Talk:Railway signalling

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Trains (Rated C-class, Top-importance)
WikiProject icon This article is within the scope of WikiProject Trains, an attempt to build a comprehensive and detailed guide to rail transport on Wikipedia. If you would like to participate, you can visit the project page, where you can join the project and/or contribute to the discussion. See also: WikiProject Trains to do list
C-Class article C  This article has been rated as C-Class on the project's quality scale.
 Top  This article has been rated as Top-importance on the project's importance scale.
edit·history·watch·refresh Aiga railtransportation 25.svg To-do list for Railway signalling:
  • Improve the overall writing
  • Improve article formatting and organization
  • Reduce and eliminate repetitive redundancies (both within the article and with other articles)
  • Identify overlap with similar articles (such as railway signals and UK railway signalling) and clearly delineate which content is appropriate for each article
  • Spin off lengthy subjects into child articles as needed

UK-centered and Europe-centered view[edit]

This seems rather a UK-centered and europe-centered view of signalling practise. I'm thinking about how it might be better done to reflect international variety. In the meantime, I'll probably be making some tuning changes ... --Morven 03:39, 21 Sep 2003 (UTC)

Yes you're probably right, although I did try to add a bit about American practices. Its difficult to write articles on the wikipedia, because its international, you have to try and cover the perspectives of many different parts of the world G-Man 13:44, 21 Sep 2003 (UTC)

I'll see what I can do to at least try and include information about British, American and European practice -- which probably works for most other places, since many other nations' railways buy signalling equipment from those.

There's a lot of variation in American signalling, too -- unlike most other countries where the same standard applies nationwide. Need to discuss route signalling vs. speed signalling, too -- British practice is exclusively route signalling, no speed indication is given by the signal aspect. Whereas, say, Pennsylvania Railroad position-light signals convey speed information to a degree also, and rarely do they indicate what route is set. Out here in California, most of the railroads do use color-light signals, but unlike the British form, in say ex-Southern Pacific signals, each light lens can display different colors; this is based on previous semaphore signals' lights, which change color depending on which aspect's filter is in front of the light.

Even until pretty modern times, many US railroads ran on timetable-and-train order -- the Nickel Plate and Wabash until the 1960s, for example. Many now run without many signals but using CTC and radio.

--Morven 21:13, 21 Sep 2003 (UTC)

mish-mash of different information[edit]

This article is still a bit of a mish-mash of different and sometimes duplicating information (always a problem when you have multiple authors), I'll have to think of a way to make the flow of the article better and to make more sense G-Man 11:53, 26 Sep 2003 (UTC)

Definitely -- the page is, however, still in a state of flux, and thus a bit of chaos is inevitable. As it gets more complete, it should also get more coherent. --Morven 18:08, 26 Sep 2003 (UTC)

Unconnected Articles[edit]

Something seems to have gone awry here, as there are 2 unconnected articles with differing spellings on the same topic. Railway signalling and railway signaling. Surely the railway signaling should redirect to Railway signalling, and the content be merged. John 15:00, 30 May 2004 (UTC)

Note to John just below above, he is exactly right in what he says. I have altered the article to correct it regarding UK signalling and have also included a note about 4 aspect sequences for fast lines. I am employed in the industry and have designed such systems so I know I am correct. --Ellendee 21:28, 22 Jun 2005 (UTC)

Position of Red Light in Britain[edit]

Also, I cannot agree with the section on colour lights in Britain. I have read that the lights are positioned so that the red is nearest the drivers eye level, not always red at the bottom, as suggested. Can someone confirm? (I have not changed this.) John 15:00, 30 May 2004 (UTC)

The red light is positioned in order to satisfy the 'fail safe' principle. In conditions of driving snow, snow can build up on the shades and obscure the signal above. Since the red aspect is the lowest aspect, there is no shade below it for snow to build up on and thus the indication should always be visible. Having said that, there are situations in which the rule is violated. For example where a two aspect signal (red/green) is co-located with a two aspect repeater (yellow/green) in the same signal head. In this situation, the main signal is usually the higher signal (for sighting reasons) and the shade for the green aspect of the repeater is immediately below it. 12:22, 21 August 2007 (UTC)

There is an example of a three aspect colourlight signal at Spondon, near Derby which has the red at the top and the green at the bottom [DY410],but this is due to the signal head being on the ground not on a post. —Preceding unsigned comment added by (talk) 03:03, 10 December 2007 (UTC)

