Between 1975 and 2014, seat belts saved 330,507 lives in car crashes. But if everyone had been wearing belts, an additional 378,983 lives could have been saved, according to a study by the Department of Transportation.

One way to promote seat belt use is to enact the strictest seat belt laws. But states may have lost the will to do so, says a nonprofit group that supports those laws.

Last year saw the fewest number of states enact highway safety laws since 2004. That’s when the group, Advocates for Highway & Auto Safety (AHAS), began rating states on progress in meeting 15 lifesaving laws regarding motorcycle helmets, text­ing, and more.

By its most recent tally, AHAS found that 34 states and the District of Columbia have “primary enforcement” laws for the front seats. Of those, only 18 states and the District have laws for front and rear seats.

New Hampshire is the only state that doesn’t require adults to wear seat belts. Sherman Packard, a New Hampshire state representative when the last attempt was made to pass a mandatory seat belt law, in 2009, currently serves on the House transportation committee.

He says he wears a seat belt “most of the time, sometimes not.” He was opposed to a mandatory law then and still is. If wearing seat belts is the law, he asks, “Where do we stop?”

“Do I think seat belts are a good thing? Absolutely,” Packard says. “But I believe it’s an issue of personal freedom and personal responsibility, and I don’t believe the government should be telling us that we have to put on a safety device. It should be up to the individual.”

All other states have some form of seat belt law, but the way they’re written makes a difference.

In states with the strictest primary enforcement laws, the police are allowed to stop and ticket people if they’re unbelted. With “secondary enforcement,” officers can give tickets to people not wearing seat belts only when they stop vehicles for another violation.

In 2015, states with primary enforcement seat belt laws had a 91.2 percent use rate; in states with secondary enforcement, it was 78.6 percent.

The difference in the usage rates directly translates to lives saved. A study by the Insurance Institute for Highway Safety found that in states that strengthened their laws from secondary to primary enforcement, driver death rates declined by about 7 percent.

Primary for All

Consumer Reports believes that every state should have primary seat belt enforcement for the front and rear seats. “Stronger seat belt laws mean fewer deaths on our roads,” says William Wallace, a policy analyst for Consumers Union, the policy and advocacy arm of Consumer Reports. “It’s time for all states to step up and pass these proven measures, which can keep a crash from becoming a tragedy.”

Advocates for Highway & Auto Safety publishes regular “Roadmap Reports” comparing seat belt laws in all 50 states.

“The U.S. still has the lowest rate of seat belt usage in the developed world,” says Chris Caruso from Automotive Safety Consulting. “Imagine how many more lives could be saved if 100 percent of occupants used their seat belts 100 percent of the time.”

Editor's Note: This article also appeared in the August 2016 issue of Consumer Reports magazine.