IIHS calculator shows how better seat belt laws can boost safety in each state

A new online tool from the Insurance Institute for Highway Safety shows how specific changes to seat belt laws would affect belt use and fatality rates in each state.

The seat belt law calculator uses statistical models that IIHS developed. The models are based on published research findings about the effects of different types of seat belt laws.

“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.

Seat belt laws vary widely throughout the 50 states and the District of Columbia. While New Hampshire is alone in not requiring belt use in the front seat, it is one of 16 states that don’t require adult passengers to buckle up in the rear.

Laws also vary according to the type of enforcement allowed. Primary enforcement laws allow police to stop a vehicle and issue a citation solely for failure to buckle up. Under secondary enforcement laws, police can only enforce seat belt requirements if they have pulled the driver over for another violation first.

Although most people buckle up, failure to use a seat belt remains a huge factor in road deaths. Among people 13 and older killed in crashes while riding in passenger vehicles in 2023, only 45% were confirmed to be using belts.

While state laws aren’t the only factor that influences belt use, use rates are generally lower in states with weaker laws. Studies have consistently shown that requiring belts can sway many holdouts and that laws with primary enforcement are more effective than those that allow only secondary enforcement.

Not surprisingly, the state with the most to gain from seat belt law changes is New Hampshire. If it enacted a belt law covering all seating positions and allowing primary enforcement, it could cut deaths of passenger-vehicle occupants 13 and older by 8.9%.

States with only front-seat laws and secondary enforcement could also make big progress with legislative tweaks. Nebraska, for example, could see a 6.6% drop in deaths if it enacted a rear-seat belt requirement and primary enforcement for the front and back.

Just moving to primary enforcement would have a substantial benefit for many states that already require belts for all occupants. Montana, for example, would see a 6.4% drop in fatalities from that change.

Georgia is an example of a state that has a primary enforcement law for the front seat, but no law for the back seat. If it enacted a rear-seat requirement with primary enforcement, it would cut overall deaths of teen and adult passenger-vehicle occupants by 0.7%, thanks to a 12% cut in rear-seat deaths.

Strengthening laws is just one way to increase seat belt use. Vehicle technology can also help. IIHS research has shown that persistent visual and audible reminders that go well beyond the 4- to 8-second reminders required under federal regulations are highly effective at changing behavior.

IIHS began rating belt reminders in 2022, prompting manufacturers to make rapid improvements. About 71% of 2025 vehicles evaluated earned a good rating for their belt reminders, compared with just 16% of 2022 models.

Despite these improvements, it will be many years before a majority of vehicles on the road have good belt reminders. In the meantime, stronger belt laws and better enforcement are tools that can yield rapid results.