There are numerous examples of where red is not the bottom aspect. This is usually due to infrastructure obscuring the view, or height limiting the height of the signal so the red would not otherwise be at driver's eye level. These, by their nature, are usually under structures such as bridges or in tunnels. At Birmingham New Street the signals lamps are mounted horizontally in the centre of the station - again, deep underground at this point. Co-acting signals, where a (usually) ground-mounted signal is present alongside a normally-mounted signal, the red is at the top. So in answer to your question, NO reds are not always the bottommost aspect. —Preceding unsigned comment added by Geoffmayo (talkcontribs) 16:18, 8 April 2009 (UTC)

Red lights are always placed where the driver will see them easily. Not nessecary at the bottom. Ralph Chadkirk (talk) 19:15, 22 May 2009 (UTC)

Page move[edit]

I have moved single-'l' to double-'l', and double-'l' to Railway signalling/Temp, and also with the Talk page (Talk:Railway signalling/Temp). Eventually (that is, when the functionality is available), we might want to merge the histories, too, which is why I didn't just delete the pages.
James F. (talk) 22:42, 7 Jul 2004 (UTC)


I don't know if it's just a terminology thing, but some of the information in this article is more properly known as safeworking. The first two sections of the article are Timetable operation and Timetable and train order, which are both safeworking systems that have no signals. I believe that we should either rename this article, or start a separate Safeworking article and move some of the information there. Philip J. Rayment 02:54, 12 Oct 2004 (UTC)

It seems that it is a matter of terminology. I now discover that safeworking is an Australian word, and its use seems to be limited almost entirely to Australia. Philip J. Rayment 14:25, 15 Oct 2004 (UTC)

Merge with Railway Signal?[edit]

It seems like that would make sense. Also, the single 'l' spelling seems much more common on google. [1]vs [2]

Night Gyr 01:08, 8 Feb 2005 (UTC)

It makes sense to me to keep them separate. Railway signalling is what I (as an Aussie—see my posts just above) know as safeworking. Safeworking is distinct from signals, although there is overlap. In Victoria in recent times, there have been the following forms of safeworking (I won't claim this to be comprehensive):
  • Staff and Ticket
  • Electric Staff
  • Double-line block Telegraph
  • Automatic and Track Control
  • Centralised Traffic Control
  • Lever Locking and Track Control
  • Three-positional signalling
  • Train Order Working
And there have been two types of signals:
  • Two-position signals (both semaphore and colour light)
  • Three-position signals (both semaphore and colour light)
The notes on UK four colour lights certainly belong in a different article - UK railway signals perhaps ?
To over-simplify the situation, the first three listed safeworking systems used two-position signals, the next four used three-position signals, and the last doesn't use signals.
This article (I gather) describes what I know as safeworking, whereas Railway signal describes the signals. Not that I've looked closely to see if they do strictly follow that demarcation.
As for the spelling, the difference is American vs. non-American spelling, and Manual_of_Style, Usage_and_spelling says, "For the English Wikipedia, there is no preference among the major national varieties of English.", so there is no reason to change it.
Philip J. Rayment 12:29, 8 Feb 2005 (UTC)
No, it's a silly idea. railway signal should concentrate on styles of signal; upper quadrants, lower quadrants, 2,3 and 4 aspect colour light, and each railway compnay had a house style. THis page should be about the operation of signals. — Dunc| 15:39, 18 November 2005 (UTC)

uniquely susceptible to collision because[edit]

"uniquely susceptible to collision because" this seems a bit of a weird construct, you could easily argue that not being able to turn into each other is a unique way of avoiding crashes. In a non track guided vehicle you generally have to observe in all directions on a track it's forward and back.--Son of Paddy's Ego 12:02, 30 September 2005 (UTC)

I agree.--John 13:52, 30 September 2005 (UTC)

red/yellow/green explanation[edit]

Minor criticism of the red/yellow/green explanation. Green doesn't mean "full line speed" necessarily, it means that the next signal is not red. Also yellow doesn't mean the next signal is red... often the next signal is yellow as well. (In the ABS section of the Chicago 'L', the usual sequence is red, two yellows, then green; assuming the red isn't an interlocking home signal). Anyway, I think the signal color rules are dependent on individual railways, so this could be difficult to integrate into the page. (For example, yellow on the L means that the operator must not exceed 30/35MPH, so some signals around sharp corners are never green.) Jrockway 04:45, 1 December 2005 (UTC)

Proposed merge[edit]

There is significant overlap of content and subject matter in Railway signal and Railway signalling and I propose the content from Railway signal be merged to Railway signalling, which is a more appropriately-named article.

