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| Failed track circuit colour 31/05/2013 at 08:05 #45316 | |
maxand
1637 posts |
I have never felt comfortable about seeing failed track circuits shown in red, the same as the colour used when that section of track is occupied. Is this also the way they are displayed on real life IECC screens? If not, could they be shown in a different colour such as yellow or magenta to distinguish them? The only rationale I can see for colouring them red is that the signaller must treat them AS IF they were occupied, not knowing they have failed; but in this day and age, surely it must be possible and more sensible to colour them differently. I find it difficult to distinguish a stationary train that has lost its headcode from a failed TC, without resorting to the Train List. Last edited: 31/05/2013 at 08:14 by maxand Log in to reply The following user said thank you: Deanotation |
| Failed track circuit colour 31/05/2013 at 08:34 #45317 | |
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sorabain
72 posts |
This reminds me, i've often wondered if the "Failed track circuit" is something that is always reliably detected in real life, and what the correct procedure is when the next train approaches it. I was guessing that there might be some fail-safe such that if the circuit is broken then it fails to "on", but also that it might be a working circuit but something is left bridging the circuit (worst case some wagon came off the back) For detection it seemed plausible that if the software knew one train came in but looked like it turned into "two trains" then it could warn about "track circuit failure", but i've been treating it as "something could be on the track!" so have tended to ask the first driver to be stopped before it to "examine the line" rather than just plain old authorized SPAD.. is this what happens in the real world? Not sure if the options refer to some official procedural rules. If examining the line do they go at walking pace? If authorized SPAD do they treat it as "treat next signal as red", or more restrictive such as treating it like a shunt authorization? Hope I haven't gone and hijacked the thread here... Log in to reply |
| Failed track circuit colour 31/05/2013 at 08:51 #45318 | |
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ralphjwchadkirk
275 posts |
If you think about what a failed track circuit is then you will realise how the interlocking 'sees' the failure. The interlocking can only tell whether a track circuit is being short circuited or is normal. If it's being short circuited then you will see the track circuit as red on the display. If not, then it shows as clear. The interlocking cannot tell whether the circuit is being shorted by a train, a failure of the wiring, or a metal bar placed across the track. Therefore there is no way to tell whether the track circuit has failed or is occupied. This is why when a unusual occupation is noticed on the panel the line is examined to make sure that it is a failure, and not an obstruction of any form. The way to find out if it is a train that has lost its headcode or a failure is to wait and see if it calls in at the next danger signal. Last edited: 31/05/2013 at 08:51 by ralphjwchadkirk Log in to reply The following user said thank you: maxand |
| Failed track circuit colour 31/05/2013 at 08:56 #45319 | |
jc92
3690 posts |
" said:I have never felt comfortable about seeing failed track circuits shown in red, the same as the colour used when that section of track is occupied. Track circuits are either occupied, or clear. thats as smart as they get. " said: I find it difficult to distinguish a stationary train that has lost its headcode from a failed TC, without resorting to the Train List.Track circuits dont call in at signal post telephones. "We don't stop camborne wednesdays" Log in to reply The following users said thank you: maxand, Aurora |
| Failed track circuit colour 31/05/2013 at 09:06 #45320 | |
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AndyG
1842 posts |
" said:This reminds me, i've often wondered if the "Failed track circuit" is something that is always reliably detected in real life, and what the correct procedure is when the next train approaches it.See Track Section failures on the WIKI for the procedure to follow. I can only help one person a day. Today's not your day. Tomorrow doesn't look too good either. Last edited: 31/05/2013 at 09:07 by AndyG Log in to reply The following user said thank you: sorabain |
| Failed track circuit colour 31/05/2013 at 09:17 #45321 | |
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kbarber
1743 posts |
" said:" said:I have never felt comfortable about seeing failed track circuits shown in red, the same as the colour used when that section of track is occupied. That's the whole point. The only positive indication you can get from a TC is that it's not occupied and not shorted out by anything and operating correctly. " said: " said:I find it difficult to distinguish a stationary train that has lost its headcode from a failed TC, without resorting to the Train List.Track circuits dont call in at signal post telephones. Technically, a clear TC indicates only that a given voltage is being applied across the track relay; if the voltage falls below that threshold the relay drops away and the occupied indication is given. There's no way to distinguish between no volts because of a failure and no volts because of a train and I can't see any technical fix that would allow such a distinction without losing the essential failsafe feature. Even if there were, that introduces another piece of kit that could fail - so