To aid identification purposes on the introduction of the TOPS computer system in 1973, each type of unit was given a "class" number. Within each class, as with locomotives, there were often sub classes.

Initially power cars were given numbers from 100 to 131, driving trailers from 140 to 150, and centre cars from 160 to 190. In 1979 all driving trailers and centre cars received the same class numbers as their power cars, and sub classes were dropped. Also, where a class had been split only because of engine differences were amalgamated, such as the 101/2s and 105/6s.

The "NTP" column gives details of the 1974 National Traction Plan, which gave a life expectancy for remaining units. The final column gives the total number of vehicle remaining in service on the 1st January 1974. Code for the NTP :-

A1 Vehicles expected to be retained after 1981
A Vehicles likely to be retained until 1980 and withdrawn between 1980 and 1982
B Vehicles which may be withdrawn before 1980
C Vehicles to be withdrawn at any time that a surplus is identified
   
Power Cars
Class Type Builder Set Operated With NTP 1/1/74
100 DMBS Gloucester 2-car 143 C 25
101/1 DMC Met Camm 2/3/4-car 101/2, 162, 168, 171 A 94
101/2 DMBS Met Camm 2/3-car 101/1, 144 A 163
101/3 DMS Met Camm 3-car      
102/1 DMC Met Camm 2/3/4-car 102/2, 162, 171 A1 53
102/2 DMBS Met Camm 2/3/4-car 102/1, 162, 171 A1 53
103 DMBS Park Royal 2-car 145 C 12
104/1 DMC BRCW 3/4-car 104/2, 160, 166, 169 A 104
104/2 DMBS BRCW 2/3-car 104/1, 140, 169 A 55
          B 15
104/3 DMS BRCW 3-car 104/2, 169 - -
105/1 DMC Cravens 2/3-car 105/2, 170 B 27
105/2 DMBS Cravens 2/3-car 105/1, 105/3, 141, 170  B 120
105/3 DMS Cravens 2/3-car 105/2, 141 - -
106/2 DMBS Cravens 2-car 141 B 12
107/1 DMC Derby 3-car 107/2, 161 A1 26
107/2 DMBS Derby 3-car 107/1, 161 A1 25
108/1 DMC Derby 2/3/4-car 108/2, 161, 167 A1 57
108/2 DMBS Derby 2/3-car 108/1, 142, 161 A1 141
109 DMBS Wickham 2-car 146 - -
110/1 DMC BRCW 3-car 110/2, 163 A1 29
110/2 DMBC BRCW 3-car 110/1, 163 A1 28
111/1 DMC Met Camm 2/3-car 111/2, 164, 165 A1 20
111/2 DMBS Met Camm 2/3-car 111/1, 147, 164, 165 A1 22
112/1 DMC Cravens 2-car 112/2 - -
112/2 DMBS Cravens 2-car 112/1 - -
113/1 DMC Cravens 2-car 113/2 - -
113/2 DMBS Cravens 2-car 113/1 - -
114 DMBS Derby 2-car 148 A 45
115 DMBS Derby 4-car 173, 177 A1 82
116/1 DMS Derby 3-car 116/2, 172, 175 A 103
116/2 DMBS Derby 3-car 116/1, 172, 175 A 105
117/1 DMS Pressed Steel 3-car 117/2, 176 A1 42
117/2 DMBS Pressed Steel 3-car 117/1, 176 A1 41
118/1 DMS BRCW 3-car 118/2, 174 A1 15
118/2 DMBS BRCW 3-car 118/1, 174 A1 15
119/1 DMBC Gloucester 3-car 119/2, 178 A1 26
119/2 DMS Gloucester 3-car 119/1, 178 A1 26
120/1  DMBC/
DMBF		 Swindon 3-car 120/2, 179 A1 64
120/2 DMS Swindon 3-car 120/1, 179 A1 64
121 DMBC Pressed Steel 1/2-car 149 A1 16
122 DMBC Gloucester 1/2-car 150 A 12
123/1 DMS Swindon 4-car 123/2, 182, 183, 184 A1 10
123/2 DMBS Swindon 4-car 123/1, 182, 183, 184 A1 10
124/1 DMC Swindon 6-car 124/2, 180, 181 A 17
124/2 MBS Swindon 6-car 124/1, 180, 181 A 17
125/1 DMS Derby 3-car 125/2, 185 B 20
125/2 DMBS Derby 3-car 125/1, 185 B 19
126/1 DMS Swindon 3-car 126/2, 187, 188, 189 A1 23
126/2 DMBS Swindon 3-car 126/1, 187, 188, 189 A1 23
127 DMBS Derby 4-car 186 A1 58
128 MPV Gloucester 1-car   A 9
129 MPV Cravens 1-car   - -
130 Parcels Derby (converted 116s) A 4
131 Parcels Gloucester (converted 122s) A 3
             
