Level crossing at Bosham

Discussion in 'Infrastructure & Stations' started by Ianmel1969, 26 Aug 2015.

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  1. Ianmel1969

    Ianmel1969 Member

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    Forgive me I know a little about signalling but i'm no expert on the railways by any means by I wonder if anyone can offer an explanation to this.

    I was standing on the Westbound platform at Bosham. There is a level crossing and signal at this station. Trains not stopping here go through at a fair old lick.

    I heard the announcement to stand back from edge of platform as the next train wouldn't be stopping. I looked at the signal which was green but the level crossing barriers were still in an upright position. It was only about 5 or 10 seconds later that they dropped, with about another 20 seconds until the train hurtled by.

    Question is shouldn't the signal be red until the barriers have dropped? With such a short time until the train came through it seemed a bit dangerous to me!
     
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  3. swt_passenger

    swt_passenger Veteran Member

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    In the general case, if they are automatic half barriers they are not protected by a specific signal, but just lowered by the train operating a treadle on approach. What you have seen is normal, however if a train is stopping at the station it will possibly work differently in that case, to prevent the barrier being lowered too early.
     
    Last edited: 26 Aug 2015
  4. Ianmel1969

    Ianmel1969 Member

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    Thanks SWT!
     
  5. swt_passenger

    swt_passenger Veteran Member

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    Someone may well chip in with a more technical answer as to how the signaller sets the system up for through or stopping trains in this or any other case; but this is a question that comes round every now and again.

    What you see doesn't seem intuitively correct so it easily raises the question in your own mind!
     
  6. DelW

    DelW Member

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    On my drive to work I cross an automatic half-barrier crossing, usually a couple of minutes before a train is due. Half a mile or so further down the line is a manual full barrier crossing at a station (which the train will reach a minute or so later than the one I cross).

    Quite often if I glance along the track, the signal protecting that crossing is already green, which I assume means the full barriers have been closed, although the automatic closure sequence at the earlier crossing has not even begun.

    I realise that the rules and working practice for automatic and manual crossings are different, but does seem counter intutive for a later crossing to be closed before an earlier one has even got a warning. The wait at my crossing is around 30 sec from start of yellow light showing to train passing.
     
  7. DaveHarries

    DaveHarries Established Member

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    I have often thought it dangerous that the signal prior to a level crossing can clear without the crossing being closed (or, in the case of an AOCL, working properly). IMO signals prior to level crossings should interlock with the crossings in question. Might prevent any incidents taking place unless the detection fails.

    Dave
     
  8. snowball

    snowball Established Member

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    I assume the reason why that isn't done is the length of time the crossing would be closed to road traffic and the complaints it would generate about waiting with no train appearing.
     
  9. tsr

    tsr Established Member

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    The problem is that the risk generally does not stem from a wrong-side failure of the crossing, but from a road vehicle or pedestrian in the path of the train - intentionally or not - despite the crossing electronics working fine. The crossings would therefore also have to be monitored for them to be any safer - a signal clearing would just indicate that a failsafe system was working anyway.

    Crossings which are not monitored should feature emergency phones which are usually pretty visible and can alert the signaller to an incident at any time, whether or not the crossing is working correctly. There is little that can be done with these to mitigate someone jumping the barriers unless they become stranded, but they do provide an option in the event of breakdown, equipment damage etc.

    Additionally, crossings which are not interlocked with the signalling equipment will have risk assessments and restrictions on their use.
     
  10. carriageline

    carriageline Established Member

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    It's a fair point, but something you get used to (from working them). What incidents do you expect to happen?

    Nothing unsafe should happen, as the barriers should 'fail safe'. We get an alarm if any of the following happen:

    Barriers have been down too long
    Loss of up detection
    Power failure
    And I'm sure there are others!!

    That's when we will caution trains. So no chance of an incident. The only way you will have a problem is if the barriers fail
    to lower when the train strikes in, but that's a wrong side failure.
     
  11. BestWestern

    BestWestern Established Member

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    The issue with that is the additional risk it would create. The barriers would need to be down longer, which increases the risk of impatient road users (in vehicles or otherwise) making an attempt to cross while the barriers are down. The type of crossings concerned here are just the sort where it is relatively easy to dodge the barriers. Let's say barriers are down for two minutes; most people will wait. If they're down for five, and you get to four minutes and some idiot decides to start nosing over the crossing..... :-/
     
  12. jopsuk

    jopsuk Veteran Member

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    Half Barrier crossings are used because they're cheaper, because they are not interlocked with the signalling and do not need some form of signaller intervention (crossing keeper or CCTV). The saving is taken into account versus the risk of having that sort of crossing.
     
  13. GB

    GB Established Member

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    With full barrier crossings, because the signal is interlocked with the crossing, the barriers have to be down earlier to ensure the train receives green signals throughout.

    If signals near AHB crossing were interlocked there would be mayhem on the roads as the barriers will need to be down a lot longer for the same reason as above which will just invite more crossing misuse.
    --- old post above --- --- new post below ---
    ....or they are on local control and a train is signalled normally...which although extremely rare, has happened.
     
