Background: Motor vehicle crashes (MVCs) remain a leading cause of injury-related deaths in the United States. Primary seat belt laws allow vehicle occupants to be ticketed solely for not wearing seat belts, and secondary laws allow ticketing only for failure to wear seat belts in the setting of other violations.
Objective: To determine the association between MVC fatality rates and primary versus secondary seat belt laws.
Design: Retrospective time-series analysis.
Setting: United States, 2001 to 2010.
Participants: MVC fatalities in occupants aged 10 years or older identified in the Fatality Analysis Reporting System.
Measurements: Population-based rates of fatal crashes.
Results: There were 283 183 MVC fatalities in occupants aged 10 years or older from 2001 to 2010 (overall rate, 13.0 per 100 000 persons). In 2001, the mean fatality rate was 14.6 per 100 000 persons, 16 states had primary seat belt laws, and 33 states had secondary laws. In 2010, the mean fatality rate was 9.7 per 100 000 persons, 30 states had primary seat belt laws, and 19 states had secondary laws. In the multivariate regression model, states with primary seat belt laws had lower MVC fatality rates than states with secondary laws (adjusted incidence rate ratio, 0.83 [95% CI, 0.78 to 0.90]).
Limitation: Only fatalities were analyzed from the database, and the degree of law enforcement could not be ascertained.
Conclusion: States with primary seat belt laws had lower rates of MVC fatalities than those with secondary laws. Adoption of primary seat belt laws may offer optimal occupant protection.
Primary funding source: None.