Driving Trailers
Class Type Builder Set Operated With NTP 1/1/74
140 DTC BRCW 2-car 104/2 B 15
141 DTC/DTS Cravens 2-car 105/2, 106/2 B 106
142 DTC/DTS Derby 2-car 108/2 A1 99
143 DTC Gloucester 2-car 100 C 16
144 DTC Met Camm 2-car 101/2 A 122
145 DTC Park Royal 2-car 103 C 13
146 DTC Wickham 2-car 109 - -
147 DTS Met Camm 2-car 111/2 A1 4
148 DTC Derby 2-car 114 A 45
149 DTS Pressed Steel 2-car 121 A1 8
150 DTS Gloucester 2-car 122 A 5
             
Centre Cars
Class Type Builder Set Operated With NTP 1/1/74
160 TS BRCW 4-car 104/1, 166 B 24
161 TS Derby 3/4-car 107/1, 107/2, 108/1, 108/2, 167 A1 37
162 TS Met Camm 3/4-car 101/1, 102/1, 102/2 A 30
163 TS BRCW 3-car 110/1, 110/2 A1 28
164 TS Met Camm 3-car 111/1, 111/2 A 13
165 TRBS Met Camm 3-car 111/1, 111/2 A1 5
166 TBS BRCW 4-car 104/1, 160 A 25
167 TBS Derby 4-car 108/1, 108/2, 161 A1 6
168 TBS Met Camm 4-car 101/1, 162 A 27
169 TC / TS BRCW 3-car 104/1, 104/2, 104/3 A 53
170 TC / TS Cravens 3-car 105/1, 105/2 - -
171 TC / TS Met Camm 3/4-car 101/1, 102/1, 102/2 A1 70
172 TS Derby 3-car 116/1, 116/2 A 10
173 TS Derby 4-car 115, 177 A1 40
174 TC BRCW 3-car 118/1, 118/2 A1 15
175 TC / TS Derby 3-car 116/1, 116/2 A 90
176 TC Pressed Steel 3-car 117/1, 117/2 A1 39
177 TC Derby 4-car 115, 173 A1 41
178 TRBS Gloucester 3-car 119/1, 119/2 A1 25
179 TRBS Swindon 3-car 120/1, 120/2 A1 58
180 TS Swindon 6-car 124/1, 124/2, 181 A 9
181 TSRB Swindon 6-car 124/1, 124/2, 180 A1 5
182 TS Swindon 4-car 123/1, 123/2, 183, 184 A1 5
183 TC Swindon 4-car 123/1, 123/2, 182, 184 A1 10
184 TSRB Swindon 4-car 123/1, 123/2, 182, 183 - -
185 TS Derby 3-car 125/1, 125/2 B 20
186 TS Derby 4-car 127 A1 57
187 TFRB Swindon 3/6-car 126/1, 126/2, 188, 189 - -
188 TF Swindon 3/6-car 126/1, 126/2, 187, 189 A1 2
189 TF/TC Swindon 3/6-car 126/1, 126/2, 187, 188 A1 21
190 TPMU Derby 3-car 116/1, 116/2 (formerly 175) - -