A new online calculator developed by the Insurance Institute for Highway Safety (IIHS) demonstrates how changes to seat belt laws could affect usage rates and fatalities in each U.S. state.
The tool uses statistical models based on published research about the impact of different seat belt law provisions. “This calculator will help advocates and policymakers understand the safety benefits a state can reap with simple legislative changes,” said Chuck Farmer, IIHS vice president for research. “For the 22 jurisdictions that already have the strongest provisions in place, it shows the cost of any potential backsliding.”
According to IIHS estimates, if every state had optimal seat belt use laws, 277 additional lives could have been saved in 2023.
Seat belt regulations differ widely across states and the District of Columbia. New Hampshire is unique in not requiring front-seat occupants to wear seat belts, and it is among 16 states that do not mandate rear-seat belt use for adults. Enforcement methods also vary: primary enforcement allows police to stop vehicles solely for non-use of seat belts, while secondary enforcement permits citations only if another violation has occurred.
Despite high overall compliance, lack of seat belt use remains a significant factor in road fatalities. In 2023, just 45% of people aged 13 and older killed as passenger vehicle occupants were confirmed to be wearing seat belts.
Research consistently shows that stronger laws—especially those allowing primary enforcement—increase seat belt use rates. The IIHS calculator identifies New Hampshire as having the most potential for improvement; enacting comprehensive primary enforcement laws there could reduce deaths among passenger-vehicle occupants aged 13 and older by nearly 9%.
Other states with limited or secondary enforcement laws could also see reductions in fatalities through legislative changes. For example, Nebraska could experience a 6.6% decrease in deaths by requiring rear-seat belts and adopting primary enforcement statewide. Montana might see a similar benefit—a projected 6.4% drop—by switching to primary enforcement for all seating positions.
Georgia currently requires front-seat belts with primary enforcement but has no rear-seat law; adding this provision could cut total deaths among teen and adult passengers by 0.7%, including a notable reduction among rear-seat occupants.
While strengthening legislation is one approach, technology also plays a role in boosting seat belt use. IIHS research finds that longer-lasting visual and audible reminders are effective at changing driver behavior beyond current federal requirements.
Since IIHS began rating these reminders in 2022, manufacturers have made improvements: approximately 71% of evaluated 2025 vehicle models earned good ratings for their reminders compared to just 16% of models from three years earlier.
However, widespread adoption of enhanced reminders will take time due to slow fleet turnover. In the interim, stronger laws and better enforcement remain important strategies for quickly increasing seat belt use and reducing injuries.
The IIHS has contributed significantly to improving road safety through research into vehicle safety and driver behavior (https://www.iihs.org/about). Its Vehicle Research Center in Ruckersville, Virginia conducts crash tests and safety assessments (https://www.iihs.org/about). Established by three major insurance associations representing much of the U.S. auto insurance market (https://www.iihs.org/about), IIHS aims to minimize motor vehicle crash deaths, injuries, and property damage through research targeted at consumers, policymakers, and safety professionals (https://www.iihs.org/about). The organization’s efforts have influenced key policy developments such as primary seat belt laws and graduated driver licensing systems across several states (https://www.iihs.org/about).
“This calculator will help advocates and policymakers understand the safety benefits a state can reap with simple legislative changes,” said Chuck Farmer, IIHS vice president for research. “For the 22 jurisdictions that already have the strongest provisions in place, it shows the cost of any potential backsliding.”
If every state had optimal belt use laws, an estimated 277 lives would have been saved in 2023.
