America Fixed the Seatbelt Problem in 1973. Then Congress Got Letters.

In 1973, the National Highway Traffic Safety Administration did something radical: it required every 1974-model car sold in the United States to include a starter interlock that prevented the engine from turning over unless the driver's seatbelt was fastened. Seatbelt usage surged by a factor of seven, essentially overnight, because the engineering was cheap, the mechanism was simple, and the data was unambiguous.

Then the letters arrived, and everything fell apart.

Congress received more constituent complaints about seatbelt interlocks than it did about Richard Nixon firing Special Prosecutor Archibald Cox during the Saturday Night Massacre, according to Yale Law School professor emeritus Jerry Mashaw, co-author of The Struggle for Auto Safety.^[1] Apparently, having to buckle up before driving ranked higher on the national outrage index than a constitutional crisis. Congress responded by killing the interlock mandate in the Motor Vehicle and Schoolbus Safety Amendments of 1974, and for good measure, decreed that the seatbelt warning buzzer could annoy drivers for no more than eight seconds.^[2]

That was 52 years ago. In the intervening half-century, approximately 2 million Americans have died in traffic crashes. NHTSA's 2024 FARS data, released this April, reports that 22,713 passenger vehicle occupants were killed last year, and 48% of those with known restraint status were not wearing a seatbelt.^[3] That translates to roughly 10,900 people who died, in part, because they weren't buckled up in a country where the technology to make buckling up a condition of driving has existed since Gerald Ford was in office.

Today, exactly one automaker has voluntarily reintroduced the interlock concept. General Motors ships a feature called "Buckle to Drive" as standard equipment on its 2025 and 2026 models. When activated, the vehicle refuses to shift out of Park for 20 seconds unless the driver's seatbelt is fastened. Some models extend the requirement to the front passenger. It is, functionally, the 1973 interlock with a politer name, a timeout grace period, and the ability to be toggled off in the settings menu.^[4]

Nobody else has followed. Ford, Toyota, Honda, Hyundai, Stellantis, Volkswagen: none of them ship anything comparable as a standard feature across their lineups. The technology costs approximately nothing relative to the sticker price of a new car. It requires no new hardware because every modern vehicle already has seatbelt buckle sensors (they drive the warning chime and the airbag calibration). Yet only GM elected to flip that sensor from "advisory" to "gate."

The math on what universal interlocks could do is grimly straightforward. NHTSA's own research, published by Charles Kahane, found that seatbelts reduce the risk of fatal injury by 45% for front-seat passenger car occupants and by 60% for light-truck occupants.^[5] Apply those figures to the 10,900 unrestrained deaths in 2024, and even if interlocks only achieved 50% additional compliance among people who currently don't buckle up, the results range from roughly 2,450 to 3,270 fewer deaths per year. Extrapolate that conservatively across the 50 years since Congress killed the mandate, and you get a cumulative toll in the neighborhood of 125,000 preventable deaths.

That estimate is deliberately conservative. It assumes only half the unbuckled population would comply with an interlock rather than bypass it, and uses the lower 45% effectiveness figure for most of the calculation. The real number is likely higher, and it does not account for the tens of thousands of severe injuries (spinal fractures, traumatic brain injuries, ejection-related paralysis) that seatbelts prevent in non-fatal crashes.

The strongest argument against interlocks remains the one that won in 1974: personal freedom. New Hampshire, the only state without any seatbelt law, has 78.2% observed belt usage and 59% of its occupant deaths are unrestrained. California, with primary enforcement and aggressive campaigns, achieves 97.5% usage, yet still sees 43% of its occupant deaths among the unrestrained.^[6] There's a behavioral floor: some fraction of drivers will not buckle up regardless of the legal framework, and those drivers cluster with other high-risk behaviors. Speed, impairment, and belt refusal travel together in the same vehicles. In FARS data, pickup trucks show both the highest impairment rate among vehicle classes (20.1% of fatal-crash-involved drivers testing positive) and the highest unrestrained death fraction (70% of killed pickup occupants were unbuckled).^[7] The counterargument is real: a seatbelt would not have saved every one of those 10,900 people, because many of them were also driving drunk, or 40 mph over the limit, or both, in crashes severe enough that even a belted occupant might not have survived.

And pickup owners have a legitimate, if narrow, point: when you're backing a trailer two inches in a field at walking speed, a seatbelt is pure friction. GM's answer, a 20-second timeout rather than a hard interlock, acknowledges this reality. So does the ability to turn the feature off entirely in the settings menu, which is the same compromise that made the 1974 interlocks trivially easy to defeat by simply buckling the belt behind your back before sitting down.

But the existence of a bypass doesn't invalidate the intervention. Sweden mandated seatbelt interlocks on all new heavy vehicles in 2007, and belt usage among Swedish truck drivers went from around 40% to over 90% within five years.^[8] The behavioral floor is real, but the behavioral ceiling is a lot higher than 91% when the car itself participates in enforcement.

What happened in 1974 was a cost-benefit calculation performed by Congress using letters as data and reelection as the objective function. The interlock worked, and seatbelt use went up sevenfold. People were annoyed. The annoyance was politically louder than the lives being saved, because the dead don't write letters to their representatives, and the living can't imagine being in the 48%. Fifty-two years later, the same feature is reappearing, one manufacturer at a time, marketed not as a mandate but as a "technology" with a "toggle" and a "timeout," because that's what it takes to solve a problem America already solved and then deliberately unsolved.

What you can do: Check whether your vehicle has a seatbelt interlock or reminder system. If you drive a 2024 or newer GM vehicle, verify that Buckle to Drive is enabled in your infotainment settings, as it may default to off. If you have teen drivers, activate Teen Driver mode, which makes the interlock mandatory. For everyone else, the math is absurdly simple: buckling up takes 1.5 seconds and cuts your risk of dying by nearly half. If you're sitting in the rear seat of any vehicle, buckle up there too. Rear-seat usage lags the front by double digits, and the physics of a 40-mph impact don't check which row you're in.

Source: NHTSA FARS 2014–2023 (crash involvement and toxicology data) and NHTSA 2024 Annual FARS (restraint status). The 125,000 preventable-death estimate uses conservative assumptions: 50% additional compliance and 45% effectiveness applied uniformly across 50 years, without adjusting for changing fleet mix, belt technology improvements, or the higher 60% effectiveness for light trucks. Actual preventable deaths are likely higher. See methodology for caveats.