A number of different numbering and classification schemes were used for locomotives and multiple units operated by British Railways (BR), and this page explains the principal systems. This section also covers the post-privatisation period, as the broad numbering and classification arrangements have not altered since the break-up of BR.
Locomotives and multiple units (the majority being self-propelled) have frequently had similar arrangements for classification and numbering, so are considered together here.
Constituent companies In 1948, BR inherited a variety of locomotives and multiple units from the Big Four railway companies and some smaller concerns. Details of the numbering and classification systems used by the Big Four companies are covered in the following pages: Great Western Railway: GWR locomotive numbering and classification Southern Railway: SR locomotive numbering and classification and SR multiple unit numbering and classification London, Midland and Scottish Railway: LMS locomotive numbering and classification London and North Eastern Railway: LNER locomotive numbering and classification
In the main, new locomotives and multiple units built by BR to pre-nationalisation designs were numbered and classified according to the principles applied by the relevant Big Four company.
1948 numbering and classification Immediately after nationalisation, BR had to decide how to number and classify the stock it had inherited from the Big Four companies, and how newly built stock would be included. In the main, it decided to simply adapt what was already there.
Locomotives The classification systems of the Big Four were left unchanged for the inherited locomotives. However, BR decided to adopt the LMS power classification system as its preferred model and all inherited locomotives received a classification in this series as well as their traditional classification.
In order to remove the duplications of locomotive numbers, all locomotives were placed into a new number series as follows:Locomotive Renumbering Scheme The Railway Magazine issue 575 May 1948 page 203
RangeDescriptionRenumbering1-9999Ex-GWR steam locomotivesNumbers unchanged10000-19999Diesel and gas turbine locomotivesWithout reference to previous number, except pioneer mainline locos LMS 10000/10001, whose numbers were unchanged20000-29999Electric locomotivesSR CC1-3 to 20001-3, LNER 6000 to 26000, others without reference to previous number30000-39999Ex-SR steam locomotives (except Isle of Wight)Addition of 30000, except: C1 etc. to 33xxx, 21C101 etc. to 34xxx, 21C1 etc. to 35xxx, 3xxx series renumbered without reference to previous number40000-59999Ex-LMS steam locomotivesAddition of 40000, except 2xxxx series renumbered without reference to previous number into the 58xxx series60000-69999Ex-LNER steam locomotivesAddition of 60000, except 10000 to 6070070000-79999BR-design tender steam locomotivesNew Build80000-89999BR-design tank steam locomotivesNew Build90000-99999BR & War Department large freight locomotivesex-War Department locos renumbered without reference to previous number
This approach meant that the numbering arrangements adopted by the pre-Nationalisation companies were retained in the new system, and new locomotives built to the designs of the old companies were numbered appropriately in their series. Locomotives inherited from smaller concerns were numbered in the most appropriate regional list, e.g. ex-East Kent Railway stock utilised blank numbers in the 3xxxx ex-SR series.
The new series for diesel, petrol, gas and electric locomotives were arranged as follows:
RangeDescription10xxxMainline diesel locomotives11xxxDiesel-mechanical & diesel-hydraulic shunters (British Railways orders)12xxxEx-LMS shunters and over13xxxDiesel electric shunters (British Railways orders)150xxEx-LNER shunters151xxEx-GWR shunters152xxEx-SR shunters18xxxGas turbine locomotives20xxxEx-SR electric locomotives26xxxEx-LNER electric locomotives27xxxExpress passenger electric locomotives
Modern traction Numbering of electric multiple units was undertaken on a regional basis, with each region having its own series commencing from 001. Most diesel multiple units were not allocated unit numbers, though in later years numbers were allocated on a regional basis in the Scottish and Western regions, and by individual depots elsewhere. For more details on these series, see British Rail Regional Multiple Unit Numbering.
To classify electric stock, a two-letter prefix was used to indicate what type it was, followed by a number issued sequentially from 1 (e.g. EM1). This was a system adapted from that used by the LNER for its electric stock). The additional prefixes used were: AL: AC electric locomotive AM: AC electric multiple unit
The Eastern and North Eastern regions used a series of different classifications for diesel locomotives. The first method was also adapted from the old LNER system, and applied only to diesel shunters operating on those regions. It comprised a prefix, indicating the transmission type and wheel arrangement, followed by a number allocated sequentially from 1. The prefixes used were: DEJ: Diesel-electric, 0-6-0 wheel arrangement DJ: Diesel-mechanical or hydraulic, 0-6-0 wheel arrangement DY: Diesel-mechanical or hydraulic, 0-4-0 wheel arrangement
The second classification system was developed in 1955 and applied to all types then in existence on British Rail. It was based on the format Dx/y, where x was the power of the locomotive in hundreds of horsepower and y was a number allocated sequentially to specific types (e.g. D1/1 would be a shunter with a 100 to 199 hp (75 to 148 kW) rating, D33/1 would be a Type 5 locomotive). The series was extensively re-arranged in 1962 in a somewhat confusing way, but following the same basic principles.
