Do the railways have over-speed detection (not just on approach to signals at danger)

Discussion in 'Infrastructure & Stations' started by newWCMLwatcher, 8 Nov 2019.

  1. newWCMLwatcher

    newWCMLwatcher Member

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    Do railway lines have any safety mechanisms built in to bring a speeding train to halt or at least altert a signaller of this? I know that when a train approaches yellow/red aspects there are grids in the four foot which check if the train is slowing enough to stop but I wondered if there was anything that would highlight a train travelling too fast on a clear path of green lights?

    Other than the timings giving it away, if there was a huge stretch of clear line for a few miles and a train in a 125pm zone ran at 130pm or even above as some are capable of, would there be any alerts (to either driver, or signaller)? Would the train be stopped?

    I'm just interested in the railway equivalent of the roadside speed camera. Not that I am suggesting any driver would do this purposefully, but if there were mitigating circumstances such as illness or simple misjudgment in extreme cases.
     
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  3. edwin_m

    edwin_m Veteran Member

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    The TPWS grids are used to enforce the more severe reductions in permitted speed as well as signals, but in most cases there is nothing to stop the driver accelerating above the permitted speed elsewhere. However the ATP systems fitted to the GW and Chiltern lines and HS1, and the ERTMS system which is planned to become widespread but only exists on a few routes currently, will both warn the driver of overspeed and apply the brakes if the overspeed continues.
     
  4. Bevan Price

    Bevan Price Established Member

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    Don't know if they still use them, but I have seen portable radar speed guns used on railways. But I think a bigger deterrent will be on-train data recorders - if the record is examined, the driver is likely to be "in the sh*t".
     
  5. LNW-GW Joint

    LNW-GW Joint Veteran Member

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    Also TASS on the WCML (tilting 390s and 221s, at speeds over 110mph).
    The "SS" is for Speed Supervision.
     
  6. newWCMLwatcher

    newWCMLwatcher Member

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    Can you expand on what it does? I'm sorry, I know the basics of the classes (221 and 390), just not the technology of them. Many thanks
     
  7. alxndr

    alxndr Member

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    If you want to learn more about ATP, what it does, and how it works, I'd recommend these videos:


    They're old now, but still used on some training courses.
     
  8. GB

    GB Established Member

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    Most (if not all) modern stock will have some sort of on-board speed protection that will cut off power and/or apply emergency brake if the of the speed of train is above a certain threshold of its designed max speed. Not much help if the linespeed (or class of train) is lower than the trains max speed though.
     
  9. daveshah

    daveshah Member

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    Not a realtime alert, but the OTMR (on train monitoring recorder) would also record the overspeed, which could possibly then be flagged up after a subsequent download.
     
  10. LNW-GW Joint

    LNW-GW Joint Veteran Member

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    Virgin uses tilting Pendolinos (390) and Voyagers (221) on the West Coast Main Line, which are the only trains permitted to run at 110-125mph with tilt.
    The tilting is controlled by an on-board system called TASS (Tilt Authorisation and Speed Supervision) which kicks in whenever balises placed in the track say that tilt is allowed (and by how much).
    It also acts as a form of ATP, and intervenes over 110mph if the train is driven above the authorised speed for that section.
    It is a precursor to the ERTMS/ETCS systems now becoming standard in Europe and beyond.
    ETCS is being rolled out gradually by Network Rail, delivering ATP across the network.
     
  11. PudseyBearHST

    PudseyBearHST Member

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    A few pedantic comments to make but when you are speed supervised your speed is monitored not just over 110mph but at all speeds that you are speed supervised for. And you don’t have to necessarily be tilting to do EPS speeds (but speed supervised) at certain locations. Of course, you also have MU speeds at certain locations so don’t need speed supervision/tilt for the Birmingham and Manchester routes to do over 110mph.
     
  12. Llanigraham

    Llanigraham On Moderation

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    I know from experience of past cab rides, that the ERTMS units on the Cambrian will only allow a very small overspeed of the various limits along the line and it cannot be increased by the driver. If it says 80kph then that is what it will do and not more.
     
    Last edited by a moderator: 9 Nov 2019
  13. DerekC

    DerekC Member

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    I guess it depends what you mean by gradually. Being generous, let's say the process started in 2009, although rollout plans have been in course of preparation since 2002. The Cambrian Route (Shrewsbury to Aberystwyth and Pwllhelli - 213 km) was commissioned into service in 2011. The Thameslink core (St Pancras to London Bridge and Elephant and Castle - plus or minus a bit at the ends - say 10 km ) was commissioned in 2017 but is not yet in regular service. So that's a total of 223 route-km (sort of) done out of the total of 15800. I make that about 1.5% in ten years.
     
  14. Eccles1983

    Eccles1983 On Moderation

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    The short answer is no.

    The speed differentials would take some sort of programming, as different units can go different speeds on the same length of track.

    It's the drivers responsibility to maintain the speed according to the permissable speed for that class of train.
     
  15. Dieseldriver

    Dieseldriver Member

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    I'm farely certain that *some* modern traction self reports if the train is driven at (for example) 3mph over its design speed. Obviously if it was a 100mph unit doing 80mph in a 40mph PSR, it wouldn't flag up.
    I've also heard that hot axle box detectors record speeds of passing trains.
     
  16. HSTEd

    HSTEd Established Member

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    ETCS will enable a revolution in the way the railway is operated and how infrastructure is designed in the future.

    If they ever get it to work.
     
  17. hexagon789

    hexagon789 Established Member

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    I think the was said on another thread that Class 185 units will send a message to control if they exceed 103mph
     
  18. pompeyfan

    pompeyfan Established Member

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    It surprises me that they don’t go into a cruise control type system to regulate the engines to hold 100, 450s and 444s will sit happily on the needle with the PBC wide open.

    the biggest fear for drivers is the random download, that said mistakes do happen, and I’ve known 159s to do the ton between Basingstoke and Woking in the last 12 months, had they been downloaded, it certainly would have been a meeting no tea no biscuits.
     
