Tractor Unit

High Quality Content by WIKIPEDIA articles! A tractor unit, traction unit, road tractor, or prime mover (Australian English), is a heavy-duty commercial vehicle within the large goods vehicle category, usually with a large displacement diesel engine, and several axles. The tractor unit serves as a method of moving trailers (most often semi-trailers). Different trailers can be swapped between tractor units quickly, so the tractor unit does not stand idle whilst the load is unloaded or loaded, unlike a rigid, and is not restricted to one type of goods as trailer types can be swapped e.g. bulk tipper to a box van. The tractor-trailer combination also means that a load can be shared across many axles, yet be more maneuverable than an equivalently sized rigid truck (see trucks). The tractor unit couples to the trailer using some sort of mechanical lock system, usually a fifth wheel coupling. A tractor unit is primarily designated a freight vehicle, and is most common in the heavy goods vehicle (HGV) class of vehicles, although smaller van based tractor units do exist.... Mehr