List of British Rail power classifications

The British Transport Commission, later British Railways, used engine power output to categorise its new main line diesel locomotive fleet following the 1955 modernisation plan. These categories were from Type 1 to Type 5 and are listed below. 

Type 1
Up to 1,000 bhp
Class 14
Class 15
Class 16
Class 17
Class 20

Type 2
From 1,001 bhp to 1,499 bhp
Class 21
Class 22
Class 23
Class 24
Class 25
Class 26
Class 27
Class 28
Class 29
Class 30/31

Type 3
From 1,500 bhp to 1,999 bhp
Class 33
Class 35
Class 37

Type 4
From 2,000 bhp to 2,999 bhp
Class 40
Class 41
Class 42
Class 43
Class 44
Class 45
Class 46
Class 47
Class 48
Class 50
Class 52
Class 53
Class 57

Type 5
From 3,000 bhp
Class 55
Class 56
Class 58
Class 59
Class 60
Class 66
Class 67
Class 68
Class 70

References
List of types

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British Rail Power Classifications