Please discuss at Talk:Railway signal#Proposed merge. — JonRoma 21:35, 4 February 2006 (UTC)

dont merge; more info regarding US signalling needed[edit]

I am against the proposed merger. On a different note, the article could use more information regarding the many types of signalling used in the U.S.
--Wump 18:24, 15 March 2006 (UTC)

I added a bit of information on "signalling" methods used in the U.S. Upon skimming the remainder of the article, I think I may have repeated a bit of what was already there. Perhaps it would do well for someone (me, included, but only after at least a dinner break) to go back through the article and see what belongs where. In fact, the article is a bit jumbled and could stand some reorganization. There's a lot of information here, but (pardon me for saying so) it's rather poorly presented. As I always say, I'll see what I can do...but every time I promise to work on it, I forget and go off and do other things...
On another note, too, I'm guessing that "signalling" is a British term for what I here in the U.S. would call, more or less, "methods for granting main-line authority" or something similar--perhaps someone could come up with a better word--and what, as Mr. Rayment mentioned above, Aussies call "safeworking" (a nice, concise term, but one I would associate with our Safety Rules Manual, which stresses things like lifting properly and wearing hearing protection...). While authority for movement on tracks *is* largely done with signals today, there are still many places that don't use signals, and I would say the overall subject of granting authority really don't have much to do with "signalling." So, is the word "signalling" really the British term for safeworking/granting authority, or is it the title of this article because some railfan thought that's what it should be called?
cluth 02:33, 17 August 2006 (UTC)
In the last few minutes, I thought of a few terms that I think might be better than "signalling":
  • Railroad (or railway, if you insist on being British) traffic control
  • Railroad (ditto) methods of operation (in my railroad's timetable, CTC, DTC, and TWC are referred to as "methods of operation," so this has some official backing
  • Railroad track occupancy
  • Train authority (according to GCOR, the definition of a "train" includes "...and authorized to operate on a main track." "Authority" is what is given by dispatchers and signals, so this may be appropriate.
  • Railroad signal rules (to me, "signalling" sounds like "the act of creating a signal" and evokes images of a flagger or a semaphore operator throwing the signal--which isn't what this article is about. That term belongs over at That Other Article That People Keep Suggesting Needs To Be Merged With This One--and the very similar titles may have something to do with everyone's perceived need to merge the articles (hey, I almost argued for them to be merged when I first skimmed them and didn't realize they WERE describing separate issues until after I read them in more detail to argue why they did need to be merged!).
Now, to be fair, I do see lots of other web sites out there that cover this subject and have the word "signalling" in their title. However, I also notice that most of them are pages created by Brits, so perhaps it is a valid British term (and this article was clearly originally created or at least quickly evolved with a British focus). Maybe railways developed more in conjunction with signals in Britain than here in the U.S., where train orders and other methods of working in dark territory reigned for so long, so the terminology evolved to reflect that (I'm purely throwing out a wild guess, here). In any case, it's just a point I wanted to bring up, and this whole post was firmly tongue-in-cheek, lest anyone get mad at me for offending British sensibilities and spellings...
cluth 02:56, 17 August 2006 (UTC)

British absolute block signalling[edit]

Found this article that appears to be completely isolated and unlinked - British absolute block signalling. Probably should be deleted and merged with this or linked much better with other rail signalling pages. Pickle 22:04, 7 May 2006 (UTC)

Cleanup tag[edit]

I added a cleanup tag to the article--after rereading the whole thing, I really think that it's a mishmash of a lot of good, but poorly organized, information. Based on the other comments in this talk page, I think everyone else agrees that it needs a bit of help in this area, so I hope I'm not offending anyone by tagging it. cluth 18:53, 17 August 2006 (UTC)


I've completely reordered this article without actually editing (much) of the text. I believe it flows much more smoothly now and appears to be much less focused on the signals themselves (which is really the domain of the railway signal article) and more on the operation and history of signalling/safeworking/operation methods. Before, it looked like it was a bunch of separate articles pasted together, and it really didn't flow.

There is still a bit of overlap and/or material in this article that may belong in the signals article, but it's more clearly delineated now, I believe. I hope you agree.

Also, there is still a small bit of repetitiveness in this article and it could still use some cleaning up, so I'm leaving on the cleanup tag. cluth 05:07, 18 September 2006 (UTC)

Safeworking/signalling topic organisation[edit]

Although much has been done in recent times to better organise this article (Railway signalling) and Railway signal, there is still much that could be done.

I come at this topic as a Victorian, but have made some attempt to use more generic terminology and include systems foreign to Victoria, although my knowledge of non-Victorian systems is quite limited. As I mentioned above two years ago, what is covered in this article is known in Australia as safeworking. Whilst on one hand I accept that it is unreasonable for an Australian-specific term to be used as the overall name of this topic, on the other hand I can't see that any other term adequately covers the topic. As I mentioned there, some of what is covered by the term railway signalling has nothing to do with signals!

