The **bodywork** and **chassis** of a vehicle are passive safety elements that help protect occupants in the event of an accident. Although these structures are strong and designed to deform and absorb impact, they are not sufficient on their own to ensure passenger safety.

The **seat belt** is a crucial device that complements the protection offered by the bodywork and chassis. Its main function is to keep occupants in their seats during a crash or rollover, preventing them from being ejected from the vehicle. Wearing the seat belt correctly fastened **doubles the chances of surviving an accident**. Furthermore, since its implementation, there has been a significant reduction in traffic accident fatalities.

Therefore, even if the bodywork is strong, **it is essential to use the seat belt** to maximize occupant protection. Not using it would be a mistake, as it would mean losing a fundamental part of the vehicle's passive safety.