All occupants of a vehicle, including passengers, must **wear the seat belt fastened and correctly buckled** at all times, regardless of whether they are on urban or interurban roads. This is an essential safety measure to protect all occupants in the event of an accident.

- **Use of the seat belt**: All passengers must use the seat belt on any type of road or street. The exceptions are very specific and do not apply to common passengers.

- **Correct positioning of the belt**: The belt must be well adjusted to the body. The **chest strap** should pass over the collarbone and the center of the chest, while the **lap strap** should be over the hip bones. This ensures that the belt functions correctly and minimizes the risk of injury.

- **Child restraint systems**: Children who are less than 135 centimeters tall must use child restraint systems appropriate to their size and weight. These systems must be well secured and placed in the rear seat for greater safety.

In summary, all occupants of a vehicle must wear the seat belt correctly buckled to ensure their safety in the event of an accident.