List of British Rail power classifications
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The British Transport Commission, later British Railways, used engine power output to categorise its requirements for the new main line diesel locomotive fleet following the 1955 modernisation plan. The locomotives built and put into service are listed below classified with the TOPS class numbers that were introduced in the early 1970s.
For locomotive power classes used by British Railways between 1948 and 1959, see LMS locomotive numbering and classification.