it, too, has to be built to fail safe (even more complication therefore even greater vulnerability to failure) which means you could still get your failed TC showing occupied rather than failed. Also, remember a TC failure could be for something like a broken rail - not immediately visible but potentially a real hazard. It's absolutely drummed in to any signalman that if a TC gives an occupied indication it should be treated as if working correctly and occupied by a train. (The same with any other failure of signalling equipment.) Ultimately, that's the only safe way to do it. For as sure as eggs are eggs, one day a signalman will get the job around his neck and start treating an occupied TC as a failure and the next thing will be a pitch-in. In spite of the pressures, delays are much preferred to failures even in our day. When I passed out for my first box (OK, things have changed since 1978...) part of the procedure was an interview with a senior operating official. There it was impressed on me that safety came first. I can still recall his words: "...if you find it's all going wrong and you're under pressure, put the kettle on, have a cup of tea and check the rules to make sure you know what to do next..." Waiting for a train to phone in and tell you his headcode is rather lesser a sin than a collision. Log in to reply The following user said thank you: maxand |
| Failed track circuit colour 31/05/2013 at 09:19 #45322 | |
Steamer
3985 posts |
" said:I find it difficult to distinguish a stationary train that has lost its headcode from a failed TC, without resorting to the Train List.Personally, I place a sticky note with 'TCF' written on it on top of/next to the failed TC. If you really want a different colour, you could use the F11 Track Circuits tab to apply a possession to the failed TC, but I don't know if this is correct from a Rules perspective. Also, F11 is a fairly recent feature so it may not be on the simulation you're playing. "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Log in to reply |
| Failed track circuit colour 31/05/2013 at 09:24 #45323 | |
KymriskaDraken
963 posts |
" said:Some train drivers have difficulty with that as well. Especially when it's raining. Log in to reply |
| Failed track circuit colour 31/05/2013 at 10:24 #45324 | |
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dwelham313
139 posts |
I always treat it as 'something may be on the track' too, and in real life the first train will always be asked to examine the line for an obstruction. I think the rule book terminolgy is 'proceed at caution being prepared to stop short of any train, obstruction or buffer stop'. I usually go between 10 and 20mph. The Maximum you can travel when examining the line in a tunnel is 10mph. There are exceptions - in the Moorgate tunnels its 3mph maximum when passing a signal at danger or examining the line etc. You have to be able to stop your train in the 'distance you can see to be clear' incase the local hoodlums have piled a load of shopping trolleys on the track! Because you're passing the signal at danger when you enter the section you always treat the next signal as being red, and you can't increase speed/stop running at caution until the rear of you train passes the signal. And luckily with CSR radio I can start annoying the signaller the second I stop come rain or shine! Log in to reply |
| Failed track circuit colour 31/05/2013 at 10:57 #45326 | |
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Firefly
521 posts |
This is a bit like saying that you have a light in a room which is either on or off. You're not very happy that when the bulb blows it looks the same as it does when it's switched off. As previous posters have said the interlocking gets an input stating the track is clear, this input allows signals to clear, points to move and allows the track circuit on your IECC to show grey or white. If that input doesn't come back to the interlocking for any reason the track will show red, affected points will be locked and affected signals will return to danger. That input may not be coming back because a trains wheels are on the track and have correctly shunted the voltage away from the track relay (normal operation), however any of the following things could also prevent the input from going back to the interlocking:- Flooded track causing a short circuit A metal object across the track (shopping trolley) A blown power supply A faulty piece of track circuit equipment A faulty track insulation A broken rail A broken wire The list is endless, but the net result of any of the above is that the interlocking and hence the IECC will not get an input from the trackside. Arguably what you're talking about is not know to a signaller as a track circuit failure, it's known as a "track circuit showing occupied when clear". FF Log in to reply The following user said thank you: maxand |
| Failed track circuit colour 31/05/2013 at 11:05 #45327 | |
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Firefly
521 posts |
In the picture below there is only one train on this screen, it's a tamper and it's somewhere in the pointwork at the bottom left of the screen. There are numerous other track circuits showing occupied because there are either bits of rail missing, cables not connected to the rail or axel counters that have odd counts because road rail machines, and track equipment have messed up the count or in fact the counter heads have been removed. The signaller has put cyan highlights around most of the affected area to show that it's under engineers possession. However the point is that there's lots of red track circuits and only one of them is a train. 
