Motive power depot

A motive power depot (MPD) or locomotive depot, or traction maintenance depot (TMD), is where locomotives are usually housed, repaired and maintained. They were originally known as "running sheds", "engine sheds" or just "sheds". Facilities are provided for refuelling and the replenishing of water, lubricating oil and grease and, for steam engines, the disposal of ash. There are often workshops for day-to-day repairs and maintenance, but locomotive building and major overhauls are usually carried out at locomotive works. (Note: In American English, the term depot is used to refer to passenger stations or goods (freight) facilities, not to vehicle maintenance facilities.)

The equivalent of such depots in German-speaking countries is the Bahnbetriebswerk or Bw, which has similar functions, with major repairs and overhauls being carried out at Ausbesserungswerke. The number of those was reduced drastically following the changeover from steam to diesel and electric traction, and most modern Bw in Germany are specialised depots, often responsible for a single locomotive class.

Engine sheds could be found in many towns and cities, as well as in rural locations. They were built by the railway companies to accommodate the locomotives that provided their local train services. Each engine shed would have an allocation of locomotives that would reflect the duties carried out by that depot. Most depots had a mixture of passenger, freight and shunting locomotives, but some, such as Mexborough, had predominantly freight locomotives, reflecting the industrial nature of that area in South Yorkshire. Others, such as Kings Cross engine shed in London, predominantly provided locomotives for passenger workings.

Nearly all depots at that time had a number of shunting locomotives. Normally 0-4-0T or 0-6-0T tank engines, they would be allocated to shunting duties in goods yards, carriage sidings, goods depots and docks.

Many large rail connected industrial sites also had engine sheds, primarily using shunting locomotives.

Each railway company had its own architectural design of engine shed, but there were three basic designs of shed:

The turntables for straight and dead end sheds were generally outside. Those in roundhouses could be inside, such as those at York in the UK, or outside, such as that at the East Broad Top Railroad & Coal Company in Rockhill, Pennsylvania, USA.

There were six primary activities that took place at sheds.