Long-term safety evaluation of the primary seat-belt law

Many states in the United States have passed the primary enforcement seat-belt law. Though there is strong evidence from previous studies that enhanced seat-belt enforcement interventions can substantially increase seat-belt use, thereby reducing fatalities. It is still necessary to evaluate the long-term effects of implementing the primary seat-belt law. In this study, changes in fatalities over time after the primary seat-belt law enactment are investigated using before-and-after study with the comparison group methods for fatality modification factors (FMFs). This study confirms that the number of adult fatalities without seat-belt has significantly decreased by 17.29%. Another key finding is that the fatality rates in states with a higher maximum fine amount are significantly lower than those with a lower one, however, the decrease in fatality trend is not as effective above about $100 fine. Implementing the primary seat-belt law is significantly effective in reducing fatalities without seat-belt in the long-term. Meanwhile, the relationship between fatalities reduction and the maximum fine amount is not positively linear related. It is imperative that states with the secondary seat-belt laws must reform their seat-belt laws to the primary seat-belt law. An appropriate fine amount can be determined to maximize the effectiveness of the primary seat-belt law.