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Post by melikepie on Nov 12, 2015 18:12:08 GMT
Many services on the Moorgate branch are being cancelled or diverted due to "poor rail conditions". Can someone explain to me what "poor rail conditions" are?
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Post by philthetube on Nov 12, 2015 18:14:02 GMT
leaves on the line, these genuinely cause huge problems
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Post by domh245 on Nov 12, 2015 18:30:07 GMT
Basically, when the leaves fall on the line, they are compacted by the trains passing over them, and combined with water from rain, creates a very slippery rail surface. In turn this means that the train can no longer accelerate or brake as well as it could (because there is less friction between the rail and the wheel, a bit like black ice) so trains are often delayed because they can't get up to speed as quickly, and have to start braking much earlier than usual. There might be an issue here as well with some inclines, if they are particularly slippy, you may end up with a situation where a train can't actually get up it.
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Post by Deleted on Nov 12, 2015 18:55:16 GMT
I believe leaves on the line can also cause problems with train detection for the signalling. The leaves can insulate trains from the rails so that track circuits may not pick trains up. Also, when domh says slippery, I've heard it can be an absolute nightmare. See for example this video about a SPAD at D1002 where train 1B47 came to a stop 1,710 yards in advance of D1002, passing the signal at danger at about 70 mph, despite commencing appropriate braking at the distant D1002R. This was due to poor rail adhesion. |
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Post by spsmiler on Nov 13, 2015 0:28:07 GMT
I am trying to work out about the Moorgate branch. Since all routes which serve Moorgate are either 'almost entirely' or 'fully' underground how can leaves affect the line?
Simon
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Post by class315 on Nov 13, 2015 1:02:33 GMT
I work for GN,, many services as of late have been late due to poor rail conditions. Leaves stick to the damp rails Which ultimately creates a thin teflon based layer on the rails. Which in turn drivers reduce speed to stop at signals and prevent overshooting stations. The earlier break application means it takes longer for signals to clear and trains to serve passengers, which isn't the greatest thing when you try and run an intensive service.
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Post by bassmike on Nov 13, 2015 2:02:22 GMT
I am trying to work out about the Moorgate branch. Since all routes which serve Moorgate are either 'almost entirely' or 'fully' underground how can leaves affect the line? Simon Still no reason for Moorgate branch leaves on line. |
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Post by MoreToJack on Nov 13, 2015 4:02:22 GMT
I would imagine the OP relates to the Northern City line to Moorgate, with leaf-fall issues occurring in the Finsbury Park/Drayton Park areas.
AIUI there is no railhead treatment train scheduled along that stretch, so poor rail conditions are possible with services being delayed or diverted (to KX) as a result.
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Post by Deleted on Nov 13, 2015 21:29:08 GMT
I am trying to work out about the Moorgate branch. Since all routes which serve Moorgate are either 'almost entirely' or 'fully' underground how can leaves affect the line? Simon Still no reason for Moorgate branch leaves on line. Since the trains mainly run above ground before going on the Moorgate branch, they'll be delayed going onto the branch. The branchline itself probably having some of the best railhead conditions of the whole route! |
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Post by phil on Nov 13, 2015 22:25:50 GMT
Still no reason for Moorgate branch leaves on line. Since the trains mainly run above ground before going on the Moorgate branch, they'll be delayed going onto the branch. The branchline itself probably having some of the best railhead conditions of the whole route! You also need to consider that (1) Leaves can be sucked into the tunnels through the trains slipstream / the vacuum effect behind it. (2) While running on the surface the wheel tread can become contaminated and this contamination can then be carried along and deposited by the train onto the rails well beyond the original contamination site. In the worst case scenario the train itself has to be taken out of service asap and the wheels scrubbed (which may require it to be dragged by a good unit back to the depot for attention). It is important to remember that leaf debris build up is not laughing matter - if it track circuits do not operate correctly or drivers cannot stop in time then I refer you to pictures of Clapham Junction (1987) or Purley in (1989) to see the worst case results. |
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Post by norbitonflyer on Nov 13, 2015 23:05:15 GMT
It is important to remember that leaf debris build up is not laughing matter - if it track circuits do not operate correctly or drivers cannot stop in time then I refer you to pictures of Clapham Junction (1987) or Purley in (1989) to see the worst case results. To avoid any confusion, it should be stressed that neither of those accidents were actually caused by slippery rail conditions - they were respectively a wrong side track circuit failure because of a wiring fault, and cancelling an AWS warning but not acting on it - typically overlooking that after passing a long sequence of double yellows, THIS one was a single. However there have been cases where trains have overshot signals because of slippery rails (although I know of no fatalities). |
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Post by phil on Nov 13, 2015 23:51:35 GMT
It is important to remember that leaf debris build up is not laughing matter - if it track circuits do not operate correctly or drivers cannot stop in time then I refer you to pictures of Clapham Junction (1987) or Purley in (1989) to see the worst case results. To avoid any confusion, it should be stressed that neither of those accidents were actually caused by slippery rail conditions - they were respectively a wrong side track circuit failure because of a wiring fault, and cancelling an AWS warning but not acting on it - typically overlooking that after passing a long sequence of double yellows, THIS one was a single. However there have been cases where trains have overshot signals because of slippery rails (although I know of no fatalities). You are indeed correct, however I was deliberately being dramatic about the consequences for a reason as Clapham was caused by a track circuit not telling the signalling system it had a train standing on it and at Purley, the driver was unable to stop in time. Both of these can happen through poor railhead conditions and as such it is entirely possible to have a major disaster occur if the appropriate precautions are not taken and reports relating to poor railhead conditions are not acted on immediately - which can mean signifficant disruption for passengers. |
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Post by philthetube on Nov 14, 2015 2:43:54 GMT
I am sure that a few years ago a train demolished Windermere station, the black box exonerated the driver who was proven to have been driving correctly.
However I cannot find anything about it on the net
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Post by rincew1nd on Nov 15, 2015 17:15:25 GMT
Windermere station was turned into a Booths several years ago, before OTMR; something doesn't quite sit right with me with that story. I have however found this, from the RAIB regarding leaf-fall adhesion issues. |
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Post by Chris M on Nov 16, 2015 14:25:35 GMT
Well there does seem to have been an accident that demolished part of a wall attached to the station buildings at Windermere - but it occurred in 1869 and adhesion doesn't seem to have been a significant issue - www.railwaysarchive.co.uk/docsummary.php?docID=4338 |
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Post by brigham on Nov 16, 2015 14:52:29 GMT
Problems with leaves and track circuits started to appear when stock without clasp brakes became popular. Mineral wagons with clasp brakes on one axle have appeared, to help alleviate the problem.
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