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Rail Data > Articles > Articles list > Article 10: Stock Classification - Coaches
Title:Stock Classification - Coaches
Category:Classification
Summary:Details of the classification schemes used for coaching stock from 1948 to the present
Added:31st Dec 2019

Article:
Introduction
Compared to some other groups of rolling stock, the classification of coaching stock has always been quite straightforward and consistent. Technical classification was nearly always by diagram number, while operational classification was basically just a summary of the vehicle's features (eg 'Brake Corridor Composite').
Coach 'families'
References to particular coach types often combine the operational classification (q.v.) with what I have called the 'family' designation, as in 'Mk1 Corridor First'. Most railway companies built a range of coaches to the same overall design and shape, or with similar features. These were often built for a period of many years, until replaced by a successive family. For pre-nationalisation coaches, references to the 'families' appears to have been made retrospectively, such as those created by authors David Jenkinson and R J Essery to describe the various generations of LMS coach design. An example of this would be 'Period III Corridor Third'. Other families are identified by their designer (as in 'Maunsell Composite') or by a characteristic (as in 'Ironclad Corridor Third'). BR developed its own standard coach design, the first of which appeared in 1950. When a radically different design was introduced in 1963 this was known as the Mk2 (or Mk.II), and the previous family was retrospectively termed Mk1. It should be mentioned that the Mk1 design continued to be constructed for certain types, including EMUs, up until the mid-1970s. While the Mk1 family had no variants, the Mk2s did, going through plain Mk2, then Mk2a, Mk2b etc up to Mk2f, each having slight changes to doors/windows or fittings such as air-conditioning. The next major change was the introduction of the 75ft long Mk3 in the early 1970s, followed by the Mk4 in the late 1980s. More recently, coaches built by CAF for Caledonian Sleeper and Trans-Pennine Express services have been dubbed Mk5s.
'Traditional' operational classifications
For many years the operational classification of coaching stock was based on the key features of each type. For example, a coach with first class compartments accessed from a side corridor would be known as a Corridor First. BR coach diagrams available to view on the Barrowmore Model Railway Group (BMRG) website [5] show that each page was headed with the type written in full, such as 'Brake Composite - Corridor'. However, most publications referring to coaches use abbreviated codes such as BCK, describing these as 'traditional' type codes or 'Operator Codes'. I have not been able to find out when these were first used, and they do not appear on BR pre-TOPS coach diagrams. Hugh Longworth, in his book on BR Mk1 and Mk2 coaches [6], says these codes were based on LNER telegraphic codes, though curiously his later book on LNER coaches does not appear to mention any. The codes were normally painted on the end of each coach and the earliest examples seen in photographs are dated 1954 (ex-LNER type) and 1957 (BR type).
The 'traditional' coach type codes are a useful way of quickly referring to the characteristics of a particular type. The basis of the system is a code made up of a number of letters where each letter indicates a particular key feature a coach can have. However, certain letters can have more than one meaning. B, for example, can stand for Brake, Battery or Buffet. Furthermore, the omission of a letter can also give details. S on its own would indicate a second class coach, but it would be the lack of a K (for corridor) or O (for open) that would tell you that this was a compartment coach (non-gangwayed). As such it is not practical to provide a list saying that any given letter always has a particular meaning. The significance of each letter can only be determined in conjunction with the other letters in the code, and the order in which they appear.
The amount of detail given by the type codes has varied over the years, particularly in terms of multiple unit coaches. Initially the codes were based on the type title as it appeared on the diagram. So (for example) BR diagrams 407 and 409 were both titled as Motor Open Second Brake and were thus coded MBSO, even though coaches to diagram 407 had a cab and no pantograph, and coaches to diagram 409 had the opposite. By 1978 [7], a prefix of D had been added to coaches with a driving cab and a further prefix of B to indicate coaches with auxiliary equipment including batteries. Around 1983 a P prefix was added for trailer coaches with pantographs (eg PTS), although this was initially shown as a hyphenated suffix (TS-P) [8]. Conversely, some detail has been dropped when deemed no longer pertinent. Codes K and O (for corridor and open respectively) were officially dropped from multiple unit coach codes [9]. The letter L for lavatory seems to have gone in and out of fashion, while I have also found that published references often differ on the exact codes used. Other changes to codes have been determined by outside factors. When second class was dropped in 1955, the existing third class was renamed second. This led to changes such as TK coaches being recoded SK. The later change of nomenclature from 'second' to 'standard' in about 1988 obviously avoided this issue.
