The agricultural tractor shown in the photograph has a maximum authorised mass not exceeding 3,500 kg. Is it allowed to drive along the hard shoulder?

Why this is the correct answer

Under Spanish traffic regulations, certain slow or special vehicles are required to travel on the hard shoulder (arcén) when it is passable and wide enough. These include: bicycles, mopeds, animal-drawn vehicles, reduced-mobility vehicles, and special vehicles (such as agricultural tractors) with a maximum authorised mass (MMA) not exceeding 3,500 kg. Since the tractor in the photograph does not exceed 3,500 kg, it is obliged to use the hard shoulder — it is not just allowed, it is mandatory. This is because tractors are very slow vehicles (often limited to 25 km/h with a trailer) and would create a serious safety hazard if they occupied a lane on a road where other vehicles travel at 80-90 km/h. Regular cars (turismos) are NOT special vehicles, so they must always travel on the roadway (calzada) and are generally prohibited from using the hard shoulder. Important: if a special vehicle exceeds 3,500 kg MMA, it must travel on the road (not the shoulder), except in emergencies.