Railway Acronyms, Words and Sayings

Many acronyms words and sayings are used on the railway, they provide ease of communication when passing important messages, or just as a concise non cluttered way of getting across a meaning without ambiguity.  I use some of these in my blog, and provide this list (though not exhaustive) in a way to explain some of these terminologies.  Some do not require much explanation, some a little more so!

  • 3rd Rail – Electrification of the railway by means of a 3rd rail, usually beside one of the running rails.  Common in the UK in the South East of the country
  • AHBC – Automatic Half Barrier Crossing – a crossing which doesn’t go the full length of the roadway.
  • AOCL – Automatic Open Crossing – a crossing with no barrier, which is controlled by the train crew before they proceed.
  • AWS – Automatic Warning System – An in cab warning system for use in Block Signalling operations.  A disc inside the cab either shows black, which means the signal approaching is green, or is yellow/black (in the style of a sunflower) which indicates the next signal is at caution (yellow/double yellow) or stop (red).  A horn will sound inside the cab to indicate the next signal is not green, and the diver will have to push  an acknowledgement button within 2.75 seconds, otherwise emergency brakes will be applied. The indicator will then change from black to “sunflower”, and remain like this until a green signal is approached, where it will change to black again.
  • Catenary –  Overhead wires which power a train, via a Pantograph on the train.
  • DEMU – Diesel Electric Multiple Unit – a train which can use both diesel and electric power.  An example of which is the British Rail class 205 unit which worked in the South East of the UK between 1957 and 2004, and which were part of the British Rail “slam-door” stock.
  • DLR – Docklands Light Railway – a railway system in London which uses driverless trains.
  • DMU – Diesel Multiple Unit – a diesel only train, many in use today such as the 153 unit seen on many rural lines in the UK.
  • DOWN – Typically the railway line moving away from London.
  • DSD – Drivers Safety Device – a switch on the floor which the driver must keep depressed in order to enable the train to move.  Think of it as a dead mans switch, if it is not depressed then the train cannot take power.
  • EMU – Electric Multiple Unit – a train solely powered by electricity.
  • ERTMS – Part of The Digital Railway , Signalling within the cab, not trackside.
  • ETCS – Again, part of  The Digital Railway , a European signalling system.
  • HS (1,2 etc) – UK High speed lines.
  • Pantograph – Located on the roof of a train or locomotive, connects to a Catenary to provide power.
  • PERTIS – Permit to travel – usually in relation to machines at unmanned stations, these PERTIS machines would give you a ticket to enable you to start your journey.  You would then show this on the train to the guard to obtain a real ticket.  These are being superseded by self service ticket machines.
  • RAKE –  more than 1 coach or wagon coupled together will form what is known as a RAKE.
  • SPAD –  Signal Passed At Danger. When a train or locomotive passes a red signal, emergency brakes will be applied.  This generates a SPAD, which is reported to the relevant authorities.
  • TPWS – Train Protection and Warning System, advance system of the AWS.
  • UP – typically the railway line moving Towards London.

As previously said, this list is not exhaustive, I will update this blog page as and when new acronyms are used in my blog.


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Many thanks for reading, I’ll blog again soon.

Published by

rainhamrailenthusiast

I am a railway enthusiast based in Rainham, Kent. I enjoy mainly modern traction, however the history of rail, especially in places I visit, also interests me. I also have a static model railway, Mistydale, which has its own Facebook page. Thanks for visiting.

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