are analysed to show that certain vehicle characteristics, notably car age and type, have a significant relationship with occupant belt usage rates under voluntary conditions. Data on the first post- law period are presented showing general belt usage rates rising to some 90%.