A Shunt truck, also known as a Spotting tractor, Yard truck, Yard Dog, Yard jockey, mule, etc. 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 hitch to carry the freight. The truck picks up the semi trailer via an adjustable hight fifth wheel, to suite differing pin heights of trailers in transit.


Originally companies used an old articulated tractor unit(Semi-trailer truck in US) to move trailers in the yard. But getting in and out to un hitch the trailer and the large cabs made manuvering hard in tight spaces, so many were fitted with stripped down cabs. The rise in Ro-Ro ferry traffic in Europe lead to the introduction of purpose designed tugs by dock & ferry operators with automatic coupling and the ability to adjust the hitch hight from the cab which was made smaller to fit in the ships hold & turn in confined spaces.

The Shunt truck of this design seems to be a distinctly North American Idea.[clarification needed] There are only 2 manufacturer that use generally the same specs, both are located in North America.[clarification needed]


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. Distinctions between a Shunt truck and a regular Truck are several and noticeable:

  • The typical Cab over design is held to, but with no passenger (or sleeping) space provided, as it is exceptionally rare for these vehicles to be on public roads.
  • 12-gauge steel side wall Cab construction with 1/2-inch (13 mm) steel floors for protection in abusive & dangerous work environments.[1]
  • the semi-trailer hitch has an integrated lifting mechanism designed to allow the semi-trailers legs to remain in the down position during movement. 5 inches (130 mm) and 70,000 lb. of Hydraulic lift are typically.
  • 360 Degree View for to facilitate five to six moves an hour


Several alternatives were tried before the modern design evolved and gained in popularity

  • Ex WD aircraft tugs and a fifth wheel dolly
  • Tractors - county built a prototype tractor for the army for a similar roll, unloading troup and supply craft onto beaches
  •  ?



  1. "Capacity Texas".

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