What is a tractor head?
A tractor head, also known as a prime mover, semi-tractor, truck, semi-truck, rig or big rig, or simply a tractor, is a heavy-duty towing engine that provides motive power for towing or trailering a load.
A tractor head is made up of a cab and a short chassis behind it for connecting to a semi-trailer. Both tractor heads have a universal fifth wheel coupling that can be used with any kind of semi-trailer. Tractor heads are distinguished by their cab design, which can be either high or low with a high-capacity towing engine that generates motive power.