For decades, the automotive seat belt has stood as the most fundamental and effective tool of passenger safety. Yet, despite its proven efficacy, seat belt use in the United States remains a fragmented landscape of compliance, cultural resistance, and inconsistent legal frameworks. In 2023, the consequences of this patchwork were stark: among passengers ages 13 and older killed in traffic crashes, only 45% were confirmed to be wearing a seat belt at the time of the T
The Insurance Institute for Highway Safety (IIHS) released a new digital tool designed to transform static mortality data into a roadmap for legislative action. Known as the “seat belt law calculator,” this online platform utilizes statistical models built on years of peer-reviewed research to simulate how specific changes to state statutes would directly impact belt use and fatality rates. The tool serves as a sobering reminder that the difference between life and death on the highway is often dictated by the specific phrasing of a state’s vehicle code.
The potential for life-saving intervention is significant. According to IIHS estimates, if every state and the District of Columbia had optimal belt use laws in place, 277 lives could have been saved in 2023 alone. “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.
The primary point of contention in statehouses often centers on the method of enforcement. Under “primary” enforcement laws, police officers are permitted to stop a vehicle and issue a citation solely because an occupant is unbuckled. In contrast, “secondary” enforcement laws—currently active in 16 states—prohibit an officer from stopping a driver for a seat belt violation unless they have first pulled the vehicle over for another offense, such as speeding or a broken taillight.
The IIHS calculator demonstrates that simply moving to primary enforcement can yield dramatic results. In Montana, for example, transitioning to a primary enforcement model would likely result in a 6.4% drop in fatalities. Similarly, the tool highlights the “rear-seat gap.” While most states require front-seat occupants to buckle up, many do not mandate the same for adult passengers in the back. Georgia, which has primary enforcement for the front seat but no requirement for the rear, could cut overall teen and adult passenger deaths by 0.7%—and rear-seat deaths specifically by 12%—simply by closing that loophole.
New Hampshire remains the nation’s most prominent outlier. It is the only state that does not require adult front-seat passengers to wear seat belts. The IIHS estimates that if New Hampshire enacted a comprehensive law covering all seating positions with primary enforcement, it could reduce passenger-vehicle deaths by 8.9%.
While legislative efforts continue, automotive technology is attempting to fill the gaps. The IIHS has found that persistent audible and visual reminders—those that continue well beyond the federal minimum of eight seconds—are highly effective at changing driver behavior. Since the institute began rating these systems in 2022, manufacturers have made rapid improvements; approximately 71% of 2025 models evaluated earned a “good” rating for their reminders.
However, because it will take years for these newer, safer vehicles to saturate the used-car market, the IIHS maintains that stronger laws remain the most immediate lever for public safety. In the interim, the new calculator offers a clear, data-driven choice for lawmakers: wait for technology to catch up, or enact the simple legislative fixes that could save hundreds of lives this year.
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