British Rail TOPS first arrangement

At the end of the 1960s, British Railways adopted the Total Operations Processing System (TOPS), a computerised system developed by the Southern Pacific Railroad in the United States. All types of locomotive and multiple unit received a TOPS classification, but the first attempt at applying TOPS was soon modified. This page explains the first attempt at using TOPS and cross-refers the classes allocated with those adopted in the successful re-arrangement. An explanation of the final arrangements for TOPS classification may be found here.

Locomotives

The first attempt to apply TOPS differed from the latter approach in two significant ways:

• xx/0 was not a valid subclass number. When the second arrangement was applied, original subclasses xx/1 became xx/0, xx/2 became xx/1 and so on.
• Some detail differences within classes were considered sufficient for a different class number to be allocated, rather than indicate it with a subclass. In addition, there are a number of cases where conversions led to complete reclassification, where similar circumstances later would be indicated simply by allocating a new subclass. The change in approach led to some odd gaps in the list of locomotive classes when they were re-arranged, as the principal class numbers were retained unaltered. Classes affected by this change in approach include:
  • Class 29 (re-engined Class 21)
  • Class 31 (re-engined Class 30)
  • Class 34 (became Class 33/1)
  • Class 43 (North British Locomotive-built Class 42 with different make of engine and torque-converter)
  • Class 48 (Class 47 with experimental Sulzer vee-formation engine; later rebuilt to standard class 47 with in-line twin-bank engine)
  • Class 72 (became Class 73/0)

Diesel Multiple Units

The first attempt to apply TOPS to diesel multiple units saw each carriage within a unit being allocated its own unique class number. This was probably because most DMUs were not kept in permanent formations. Classes were allocated according to the following division:

100-131: Driving Motor cars
140-150: Driving Trailer cars
160-190: Trailer cars
201-203: DEMU Driving Motor cars
211-212: DEMU Driving Trailer cars
221-225: DEMU Trailer cars
    251: Express DEMU Driving Motor cars
    261: Express DEMU Trailer cars

However, this arrangement was later revised so that each unit adopted the class number previously given just to the main type of Driving Motor car (the exception being the DEMU units, which were completely changed). The table below cross-references the old and new TOPS classes:

First TOPS	Second TOPS		First TOPS	Second TOPS		First TOPS	Second TOPS		First TOPS	Second TOPS
102	101		106	105		140	104		141	105
142	108		143	100		144	101		145	103
146	109		147	111		148	114		149	121
150	122		160	104		161	107 & 108		162	101
163	110		164	101		165	111		166	104
167	108		168	101 & 111		169	104		170	105
171	101		172	116		173	115		174	118
175	116		176	117		177	115		178	119
179	120		180	124		181	124		182	123
183	123		184	123		185	125		186	127
187	126		188	126		189	126		190	130
201/1	201		201/2	202		201/3	203		202/1	206
202/2	207		202/3	205		203	204		211/1	206
211/2	207		211/3	205		212	204		221/1	201
221/2	202		221/3	203		222/1	206		222/2	205
223/1	201		223/2	202		223/3	203		224	207
225	203		261	251

Electric Multiple Units

The first attempt to apply TOPS to the Southern Region's fleet of electric multiple units, saw classes being allocated according to the following division:

• 40x: Southern Railway designed units
• 41x: 1951-type British Railways designed units
• 42x: 1957-type British Railways designed units
• 43x: 1963-type British Railways designed units
• 44x: 1967-type British Railways designed units
• 45x: Underground ('Tube'-sized) units
• 46x: 1971-type British Railways designed units

In comparison with the later re-arrangement, it is worth noting that types that were different were given the same class (e.g. the single-car luggage vans) and identified only by subclass, while those that were later treated as variations of the same class, were separated according to their construction period (e.g. early or late 1950s builds). When the new arrangement was applied, 40x classes were left untouched, but the others were changed as follows:

SR code First TOPS Second TOPS 4-EPB 411 415/1 2-HAP 412 414/1 & 414/2 2-EPB 413 416 4-CEP 414/1 411/1 4-BEP 414/2 410/1 4-CEP 421/1 411/2

SR code First TOPS Second TOPS 4-BEP 421/2 410/2 MLV 422/1 419 TLV 422/2 499 4-EPB 423 415/2 2-HAP 424 414/3 4-CIG 431/1 421

SR code First TOPS Second TOPS 4-BIG 431/2 420 4-VEP & 8-VAB 432 423 & 480 4-REP 441 430 3-TC 442/1 492 4-TC 442/2 491

SR code First TOPS Second TOPS 3-TIS 451 486 4-VEC 452 485 WC 453 487 2-PEP 461 446 4-PEP 462 445