A semi-trailer truck, also known as a semi, tractor-trailer, or (in the United Kingdom and Ireland) articulated truck or articulated lorry, is an articulated vehicle consisting of a towing engine (tractor in the United States, prime mover in Australia or truck in Ireland, the United Kingdom, Canada and New Zealand), and a semi-trailer (plus possible additional trailers) that carries the freight. A semi-trailer does not trail completely behind the towing vehicle, but is attached at a point that is forward of the rear-most axle of the towing unit, so that some fraction of the weight of the trailer is carried by the rear axle(s) of the prime mover. This arrangement requires both tractor and semi-trailer to be distinct in design from a rigid truck and trailer. |
