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

British Rail Power Classifications

List of British Rail power classifications