  14. jopsuk

    jopsuk Veteran Member

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    a signal at a platform end immediately followed by a level crossing wouldn't be the one "protecting" the crossing anyway, surely? The crossing would then be in the over-run. A train wouldn't be allowed to pull up to the signal at danger with the crossing open (at a controlled crossing) as far as I'm aware- eg on the up at Shelford, both directions at Roydon the crossing is closed before stopping trains
     
  15. GB

    GB Established Member

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    Level crossings are not considered obstructions as far as signalling is concerned thus can be well within the overlap of its protecting signal so entirely possible to have a train approach with barriers still up. Local instructions or an ounce of common sense may mean the crossing operator (where provided) lowers the barriers for a stopping train even if the section ahead is occupied...just in case.

    Though you still have stations with AHBs within the overlap that stay up for stopping services untill a few moments before departure.
     
    Last edited: 26 Aug 2015
  16. BestWestern

    BestWestern Established Member

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    Cosham, on the outskirts of Portsmouth, has a full barrier CCTV crossing immediately after the platforms. It isn't uncommom if a train is a little early to pull in with the barriers up and the signal at danger. Protection in the event of a SPAD would be nearly zero.
     
  17. Deepgreen

    Deepgreen Established Member

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    Betchworth full barrier, controlled level crossing is immediately beyond the platform end and is protected by the starter. Stopping trains quite often draw up at the signal with the barriers up, although not often enough for those who are caught out on the much more frequent occasions when the barriers are lowered several minutes before arrival, let alone departure, and miss the train!

    The same situation exists at Reigate (for both through and terminating trains), Ashtead, Motspur Park and Teddington, to name a few.
     
    Last edited: 26 Aug 2015
  18. carriageline

    carriageline Established Member

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    I have a couple of crossings where it's literally on top of the platform starter, but they are protected by Stowmarket controls.

    The CCTV one sounds an alarm when the train enters the platform and the red road lights are not yet on, the ODs automatically start the red road lights for a set period if the barriers are not in auto.
     
  19. louis97

    louis97 Established Member

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    At an automatic half barrier (the type at Bosham) level crossing 27 seconds must elapse between the closing process starting (when the lights first come on) and the train going over the crossing.
     
  20. sarahj

    sarahj Established Member

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    IIRC there are two set-ups for signalling on the Chi to Havant line. Fast and stopping. Stopping you end up with reds at most stations such as Fishbourne, Bosham, though the crossing is usually down or going down. Fast, its greens all the way. A lot of the crossings on that route are AHB and you can see the treadles just past the crossing.

    Sometimes of course signals are on and barriers open, but a train might pass. Then the brown stuff hits the fan. Might have even happened close to where you mention, or might not. You never know.
     
  21. carriageline

    carriageline Established Member

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    Sarah, do you do the east coast (down to Eastbourne etc?)
     
  22. sarahj

    sarahj Established Member

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    I'm from Brighton, we go everywhere ;) (except Dorking, East Grinstead, Ore to Ashford and Uckfield)
     
  23. tsr

    tsr Established Member

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    Or Guildford, Reigate, Tonbridge, Mitcham Junction, West Croydon, Milton Keynes, Herne Hill or [?]South Bermondsey. But apart from that, I shall stop nit-picking... ;)
     
  24. Tomnick

    Tomnick Established Member

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    As others have suggested, the principle of AHBs is that the barriers are down for only a short period of time. If they're down for too long, the risk of impatient motorists zig-zagging increases to unacceptable levels, which is why we must start to caution trains in the event of a failure indication (not because we think they might have failed 'raised').

    I'm sure this has been discussed recently, but I wonder whether there's ever been a case of a train striking in but the barriers failing to lower? The handful of wrong-sider equipment failures that I'm (indirectly) aware of were, as far as I know, caused by the equipment not detecting the train's approach in the first place (so wouldn't have indicated failed either). There are, of course, those well-publicised (RAIB) examples of trains approaching AHBs on local control at linespeed...!

    Hopefully your Stowmarket Control is implemented better than ours. Apart from the fact that the alarm was initially far, far louder than any sort of decent level (as evidenced when they tested it around 0300 on a Sunday morning), there's no way out if the barriers are already being lowered when the train gets to the treadles, other than to wait for it to come to a stand, raise them and start again. Fantastic stuff if you've got one approaching the distant on the opposite road at the time.
     
  25. Llanigraham

    Llanigraham On Moderation

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    Para 1 : Correct.
    Para 2 : They do, but as AHB's are unsignaled the only option the signaller has is to hit the All Stop button.
    Para 3 : They do have RA's but I'm not sure what you mean about "restrictions on their use".
     
  26. carriageline

    carriageline Established Member

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    To be fair, they've done a decent job with ours. Well except the alarm is the same as the emergency alarm in the PSBs I've been in, and it's far far too loud. And oh, if you take them out of auto raise, the Stowmarket times out even after the train has passed, thus locking the barriers down for nearly 5 minutes, but auto raise it doesn't!

    Apart from that, it works fine lol!
     
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