Reduced Speed at Closed Stations

Discussion in 'London Underground' started by wheelnrail, 14 May 2015.

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  1. wheelnrail

    wheelnrail Member

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    I was in London the other day traveling on the Central Line heading West. On our journey we had to pass the closed station of Tottenham Court Road, and as we passed we were going, perhaps 15mph, through a fenced off platform area. Its the same for other closed stations I passed through in the past. Im just curious as to why the speed restriction. Is it a rule in the book, or a health and safety aspect for workers? Signalling? I figured it would be nice to just whizz through a closed station at line speed.
     
  2. TheNewNo2

    TheNewNo2 Member

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    I believe it's in the rulebook, and it probably also stops having to create entirely new timetables for when a station is closed to deal with the lack of stopping time.
     
  3. theshillito

    theshillito Member

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    Also, if there's workers on the platform, a passing train at full speed would cause considerable wind (no jokes please).
     
  4. NSEFAN

    NSEFAN Established Member

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    Might it also be for signalling reasons, as the signalling is probably designed with trains slowing down to stop in the station in mind?
     
  5. Domh245

    Domh245 Established Member

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    On conventionally signalled lines, there is an aspect of signalling to do with it, because station starter signals will usually have a shorter overlap because of the fact that usual speeds are very low, which is why conventionally signalled lines have got a 5mph speed limit.
     
  6. steamybrian

    steamybrian Established Member

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    If the work is on the platform close to the open line then a speed restriction will be imposed.
    I presume the timetable is not altered (apart from obviously trains not stopping at the temporarily closed station) then if trains whizzed through at line speed then they would only then sit and wait several minutes at the next station to wait scheduled departure time.
     
  7. A-driver

    A-driver Established Member

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    Not sure that is an issue but believe it's a myth. On the northern city line we can run through stations at line speed with sets of empties and that's not even closed stations. This rule only applies to the tube, not Undrrground mainline trains.
     
  8. Nym

    Nym Established Member

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    It's also quite a lot to do with the platform starters not having full speed overlaps, so the train needs to slow down to pass at starting speed rather than line speed.
     
  9. adrock1976

    adrock1976 Established Member

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    Furthermore, is it also to do with waiting for the tripcocks to retract/fold down before the train can increase its speed again while passing through?

    In peace

    Adam
     
  10. A-driver

    A-driver Established Member

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    Surely the trip clocks only activate if the starter signal is red? Trip clocks are to do with signals, not platforms.
     
  11. Nym

    Nym Established Member

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    I doubt it as the Central Line is not fitted with Trainstops in this area, using Westinghouse Coded Track ATP.

    Where you see that kind of thing happening it is normally due to a timing loop of some kind, such as those that are used to ensure a train has stopped or is going sufficiently slow for a low speed overlap.

    Those at station starters will have associated signals (although this does depend on when the signalling was designed) , but in other areas there may be a 'blind trainstop' that does not have an associated signal head for slow speed overlaps and other situations like TETS (Train Entering Terminal Station).

    Regardless of this, station skip on the Central Line takes account of the low speed overlaps.
     
    Last edited: 14 May 2015
  12. Mojo

    Mojo Administrator Staff Member Administrator

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    Did you perhaps mean trainstop (the thing on the track by the signal) rather than the tripcock (the thing on the train)? There are only a few locations where an automatic starting signal would normally display danger, which comes off when certain track circuits are occupied. I believe these are typically associated with stations that used to have part-time opening hours.
     
  13. matt_world2004

    matt_world2004 Established Member

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    I would have thought it would have been to ensure a passenger train does not get stuck right behind an engineering train which would still have to stop at a temporarily closed station to phone the signaller to be told to proceed.
     
  14. Nym

    Nym Established Member

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    Why would an engineering train need to stop? Do we not have signals at closed stations nowerdays?

    I'd have thought you want to minimize the amount of starting and stopping these trains do, does tend to use up a lot of air to stop and start all the time.
     
