Terminal tractor
A terminal tractor, known in the United States as a shag truck, shunt truck, spotter truck, spotting tractor, yard truck, yard shifter, yard dog, yard goat, yard horse, yard mule, yard jockey, yard spotter, hostler, or mule, is a kind of semi-tractor intended to move semi-trailers within a cargo yard, warehouse facility, or intermodal facility, much like a switcher locomotive is used to position railcars. In the United Kingdom they are known as terminal lorries or terminal trucks.In the United States the term is most often called a yard driver or switcher, often given the nickname yard dog, affectionately not derogatively.