British Railways numbering scheme

The current British numbering system for locomotives dates from the early 1970s. It is named after the computer system TOPS (Total Operations Processing System) around which it was designed.

EMUs started to receive TOPS unit numbers in 1976, DMUs in 1981. However, the numbering of individual vehicles within multiple units was unchanged; the series in use for these date from the late 1950s.

Notes on Class number ranges:


Locomotives carry five digit numbers. The first two are the TOPS Class, which identifies the different types of locomotive. TOPS Classes are always two digits, of which the first may be a zero.

Example: 08611 is a Class 08 locomotive (a diesel shunter, to be precise).

The last three digits identify individual locomotives and normally start at 001 for each Class. However, some Classes are divided into Sub-Classes, and separate blocks may be used for these.

Example: Class 66/0 starts at 66001, Class 66/5 starts at 66501.

However, the third digit does not necessarily indicate the Sub-Class of the locomotive. For example, there are 250 locomotives in Class 66/0, so 66250 is still a Class 66/0.

There are also a few other oddities to look out for:

So, although it is easy to tell a locomotive's Class from its number, to identify the Sub-Class you will need to remember where each one starts!

Diesel Locomotives

These are allocated TOPS Classes in the range 01-69. They are allocated in such a way that the higher the Class number, the more powerful the locomotive type:

An exception is that Class 57 is only 2500hp, but its classification is apparently due to the fact that modern traction equipment gives it a hauling power equivalent to a Type 5.

Electric Locomotives

These are allocated TOPS Classes in the range 70-95. This includes electro-diesel locos (which can either use power from the third rail, or generate their own using their diesel engine and generator).

The standard electrification systems in Britain today are 25 kV AC overhead, or 660 - 750V DC third rail, but other systems have been used in the past.

For a complete list of British Locomotive Classes and Sub-Classes, click here.

Multiple Units

Most multiple units have a six-digit unit number which is carried on the ends of the set. The first three digits are the TOPS Class. The last three digits identify the unit, but unlike locomotives, it is not usual for the sequence to start at 001. Instead, numbers are usually allocated in a range that does not coincide with other units operating in the same area. This way, staff can refer to units by the last three digits without risk of ambiguity or confusion.


Diesel Multiple Units (Mechanical or Hydraulic Transmission)

These are allocated Classes in the range 100-199:

Diesel-Electric Multiple Units

Diesel units with electric transmission (DEMUs) are allocated Classes in the range 200-299:

Classes 253 and 254, also known as HSTs (High Speed Trains), have since been reclassified as locomotives and coaching stock.

Electric Multiple Units

EMUs are allocated Classes in the range 300-599:

It is important to note that many Class 4xx units still carry traditional style four-digit unit numbers. However, the first digit of the number equals the last digit of the class, so they are effectively six-digit numbers without the first two digits!

Multiple Unit Sub-Classes

As with locomotives, some multiple unit Classes are divided into Sub-Classes. Sometimes the Sub-Class is reflected in the fourth digit of the unit number (for example, Classes 150/1 and 150/2 start at 150101 and 150201 respectively) but this is not always true (for example, Classes 312/0 and 312/1 start at 312701 and 312781 respectively).

Individual Vehicles Within Multiple Units

The unit numbers previously described refer to an entire set, consisting of up to nine vehicles. Individual vehicles within the set carry five digit numbers in the following series:

Within these series there are various sub-series for different types of car, but these are quite complex and in recent years they have not all been adhered to anyway.

Sometimes an effort is made to allocate numbers which "match" the unit number. For example, 158716 consists of vehicles 52716 and 57716. Sometimes this is not done, for example, 142003 consists of vehicles 55544 and 55594.

Multiple unit vehicles are not allowed to have the same number as a locomotive. Around 1983 it was necessary to renumber quite a lot of DMUs to remove such duplications.

Multiple unit vehicles may not stay in the same set for their entire lives - reformations of units, both temporary and permanent, sometimes take place.

For more information on British Multiple Units, try this page.

Coaching Stock

Locomotive-hauled coaches are numbered between 1 - 99999 but are not allowed to have the same number as a locomotive or multiple unit vehicle.

There are quite a lot of individual series in use but the most common ones currently in service are as follows:

Many older types are in use by charter operators, or in store.

Older Numbering Systems

1948 System

When British railways were nationalized in 1948, locomotives were numbered in the following series:

Some pre-nationalization designs continued to be built for a short time after nationalization. These continued to be numbered in the relevant series.

Coaching stock from the four companies retained its old numbers but with a suffix W, S, M or E respectively for stock of GWR, SR, LMS or LNER origin. BR standard coaches built from 1951 had no suffix. All coaching stock had a prefix letter to indicate which Region it was allocated to. Regions largely corresponded to the old company areas, and the letters were as above, with the addition of Sc for the new Scottish region. The same suffices and prefices were applied to multiple unit stock.

Suffices were dispensed with when they were no longer considered necessary, and Regional prefices were dispensed with in the mid 1980s.

1957 System

In 1957 new series were introduced for diesel and electric locomotives. Diesel locomotives were numbered in the series D1 - D9555, whilst new electric locomotives were numbered in the series E1000 - E6110. Existing electric locomotives retained their existing numbers, but prefixed by E (example: E27000). Some existing diesel locomotives were renumbered into the new series, although some others were not, and a few lasted until 1972 with old 1xxxx numbers.

The blocks in the D number series were at first allocated reasonably logically, but sometimes they were outgrown and new ones started elsewhere for the same type. Here is a rough guide:

TOPS numbers replaced D numbers from 1973, although some locomotives which were due to be withdrawn did not receive TOPS numbers and lasted until 1977 with their old numbers.

Page by Dave Root ( - April 2002