The **seat belt** is a crucial element for the protection of vehicle occupants in the event of an accident. Its main function is to keep people in their seats and prevent them from being ejected from the vehicle, which significantly increases the chances of surviving an accident.

However, there are exceptions to its mandatory use. One of these exceptions is in the case of a **serious illness duly justified**. This means that if a person has a medical condition that prevents the safe use of the seat belt, and this condition is documented and justified by a healthcare professional, they may be exempt from using it.

It is important to remember that, in general, the seat belt must be properly adjusted to the body to be effective. The **shoulder strap** should pass over the collarbone and the center of the chest, while the **lap belt** should be over the hip bones, always below the stomach. A poorly positioned belt can cause serious injuries in the event of an accident.


Therefore, although the use of the seat belt is generally mandatory and vital for safety, there are specific situations, such as certain serious illnesses, where its use may not be required.