Multiple Units
The multiple unit series were divided up as follows:
| Class | Type | |
|---|---|---|
| 100-114 | Diesel-Mechanical | 'Low Density' passenger units (i.e. few doors per carriage) - mostly short (57'0") frame, but Class 114 are long |
| 115-127 | Mixture of 'High Density' (i.e. doors to every seating bay) and 'Cross-Country' (long distance) passenger units - long (63'6") frame | |
| 128-131 | Parcels units - mostly long frame, but Class 129 are short | |
| 140-144 | Second generation railbus (4-wheel) units ('Pacer') | |
| 150-199 | Second generation bogie units ('Sprinter', 'Networker', 'Turbostar', 'Coradia') | |
| 200-207 | Diesel-Electric | First generation units |
| 210-249 | Second generation units | |
| 250-299 | Express units | |
| 300-312 | AC Electric | First generation units |
| 313-369 | Second generation units | |
| 370-399 | Express units (since the privatisation of British Rail, this series has included other second generation units) | |
| 920-935 | Departmental units | Southern Region departmental units |
| 936-939 | Other departmental electric multiple units | |
| 950-960 | Other departmental diesel multiple units (since the privatisation of British Rail, this series has included electric multiple units) | |
AC electric multiple units AM1-AM11 became 301-311 in order (in fact the AM1 units had already been withdrawn, so Class 301 was never actually used). The 1xx and 2xx series were originally arranged so that driving motors, driving trailers and trailer cars all had their own individual class numbers (presumably because these units were more prone to being reformed), but this was subsequently revised so that each type of unit had a single class number, as allocated to the driving motor car.
Whereas within most ranges class numbers were allocated sequentially as new types were constructed, the Southern Region adopted a more complicated system for their electric multiple units, with the second and third digits indicating in more detail the type of unit. Second digits were allocated as follows:
| Class | Type |
|---|---|
| 40x | Southern Railway-designed units |
| 41x | 1950s British Railways-designed units |
| 42x | 1960s British Railways-designed units |
| 43x | 1967 Bournemouth Electrification units |
| 44x | 1970s British Railways-designed units |
| 45x | 1980s British Railways-designed units |
| 46x | 1990s Networker units |
| 48x | Underground ('Tube'-sized) units (also temporary formations and, later, 'Gatwick Express' units) |
| 49x | Unpowered trailer units (later 4x8) |
Third digits were allocated as follows:
| Class | Type |
|---|---|
| 4x0 | Express units with buffet (later 4x2) |
| 4x1 | Express units |
| 4x3 | Four-car outer-suburban units |
| 4x4 | Two-car outer-suburban units |
| 4x5 | Four-car inner-suburban units |
| 4x6 | Two/three-car inner-suburban units |
| 4x7 | Special purpose units (e.g. first 'Gatwick Express' units) |
| 4x9 | Single car units |
Of course, many exceptions arose over time. One major change was to change the classification of unpowered trailer units from 49x numbers to 4x8 numbers (which involved reclassifying Class 491 to Class 438). When Southern Region unit numbers were changed to fit with the TOPS classification system, former 4x0 classes were all reclassified to 4x2. This was necessary because Southern Region units only displayed the last four digits of their six-digit TOPS number, and it was decided that no painted unit number should commence with a '0'. It is worth noting that despite only showing the last four digits, the actual number of the unit was still the six-digit TOPS number. This often causes confusion both to enthusiasts and those outside the field alike.
Read more about this topic: British Rail Locomotive And Multiple Unit Numbering And Classification, 1973 Numbering and Classification, TOPS
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