The Southern Railway created numbering and classification systems for its large fleet of Electric multiple units that were perpetuated by the Southern Region of British Rail until the early 1980s, when the impact of TOPS was felt. Even now, some stock have still been allocated Southern-style classifications in a semi-official manner.

Unit Numbering

Unit numbers were allocated in a series commencing from 1001, which followed the set numbers given to semi-fixed formations of hauled coaching stock, 1-1000. Different types of unit were given numbers according to the following division:

 1001-1200: Unpowered trailer units for working with 3Sub stock (this series was later expanded to include unit numbers 989-1000) 1201-1800: 3Sub stock (ex-LSWR units had 1200 added to their original number) 1801-1999: Two-car inner-suburban stock (e.g. 2Nol) 2001-2899: Two-car outer-suburban stock (e.g. 2Bil) 2901-3999: Four- Five- and Six-car outer-suburban stock (e.g. 4Lav) 4001-4999: Four-car inner-suburban stock (4Sub and 4DD) 5001-5599: British Railways four-car inner-suburban stock (4EPB) 5601-6999: British Railways two-car stock (e.g. 2Hap) 7001-7999: British Railways four-car outer-suburban stock (e.g. 4Cig) 8001: Temporary eight-car formation (8Vab) S1-S101: Departmental (non-revenue earning) stock 

This series was perpetuated by the Southern Region of BR, though with modifications, as older set numbers were reused for the following different types:

 001-099 : Parcels and departmental stock (Former Sxxx units renumbered into this series) 301-999 : Trailer Control stock (first digit indicated number of cars, e.g. 301 = 3TC) 1001-1499: Diesel Electric Multiple Units (e.g. 6S) 

The 2Pep stock reused number 2001, the 4Rep stock reused numbers from 3001 and the 4Pep stock reused numbers 4001/4002. This series was abandoned only in 1983, when units were renumbered to fit in with the TOPS classification system, which had already (nominally) been in use for a decade!

Classification

The early AC overhead electric multiple unit types were referred to by a two-letter code. This was adapted for the DC third rail system that was adopted as standard by the Southern Railway, with unit type being given a three-letter code (sometimes two-letters) prefixed by the number of carriages within each unit, e.g. 4Sub for a 4-car Suburban type set.

The Southern Region of British Rail perpetuated this method of classification, and the same principles were also adopted for their fleet of Diesel Electric Multiple Unit stock, but these types only used single letter codes. The last types to be officially allocated a designation in this series was the Pep stock of the early 1970s. However, some types built since then have been given semi-official designations in this style.

NB: This was different from the system used by British Rail (adopted from the LNER) to indicate the type of non-powered coach -- see British Rail coach designations.

AC Overhead EMUs

DC Third Rail EMUs

Diesel Electric Multiple Units

See Also:

• British Locomotive and Multiple Unit Numbering and Classification
• List of British Rail classes
• British Rail brand names