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| Weird signal between WEA and EAL 07/09/2013 at 17:00 #49194 | |
jetblast787
62 posts |
Anyone care to explain this? I went past it a couple of times on the up slow, but was really confused as its not the new LED signals which are being installed around the area and I've never seen it before. There is a green on the left signal and a single amber on the right. http://i.imgur.com/FkNc6gl.jpg Log in to reply |
| Weird signal between WEA and EAL 07/09/2013 at 17:04 #49195 | |
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Late Turn
699 posts 
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'tis a splitting distant, indicating in this case that the diverging route is set from the next signal (which is also showing YY or better). There's no amber to be seen though, nor slow lines...yellow and relief lines sound much better ;-)
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| Weird signal between WEA and EAL 07/09/2013 at 17:41 #49196 | |
GeoffM
6376 posts |
Excellent explanation of splitting distants on Clive's website.
SimSig Boss Log in to reply The following user said thank you: jetblast787 |
| Weird signal between WEA and EAL 07/09/2013 at 19:48 #49206 | |
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jetblast787
62 posts |
Seems complicated 
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| Weird signal between WEA and EAL 07/09/2013 at 20:41 #49212 | |
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JamesN
1608 posts
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I only know of 5 colour light Split Distants, and they're all within a 35 mile stretch of the GW mainline: The first was SN271, commissioned 11/05/1997 (picture) - SN271 is situated on the Down Main, between Southall West Jn and Hayes & Harlington station, and is provided to give advance warning to Down HX trains of the route set at Airport Jn (the down main is not wired). MAF-SD (Main Aspect Free - Split Distant, the 'official' name for this type of route control) was chosen over flashers or free green as the original turnout speed was 95mph and other methods of approach control were considered too restrictive. Second came (T)R39, on the Up Main between Pangbourne and Tilehurst commissioned 26/11/2001 (picture). This was provided in conjuction with the speed enhancements across Tilehurst East and other improvments in the Reading area prior to Virgins ill-fated operation princess TT. In a similar vein to the previous installation at Airport Jn, the relative speed reduction from linespeed was considered to small to warrant flashing aspects or approach control. Third was UR30B picture which was brought into use Spirng 2008 inconjunction with the Airport Jn - Reading speed limit enhancements. It is situated on the up relief between Twyford and Ruscombe Jn and replaced an unrestricted sequence for up trains crossing to the up main. The SD was provided as trains booked to call at Taplow and Burnham could only travel on the relief from Ruscombe. Fourth came the above pictured SN212, between West Ealing and Ealing Broadway on the Up Main. As part of the crossrail upgrade programme signal positioning and linespeeds on the reliefs between Airport Jn and Ladbroke Grove are being tweaked to allow better signalling thoughput. This has also seen the remodelling of the Western access to Acton Yard. MAF-SD replaced MAY-FA on the route from Up Main to Up Relief at Acton West thanks to increased crossing speeds. The newest addition to the split distants is SN312R, situated on the up relief between West Drayton and Airport Jn. This has been provided as the aspect controls for the additional crossover provided at Stockley Bridge, which now permits trains to cross up relief to up main. Log in to reply The following users said thank you: jetblast787, officer dibble |
| Weird signal between WEA and EAL 07/09/2013 at 22:56 #49217 | |
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Danny252
1461 posts |
I know there's (at least) one LED splitting distant up in Glasgow, so they seem to be in fashion again.
