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| Confusing signal at Preston 21/06/2012 at 14:27 #33220 | |
320322
86 posts |
Just perusing the goings on at Preston and i noticed something unusual. A signal was pulled off at the south end of platform 1 , the signal in advance was also cleared. The first signal was showing 2 yellows but the signal in advance was displaying green. Strange one to me. Anyone know how that occurs?
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| Re: Confusing signal at Preston 21/06/2012 at 15:11 #33223 | |
DriverCurran
688 posts |
Sounds to me very much like a S&TE restriction on the green aspect. Paul You have to get a red before you can get any other colour Log in to reply |
| Re: Confusing signal at Preston 21/06/2012 at 19:37 #33226 | |
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Backup
89 posts |
Additional detail that might be relevant: TSRs were in effect in the area; there had been orange HiVi all over the place earlier that morning, and broadly parallel tracks cleared down the line green following green. Could it have been as simple as a green lamp failure? Double yellow would have been the next most restrictive aspect to default to, and it would still show as a proceed aspect on panels and "off indicators", potentially slowing reporting/repair, right? Log in to reply |
| Re: Confusing signal at Preston 21/06/2012 at 19:43 #33227 | |
Steamer
3984 posts 
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" said:Additional detail that might be relevant: TSRs were in effect in the area; there had been orange HiVi all over the place earlier that morning, and broadly parallel tracks cleared down the line green following green. I saw this a few months ago, so I don't think it's temporary. "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 |
| Re: Confusing signal at Preston 21/06/2012 at 22:35 #33231 | |
GeoffM
6376 posts |
" said:Could it have been as simple as a green lamp failure? Double yellow would have been the next most restrictive aspect to default to, and it would still show as a proceed aspect on panels and "off indicators", potentially slowing reporting/repair, right?UK signals don't attempt to revert to a different aspect if they can't show the driven aspect. SimSig Boss Log in to reply |
| Re: Confusing signal at Preston 22/06/2012 at 19:17 #33264 | |
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Stephen Fulcher
2078 posts |
Failure of the DR lines on that signal is a possibility, however I would have thought if it has been the case for months a driver would have reported it as a fault by now. As a query, does the same signal ever go green for another route? Last edited: 22/06/2012 at 19:19 by Stephen Fulcher Log in to reply |
| Re: Confusing signal at Preston 22/06/2012 at 21:01 #33277 | |
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Backup
89 posts |
It seemed the same route both times. Platform 1, southbound on the Down slow, passing PN106, passing PN85, onto the Up slow. Having checked a photo, PN106 lacks a theatre or shunt indicators like all the other station starters at that end, and can only run to PN85 (which *seems* to have feathers, shunt, and theatre; but the photo is poor quality). PN85 is where the Down slow stops being bi-directional, and southbound trains must take crossovers to the Up slow, Up fast, or Goods lines. So, I'm now assuming its some regulation chicanery, maybe to do with reducing speed for crossovers. Or magic. Yeah, that works. :silly: Last edited: 22/06/2012 at 22:47 by Backup Log in to reply |
| Re: Confusing signal at Preston 23/06/2012 at 12:23 #33287 | |
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Stephen Fulcher
2078 posts |
If there is only one route from the signal and it always does that, there is either a very weird quirk in the design of the system, or a fault. If it were a reduced speed for the crossovers, one would expect the whole lot to approach release from red.
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| Re: Confusing signal at Preston 23/06/2012 at 17:05 #33292 | |
DazrahT
47 posts |
We have a similar scenario at Lichfield North Junction. If we set a route from LS3517 on the Down TV Fast to LS5519 on the Down TV Slow, the train on approach will receive flashing yellows in rear of LS3517 and on approaching LS3517 the signal will step up to a double yellow, even though LS5519 is showing green. Can only deduct that this is due to the points being 50mph from 125mph linespeed. Log in to reply |
| Re: Confusing signal at Preston 23/06/2012 at 17:18 #33295 | |
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DazrahT
47 posts |
Or another quirk we have is two signals that show double yellow in succession. If NL3449 on the Down TV Fast is at Danger at Ashby Junction (Nuneaton) the signal in rear on platform 4 at Nuneaton (NL3443) will exhibit a single yellow, RN3435 in rear at Nuneaton South will show a double yellow, as will RN3433 at Attleborough. When NL3449 clears to a single yellow then everything steps up to the correct 4 aspect sequence. Again this must have something to do with insufficient braking distance to the red at NL3449 Log in to reply |
| Re: Confusing signal at Preston 25/06/2012 at 08:56 #33338 | |
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kbarber
1742 posts |
Successive double yellows are allowed in the standards, although I think I'm right in saying that's as an exception these days. Used to be more acceptable - the 1949 signalling between Liverpool St and Shenfield included sequences of up to three double yellows on pretty much all Main line signals between Stratford and (I think) Ilford Car Sheds. Even on the Electric lines (lower speed limit) the norm over that stretch was two double yellows!
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| Confusing signal at Preston 04/08/2012 at 15:47 #34628 | |
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button_pusher
56 posts |
That signal has no green aspect. If you look carefully the Green Lens is plated over. The only route available from that signal is Down Slow (P1) to Up Slow. IIRC it is to keep the train running under caution until it is over the crossover. Log in to reply The following user said thank you: 320322 |