I also noticed that the article Railway signal begins by defining a signal as "a mechanical or electrical device that ...", but, at least in my experience, that is only one type of signal, what is known as a fixed signal. There are also hand signals, audible signals, and train (lamp) signals. Fixed signals are called that because, unlike the other ones, they are in a fixed location.

Part of the problem is a lack of a clear explanation (in the articles as they currently stand) between railway signalling and the signals themselves.

  • The former, which I have listed below as safeworking systems are the rules and devices by which trains are prevented from being in the same place at the same time.
  • The latter, signals, are how information (about the state of the section ahead, etc.) is conveyed to the train driver and others.

There is not a one-to-one correspondence between the two, as a number of different signal types can be used for each of the different safeworking systems.

There are already a number of articles covering this overall topic, as can be seen in category:Railway signalling, but the main ones for this discussion are Safeworking, Railway signalling, Railway signals, and Token (railway signalling).

Below I have listed a hierarchy of safeworking, the two main groups of which I've labelled safeworking systems and signals. This is my own thoughts on what I think the relationships between them are, and while meant to be fairly comprehensive is not intended to be exhaustive.

--Signal127 (talk) 05:17, 10 July 2013 (UTC)This section on safeworking/signals makes sense to me. In my attempt to understand New Zealand Signalling I wrote the following: "The safe operation of a railway depends both on the signalling (i.e. the hardware) and the safeworking rules (the software) that define how the hardware is used." This may not be strictly correct but it helped me understand the subject. The rules (software) applying to a particular signal can be changed by issuing a bulletin which changes the classification of a signal. I know of an example where a Departure signal temporarily became a Starting signal so that it could be passed at stop without any paperwork. See On my web site I also said: "Two systems are used in New Zealand - Automatic signalling (with several variations) and procedural (in non-track circuited territory - points indicators/signals at crossing locations only).". To see how I use this to explain NZ signalling/safeworking go to

"Signalling" is probably the wrong term to use when trying to explain railway operations. I admit that when I started my web site over ten years ago I used the term "Signalling" in the title because I did not know any better. Maybe the wiki page needs a different title but I am not sure what it should be.

Because it is difficult to put a bulleted list in a table, I have repeated the various topics of the first list in a second list which shows in which article each topic is currently covered. It can be seen that some topics are not covered or inadequately covered. It also helps demonstrate how much of the overall topic each of the main articles cover, and may help to better organise those articles. According to the hierarchy below, some topics (e.g. detonators) are in the wrong article. I have not gone through every article thoroughly, so I may have missed bits, and any corrections and comments are welcome. Feel free to directly modify (but not reorganise) the lists if appropriate.

Philip J. Rayment 11:20, 18 September 2006 (UTC)

Hierarchy of safeworking topics[edit]

    • Safeworking systems
      • One engine in steam
      • Timetable working
      • Train Order working
      • Token working
        • Staff & Ticket
        • Electric Staff
          • Miniature Electric Staff
        • Radio Electronic Token Block
        • Pilot working
      • Manual Block working (telephone, telegraph, bell codes)
      • Automatic Block working (track circuits, axle counters, etc.)
      • Moving Block
    • Signals
      • Hand signals (arms, flags, and lamps)
      • Train signals (lamps on trains)
      • Audible signals
        • Train whistles
        • Detonators/Torpedoes
      • Fixed signals
        • Semaphore signals
        • Colour light signals
        • Position light signals
      • In-cab signals

Coverage of safeworking topics[edit]

