The **seat belt** is a **passive safety** element that must be used by **all people** traveling in a vehicle that has it installed, including truck drivers. This applies on **all roads**, whether they are highways, expressways, motorways, or streets within towns.

There are some exceptions for not using the seat belt, but these are only valid in specific situations and, generally, within towns or cities. For example, taxi drivers on duty or drivers who are parking in reverse may be exempt. However, these exceptions do not apply on highways, expressways, or motorways, where the use of the seat belt is mandatory for everyone.

Therefore, the truck driver is **obliged to use the seat belt on all roads**, regardless of the type of road or the situation, unless they are in one of the specific exceptions mentioned, which do not apply on highways.