In Class 8 tractors (using the US designation), the cab-over design allows the vehicle's wheelbase to be shorter than in the conventional arrangement, wherein the engine is placed in front of the cab, covered by a horizontal or sloping hood that opens to allow engine access. Its shorter wheelbase allows cab-over semi trucks to have a shorter overall length, thereby allowing for longer trailers to be used. For light- and medium-duty solid- or rigid-axle trucks, the cab-over design requires less length for the cab and engine, in a given wheelbase, and therefore allows a greater length for the truck body or load area.