The **seat belt** is a **passive safety** element that must be used by **all people** traveling in a vehicle that has it installed, including both drivers and passengers. This is mandatory on **all roads**, that is, on highways, expressways, motorways, and streets.

There are some exceptions to this rule, but they only apply when the vehicle is driving within a town or city. For example, taxi drivers on duty or drivers who are parking in reverse may not use the seat belt in these specific situations. However, these exceptions do not apply on highways, expressways, or motorways, where the use of the seat belt is always mandatory.

Therefore, the driver of a mixed vehicle with seat belts must use them on **all roads**, regardless of the type of highway or street they are driving on.