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| Weird signal between WEA and EAL 08/09/2013 at 10:51 #49229 | |
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Firefly
521 posts |
Quote:Second came (T)R39, on the Up Main between Pangbourne and Tilehurst commissioned 26/11/2001 (picture). This was provided in conjuction with the speed enhancements across Tilehurst East and other improvments in the Reading area prior to Virgins ill-fated operation princess TT. In a similar vein to the previous installation at Airport Jn, the relative speed reduction from linespeed was considered to small to warrant flashing aspects or approach control.James I'm not sure about your date for this one. I commissioned it and according to my logbook it was either 1998 or 1999 (can't remember which stage it was to be more accurate about the date) I wasn't working for the same company in 2001 so it cannot of been then. Also if I recall correctly the reason for putting in a splitting distant there was because there is already a flashing aspect sequence to allow trains into Plat 5 at Reading Station. You cannot have 2 consecutive flashing sequences so a splitting distant was the only option other than approach released from red which would be very restrictive. FF Log in to reply |
| Weird signal between WEA and EAL 08/09/2013 at 12:47 #49232 | |
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GW43125
495 posts |
" said:Quote:Do you mean the old P5 or New P5?Second came (T)R39, on the Up Main between Pangbourne and Tilehurst commissioned 26/11/2001 (picture). This was provided in conjuction with the speed enhancements across Tilehurst East and other improvments in the Reading area prior to Virgins ill-fated operation princess TT. In a similar vein to the previous installation at Airport Jn, the relative speed reduction from linespeed was considered to small to warrant flashing aspects or approach control.James Log in to reply |
| Weird signal between WEA and EAL 08/09/2013 at 14:37 #49236 | |
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Ron_J
331 posts |
" said:I know there's (at least) one LED splitting distant up in Glasgow, so they seem to be in fashion again.Yes, GB5188 at Muirhouse North Jn Last edited: 08/09/2013 at 14:38 by Ron_J Log in to reply |
| Weird signal between WEA and EAL 08/09/2013 at 14:42 #49237 | |
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Firefly
521 posts |
I was talking about the old P5 (Up Main Platform) Although to be honest I can't quite remember which signal/route the flashing aspect sequence applied to. I thought it was when routing from the Up Main to Platform 5, but it could of been one signal further to country and routes around Reading Triangle that had a flashing sequence. Can't quite remember, but there is/was flashing aspects on the Up Main between Tilehurst and Reading and that is what necessitated R39 being a splitting distant. As usual Danny Scroggins wonderful site provides the answer to the date with this photo - February 1998 - Tilehurst - new East Junction Log in to reply |
| Weird signal between WEA and EAL 08/09/2013 at 15:18 #49238 | |
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John
884 posts |
Completely off-topic, (not worth starting as separate thread) but I've always wondered what the 'guard' thingys are on the side of some signals are for?
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| Weird signal between WEA and EAL 08/09/2013 at 15:33 #49239 | |
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Firefly
521 posts |
Faraday cage to protect staff from electric shock from the overheads FF Last edited: 08/09/2013 at 15:36 by Firefly Log in to reply The following user said thank you: John |
| Weird signal between WEA and EAL 08/09/2013 at 16:06 #49242 | |
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Sacro
1171 posts |
It's more akin to a lightening rod than a Faraday cage.
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| Weird signal between WEA and EAL 08/09/2013 at 16:49 #49252 | |
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JamesN
1608 posts
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" said:Quote:Thanks FF, I couldn't find the notice which brought it in in my collection, and thus presumed it was done at the same time as the West End remodelling that saw the middle road between 8/9 go and alterations to pfm3. Thanks for the clarification.Second came (T)R39, on the Up Main between Pangbourne and Tilehurst commissioned 26/11/2001 (picture). This was provided in conjuction with the speed enhancements across Tilehurst East and other improvments in the Reading area prior to Virgins ill-fated operation princess TT. In a similar vein to the previous installation at Airport Jn, the relative speed reduction from linespeed was considered to small to warrant flashing aspects or approach control.James Log in to reply |
| Weird signal between WEA and EAL 08/09/2013 at 19:00 #49258 | |
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Danny252
1461 posts |
" said:It's more akin to a lightening rod than a Faraday cage.Well, not really - at least, I would hope that the signal structure isn't being hit by arcs regularly whilst S&T are on it! Log in to reply |
| Weird signal between WEA and EAL 09/09/2013 at 13:25 #49281 | |
outofsection
149 posts |
According to Wikipedia, a very rough rule of thumb is that it takes approx 1kV to jump each millimetre between two smooth spheres, so the use of such cages at the distance from the live wires shown in the photo would appear to be overkill as the theoretical distance the voltage could jump would be 25mm or an inch. HOWEVER, once you get above around 10kV, corona discharge (i.e. ionizing of the air surrounding the conductor wire) becomes quite an issue which can considerably increase the distance a spark could jump across AND not forgetting that any increase in ambient humidity will lengthen the distance the current can jump as well. Then you can add on extra "jumping distance" if the two objects are not spheres, e.g. the "jumping distance" the current can jump across is considerably higher between say two pointed objects than it would be between two spheres. So on a foggy damp day whilst holding a screwdriver in my left hand whilst working up that pole, I'd be very grateful for that cage! It also provides a physical barrier as well to prevent the S&T engineer accidentally getting too close to the overhead conductor wire. Last edited: 09/09/2013 at 13:26 by outofsection Log in to reply The following user said thank you: John |
| Weird signal between WEA and EAL 09/09/2013 at 15:05 #49282 | |
Peter Bennet
5402 posts
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I could feel the "buzzing" on my Umbrella this morning from the OH wires. Peter I identify as half man half biscuit - crumbs! Log in to reply |
| Weird signal between WEA and EAL 09/09/2013 at 19:49 #49292 | |
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Backup
89 posts |
Theoretically, I imagine it also shields people doing fiddly work from being buffeted by the wind of passing trains. That reminds me; I once had to dissuade someone bored from twirling around a folded-up umbrella whilst standing alarmingly close to the platform edge. It was dark, raining, on a 25kV line with occasional non-stops passing at speed. :yikes Fortunately they heeded my advice to stop waving a conductive pole around near the OLHE, and moved out of turbulence range. Log in to reply |
| Weird signal between WEA and EAL 22/10/2013 at 21:14 #50275 | |
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bill_gensheet
1413 posts |
" said:" said:Is that really showing G and R ?I know there's (at least) one LED splitting distant up in Glasgow, so they seem to be in fashion again.Yes, GB5188 at Muirhouse North Jn I'd have thought a splitting distant would show G and Y. Was it not in active use ? Bill Log in to reply |
| Weird signal between WEA and EAL 22/10/2013 at 21:16 #50276 | |
Steamer
3985 posts |
According to the caption, yellow aspects on VMS signals come out a bit weird in photos.
