Traction Maintenance Depot

In the United Kingdom, a traction maintenance depot, or TMD, is a railway depot where locomotives are serviced and maintained. A traction and rolling stock maintenance depot, or T&RSMD, is a maintenance depot where locomotives, multiple units and are serviced and maintained. Each rail locomotive in the UK is allocated to a depot. Traditionally, locomotives would have normally been maintained at the depot where they were allocated.

Today, this is still the same for some train operating companies (TOCs). However, other train operating companies (such as Freightliner) have general codes with no specific location, whilst others (such as Southeastern) allocate entire class of trains to specific depots, but maintain their trains at any depots, including those with no trains allocated to them.

A small depot with minor facilities where locomotives are merely stored is often known as a stabling point in the UK.

At one time they were known as motive power depots. Such depots, particularly in the days of steam locomotives, would have more facilities than the modern stabling point, but did not carry out major repairs.

...
Wikipedia