The Southern Region followed existing numbering (for its multiple units) and classification systems (for both multiple units and locomotives) inherited from the SR. The EMU classification system (e.g. 4SUB) was also extended to include their diesel-electric multiple units, but with a single letter. Locomotives were given a two-letter code, with the second letter indicating detail differences within the main type. For instance, what were to become Class 33 locomotives from 1973, were Class KA or KB depending on whether they were the standard design or that fitted for push-pull working with 4TC units.
1957 numbering and classification In the early period of British Railways, steam locomotion had continued to be of prime importance. Apart from a growing selection of diesel shunters, there had been almost no development of mainline diesel or electric traction beyond the few locomotives ordered by the Big Four companies.
The 1955 Modernisation Plan heralded big changes in this situation, and from 1957 a new numbering system was used for diesel and electric locomotives ordered by British Railways, including those shunters ordered before 1957, which were renumbered into the new system. All steam and gas-turbine locomotives, and diesel and electric locomotives built to pre-nationalisation orders retained their existing numbers under the 1948 arrangements, though some had a 'D' or 'E' prefix added to their number in error.
Diesel locomotives The numbering system matched up the new 'Type' classification that had been adopted for diesel traction, and which was based on the power of the locomotive. The broad categories were as follows:
RangeTypeEngine power
Of the shunters that were renumbered, the only transparent renumbering was for those that had been numbered in the 13xxx series, for which the '1' was simply replaced with a 'D'. All the others were completely renumbered to separate out the different classes.
As always, there were some oddities. The 650 hp diesel hydraulic locomotives later Class 14 were numbered from D9500 upwards. When the Type 2 series got too crowded later on, new Sulzer Type 2 locomotives (later class 25) were numbered from D7500 upwards. Some experimental locomotives carried D0xxx numbers.
When the last mainline steam locomotive was withdrawn in August 1968 (leaving only three on the self-contained narrow gauge Vale of Rheidol Railway), the 'D' prefix was dropped.
Electric locomotives The numbering system was divided into two series, one for AC locomotives and one for DC locomotives. DC locomotives were numbered from E5000 upwards, and DC electro-diesel locomotives, with a diesel generator for working off electrified lines, were numbered from E6000 upwards.
For AC locomotives, the first number was to be an indication of power. For example, if the power was in the range 2000 to 2999 hp, it would be numbered between E2000-E2999, and so on. In fact, apart from E2001 (the prototype AC locomotive, converted from a gas turbine locomotive, later Class 80), all AC locomotives were numbered from E3001 upwards. When new 5000 hp locomotives were under construction (later Class 87), these were allocated numbers from E3201 upwards, though they never carried these numbers as the 1973 arrangements were already in place by the time the first one was built.
1973 numbering and classification - TOPS At the end of the 1960s, British Rail adopted the Total Operations Processing System (TOPS), a computerised system developed by IBM, the Southern Pacific Transportation Company and Stanford University in the United States. All types of locomotive received a TOPS classification, and multiple units were later included according to this broad division:
ClassAllocation(0)xxLocomotives and Ships (leading zero was ignored)1xxDiesel-Mechanical (including hydraulic) Multiple Units2xxDiesel-Electric Multiple Units3xxAC and Multi-Voltage Electric Multiple Units4xxSouthern Region DC Electric Multiple Units5xxOther DC Electric Multiple Units9xxDepartmental (non-revenue earning) Multiple Units
From late 1970, British Rail started to apply new numbers to locomotives and multiple units based on the TOPS classification system, the first classes to be dealt with being the LNER-design EM1 type (TOPS class 76) and the AL3 and AL4 types of AC electric locomotives (TOPS classes 83 and 84). The format of these numbers is xxxyyy, where xxx is the class number and yyy the unique identifier for that locomotive or unit. All locomotive classes have unique identifiers that commence at xx001, except classes 43 (High Speed Train power cars, originally classified as multiple-unit vehicles), 97 and 98 (departmental and steam locomotives). Multiple unit classes are treated differently, because an attempt has been made to give units working within the same region or sector unique identifiers (for more information see British Rail Regional Multiple Unit Numbering). In recent years, unit numbers have also been tied in with the numbers of the carriages within a unit (e.g. 150201 is formed of carriages 52201 and 57201). As a result, very few multiple unit classes commence from xxx001.
Where there are variations within a class, subclasses are used in the format xxx/y. When the main renumbering scheme was published in 1973, many sub-classes were redesignated to better align the locomotives to be numbered in that sub-class with the sub-class number. Thus, class 47 was originally divided into sub-classes 47/1 (locomotives fitted with steam-heating equipment), 47/2 (not fitted with train-heating equipment) and 47/3 (fitted with electric train-heating equipment), but in 1973 these sub-classes were redesignated 47/0, 47/3 and 47/4. Usually, the subclass is connected to the first digit of the unique identifier, so that the first locomotive in subclass 47/3 was 47301. However, some caution is required on this point for the following reasons: Where there are more than 100 examples in a subclass the identifier becomes obscured, e.g. 31201 is in subclass 31/1, which runs from 31101 to 31327.