big rigs

A semi-trailer truck is the combination of a tractor unit and one or more semi-trailers to carry freight. It is variously known as a transport (truck) in Canada; semi or single in Australia; semi, tractor-trailer, big rig, or eighteen-wheeler in the United States; articulated lorry, abbreviated artic, in Britain and Ireland. A semi-trailer attaches to the tractor with a fifth wheel hitch, with much of its weight born by the tractor. The result is that both tractor and semi-trailer will have a distinctly different design than a rigid truck and trailer.