  19. hexagon789

    hexagon789 Established Member

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    185s have speedset
     
  20. edwin_m

    edwin_m Veteran Member

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    It works and is used on many continental lines as well as a couple in the UK. The difficulty for Network Rail is making it (or any other form of new signaling) affordable.

    Unless you're referring to "Level 3", which was promised by the then Railtrack when it was formed and still doesn't exist.
     
  21. HSTEd

    HSTEd Established Member

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    Well this hasn't been helped by the FOCs and others demanding that existing signalling be maintained,
    Has anyone ever tried an overlay on ETCS and have it work properly?
     
  22. carriageline

    carriageline Established Member

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    Thameslink is Level 2 overlay. It works. Ok, we haven’t run a full train service through it yet. But it’s in, and it’s commissioned. Just waiting for driver training.
     
  23. DerekC

    DerekC Member

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    It has been working on Cambrian since 2011 - and that's an early version.
     
  24. HSTEd

    HSTEd Established Member

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    The project drastically slipped it's deployment schedule, and a tonne of other schemes that were meant to have happened since then... haven't
     
  25. carriageline

    carriageline Established Member

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    Is the fact that the first ETCS scheme in the country slipped its deployment date that much of a surprise? It was a novel thing, and no doubt many unexpected obstacles and issues cropped up.

    Thameslink was a first in that it’s overlay, and on a metro style railway. As far as I’m aware that was commissioned on time.

    Personally, I would prefer a slower approach. Jumping on something because it’s the new toy isn’t the best answer. Let the trial schemes go ahead, and find the problems. That way best practice can be shared, as well as problems and issues picked up along the way.

    As an industry we are notoriously slow at picking up new technologies. Whether that’s right or wrong is another debate.
     
  26. Llama

    Llama Established Member

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    The 195s and 331s do likewise. They are restricted to 110mph, if you get to that speed you won't be driving again for a while and you won't be allowed any tea or biscuits while you are interviewed afterwards as you will be waiting for medscreen.
     
  27. edwin_m

    edwin_m Veteran Member

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    There's an interesting article on train protection in the latest Rail Engineer by Rod Muttram, who was in charge of the ATP/TPWS/ETCS decisions by Railtrack in the 90s. Unfortunately at present it's not on its own web page, just the horrible e-reader which won't even let me copy a quote.
    https://www.railengineer.co.uk/2019...nders-imeche-technical-tour-dawlish-cornwall/ (page 48 onwards)
     
  28. HSTEd

    HSTEd Established Member

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    The problem is we are decades behind the times on signalling systems.

    We would have been in a much better place if we had adopted TVM-430 or LZB or similar in the 90s, or even one of the pulse code systems long before that.
    We are stuck with ancient signalling infrastructure that is a serious operational constraint and a constraint on improvements to the railway, and trying to change it is impossible due to our insane industry structure where a handful of operators are able to block improvements that will benefit the industry so they can avoid spending anything on their obsolescent equipment.

    The priority in resignalling should be rapid adoption of ETCS L2 so we can break out of this spiral and actually catch up.
     
    Last edited: 10 Nov 2019
  29. edwin_m

    edwin_m Veteran Member

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    These systems were intended mainly for high speed lines with long blocks and overlaps. For example the lowest supervised speed on TVM430 is 80km/h and the block (and therefore effectively the overlap) is typically 1500m. TPWS can supervise down to very low speeds as necessary and work with typical UK overlaps of 180m, less in some places. If applied to the classic UK railway the result would be a capacity penalty, as indeed happened with the ATP systems on GWML and Chiltern. TPWS avoids this problem by deliberately not trying to mitigate 100% of ATP-preventable casualties, actually forecast to be about 80% and as my link above mentions there hasn't been an ATP-preventable accident since Ladbroke Grove.

    Unlike these older systems, ETCS is actually capable of delivering a capacity increase. The government is putting a fair bit of funding into ETCS train installations.
     
  30. HSTEd

    HSTEd Established Member

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    Not technically correct, because TVM430 has the Channel Tunnel mode, which has considerably shorter block lengths and lower speeds.
    LZB has been used with 50m blocks on various S-bahn installations.

    But it is true that in the relay era the cost of making shorter blocks could have been substantial, but that ofcourse falls away with SSI in the 90s.
    So when can we expect our first post-Cambrian ETCS only line?
     
  31. edwin_m

    edwin_m Veteran Member

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    Does the Channel Tunnel mode still allow speeds up to 200km/h?

    Even with SSI there is a cost to blocks, you still need the track circuit or axle counter equipment itself plus the modules that interface to the interlocking. The interlocking itself also has a limit on the number of track circuits, so having more of them may trigger a need for extra interlockings. These limits would also apply to blocks in ETCS, although modern CBIs are less restricted than the original SSI.

    The Thameslink core will effectively be ETCS only, and there are plans to install it on part of the ECML. As well as the article I mentioned, the Rail Engineer I linked above has a piece on the ETCS programme - although the funding isn't yet in place for that and the costs may need to come down first.

    Adopting a proprietary ATP system in the 1990s would have cost far more than TPWS for little extra safety benefit and for an operational disbenefit as well as being tied to a single supplier. That was the conclusion of the studies into the two ATP systems actually adopted (some of which I contributed to). And we would have been in a technological dead end now with all European countries moving towards ETCS instead. TPWS was of course also a bespoke system, but was at least designed to be easily installed on British traction and signaling rather than requiring complex extra interfaces as the BR ATP systems did.
     

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