Train Formation Diagrams
Trains used on the Underground are operated in fixed formations with the number of cars in each formation determined by the line upon which they operate. The way trains have been used over the years has dictated the formations and these have appeared in various forms as we see below.Fig. 1: Gate Stock Train Formations 1903 - 1906
The diagram below shows the train formations adopted by the new tube railways which started multiple unit operation in the period 1903 to 1906. The upper diagram shows a Central London Railway train, where the unit indentification lettering would look like this, reading from west to east: 'B' DM - T - 'B' CT + 'A' CT - T - 'A' DM. Half the train was the "A" half and the other was the "B" half. Put another way, there was an "A" unit and a "B" unit. Either unit could run as a 3-car train. When being driven from the Control Trailer end, power was provided by the motor car at the rear.
The Central London formation was unique in the way a 3-car unit had the same letters at each end. The orientation was also unique in that "A" units normally faced east and "B" units faced west. This was the opposite way round to the normal orientation adopted by other lines. The lower diagram shows the LER formation, with the Piccadilly Line as the example. The Bakerloo and Hampstead formations were similar to the Piccadilly but orientated north to south. The same 6-car formation was used for Standard Tube Stock until the introduction of 7-car trains in the late 1920s.
The reason for needing to have cars facing round the right way is because of the couplings. You have very little space under tube cars for air hoses and electrical jumpers. There was only space for one set of each, so they had to match other cars, hence thay all had to be facing the same way round.
Fig. 2: 7-car Standard Stock Train Formation
The original, Standard Tube Stock 6-car train formation was increased to 7-cars by the insertion of an additional trailer car and replacing a control trailer with a DM car. Trains were now formed: 'A' DM - T - T - 'D' DM + 'A' CT - T - 'D' DM or 'D' DM - T - T - 'A' DM + 'D' CT - T - 'A' DM, depending on the line of use and orientation.
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Fig. 3: District Railway Train Formation
The original District Railway electric stock formation of 1905 is shown in the upper diagram. The middle motor car (MM) had a cab at each end and could be used to split off a 4-car set at either end of the train. Later 3+3 and 4+2 trains were operated. From 1908, control trailers (CTs) were introduced so that short trains with one motor car could run in service. After the first world war, the new F Stock was delivered in a 5+3 formation but the remaining stock developed into a 4+2+2 formation.
The 4+2+2 arrangement looked like this: 'A' DM - T - T - 'D' DM + T - 'D' DM + T - 'D' DM. It was developed in the late 1920s and survived until the early 1970s. It suffered from a significant limitation in that there was no driving position at the west end of the 2-car units so all uncoupling was limited in method and location.
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Fig. 4: 1938 Tube Stock Train Formation
This diagram shows two versions of the 1938 Tube Stock train formation as used between 1938 and 1988. The lower version with the UNDM was seen regularly from the early 1950s. The 1972 Tube Stock currently on the Bakerloo has the same formation with the "A cars facing south and the "D" cars facing north.
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Fig. 5: 1973 Tube Stock and D Stock Train Formation
1973 Tube Stock trains were formed of single-ended 3-car units coupled back to back to form 6-car service trains. The 3-car single-ended units were provided with UNDMs equipped with automatic couplers and shunting control panels. A batch of 20 double-ended 3-car sets were kept for flexibility and to allow a unit to work the (now closed) Aldwych branch.
The D Stock, built from 1978-81 for the District Line, was simply a surface line version of the 73TS. The main fleet was made up of single-ended units and some double-ended units were included to provide flexibility.
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Fig. 6: 1996 Tube Stock Train Formation
This diagram shows the 1996 Tube Stock for the Jubilee. Both '95 and '96 stocks have the 3 + 3 formation with cabs at the outer ends and UNDMs in the middle. There are no double-ended units.
The 1995 Tube Stock on the Northern Line is similar except that the "universal" couplers allow "A" units to couple to other "A" units and likewise with "D" units. The 95TS on the Northern gets turned on the Kennington loop and therefore universal couplers are used to allow "A" ends to couple to other "A" ends as well as "D" ends. The 96TS doesn't get turned and is "handed" so only "A" ends will couple to "D" ends. Curiously, both stocks are equipped with automatic couplers at the cabs ends.
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Last updated 25th November 2009 © Copyright Tubeprune 2001 - 2009.
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