  15. matt_world2004

    matt_world2004 Established Member

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    Certainly in tunneled sections engineering stock has to phone the signaller before proceeding because the signaller has no way of seeing where it is unlike passenger stock.
     
  16. Mojo

    Mojo Administrator Staff Member Administrator

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    No they don't! Engineering trains activate track circuits just like normal trains.

    Engineering trains contact the Controller (not the signal operator) by radio to provide their radio numbers, and to confirm their train number, shortly after they have come onto the appropriate line.
     
  17. rebmcr

    rebmcr Established Member

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    You can see passenger stock through tunnels, where engineering stock is invisible?

    Track circuits and identification berths are all that is required for the signaller to know where trains are.
     
  18. matt_world2004

    matt_world2004 Established Member

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    Why does it say at the end of nearly every central line platform something along the lines of engineering stock please contact signaller before proceeding?
     
  19. Mutant Lemming

    Mutant Lemming Established Member

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    I was taught that there were short overlaps on station starters but that was back in the day before TBTC and automatic working so am unsure as to why you would still need a restriction on a Central Line station. Is it one of those 'operational over rides' to keep a common rule throughout the network?
     
  20. Daniel

    Daniel Established Member

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    Only on lines where there are track circuits! ;)

    ATO lines such as the Northern and Jubilee aren't necessarily track circuited. As a secondary to the TBTC loops they are, however, fitted with axle counters, so a non-communicating train can still be traced.
    However, if a train, whether passenger, empty, or engineering, is being moved outside of the protection of the TBTC system, (in Restricted Manual, the equivalent of the tripcock being cut out on conventional lines), the train is authorised by the signaller to proceed with distances no longer than RM hold board to RM hold board.

    Although I don't work on the central line and don't pretend to know about their particular (unique to LU) system, I would imagine the boards on platforms mentioned refer to trains operating outside of the protection of the signalling system.

    Although as Mojo correctly points out, that engineers trains speak directly to the controller, it should be noted that movement is authorised by the signaller.
     
  21. TheNewNo2

    TheNewNo2 Member

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    I know that in the world of TBTC, Tampers can be "hidden" in sidings. Presumably due to their being "go anywhere" they don't have TBTC fitted.
     
  22. matt_world2004

    matt_world2004 Established Member

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    So can in really simple terms, can engineering stock be seen on the central line :/
     
  23. bluegoblin7

    bluegoblin7 Member

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    Yes.
     
  24. Met Driver

    Met Driver Established Member

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    On the Central line the blanket rule is that trains non-stopping a platform will do so at a speed not exceeding 20kph. Why this speed was chosen I couldn't say with certainty, but it was likely chosen because it was felt that it was inappropriate/unsafe for a train to non-stop a platform - potentially with customers waiting - at normal line speed. Clearly this is flawed logic, because trains can and do hit platforms at 65kph in places when stopping anyway. It is certainly nothing to do with the signalling system, because on the outer reaches of the line there are stations which could, theoretically, be non-stopped at normal line speed (100kph, although 85kph is the maximum permitted speed for 92 stock).

    A proportion of the battery loco fleet is fitted with Central line ATP equipment and can work under normal operating rules on the Central line as required. There is no requirement to telephone the signaller at every station, and the signs mentioned upthread do not exist. Some of the fleet is also fitted with TBTC equipment for working on the Jubilee & Northern lines on the same basis.

    The 5mph at the starter rule covering most of the tripcock railway is due to the overlaps on the following signals (particularly the home signal(s) for the next station) being calculated on the basis that all trains will have stopped at the previous station. Were a train to pass the starter at the previous station at a higher speed, there is potential that it would not be stopped within the overlap of the next home signal were it to pass it at danger. Although most station starters do have short overlaps in order to increase line capacity, this is not the primary reason for the 5mph rule.
     
    Last edited: 20 May 2015
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