Topic Article(s) currently covering topic
SAFEWORKING Safeworking, Railway signalling
Safeworking systems Safeworking, Railway signalling
One engine in steam Safeworking
Timetable working Safeworking, Railway signalling
Train Order working Safeworking, Railway signalling
Token working Token (railway signalling)
Staff & Ticket Token (railway signalling), Safeworking (placeholder only)
Electric Staff Token (railway signalling) (briefly)
Miniature Electric Staff Safeworking (placeholder only)
Radio Electronic Token Block Radio Electronic Token Block
Pilot working Token (railway signalling) (briefly)
Manual Block working Railway signalling, British absolute block signalling
Automatic Block working Railway signalling, Automatic Train Control (axle counters not mentioned in either article)
Moving Block Railway signalling
Signals Railway signal
Hand signals not covered
Train signals not covered except for a mention of tail signals in Railway signalling
Audible signals not covered
Train whistles not covered
Detonators/Torpedoes Railway signalling
Fixed signals Railway signalling (mention only, not defined)
Semaphore signals Railway signal
Colour light signals Railway signal
Position light signals Railway signal
In-cab signals Railway signalling, Cab signalling
In terms of railway signal I think it is reasonable to limit it to fixed signals; however I agree it should note other sorts of signals (hand signals, horn/whistle, crossing).
In the bigger picture I'm not sure exactly how "safeworking" fits into this. Signals are fundamentally about directing traffic; safety enters into the picture as a factor dictating how that control is to be exercised. In train order operation and its various relatives, safety is based first of all on rules as to how orders are to be written and conveyed, and secondarily by the presumption that engineers/drivers will obey them and will follow certain other rules when it becomes impossible to obey them. In automatic block systems, safety enters in theough the system's automatic modification of the signals to reflect the presence of trains. Right now the article is way too safety-oriented.
It seems to me that we need to work it something like this:
  • Basic issues
    • Control/Direction
    • Safety/Protection
  • "Local" signals (need better word)
    • Hand signals
    • Horn/whistle signals
    • Bell
    • Flares/torpedoes/flagging
    • Marker lights
    • etc.
  • Traffic Control
    • Order-based systems
      • Time Table & Train Order
      • Track Warrants
      • etc.
    • Single occupancy systems
      • Token
      • Train register
    • Signal based systems
      • ABS
      • CTC
      • Other?

We also need to address the different systems of signal meaning. I can address NA "speed signalling" practice, whose diversity fortunately requires a general approach. The other types of system need to be addressed without succumbing to the temptation to spell out every little variation as if it were of major importance. Right now, the articles on British practice seem to have a lot of trouble seeing the forest for the trees. For instance, the articles on home signal and distant signal probably ought to go away. The terms are used universally in block systems and interlocking protection, and there's really no way of writing a stand-alone article on either that is accurate and that works in all contexts. Mangoe 16:10, 18 September 2006 (UTC)

