A semi-trailer truck is a type of large vehicle, made to pull a large trailer of some sort behind it. (Note: most of the posts pertaining to this are in the ambiguous trailer tag instead) In order to pull the heavy amount of cargo, they have powerful motors and are usually rated as heavy duty trucks or medium duty trucks.

The vehicles are very wide, but just wide enough to fit inside a road lane, and are tall to accommodate for better visibility and better aerodynamics for the following trailer(s).The driver's cabin sits up higher (usually twice as high or more) from the road than a typical car, and are boxy in shape.