How Seat Belts Work
While most people agree that seat belts can be a life-saving feature of any vehicle, many people do not understand how seat belts work. The seat belt was engineered to keep you in the seat and to prevent you from being thrown out the front windshield or out the door if it should open during an accident.
When a vehicle suddenly stops your body continues to move forward at the original speed of the vehicle. To prevent you from going through the windshield or into the dashboard, the seat belt spreads out the pressure from the force to various parts of your body. These areas may still receive injury from the seat belt, but these parts of your body are able to withstand the force of the seat belt much better than your head could handle the force of hitting the windshield or dashboard.
To learn how a seat belt works you need to understand the location and design of the seat belt. The lap belt crosses your pelvis and the shoulder belt crosses your rib cage. Both of these areas have a better chance of withstanding the force of a sudden stop. The material or webbing of a seat belt will give slightly even when the brakes are applied. This little bit of give in the material is better than hitting the solid material of the dashboard or glass.
The vehicle determines when the seat belt is locked. If you try to lean forward while applying the brakes at a stop sign you will notice that you are only able to move an inch or two. The vehicle has a sensor that is activated when the brakes are pressed and also activates when the car is in an accident, similar to a sensor for an air bag.