Thanks for the response, Mangoe. In your list, you have 'local' signals, but I can't see where fixed signals fit in (fixed signals being used in more than just ABS/CTC-type situations). Also, where does what I know as Double Line Block Telegraph fit? Is that the same as Train Register?. Philip J. Rayment 09:20, 19 September 2006 (UTC)
Well, that is a good question. In NA practice fixed signals fall under "traffic control" because they function as part of the overall system of controlling how the trains move. What I have inadequately lump together under the "local signals" heading (which is a terrible name, I agree) are all the various methods used for communication among the train crew and other people on the ground for such basic messages as "come here", "watch out, the train is about to move", and "everyone stop what they're doing!" I would tend to put the British system you describe under "traffic control" as well. "Train register" is strictly a safety mechanism used to protect a branch; the conductor for a train entering the branch has to sign the register before entering, and cannot enter if any previous train hasn't signed out. The register acts in the same manner as a token, which is why I've put them together.
Somewhere along the line the article has to step out to a much bigger picture, which in NA is that the dispatcher directs where the trains will go, and that the rest of the system has the two-fold purpose of informing the various personnel what to do, and to keep them from taking unsafe actions. Safety has priority in any single action, but in overall purpose traffic direction is the first priority. British/continental/wherever practice needs to be compared/contrasted with NA practice on this level. The impression I have is that control is very centralized in NA and very distributed in Britain; if this is true, the article needs to say this.
There is also the problem that in NA no large railroad ever used a single system once fixed signals came into the picture. B&O operating rules in the last years had rules for train register, TT&TO, automatic block and CTC operation, each of was used in different territory and could supplant each other in emergencies or as system installations changed. I don't know how this relates to British practice. In any case explanations have to be more systematic than simply listing the various methods without any common context. Mangoe 11:13, 19 September 2006 (UTC)
Somewhere along the line the article has to step out to a much bigger picture, which in NA is that the dispatcher directs where the trains will go, and that the rest of the system has the two-fold purpose of informing the various personnel what to do, and to keep them from taking unsafe actions. ... British/continental/wherever practice needs to be compared/contrasted with NA practice on this level. The impression I have is that control is very centralized in NA and very distributed in Britain; if this is true, the article needs to say this.
Victoria was/is very similar to British practice, I believe. Train Controllers (dispatchers?) sort out problems when things run late, but otherwise it is all up to the local signalmen. In Double Line Block Telegraph, the signals are for conveying information from the signalman at each block section to the train crew. The signalman operates the signals according to the timetable, communication from adjacent signal boxes, and of course the availability of the track. Apart from perhaps reporting progress to the Train Controller, he did this with little if any communication with the train controller, unless necessary to recover from late running, etc. Some fixed signals were actually operated by the guard (conductor); if the train was delayed in the section he was required to protect the rear of his train from a possible following one. This would normally be with detonators, but at some stations a fixed signal was provided with a lever on the platform that he could use instead. Also, gatekeepers (at level crossings) might have a fixed signal that they control.
Some train signals were not just for communication with on-ground staff, but with signalmen, so the "level of communication" (i.e. between signalman and driver) was the same as with fixed signals.
On Staff & Ticket or Electric Staff lines, the station might even be worked under guard-in-charge conditions. The down arrival signal would have been left to proceed to allow the down train to arrive. Before proceeding further down the line, the guard would then change the down arrival signal to stop, and the up arrival signal to proceed, ready for the return trip. If two trains were to cross, the guard would return the down signal to stop, operate the points and signals to allow the up train to arrive and depart, then reset everything for the next expected arrival (up or down) before proceeding. All without necessarily any contact with the Train Controller, but all involving fixed signals.
This was all with 'two-position' manually-operated signals, but there were/are even a few locations where there were isolated 'three-position' power-operated signals. Also, these same three-position signals (whether semaphore or light) were used for Centralised Traffic Control, Automatic and Train Control, Lever Locking and Train Control, (all single-track systems) or what was known as simply 'Three Position Signalling' on double track, and which are all now known here as Automatic Block Signalling.
My point, I guess, is that there is a fairly-clear distinction between the signals themselves and the various systems that used those fixed signals, so we ought to discuss them separately (which is already the case, with separate Railway Signal and Railway Signalling articles).
However, Traffic Control is a good term in lieu of (my preferred!) safeworking, and your breakdown of that into Order-based, Single-occupancy, and Signal-based systems seems to me to be a sensible arrangement. My own breakdown of Safeworking Systems is not all that different, and is probably a bit more of a British historically-chronological order than anything.
Somewhere along the line the article has to step out to a much bigger picture, which in NA is that the dispatcher directs where the trains will go...
As you mention, this would be more North American practice than anything. It explains to me why there is a system called "timetable and train order", which seemed odd to me because (in my experience) all systems (other than One Engine in Steam) that I am familiar with are timetable-based.
Perhaps we need to say something like, "Either the timetable (Britain et. al.) or the Dispatcher (North America) directs where the trains will go, and the rest of the system has the two-fold purpose of informing the various personnel what to do, and to keep them from taking unsafe actions".
Philip J. Rayment 04:16, 20 September 2006 (UTC)
In case anybody is interested, I've added a paragraph about my safeworking background on my user page. Philip J. Rayment 10:40, 20 September 2006 (UTC)
Reviewing comments above, I would adjust my outline as follows:
    • Signal based systems
      • Route signalling
        • systems used in UK which I don't have names for
      • Speed signalling
        • Automatic block
        • CTC
        • Other?

Discussion of the American systems here would be limited to how the signals are interpreted, with the control details pushed off into separate articles (or earlier sections). I suspect that the UK discussions would divvy up content differently, but the main thing is to avoid burdening this article with variants and exceptional examples, which would be better placed in some sort of UK signalling article. Mangoe 17:39, 20 September 2006 (UTC)

Just a quick interjection (since I have to leave here soon): I wonder if this article started out being called "signalling" because British railroading (railwaying?) has been inextricably linked with (fixed) signals--specifically locally-operated signals--whereas in the U.S., signals, whether automatically or manually operated, were not a major part of railroading until recently (as indicated by the plethora of non-signal-based methods of safeworking/traffic control (a term I like a lot!), such as track warrants, DTC, timetable/train order, etc.
I like this discussion! Let's keep it up and see if we can sort this all out once and for all! I'm currently rewriting the CTC article; once I've gotten around to finishing that, I'll see if I can help sort the mess here. :-) cluth 00:32, 28 September 2006 (UTC)

signalman and signalman (rail)[edit]

Just trying to sort out serveral articles on signalmen, and would be greatful if someone who knows a little more about the subject could make a half decent stub of signalman (rail). Renski 15:53, 20 September 2006 (UTC)

This article is too long and should be more general.[edit]

This article should aim to explain the overall principles of railway signalling that apply throughout the world, rather than mentioning details specific to any particular country (for which there may be separate articles). The huge section headed "Modern signaling in the U.S." is just a copy of what is written in the article North American railway signaling, the latter being the proper place for that information. I therefore propose to delete that whole section from this article as a first step to improving it. Any comments? Signalhead 19:30, 3 January 2007 (UTC)

