TOPS is the Total Operations Processing System, a network of computer terminals and databases that track and record the movements and status of rolling stock. Since its introduction in the early 1970s, all locos, coaches, wagons and other items that are permitted to work on the national rail network have been included. Much has been written about TOPS in various books so I will limit myself to looking at how it affected wagons in particular.
The most familiar aspect of TOPS are the three letter codes painted close to the numbers on most wagons. These are generically referred to as TOPS codes and give operationally relevant information about each vehicle. A full TOPS code in fact comprises four letters and some recent wagon types (e.g. FEA, HQA) have displayed the full code. The three-letter codes are officially known as CARKNDs, while the fourth letter is the AARKND.
In all TOPS codes, the first letter (officially the GENKOC) indicates the general group that the vehicle belongs to. For example codes starting A are used for passenger-carrying coaches, B for bogie steel wagons and so on. A full list is given in Table 1. Changes in the make-up of the fleet have resulted in some changes over the years, primarily intended to ease pressure on the ever-growing private-owner types. These were originally all in GENKOC P (apart from tank wagons). Changes in October 1983 saw the J, K, U and X GENKOCs freed up by the recoding of the affected (mainly steel-carrying) wagons into the B, F, O and S sections. In 1990, J and K were reused to allow for more detailed codes on private wagons. GENKOC X reappeared in 2003.
The second letter gives a more detailed type breakdown and is dependant on the GENKOC. For example, the first design of hopper wagon might be HAA but the A in the second position would have no relation to the A in FAA. The allocation of second letters was not always done on a sequential basis, some types taking letters derived from their configuration. As an example, the first air-braked timber wagons were given code OTA, while bogie and 2-axle plate wagons were in the BPx and SPx series respectively. Examples of sequential allocations include the OAA-OBA-OCA and VAA-VBA-VCA-VDA evolutions. As more types have been introduced, some of the series have become rather full, with vacant letters being used when required. The second letter within a GENKOC is often reused for other types but usually only when there has been a gap of at least a few years. Illustrating this, the last HTV coal hoppers were withdrawn in about 1991 and in 2001 the code HTA was used for a new build of bogie hoppers. More confusing are the cases of re-use with the same brake type. During the 1990s, code BXA (which had until 1988 been used for bogie trestles) was applied to ex BAA coil carriers then later to ex BBA wagons fitted with covers.
For many years wagons that were registered to work on the continent would have the letter I in the second position, irrespective of type or design. This meant that a PIA could be anything from a 2-axle flat to a multi-bogie flask carrier. Similarly, wagons allocated to the Electrification Engineer were generally assigned codes with a Y in the second position, though this only applied to GENKOCs Q, Y and Z (e.g. YYR and ZYA).
The third letter (the BRAKTY) indicates the brake type and uses a series common to all TOPS codes. When forming trains it is important that wagons with compatible brake types are marshalled together, this being particularly vital in the days when the fleet was a mixture of air-braked, vacuum-braked and unfitted wagons. The BRAKTY tells staff what brake type the wagon is equipped with and also whether it has any through pipes. A list of the codes used is in table 2.
The fourth letter is the AARKND and this provides a more detailed breakdown of the wagon type. Assignment of these letters appears to have been generally sequential but did not always start at A. The first OTA wagons were OTA-A, these being followed by OTA-B, OTA-C, OTA-D, OTA-E and OTA-F. The first AARKND for the HAA fleet seems to have been M (perhaps for Merry-go-Round) and this was followed by HAA-N, HAA-R, HAA-S etc. In some cases, the AARKND has a relation to the variation it describes. BAA-H refered to a hooded version of the basic BAA-F, while FLA-I and FLA-O related to inner and outer versions respectively.
Throughout this site the hyphenated convention has been used for clarity (eg BAA-H) although the actual full TOPS codes do not feature this (BAAH).
The FLA example shows how the mixture of sequential and meaningful lettering can become confusing. As mentioned, the first FLAs were divided between FLA-I inner wagons and FLA-O outers. When the prototype set was purchased and recoded FLA, sequential AARKNDs were applied (FLA-J inners and FLA-P outers). A later build of just outer wagons were coded as FLA-Bs. In recent years most new TOPS codes introduced have had AARKNDs starting at A. Since 2003, certain types of wagon have had the full four-letter TOPS code applied. These include FEA container wagons, HQA Autoballasters and MRA ballast tippers. This is thought to be for the benefit of operational staff even though in most cases the differences indicated by the AARKND are physically obvious (such as the fitting of a generator).
|Table 1: TOPS GENKOCs (first letter)
|Pre-10/83: Bogie steel-carrying wagons (Excluding coil)
Post-10/83: Bogie steel-carrying wagons
|CAx: Brake Vans
CBx-CZx: Covered bulk-carrying wagons
|Diesel Multiple Unit vehicles
|Electric Multiple Unit vehicles
|HST coaches and power cars
|Pre-10/83: Bogie steel coil carrying wagons
Post-1990: Private-owner bogie wagons
|Pre-10/83: 2-axle steel coil carrying wagons
Post-1990: Private-owner specialist wagons
|APT coaches and power cars
|Mineral wagons (excluding hoppers)
|Pre-1990: Private-owner wagons (excl. tanks)
Post-1990: 2/3-axle Private-owner wagons (excl. tanks)
|Railway operating vehicles (non-revenue)
|Pre-10/83: 2-axle steel-carrying wagons (Excluding coil)Post-10/83: 2-axle steel-carrying wagons
|Private-owner tank wagons
|Pre-10/83: Uncovered open bulk-carrying wagons
Post-10/83: Not used
|Pre-1984: Containers. Later for specialised RIV wagons
|Pre-10/83: Exceptional and special purpose vehicles
10/83-2003: Not used
2003-present: Special Private-Owner wagons
|Bogie departmental wagons
|2/3-axle departmental wagons
|Table 2: TOPS BRAKTYs (third letter)
|Air brakes with through vacuum pipe
|Vacuum brakes with Accelerated Freight Inshot (AFI)
|Vacuum brakes with AFI and through air pipe
|Dual (air and vacuum) brakes with vacuum AFI
|No continuous brake (unfitted)
|No continuous brake, through vacuum pipe
|No continuous brake, through air pipe
|No continuous brake, through air and vacuum pipes
|Vacuum brakes with through air pipe
|Dual (air and vacuum) brakes
|No continuous brake (for track machines)