The variations in detail, along with the introduction of new coach types, resulted in the number of coach type codes growing considerably. I have located references to just over 200 distinct codes, which can be found listed here. The longest code seems to be the seven letter BTDBSOL, although I suspect this should actually be a BDTBSOL. Despite the introduction of TOPS codes for coaching stock in the 1970s and 1980s (q.v.), the traditional codes have remained in use, and the development of new trains, in particular those with hybrid or alternative power sources, may result in yet more codes being added in the future. So far the only new code known of is PP, for the short 'power pack' coach in Stadler Flirt bi-mode units of class 755 [10]. Surely M (for Motor) would have been just as appropriate, and less confusable.
BR appears to have attempted to introduce a new set of coach type codes in the early 1950s, although it did not last long. Some of the diagrams on the BMRG website have additional text below the diagram title. For example, diagram 126 is titled 'Composite Corridor' then 'BR Type B'. Other letters featured this way are A (Corridor First), C (Corridor Third), D (Brake Composite Corridor), E (Brake Third Corridor), G (First Open), H (Restaurant First), J (Third Open), K (Restaurant Third) and M (Kitchen Car). Some non-gangwayed types are indicated as numerical types, such as BR Type 1 (Third), 2 (Brake Third), 5 and 6 (both Composites). No more is known about this scheme, though the diagrams that they are mentioned on all date from the 1951-1955 period.

BR diagram 56, clearly marked as 'BR Type K'
TOPS operational classifications
The introduction of TOPS in the 1970s assigned 2 or 3 digit numerical class codes to locomotives and multiple unit sets, while coaches and wagons were to be given 3/4 letter type codes. Of the latter, the first letter (known as the GENKOC) identified the type of vehicle in the broadest sense. Letter A was assigned to passenger-carrying, loco-hauled coaching stock, D to coaches in Diesel Multiple Units, E to coaches in Electric Multiple Units and N to non-passenger carrying coaching stock (e.g. parcels vans). Later additions were G for High-Speed Train coaches and L for APT (Advanced Passenger Train) coaches.
The second letter of each TOPS code would identify the sub-type and in terms of coaching stock, sub-types were created for each GENKOC (such as AA being for Gangwayed Corridor coaches, EA for Driving Motor coaches and so on). These formed the basis of the new diagrams and design codes (q.v.) but actual TOPS codes were at first only applied to non-passenger carrying coaches (GENKOC N). These codes followed the practice used for wagons, whereby the third letter (the BRAKTY) would indicate the braking system fitted and the fourth (the AARKND) would cover minor variations. So for example, the code NAVS related to a non-passenger carrying coach (N) that was a gangwayed bogie brake (A) fitted with vacuum brakes (V). The letter S does not have a specific meaning and it appears that this was the only variant of this type - AARKNDs did not always start at A. As with wagons, the first three letters of the code (known as the CARKND) were displayed on the vehicles themselves. Because of this, full codes are often shown in the format NAV-S (as they are on this website), even though it would appear as NAVS on the TOPS computer.
When passenger-carrying coaches eventually gained TOPS codes in 1984 [11], a different method was used. The third character was a number to indicate the class of accommodation (1 for first class, 2 for second/standard, 3 for composite, 4 for unclassified and 5 for none), while the fourth indicated the design of the coach. When BR introduced a new coach design in 1963 it was called the Mark 2, and the previous standard design was retrospectively named the Mark 1. Variations of the Mark 2 followed (2A, 2B etc up to 2F), then the 75ft long Mark 3. For the TOPS codes, Mark 1s were indicated by a 1, Mark 2s by a Z, Marks 2A to 2F by a letter A to F and finally G and H for Mark 3/3A and Mark 3B respectively. The digit 0 was used for older stock, such as preserved pre-nationalisation coaches. So, a Mark 1 Kitchen Buffet (RKB) would now be classified as an AK51, and a Mark 2E Open First as AD1E. The new codes were applied in full on the coach ends, usually together with the old operating code.
It appears that no TOPS codes relating to GENKOCs D and E (for DMUs and EMUs respectively) have been issued, the TOPS class code of the complete set being used instead. The only exception to this seems to have been the application of TOPS codes to some departmental EMUs, with codes EZA-Y and EZE-Y having been seen in TOPS reports. Curiously, despite the allocation of codes in the DZxx range to departmental DMUs, all known examples have gained Qxxx TOPS codes instead.
Pre-nationalisation technical classifications
Up until the introduction of TOPS, most technical classification of coaching stock was based on diagram numbers. Each new type was given a numbered page in the diagram book, this showing a drawing of the type with key dimensions and other technical data. GWR diagram numbers were based on a letter to indicate the type followed by a sequential number for individual designs [1]. Thus A1 was the (nominally) first design of bogie first class coach. The numbers were distinct to the type, so there could be an A1, B1, C1 etc. The highest number reached appears to have been E167, a Hawksworth design Brake Composite actually introduced under BR in 1952. Both the LMS and the LNER generally retained the diagram numbers for stock inherited from their various constituents and had separate series (purely numerical) for their own designs [2] [3] . The SR assigned new diagram numbers in the range 1-1300 to its inherited stock, and between 2001-3200 for its own designs, in both cases the ranges being divided into blocks for particular types (eg inherited Brake Thirds took digram numbers in the 96-249 range, while new-build Brake Thirds were allocated 2101-2200 [4]).