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| Failed track circuit colour 31/05/2013 at 12:44 #45328 | |
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vontrapp
210 posts |
It has to be red as it is a built-in fail-safe. Rather than not work at all, it has to fail on the safe side. It puts signals to danger. A failed TC could be a TC operating clip placed on the rail, by the driver or guard to place signals at danger, not just on the running-line where the train is but adjacent lines too. All in all, a red TC is showing the line blocked/obstructed by whatever.
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| Failed track circuit colour 31/05/2013 at 13:11 #45329 | |
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Aurora
183 posts |
Which is why when a TCF occurs, I wait until the driver of the first train to traverse over the failed TC to call in and I then authorise him to examine the line from the signal prior to the failure. If he comes back with "no obstruction", then I simply talk each following train through (authorise driver to pass signal at danger) once each one calls in at that signal. This occurs until the TCF is fixed or there are no more trains left to run. Yes, there are some delays, but safety is the number 1 policy. Until it is advised by a competent worker that there is no obstruction, you assume that there is something there. Nil. Last edited: 31/05/2013 at 13:12 by Aurora Log in to reply |
| Failed track circuit colour 31/05/2013 at 13:12 #45330 | |
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KymriskaDraken
963 posts |
" said:I would say "A track circuit unexpectedly showing occupied". You should never assume that a TC is clear when it's showing occupied. Log in to reply The following user said thank you: maxand |
| Failed track circuit colour 31/05/2013 at 14:06 #45331 | |
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maxand
1637 posts |
Thanks everyone for clearing that up. TCs aren't as smart as I imagined. What's interesting is that the voltage drops not only when there's a train or other conductive object across the tracks, but also if there's a broken rail or wire causing failure to maintain the relay energized, as Firefly pointed out. Thus even an open circuit triggers a low voltage signal. I was interested to read about the latest AF TCs used in jointless rail systems. Do they give the signaller any more information about the cause of the failure/occupation than the simple old-fashioned ones? Log in to reply |
| Failed track circuit colour 31/05/2013 at 14:42 #45332 | |
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Steamer
3985 posts |
" said:I was interested to read about the latest AF TCs used in jointless rail systems. Do they give the signaller any more information about the cause of the failure/occupation than the simple old-fashioned ones?As far as I can tell, no. They still seem to work on the same principal as the basic track circuit, the only change being the different frequencies used on different sections. It can't tell what type of metal the electrons are being conducted through (axle, track circuit clip, shopping trolley etc.). To build a circuit that could do that would be a pretty large undertaking under controlled conditions in a lab, building thousands one that can do it exposed to the elements (with the reliability and fail-safe requirements required by a signalling system) would be neigh-on impossible. "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Last edited: 31/05/2013 at 15:03 by Steamer Log in to reply The following user said thank you: maxand |
| Failed track circuit colour 31/05/2013 at 16:38 #45334 | |
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Danny252
1461 posts |
" said:It can't tell what type of metal the electrons are being conducted through (axle, track circuit clip, shopping trolley etc.). To build a circuit that could do that would be a pretty large undertaking under controlled conditions in a lab, building thousands one that can do it exposed to the elements (with the reliability and fail-safe requirements required by a signalling system) would be neigh-on impossible.I'd say that is actually impossible, given the nature of the problem - there's no simple way to tell if it's a high resistance short near the feed, or a low resistance one far away that looks the same due to the added resistance from the rails. Even if you can do that, how do you then differentiate those from the legitimate short that a train causes? Last edited: 31/05/2013 at 16:40 by Danny252 Log in to reply The following user said thank you: maxand |
| Failed track circuit colour 31/05/2013 at 17:00 #45336 | |
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Colourlight
117 posts |
Going by Statistics it is rare for a track circuit failure to be caused by an obstruction or a broken rail. So Network Rail relaxed the rules on cautioning some time ago. If a Signaller sees a track Circuit occupied which he thinks should be clear then he/she should establish that the last train has passed clear of the track circuit. This can be done be either visually inspecting the affected area if it is close to the box, asking a signaller in an adjoining box if the train has got to him or by observing the train on the diagram occupying and clearing track circuits ahead of the suspected failed track circuit. If the track circuit is clear then the signals should be cleared for the next train if possible. This proves whether it is a track circuit failure or an indication only failure. In the event of a track circuit failure then as somebody said the line should be examined by the next train.