Well, it's been three months and so you've already deleted it--but I'm not saying I disagree with your edit. I agree that the North American railway signaling article is a better place for it. I actually created that article by copying the info from this article to that one, so yes, it was a duplication. I didn't remove it from here, though, because there were some comments about a lack of info about U.S. operations, and the whole direction of the article was/is still in flux.
As I said, I agree with your statement that this was better addressed in the other article. But I'm still not satisfied with how this topic is being addressed here and subdivided elsewhere. There are too many different ideas and discussions going on among too many different articles using too many different terms (we can't even agree what this is called, much less how to address differences). We really need to have a comprehensive analysis and discussion of the subject--I'm not sure how to do it, myself; all I know is that it's poorly done now, and no one (except for Philip J. Rayment) has provided any useful ideas. I don't mean to be harsh, but it's hard to contribute to this topic when no one knows what the topic is... cluth 05:09, 7 April 2007 (UTC)

== Move the discussion? ==Afterbrunel 13:06, 31 July 2007 (UTC)

Since there are so many different discussions on this subject involving so many different articles, I've started the discussion over on the Operations Task Force talk page, which seems like a better place to see the big picture. I've put a list of articles with significant overlap over there, and perhaps those of us interested in trying to figure this out should join the Operations Task Force so we can work together instead of everyone being on different wavelengths.

I wonder if this article (railway signalling) should just go away completely and all of the content be merged into the various national articles (e.g. Safeworking in Australia, Railway signalling in the United Kingdom, Railroad Methods of Operation in North America, etc.--we'd need to do some name changes on some of these articles, which I also propose).

Thoughts? cluth 02:22, 8 April 2007 (UTC)

Yes do it.

The introduction is also very confusing to an uninformed reader. And if accurate timekeeping was so important in the US, why did it take until 1891 to do it. And who is the general time inspector, Ohio?

Afterbrunel 13:06, 31 July 2007 (UTC)

colour signals: international comparisons[edit]

The article states "Although signals vary widely between countries, and even between railways within a given country, ..."

Then there are separate wiki pages for individual countries.

I would be interested in seeing a discussion of why different countries have created different systems, and what advantages each one is attributed to have.

I am sure some systems are created as responses to percieved deficiencies in earlier systems of neighbouring countries. 12:31, 16 August 2007 (UTC)

Double coloured light signalling[edit]

I'm not an expert (just an individual with a certian level of professional interest) but can this section really be right about a green light over a red light indicating that the next signal is red? Wherever a red light is shown, it surely has to mean "stop here" - making any exception to this would make red lights elsewhere open to interpretation by the driver. And why bother with green over red, when yellow indicates that the next signal is red? viking10000 14:08; 15 Aug 2007 (UTC)

In-cab signalling vs automatic train protection[edit]

I don't think this article makes the difference between ATP and In-cab signalling clear, especially when it talks about ATP being used in fog. ATP is typically a lower safety-level device than in-cab signalling. It is designed to replace a second driver in protecting the train rather than allowing operation in the absence of visible track-side signalling. For example, an ATP system might be SIL2 and apply the emergency brakes when the train moves out of established parameters (speed, movement authority, etc). The driver must still be aware of track-side signals and drive the train correctly in order to avoid the emergency brake from applying. Noone should die if the ATP gets it wrong. The driver is still responsible for following the signals.

An In-cab signalling might be SIL4, and thus would allow the train to be operated in fog and on railways with different signalling conventions to what the driver is trained for. It can replace, rather than merely supplement the track-side signals. A malfunctioning in-cab signal could allow a train to be driven into danger, and there would be nothing the driver could do to anticipate that danger. In the absence of a second driver in-cab signalling can provide train protection capabilities that less drastic braking solutions than ATP, due to its higher safety level. —Preceding unsigned comment added by FuzzyBSc (talkcontribs) 06:09, 3 October 2007 (UTC)

Double yellow[edit]

I think Signalhead's edit of 8 September 2008 is unnecessarily restrictive. Double yellow signals do exist so they should be mentioned somewhere. Biscuittin (talk) 09:14, 9 September 2008 (UTC)

OK, found it at British railway signals. I think we need better cross-referencing though. Biscuittin (talk) 09:26, 9 September 2008 (UTC)

Suggested image[edit]

Chicago Transit Authority control tower 18 guides elevated Chicago 'L' northbound Purple and Brown lines intersecting with westbound Pink and Green lines and the looping Orange line above the Wells and Lake street intersection in the loop. (viewed facing northwest)

