British Rail locomotive and multiple unit numbering and classification

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. There are also links to other pages that deal in greater depth with the particulars of individual types.

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:

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.

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.

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:

Note: *Isle of Wight locomotives retained their existing numbers in a separate series commencing at W1, and locomotives transferred to the island by BR were renumbered into that series - and vice versa for those returned to the mainland.

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:

Note: * Number 13000 was initially allocated to a 250 hp (186 kW) ex-LMS shunter, but this locomotive was withdrawn before being renumbered.

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