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| Failed track circuit colour 31/05/2013 at 17:01 #45337 | |
GeoffM
6377 posts |
Add overhead catenary to certain types/setups of TCs and you can get some interesting indications. My old boss did some analysis of the TCs in Ashford which has both 3rd rail and overhead to ensure they would work as intended. Lots of fancy graphs and analysis that I don't understand.
SimSig Boss Log in to reply The following user said thank you: maxand |
| Failed track circuit colour 31/05/2013 at 20:02 #45345 | |
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Stephen Fulcher
2084 posts |
" said:Thanks everyone for clearing that up. TCs aren't as smart as I imagined. What's interesting is that the voltage drops not only when there's a train or other conductive object across the tracks, but also if there's a broken rail or wire causing failure to maintain the relay energized, as Firefly pointed out. Thus even an open circuit triggers a low voltage signal.AF track circuits are actually worse in some respects because there is a lot more that can go wrong with them. Log in to reply The following user said thank you: maxand |
| Failed track circuit colour 03/06/2013 at 11:44 #45412 | |
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sorabain
72 posts |
Have we ever considered simulating some of the "wrong side failure" track circuit modes such as mechanical failure of the relay?
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| Failed track circuit colour 04/06/2013 at 09:21 #45440 | |
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kbarber
1743 posts |
" said:Have we ever considered simulating some of the "wrong side failure" track circuit modes such as mechanical failure of the relay? WSFs are extremely rare in track circuits. I only ever knew one and that was because of rust on a rarely-used bit of siding (it was tracked because that end of it had a crossover out on to the main line). Every aspect of TC design is carefully considered to ensure failsafe operation (right down to the relay contacts, which consist of silver on one side and silver-impregnated carbon on t'other so an unexpected surge of high current can't weld them together). Mechanically, relays are extremely simple and inherently unlikely to fail wrong-side; I believe that where a 'special' might have that propensity, circuits are designed to avoid it (e.g. it must be proved 'down' before the function that might need it is activated). Taken with the Simsig policy of not simulating accidents, I think simulating WSFs is pretty much a no-no. Log in to reply The following user said thank you: AndyG |
| Failed track circuit colour 04/06/2013 at 09:42 #45442 | |
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jc92
3690 posts |
I've had a WSF on a TC before, but from what I recall, it was primarily due to railhead contamination, rather than an electrical or mechanical fault. Still not a pleasant experience...
"We don't stop camborne wednesdays" Log in to reply |
| Failed track circuit colour 04/06/2013 at 10:11 #45443 | |
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sorabain
72 posts |
Is there anything in IECC software that attempts to detect WSFs? Simsig (maybe the real thing?) detects when a track circuit stays occupied and "drops off the back" of a train, so was wondering if there was anything to notice a train vanishing into a black hole and then reappearing on the other side.
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| Failed track circuit colour 04/06/2013 at 16:00 #45452 | |
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Steamer
3985 posts |
" said:Is there anything in IECC software that attempts to detect WSFs? Simsig (maybe the real thing?) detects when a track circuit stays occupied and "drops off the back" of a train, so was wondering if there was anything to notice a train vanishing into a black hole and then reappearing on the other side.I'd guess that nothing can detect a Wrong Side Failure, otherwise it wouldn't be a wrong side failure! "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Log in to reply |