Outside built-up areas, **special vehicles with a Maximum Authorized Mass (MMA) exceeding 3,500 kilograms** must travel on the roadway and not on the hard shoulder. This is because these vehicles, like automobiles, are required to use the right lane of the roadway, except in specific situations that require the use of another lane, such as traffic or road conditions.

On the other hand, **special vehicles with an MMA not exceeding 3,500 kilograms** must travel on the hard shoulder if there is no specific lane for them. This includes vehicles like mopeds and bicycles, which must also use the hard shoulder when possible.

In summary, the regulations establish that heavier vehicles, such as special vehicles with an MMA exceeding 3,500 kilograms, must travel on the roadway, while lighter ones must do so on the hard shoulder when there is no specific lane for them.