London Underground rolling stock numbering and classification

Rolling stock used on the London Underground and its constituent companies has been classified using a number of different schemes. This page explains the principal systems.


 * Rolling stock for the Central London Railway (CLR), the Underground Electric Railways Company of London (UERL), the Metropolitan District Railway (MDR) and the Metropolitan Railway are described
 * For information about individual classes of locomotives and other rolling stock, see: London Underground rolling stock

Electric Multiple Units
The numbering and classification of electric multiple unit stock on the London Underground is usually related to the type of line that the trains are used on. There are two distinct types of line: 'Sub-surface' lines (earlier lines built on the cut-and-cover method, which use trains of similar size to those on the national railway network), and 'Tube' lines (deep-level lines, built to a more restricted size). The 'Sub-surface' lines are the Circle, District, East London, Hammersmith & City and Metropolitan lines; all the other lines are 'Tube' lines.

Unit Classification
The method of classification depends on the type of line the train operates on:

Tube Stock
Tube Stock is classified by the year in which it was anticipated at the time of ordering that it would be delivered (this sometimes proves optimistic), e.g. 1992 Stock. This system was commenced by London Underground with the 1935 Stock. The large number of broadly similar Tube trains built for the UERL during 1923-1935 were called 'Standard Stock', although there were many detail differences. They replaced the UERL's original 'Gate Stock', introduced for the opening of the Bakerloo, Piccadilly and Hampstead (Northern) lines, and the CLR's 1903 Stock, constructed to replace the locomotive and carriage sets used at its opening in 1900.

Sub-surface Stock
Sub-surface Stock is classified by a letter, usually issued sequentially, and which is sometimes followed by the last two digits of the year of delivery, e.g. Q23 Stock. This system was commenced by the MDR for its stock. When the London Underground was formed the ex-Metropolitan Railway units were fitted into this series (types MV, MW, T, V, VT and W). By 1960, most letters had been allocated, and the decision was taken to re-issue 'A' (for the Amersham electrification) to the new Metropolitan stock. The next sub-surface types were built for the Circle and District lines, and the opportunity was taken to allocate 'C' and 'D' respectively, omitting 'B'.

Types of Unit
On most lines, trains are formed from a pairing or triplet of units. Units are 'single-ended', where there is a driving cab at one end only, or 'double-ended', where there is a driving cab at both ends. In addition, some units have no driving cabs, and thus must always be included in the middle of a formation of units.

Car Classification
The different types of car used to make up electric multiple units are referred to by a series of codes, described below:

On most lines the end cars of units are described as 'A' end cars or 'D' end cars ('B' end until the 1930s). In general the 'A' end is the north or west end and the 'D' end is the south or east, but the reverse applies on Bakerloo Line. On lines with a loop at the end that allows trains to turn round (e.g. at Heathrow on the Piccadilly Line, and Kennington on the Northern Line), this system cannot apply rigidly.

Car Numbering
Each car carries its own unique number (although many numbers below 10000 have been reused by newer cars after the withdrawal of older trains), and unit numbers are not applied. Although car numbers have been allocated in a variety of different series over the years, two basic principles can be identified:
 * A-end cars have even numbers and D-end cars have odd numbers; cars will usually be renumbered if they are turned to the opposite end. (This principle was applied by the MDR and continued by London Underground.)
 * Cars within a unit usually either share the same last two digits, or one end uses the next odd digit after the other end's even digit; frequently when cars are swapped between units they will be renumbered to maintain this approach. (This principle was introduced by the London Underground.)

1931 Numbering Series
In 1931, the UERL began a major renumbering of all its multiple unit cars. The series was adopted by the London Underground when it took over in 1933 and renumbered stock inherited from other lines into the UERL's series. The table below shows the number ranges used for the inherited stock and initially used by the UERL/London Underground for new stock (including the LU-design M and N Stock and Q38 Stock DM cars - Q38 Stock trailers were allocated numbers in one of the new numbering series described later):

Notes:
 * Ex-Metropolitan Railway hauled stock retained their original numbers as they did not conflict with any of the numbers allocated to the multiple unit stock; they were all numbered between 41 and 510 (511-519 were later allocated to cars converted from multiple unit to hauled stock).
 * A 'Composite' car had both First and Third class seating. All Tube stock was Third class only; all ex-MDR stock was Third class except those trailers identified as Composite. In the ex-Metropolitan Railway ranges First class stock took the lowest numbers, then Composites, then Thirds. London Underground gradually declassified all stock to Third class, the process being completed in the early years of World War II.
 * Some cars converted to Trailers after 1935 carried a '0' prefix to their numbers, as was applied to new-build trailer cars in this period. In some cases, such cars briefly retained their original DM numbers but with a '0' prefix before being renumbered into the appropriate range for trailers.

Later Developments
This standard number series proved to be short lived; from 1935 onwards a variety of different series have been used, so the current list of numbers looks rather random. The table below sets out the numbering systems used for each type of London Underground stock:

Notes:
 * 17000 and 20000 were used for cars converted from T Stock in 1946/1947 as prototypes for A Stock. 17000 was renumbered 17001 following further modifications.