Semi-trailer truck
combination of a tractor unit and one or more semi-trailers to carry freight / From Wikipedia, the free encyclopedia
A semi-trailer truck, also known as a semi, tractor-trailer, big rig, eighteen-wheeler, or (in the United Kingdom and Ireland) articulated lorry or artic is a vehicle that has a towing tractor and a semi-trailer that carries the freight. They use diesel fuel.
![US type convential semi-tractor](http://upload.wikimedia.org/wikipedia/commons/thumb/9/92/Red_freightliner.jpg/320px-Red_freightliner.jpg)
![UK type cab-over-engine semi-tractor](http://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/Royal_Mail_PL05SFF.jpg/640px-Royal_Mail_PL05SFF.jpg)