 A road tractor coupled to a semi-trailer is often called a semi-trailer truck or "semi" in North America & Australia, and an articulated lorry or "artic" in the UK.Semi-trailers with two trailer units are called B-doubles (Australian English) or tandem tractor-trailers, tandem rigs, or doubles (American English).Other terms used are "B-train" or (when there are three or more trailers) "road train".