Weird signalling issue

Discussion in 'Infrastructure & Stations' started by Peter Mugridge, 26 Aug 2015.

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  1. Peter Mugridge

    Peter Mugridge Established Member

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    I have recently observed ( not naming the location ) an instance where a platform is bi-directionally signaled displaying something unexpected.

    The signal at the down end of the platform was off and the "DN OFF" indicator on the platform was lit. There was a train due imminently.

    A moment later, the signal at the up end of the platform cleared to off.

    So the signals at both ends of the platform were off simultaneously although only a down train was due.

    Did I observe a wrong side failure or an error?
     
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  3. Tomnick

    Tomnick Established Member

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    It is often possible to clear a signal in both directions away from the same location, although I'd have expected the Up direction signal to be held at danger in most cases by the approaching Down train! What type of signal is the Up direction signal, and which is the 'normal' direction of traffic on that line, if there is one?
     
  4. Philip C

    Philip C Member

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    This is/was quite common at Tunbridge Wells when a down train was splitting and the detached portion working back to Tonbridge. The two boxes showning "DN OFF" and "UP OFF" are/were alongside each other and both glowing nicely.
     
  5. causton

    causton Established Member

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    Was the actual signal cleared, did you see, to amber or green, or was it just the OFF indicator? And was the approaching train past that signal or still behind it? Odd!
     
  6. edwin_m

    edwin_m Veteran Member

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    In the past starter signals at opposite ends of a platform were interlocked, the reason I believe being the risk that if there was a loco on each end of the same train two drivers could try to drive them away simultaneously. This always seemed rather a spurious reason to me, but with trains being almost exclusive MUs with interlocks to prevent both cabs being switched in, I don't believe this is done today.
     
  7. LAX54

    LAX54 Established Member

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    or.. S&T fault finding and getting Signaller to set a route to try and locate, Signaller clearing signal for similar reason, maybe trying to find a First Filament ? Lamp changed in the 'OFF' and testing ? Clearing signal to get rid of an errant TRS indication in box...??
     
  8. class 9

    class 9 Member

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    You'll never see amber in a railway signal, one or two yellows!:D
     
  9. Deepgreen

    Deepgreen Established Member

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    I believe I have seen something very similar to this at Canonbury, where signals at either end of platform 3 were both showing yellow, double-yellow or green simultaneously.
     
  10. Aictos

    Aictos Established Member

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    Same at Stevenage's Platform 4, it is often the case that the signal for the Down Slow towards Hitchin and the BiDi back to Hertford will show a proceed signal in the form of a green signal so as Tomnick has said it is quite possible.
     
  11. A-driver

    A-driver Established Member

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    If the line ahead of the signals is clear then the signals can both show proceed. Often they won't as the signaller won't clear all signals at a busy station until departure time as often the points need setting first.

    At Stevenage a terminating train from Hertford will run in on a clear signal providing the section ahead of the down starter signal is clear. The driver will change ends and the signal heading back up to Hertford will be cleared. In effect, the down signal is automatic (although technically it's controlled but as the points are rarely set to the fast line it's allowed to act automatically and so display a proceed as soon as the road is clear).
     
  12. Metobusfan

    Metobusfan Member

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    This happens at city thameslink a few times when a train has come out of Smithfield sidings
     
  13. LAX54

    LAX54 Established Member

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    That reminds me of a Signaller who was talking to a handsignaller at the set of AHB's on local, the fact that the h/sig had it wrong in the first place is irrelevent, it's quite common ! but the attendant rang the Signaller and said
    "Can I give the Driver an Orange" ?
    Signaller replied..."You can give him a bloody apple for all I care " ! :lol:
     
  14. causton

    causton Established Member

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    I forgot which way round it was. Plus I am colourblind so if I saw one yellow it could be red anyway! ;)
    --- old post above --- --- new post below ---
    That is a good one :D :lol:
     
  15. Peter Mugridge

    Peter Mugridge Established Member

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    The down signal was yellow and the indicator said OFF DN.

    The up signal was green at the same time.

    The next train due was a down train within the next five minutes; this was showing on the screens on that platform.
     
  16. ComUtoR

    ComUtoR Established Member

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    That is a significant amount of time. For as long as the section is clear then the signal can show a proceed aspect. Did you note the kind of signal it was ? Was it a Controlled Signal ?
     
  17. Peter Mugridge

    Peter Mugridge Established Member

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    Errr.... pass!

    There is a TRS plunger system at the station in question.

    On the route in question, signals do normally clear to off automatically - they are only held on until a train is due where there would be a potential for a conflicting move.



    The "next five minutes" is until the departure time. The station is a timing point and the services in question are often in the platform for 2 - 3 minutes prior to departure.
     
    Last edited: 27 Aug 2015
  18. TDK

    TDK Established Member

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    Surely if it is track circuited as soon as the approaching train occupies the track circuit the signal would revert to danger?
     
  19. Peter Mugridge

    Peter Mugridge Established Member

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    One would hope so, unless it was a wrong side failure?
     
  20. ComUtoR

    ComUtoR Established Member

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    Of course. Not sure where your going with that.