Early BR technical classifications
When BR started building coaches to its own designs (the first appearing in 1950), they were given purely numerical diagram numbers in a new book. The numbers were allocated in blocks, for example Sleepers took diagram numbers from 1 upwards, Open Firsts took 71 upwards. Non-gangwayed coaches got diagram numbers in the 3xx range, non-passenger carrying coaching stock in the 7xx and 8xx ranges. Coaches formed into multiple units had diagrams in the same series, the initial allocations being 4xx for EMUs and 5xx/6xx for DMUs. These ranges were generally adhered to, although some got used up and resulted in the allocation of some numbers in the 85x range to DMU coaches and in the 375-386 and 861-941 ranges to EMUs. For a list of all known BR diagram numbers, go to the Design List page and select 'BR Pre-TOPS Carriage Diagram' in the Design Series drop-down.
TOPS technical classifications
With the introduction of TOPS in the early 1970s, there were to be two levels of technical classification. Each type of existing coach was given a new diagam number with the format AAnnn, while each diagram could have a number of variants, known as design codes, with the format AAnnnnA. The first three characters of each of these classifications is comprised of the TOPS GENKOC, the TOPS sub-type and the class of accomodation, as outlined above under TOPS operational classifications. The final two characters of the diagram number are a sequentially allocated number starting at 01. To give an example, diagram AB105 relates to the (nominally) fifth type (05) of passenger-carrying coach (A) to a gangwayed corridor brake configuration (B) with first class accomodation (1). Some publications have referred to these 5-character codes as design codes, but I prefer to call them diagrams to differentiate them from the 7-character design codes.
TOPS design codes take the five characters of the diagram number and add two further characters to cover detail variations. The first of these two characters is numerical and covers electrical differences, while the second is a letter to cover mechanical differences. Every diagram has a 'base' variant where the final two characters are 0A. For example, the basic design code for a vehicle to diagram AB105 would be AB1050A. Most references to TOPS coach design codes (including those in this website) add a period between the diagram number and the variant characters, as in AB105.0A.
Further variant characters can be added to cover minor variations from the 'base' design code, and these were allocated sequentially. Where there were permutations of electrical and mechanical differences, each character retained the same meaning. To illustrate this, the first variant of design code AB105.0A was for coaches fitted with composite brake blocks. As this was a mechanical change, the design code for such vehicles was AB105.0B. Other coaches had public address transmitters fitted. As this was an electrical change, the design code became AB105.1A. Coaches with both composite brake blocks and public address transmitters would therefore be to design code AB105.1B.
Over time, many diagrams gained a large number of variants, each with their own design code. For example, the Mk1 Restaurant Miniature Buffets to diagram AN203 got as high as design code AN203.9L, while the Mk1 Second Open diagram AC201 reached AC201.1Y. It is not clear what would happen once either of the variant series was exhausted (i.e. for an electrical variant following AC201.9A or a mechanical variant following AC201.1Z), but it is assumed that this would result in the issue of a whole new diagram.
In the BR diagram books (copies of which can be downloaded from the Barrowmore MRG website), each passenger-carrying coach diagram is given two pages. The first page has the drawings (generally side and end elevations and a plan), while the second page gives the technical data and a list of the design code variations. Non passenger-carrying coaches are treated differently, with each design code
SR type codes
To be completed.

References
[1] British Railways Pre-Nationalistion Coaching Stock, Volume 1 - GWR and LNER (Longworth, 2018), Page 10
[2] British Railways Pre-Nationalistion Coaching Stock, Volume 2 - SR and LMS (Longworth, 2019), Page 128
[3] British Railways Pre-Nationalistion Coaching Stock, Volume 1 - GWR and LNER (Longworth, 2018), Page 175-176
[4] British Railways Pre-Nationalistion Coaching Stock, Volume 2 - SR and LMS (Longworth, 2019), Page 10
[5] BMRG website, link to be added,
[6] BR Mark 1 and Mark 2 Coaching Stock (Longworth, 2013), Page 7
[7] Coaching Stock of British Railways 1978 (Mallaband and Bowles, 1978), Page 2
[8] British Rail Coaching Stock 1982 (Mallaband and Bowles, 1982), Page 117
[9] British Rail Coaching Stock 1982 (Mallaband and Bowles, 1982), Page 5
[10] British Railways Locomotives and Coaching Stock 2019 (Pritchard and Hall, 2019), Page 386
[11] Rail Enthusiast magazine, June 1984, Page 18

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