A crash is a stop. The only question that matters to the body is how much distance the stop is spread over, because the average force on a person is the energy of their motion divided by the distance they lose it in. A belted person loses it across feet of crumpling metal. An unbelted person loses it across inches of dashboard. Same speed, same crash, six times the force.
The idea. Engineers call it ride-down. The front of a car is built to collapse in a controlled way, and in a hard frontal crash the structure folds over something like two feet before the cabin stops. A person strapped to the seat is tied to the car, and so slows down with it over that whole distance, plus a few more inches as the belt stretches. The occupant rides the crash down with the structure, which is what the structure was built for. A person who is not belted is a separate object. When the car begins to stop, that person keeps traveling at the speed the car had before the crash, across the gap between the seat and whatever is in front of it, and the stop finally happens against the dashboard, the steering wheel, the windshield or the back of the seat ahead, over the few inches those things give. The Pole showed what happens when a narrow object takes the crush distance away from the car; the unbelted body takes it away from itself.
The arithmetic. It is an illustration, not any one crash. A car stopping from 50 mph over about two feet of crush averages roughly 40 times the force of gravity on the person riding it down. The same person stopping from the same 50 mph over about four inches of dashboard averages roughly 250 g. The speed is the same and the energy is the same; the force is about six times greater because the stopping distance is about six times shorter. The belt is not what hurts in that picture. It is what spreads the stop over the longer distance, across the pelvis and the collarbone, which are the parts of the skeleton built to take it. The federal safety agency’s figures for the result are plain: a seat belt cuts a front-seat car occupant’s risk of fatal injury by 45 percent and of moderate to critical injury by 50 percent, and in a pickup, SUV or van by 60 and 65 percent; in 2024, 48 percent of the passenger vehicle occupants killed in crashes were unrestrained, 56 percent of those killed at night (NHTSA). The crash that puts the arithmetic on a Texas road this weekend: early Sunday on North Loop 1604 West in San Antonio, police said a speeding driver lost control and hit a concrete support pillar, neither he nor his passenger was wearing a seat belt, the passenger died at the scene, the driver was hospitalized, and police said he was found to be intoxicated; the investigation is open and no one is named here (KSAT).
What the air bag does, and does not do. The bag is built for the belted body. The federal agency’s own words are that air bags are supplemental protection, designed to work best in combination with seat belts, and are “designed to work with seat belts, not replace them”; a frontal bag inflates in less than a twentieth of a second, in crashes about as hard as hitting a solid barrier at 8 to 14 mph or more, and frontal bags have saved more than 50,000 lives over thirty years (NHTSA). What the bag adds is a few more inches of stopping distance for the head and chest of a person the belt has already held in the seat. For a person the belt did not hold, the bag is something else to hit at full speed, which is why the agency warns that its force “can seriously injure or even kill you if you’re not buckled up” (NHTSA).
The injuries. They follow the distance. Over feet, the belted body shows belt bruising across the chest and hip, and the organs inside still move, which is the third collision that The Third Collision explains, the aorta tearing where it is anchored and the brain sliding inside the skull, but at a fraction of the force. Over inches, the unbelted body meets the wheel and the dash with the chest and the face, the windshield with the head, and, when the car rolls or the door opens, nothing at all: ejection is the end of the ride-down, and the federal agency calls it “almost always deadly” (NHTSA), which is what Thrown Clear and Thrown are about.
What the law asks. Two separate questions, and the defense would like them to be one. The first is who caused the crash, and the belt has nothing to say about it: a driver who was speeding, or drunk, or crossed the line caused the stop, belted passenger or not. The second is how much of the injury the missing belt added, and since 2015 a Texas jury may hear that question, and only for that purpose: the Supreme Court of Texas held that evidence a person was not wearing a seat belt is admissible to apportion responsibility when the failure caused or contributed to the injuries, and not to decide who caused the crash, the rule The Belt walked through. The jury sets a percentage for everyone whose conduct contributed (Civil Practice and Remedies Code Section 33.003) and the injured person is barred only when his own share passes half (Section 33.001), which is Comparative Fault. The question is always the same arithmetic in a different voice: how much of this injury was the stop, and how much was the distance.
The move. The crush. Photograph the car before it is scrapped, because the depth of the crush is the stopping distance the belted body had, and the interior tells the rest: a dented dash, a bent wheel, a starred windshield and a stretched belt webbing are the marks of where each person’s stop actually happened. The event data recorder keeps the speed change and, in many cars, whether the driver’s belt was buckled, which is Delta-V. The hospital record maps the injuries to the distance. A reconstructionist can put a number on the g the belted body saw and the g the unbelted body saw, and that number is the case.
A crash is a stop. The belt decides whether the body stops with the car, over feet, or alone, over inches, and the law asks the two questions in order: who caused the stop, and who shortened the distance.
The figures: NHTSA, Seat Belts (a seat belt reduces the risk of fatal injury to front-seat passenger car occupants by 45 percent and of moderate to critical injury by 50 percent, and for light-truck occupants by 60 and 65 percent; 48 percent of passenger vehicle occupants killed in 2024 were unrestrained, 56 percent at night; ejection almost always deadly; air bags are designed to work with seat belts, not replace them, and their force can seriously injure or kill the unbelted); NHTSA, Air Bags (supplemental protection designed to work best with seat belts; inflation in less than a twentieth of a second; deployment in crashes equivalent to hitting a solid, fixed barrier at 8 to 14 mph or higher; more than 50,000 lives saved by frontal air bags over a 30-year period); KSAT, Oct. 11, 2026, 10:09 a.m. (police called about 2:11 a.m. Sunday to the 4600 block of North Loop 1604 West, westbound; police said the driver was speeding, lost control and hit a concrete pillar; neither man belted; the passenger pronounced dead at the scene; the driver hospitalized and found to be intoxicated, police said; investigation ongoing). The law: Tex. Civ. Prac. & Rem. Code § 33.003 and § 33.001; the seat-belt rule is Nabors Well Services v. Romero (Tex. 2015), as The Belt describes it. The ride-down arithmetic is illustrative: the average deceleration over a stopping distance is the square of the speed divided by twice the distance, 50 mph over two feet against 50 mph over four inches. General information, not legal advice.
