Evaluating the North Carolina safety belt wearing law.

The North Carolina Seat Belt Law required an evaluation of the effectiveness of the act with a report of the findings to the Legislature three years after the law went into effect. This paper addresses changes in statewide belt usage and in occupant injury associated with that law. Observational data collected bimonthly from a probability sample of 72 sites stratified by geographic region, rural/urban location, road type, and time of day show that belt use rose from a baseline rate of 25% to a warning ticket phase rate of 45%. Belt use then reached 78% upon enforcement and is now nearly 64%. Time series analysis showed that statistically significant reductions in percentages of moderate and serious injuries occurred at the beginning of both the warning ticket and the enforcement phases. Forecasts of injuries and deaths were also developed from the time series models and were compared with observed totals. Warning tickets brought about a modest 5.4% reduction in serious injuries; fatalities among occupants covered by the law showed no change. In contrast, the subsequent enforcement phase saw a reduction of 11.6% in fatalities and 14.6% in serious or worse injuries. This represents an estimated annual savings of 131 lives and over 2,300 serious injuries in North Carolina during the 18 months following onset of enforcement.