Moving block

In railway signalling, a moving block is a signalling block system where the blocks are defined in real time by computers as safe zones around each train. This requires both knowledge of the exact location and speed of all trains at any given time, and continual communication between the central signalling system and the train's cab signalling system. Moving block allows trains to run closer together, while maintaining required safety margins, thereby increasing the line's overall capacity.

Communications Based Train Control (CBTC) or Transmission Based Signalling (TBS) is required to detect the exact location of trains and to transmit back the permitted operating speed to enable this flexibility.[1] Information about train location can be gathered through active and passive markers along the tracks, and train-borne tachometers and speedometers. Satellite-based systems are not used because they do not work in tunnels.

Another version of the moving block system would be the location computers on the trains itself. Each train determines its location in relation to all the other trains and sets its safe speeds using this data. Less wayside equipment is required compared to the off-train system but the number of transmissions is much greater .

Implementation

Urban

Moving block is in use on several London Underground lines, including the Victoria line, Jubilee line, and the Northern line as well as the Docklands Light Railway.[2][3] New York City Subway's BMT Canarsie Line (L train), Tren Urbano (Puerto Rico)[4], the Singapore MRT's North South line, North East line, Circle line and Downtown line, and Vancouver's SkyTrain, also employ moving block signalling. It is also used by the Hong Kong MTR, on the West Rail line and the Ma On Shan line.[2]

Inter-city

It was supposed to be the enabling technology on the modernisation of Britain's West Coast Main Line which would allow trains to run at a higher maximum speed (140 mph or 230 km/h), but the technology was deemed not mature enough, considering the large number of junctions on the line, and the plan was dropped.[5] It forms part of the European Rail Traffic Management System's level-3 specification for future installation in the European Train Control System, which will at level 3 feature moving blocks that allow trains to follow each other at exact braking distances.

gollark: In any case, if you have a planned system and some new need comes up... what do you do, spend weeks updating the models and rerunning them? That is not really quick enough.
gollark: If you want to factor in each individual location's needs in some giant model, you'll run into issues like:- people lying- it would be horrifically complex
gollark: Information flow: imagine some farmer, due to some detail of their climate/environment, needs extra wood or something. But the central planning models just say "each farmer needs 100 units of wood for farming 10 units of pig"; what are they meant to do?
gollark: The incentives problems: central planners aren't really as affected by how well they do their jobs as, say, someone managing a firm, and you probably lack a way to motivate people "on the ground" as it were.
gollark: What, so you just want us to be stuck at one standard of living forever? No. Technology advances and space mining will... probably eventually happen.

References
  1. "Moving Block — The Theory". ATP Beacons and Moving Block. Railway Technical Web Pages. 17 November 2016. Archived from the original on 9 February 2009. Retrieved 17 November 2016.
  2. "The Jubilee Line Upgrade" (PDF). London Underground Railway Society. 13 October 2009. Retrieved 22 November 2009.
  3. "IRSE Newsletter (Hong Kong section)" (PDF). March–April 2008. Retrieved 26 November 2016.
  4. https://www.railway-technology.com/projects/tren/
  5. "Background to the West Coast Modernisation Programme — The West Coast Route Modernisation began as a private sector programme" (PDF). The Modernisation of the West Coast Main Line. Comptroller and Auditor General, National Audit Office. 22 November 2006. p. 26. Archived (PDF) from the original on 26 November 2016. Retrieved 26 November 2016.
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