List of British Rail power classifications

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.

Locomotives classed as Type 1 were of 1,000 bhp or below.

Locomotives classed as Type 2 produced between 1,001 bhp and 1,499 bhp.

Locomotives classed as Type 3 produced between 1,500 bhp and 1,999 bhp.

Locomotives classed as Type 4 produced between 2,000 bhp and 2,999 bhp.

Locomotives classed as Type 5 produced 3,000 bhp or more.

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