A safety belt is a strap that holds you securely in your seat, most commonly in a car, airplane, or other vehicle. When you buckle your safety belt (also called a seat belt), it stretches across your lap and often your chest, keeping you from being thrown forward if the vehicle stops suddenly or crashes.

Safety belts work by spreading the force of a sudden stop across the strongest parts of your body. Without one, a person sitting in a car that crashes at just 30 miles per hour would be thrown forward with tremendous force, like falling from a three-story building. The belt keeps you in your seat, giving the vehicle's other safety features, like airbags, time to work.

The invention of the modern three-point safety belt (the kind that goes across your lap and chest) by Swedish engineer Nils Bohlin in 1959 has saved over a million lives. Before safety belts became standard, car accidents were far more deadly. Today, wearing a safety belt is required by law in most places because the evidence is overwhelming: buckling up is one of the most effective ways to survive a car crash.