"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 |
| Weird signal between WEA and EAL 22/10/2013 at 21:16 #50277 | |
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JamesN
1608 posts
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" said:" said:Says in the linked photos's caption that it's just the photograph, signal is showing G and Y" said:Is that really showing G and R ?I know there's (at least) one LED splitting distant up in Glasgow, so they seem to be in fashion again.Yes, GB5188 at Muirhouse North Jn Log in to reply |
| Weird signal between WEA and EAL 23/10/2013 at 09:27 #50288 | |
lazzer
634 posts |
" said:Also if I recall correctly the reason for putting in a splitting distant there was because there is already a flashing aspect sequence to allow trains into Plat 5 at Reading Station. You cannot have 2 consecutive flashing sequences so a splitting distant was the only option other than approach released from red which would be very restrictive. As a driver, I have never considered two flashing sequences in a row. Is that actually a rule that NR have when commissioning signalling? And when you say "consecutive", would it be possible to have the following setup: DFY, SFY, Y, R, DFY, SFY, etc ... As in, once you're past the signal that would be red, you can start a flashing sequence again? I was just trying to work out the minimum number of signals you'd have to go past (after a defined point) before you could see another flashing yellow again. Log in to reply |
| Weird signal between WEA and EAL 23/10/2013 at 09:34 #50289 | |
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kbarber
1742 posts |
" said:" said:Also if I recall correctly the reason for putting in a splitting distant there was because there is already a flashing aspect sequence to allow trains into Plat 5 at Reading Station. You cannot have 2 consecutive flashing sequences so a splitting distant was the only option other than approach released from red which would be very restrictive. I think the prohibition is on the situation where a signal could be involved in more than one flashing sequence. If it weren't there, you could have a situation where the flashing single yellow also needed to be a flashing double yellow for the following sequence. I've an idea it was decided the possibility of confusion was just too great. Remember a misunderstood flashing sequence was held to be a factor at Colwich http://www.railwaysarchive.co.uk/documents/DoT_Colwich1988.pdf Log in to reply |
| Weird signal between WEA and EAL 23/10/2013 at 09:56 #50290 | |
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Stephen Fulcher
2080 posts |
The top yellow is not proved in the interlocking, so if the top yellow of a double flashing yellow signal that could also display a single flashing yellow went out, the driver would get a conflicting aspect. With standard aspect sequence, the absence of the top yellow when it is supposed to be lit does not matter as the next signal will still be showing single yellow so the stopping distance is maintained. The only "risk" is the worry it could cause the driver. With flashing yellows, there may be a disparity in the speed allowed for each turnout, so in theory the absence of a top yellow flashing would fool a driver into thinking he was taking a higher speed turnout than the one he actually was, and therefore cause a nasty high-speed derailment. Nowadays, they tend to install Junction Warning Indicators (http://www.davros.org/rail/signalling/articles/jwisystem.html), although I have never seen a yellow one. Banbury South BS104 is an example of this. Before Evergreen 3, it used to be straight green for Oxford, approach released from yellow with a flashing distant (BS104R) for Bicester, and approach released from red for the Up Goods Loop. Now, there are straight greens for both Oxford and Bicester, approach released from red for the Up Goods Loop, and flashing yellows for the wrong direction move to Bicester across BS399 and BS404 points. There is now an outer distant BS108, and there are JWIs provided for both BS108 and BS104R, although none are yellow, both signals JWIs are white, and they are situated 183 metres in advance of the signals. Log in to reply The following user said thank you: kbarber |
| Weird signal between WEA and EAL 23/10/2013 at 14:40 #50292 | |
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Ron_J
331 posts |
The indicators described in your link are actually termed 'Preliminary Route Indicators', or PRIs, and their application differs from the way it is described on that site. Most significantly, there in no such thing as a yellow PRI. For a concise explanation, see this site
Last edited: 23/10/2013 at 14:42 by Ron_J Log in to reply |
