power unit

power unit (plural power units)

1. (transport) A truck (large road vehicle) capable of moving under its own power.
   • 1988 October 12, National Transportation Safety Board, “CASE NO. 9”, in Safety Study: Case Summaries of 189 Heavy Truck Accident Investigations‎^[1], archived from the original on 17 February 2017:

     The combination unit was traversing a straight section of roadway, on an approximate 4 percent upgrade, when the tractor began to jackknife. As the power unit rotated clockwise, it left the roadway to the right and traveled several feet before the driver corrected the jackknife. The unit was redirected toward the travel lanes, however, before it re-entered the roadway, it rotated counterclockwise, and the driver lost control. The power unit crossed into the eastbound lane where it was struck in the right side by an eastbound van. Although a saddle tank on the power unit ruptured, there was no fire.

2. Any other unit capable of providing power.
   • 1944 November and December, T. F. Cameron, “Motor and Cartage Working”, in Railway Magazine, page 335:

     For many years the horse provided a cheap and effective power unit for town cartage, but in recent years it has been replaced largely by mechanical power.

• straight truck
• tractor, truck-tractor

• auxiliary power unit