Mandatory Belt Use and Driver Risk Taking: An Empirical Evaluation of the Risk-Compensation Hypothesis

Abstract

Despite empirical evidence of the lifesaving and injury-reducing benefits of federal motor vehicle safety standards, seat belt use laws, motorcycle helmet laws, and other government requirements for protecting people in crashes, the value of such policies has been challenged. The challengers hypothesize that the effectiveness of mandatory approaches are partially or wholly offset by changes in behavior by drivers who take greater risks, thus maintaining the same level of overall risk as before.

Results of a study of driver behavior in Newfoundland and Nova Scotia before and after Newfoundland’s seat belt use law did not support this hypothesis. There was no evidence of risk compensation among Newfoundland drivers in their travel speeds, following headways, turning headways, or responses to yellow signals.

In a second, longer-term study, drivers in England were found to travel significantly slower around sharp curves eight to nine months after a belt use law became effective than one year earlier (three to four months before the law became effective). This speed reduction is contrary to the prediction of the risk-compensation hypothesis. In another setting, women drove significantly faster on two-lane straight roads after the law, but men drove at the same speeds before and after the law. Two other measures of risk taking, speeds on four-lane roads and following headways on two- and four-lane roads, were not affected by the law.