I do not fully understand this topic and am not able to optimally place this image. I suggest someone who has a better understanding of the topic do so.--TonyTheTiger (T/C/BIO/WP:CHICAGO/WP:FOUR) 04:54, 11 June 2010 (UTC)

speed signaling does not always require "far greater range of signal aspects"[edit]

I'm operating under such a system and having a additional yellow light by the green light (Hp2 in H/V Signalling System restricing speed to 40 km/h instead of full speed) is the same as having a route indicator. I other systems (Germany Ks, Swiss System N a number just shows the allow restricted speed for the diverting route - also just one additional signal lamp in copamre with the route indicator) I don't see what it requires a far greater range of aspects. So i'm not very happy with this sentence. Since i'm not native english speaking, i don't make any corrections to avoid mistakes. -- (talk) 17:30, 12 February 2011 (UTC)

I think the problem here is that "route signalling aspects + posted speed limits + driver's route knowledge" is probably similar to "speed signalling aspects", but the shift from driver's route knowledge to posted speed limits and "approach release" (or other speed signalling type aspects) means ...? How about one of:
  1. "Speed signalling requires a far greater range of signal aspects than route signalling if the latter places a greater dependence on drivers' route knowledge."
  2. "Route signalling requires fewer signal aspects [than speed signalling] as more dependence may be placed on drivers' route knowledge."
I'm not an expert, but I am a native English speaker. Tim PF (talk) 03:41, 13 February 2011 (UTC)

19-inch rack[edit]

The norm of the 19"-rack has been developed for / with railway signalling says that article. Should possibly be mentioned here. --Helium4 (talk) 13:03, 11 February 2012 (UTC)

That information is too detailed for this particular article in my opinion. I would also like to see a reference.–Signalhead < T > 13:47, 11 February 2012 (UTC)
I agree wholeheartedly with Helium4 above and disagree wholeheartedly with Signalhead above. As a long-time user of the 19-inch (i.e., 450mm aperture) rack in the telecom & datacom industries, I have recently come across a thread of apparent history that indicates that the 19-inch rack in the railroad signaling industry predates (by decades) Western Electric's 23-inch rack in the telecom industry. If true, then the most important aspect of this article is the contribution that railroad signaling has made to modern telecom & datacom technology: the 19-inch rack, which is now eclipsing the 23-inch rack. I came to this article specifically looking for this 19-inch rack information instead of the dreck that fills this article. —optikos (talk) 18:31, 15 July 2013 (UTC)

Mish mash[edit]

Several previous comments suggest that the page is a mish-mash, and I agree. We need to separate out the issue of signalling -- which I take top mean the procedure to give messages to control train movements to prevent collision, from a lot of the mechanics.

The contrast between UK and US + Australian practice is also very stark, and fundamentally different and conflicting assumptions are made.

I was also surprised not to see "Time interval working" described (as a historical method) and not much about single line operation.Afterbrunel (talk) 06:48, 22 September 2012 (UTC)

Mish mash[edit]

Several previous comments suggest that the page is a mish-mash, and I agree. We need to separate out the issue of signalling -- which I take top mean the procedure to give messages to control train movements to prevent collision, from a lot of the mechanics.

The contrast between UK and US + Australian practice is also very stark, and fundamentally different and conflicting assumptions are made.

I was also surprised not to see "Time interval working" described (as a historical method) and not much about single line operation.Afterbrunel (talk) 06:48, 22 September 2012 (UTC)

There is a fundamental problem with signalling concepts' descriptions[edit]

The main problem with a coherent description of railway signalling is the following: Any literature on railway signalling from one of the three large "cultures" (Middle Europe, UK, and US) did and does not (or only very very very rarely) look into the other two cultures (and the same seems true of most people I know). Therefore, extracting the worldwide principles (which do exists; e.g., block signalling; distinction between train and shunting signalling; etc.etc.) always borders on "original research", which is not acceptable in WP.

Currently, I know of only one book that transgresses these divides, namely Jörn Pachl's "Railway Operation and Control". Maybe we should try to excerpt that book, or at least follow its principal concepts. There are a few mostly dormant and out-of-date web sites that tried at least to collect many signalling practices, but they can be a starting point at best. Another candidate might be Theeg, G.; Vlasenko, S., Railway Signalling & Interlocking - International Compendium, Eurailpress, 2009!). Maybe we should despair - and create unconnected pages for lots of countries, probably only in their own language (Argentina only needs a Spanish page, for example)- and that's it.

But do we really want this? --haraldmmueller 19:15, 7 September 2014 (UTC) — Preceding unsigned comment added by Haraldmmueller (talkcontribs)