    If the train was 5 minutes out then the section could easily be clear. As your and I are both well aware. As I don't sign the route it is hard to reach an accurate conclusion. Theoretically the section was clear.

    It is more than possible that even with a unit sitting a few sections out that a train could be sent to assist etc so the red only needs to protect the section the other train is occupying. Also possibly there is a set of points further down from the station so the route could be set for that and the incoming train be waiting at the signal. 5 minutes is a long time in railway terms :)

    As I don't sign the route then I'm gathering more information tbh.

    The post about this happening at City also confuses me as I do sign the route and I can't see that happening there at all.
     
  21. Tomnick

    Tomnick Established Member

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    If a route's set from a controlled signal in the Down direction from a platform, then it wouldn't normally be possible to set an opposing route towards the platform in the Up direction, so that situation shouldn't arise. If it is a controlled signal, then perhaps the route was put in with the intention of nipping a Down train through first (but then the situation changed).

    If it's an auto signal in the Down direction (provided for wrong direction movements over the Up?), then it could be that they normally work that way - some (older?) reversible signalling installations do have auto signals in the wrong direction normally 'off' ('stepping down' from green towards red as an Up train approaches in the right direction), the integrity of the reversible line being maintained by the controlled signals at either end and a 'direction of flow' indicator.
     
  22. Sebastian O

    Sebastian O Member

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    Also the same regularly at Woking down fast.
     
  23. westcoaster

    westcoaster Established Member

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    Can happen at city where a train comes out of smithfields, also any station through the core, on the mains also when turning back at Bromley South, beckingham junction, basically any Bi-di platform.
     
  24. ComUtoR

    ComUtoR Established Member

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    Bromley south I've seen on many occasions. Every morning a service runs into P2 and the signal both ends can be off. Even with a unit at Shortlands on the down As the points are directly off the platform.

    Beck Jn ? That's a bay platform you turn around in. That will need explaining on how you get a train on the platform and a signal cleared both ends :/ Turning round at Kent House has a fixed red.

    I still cant see it happening at City when a train is coming out. I think i'm missing something. If I'm sitting on the Down platform and a unit is coming out Smithfield then I'd get a red. If a unit is sitting in Smithfield and his signal is not clear then yeah, I'm signaled into Farringdon no problems with bi di I have no issue with the signal in the rear being off as the section can technically be clear.

    If a unit is signalled out of Smithfield then its a conflicting move and would be interlocked. I had to pull out my route book to check but both cannot be signaled without permissive working taking place. If your saying its possible to have both signals clear on either end of the platform when a unit has been signaled out of Smithfield then I'd love to see how. I'm either missing something important or my route knowledge is out of date. I don't have FCC maps as SE are awful at providing it. I couldn't find them at the terminal either :( but I digress..

    I can easily accept and have posted to that effect. IF the section is clear then any signal can be pulled. The technicalities of interlocking and route setting I'll leave to the Sig's.
     
  25. Tomnick

    Tomnick Established Member

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    Do they / can they ever come out of Smithfield Sidings into the Up (? - sorry, not sure where the directions change over) platform to head south, crossing over between there and Blackfriars? It's possible that, once the unit's in the platform, the signalman would put the route back in towards Farringdon (so as not to forget!) straight away. That'd be with the train already in the platform, of course, not before it arrives as in this example.
     
  26. 30907

    30907 Established Member

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    Down main to all 3 Up routes is a signalled move at Beckenham Junction, and it was regularly used at one time.
     
  27. ComUtoR

    ComUtoR Established Member

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    With the train coming out of Smithfield then I'm 99.9% sure that the starter of off the platform at City (heading towards farringdon) will never be able to clear as the route is interlocked and would be a conflicting move. The section would be occupied. Even if the platform was clear the section is still occupied :/

    My map shows P1 (up snow hill) (apologies earlier for the mention of the down platform) at City leads directly into smithfield so you would get a conflict. P2 (down snow hill) is bi-di and a unit can sit on the platform with a signal clear in both directions without conflict. If a unit is coming out onto the up then not a problem as he can be held in the platform. The down can be cleared in both directions as there is no conflict.

    Section clear = Clear signal. I think Peter and metobusfan are seeing moves that simply appear to be conflicts but are standard signalling.

    If both are on the same line then it just isn't gonna happen.
    --- old post above --- --- new post below ---
    Down Main to the bay P4 - Yep that's possible and used as the turnback. Only has one signal soooooo...

    Down main to down main platform P3 - Standard move. I have never seen that used as a turnback.

    Down main to up main - no longer used and I've been driving 10 years.

    Down main to the up platform (southern side bay) - no longer used and again I've been driving the route for some time.

    The only platform that will give you a signal clear both sides with an incoming service is the down platform and that is beyond rare. The turnback services are booked into the bay or turnback at Kent house. I've driven both regularly, although the Kent house turnback is now an FCC diagram and I've not done that in some time.
     
  28. Andyjs247

    Andyjs247 Member

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    Back to the original question, I guess it could also happen in the case where a 'box had been "switched out". Though I can't think of anywhere where this might be the case.
     
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