Compulsory Seat Belt Usage and Driver Risk Taking Behavior

Abstract

The danger compensation principle contends that the use of certain vehicle safety features such as seat belts may induce drivers to take greater risks. To test for this hypothesized effect, observational data on seat belt usage and driver risk taking were collected on 4812 drivers in Ontario, Canada, where seat belt usage is required by law. These data were compared with the results of a similar study conducted in Michigan, which has no usage law. The measure of driver risk taking in both studies was the time duration of following headway maintained by seat belt users and nonusers in high flow freeway traffic. Seat belts were worn by 51% of the Ontario drivers and by 14% of the drivers in Michigan. The Ontario usage rate before the law took effect was similar to the rate observed in the Michigan study. The results of both studies taken together are incompatible with the danger compensation principle. In the two jurisdictions a smaller percentage of users than nonusers drove at close, risky headways of less than one second, and these differences were of the same general magnitude. In the Michigan study it was concluded that voluntary usage is associated with the avoidance of risk. Likewise, in the Ontario study mandatory usage, rather than producing a tendency for increased risk taking as suggested by the danger compensation principle, was also associated with the avoidance of risk. Since the results provide no evidence for a danger compensation effect in car following behavior, it was concluded that this study presents no evidence that the safety benefits of seat belts would be diminished or neutralized by greater driver risk taking.