Semi-trailer truck
A semi-trailer truck,[1] (also known by a wide variety of other terms - see below) is the combination of a tractor unit and one or more semi-trailers to carry freight. A semi-trailer attaches to the tractor with a type of hitch called a fifth wheel.
"Big rig", "Eighteen wheeler", and "Truck and trailer" redirect here. For use of the expression in rugby union, see Glossary of rugby union terms § T. For other uses, see 18 wheeler (disambiguation) and Big Rig (disambiguation).
There are a wide variety of English-language terms for a semi-trailer truck, including:
US English:
British English
Canadian English
Role in trade[edit]
Modern day semi-trailer trucks often operate as a part of a domestic or international transport infrastructure to support containerized cargo shipment.
Various types of rail flat bed train cars are modified to hold the cargo trailer or container with wheels or without. This is called Intermodal or piggyback. The system allows the cargo to switch from highway to railway or vice versa with relative ease by using gantry cranes.
The large trailers pulled by a tractor unit come in many styles, lengths, and shapes. Some common types are: vans, reefers, flatbeds, sidelifts and tankers. These trailers may be refrigerated, heated, ventilated, or pressurized, depending on climate and cargo. Some trailers have movable wheel axles that can be adjusted by moving them on a track underneath the trailer body and securing them in place with large pins. The purpose of this is to help adjust weight distribution over the various axles, to comply with local laws.