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| "Permissive" shunt signals 19/11/2015 at 11:42 #77893 | |
Mattyq
259 posts |
I don't know what they are actually called but I'm referring to these:- The definition of these signals, as defined in the Simsig Wiki is "Shunt signals with yellow lights are sometimes found at sidings where there is need for trains to move along the sidings and into the headshunt, but without proceeding onto the running line. The yellow indication means “stop if the points are set for a movement that would take the train on to a running line”. Trains are permitted to pass the signal whilst it is displaying “ON” if the points are not set for the running line. The driver is expected to know which routes the signal has to be cleared for". We don't have these in Australia but the concept is a good one and relieves the Signaller of much work. My question is, what system is in place to prevent a movement past this signal at the exact moment the signaller wishes to call it to clear for the running line it protects? Has there ever been any history of a SPAD/derailment when the points are transitioning? Post has attachments. Log in to view them. Not fat ..... fluffy!! (G Iglesias) Last edited: 19/11/2015 at 11:45 by Mattyq Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 11:53 #77894 | |
BoxBoyKit
166 posts |
I imagine in most cases the driver or PIC of the sidings will have told the signaller there is a train waiting to come out. Likewise the PIC will be aware of a train due to arrive so won't be making any movements toward the exit. Of course that may not apply in all cases. I've never worked with yellow shunt signals so I cannot answer fully. Also, they are (as far as I know anyway) just called Yellow Shunt Signals. All shunt signals can authorise permissive movements, by definition. Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 12:52 #77895 | |
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mfcooper
707 posts |
" said:My question is, what system is in place to prevent a movement past this signal at the exact moment the signaller wishes to call it to clear for the running line it protects? " said: I imagine in most cases the driver or PIC...(Person in Charge, sometimes known as a "Shunter") " said: ...of the sidings will have told the signaller there is a train waiting to come out. Likewise the PIC will be aware of a train due to arrive so won't be making any movements toward the exit. This is pretty much how I have always understood/expected it to work, but I have never had to deal with them myself. Last edited: 19/11/2015 at 12:54 by mfcooper Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 13:32 #77896 | |
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hayleysmith
14 posts |
I used to work with one and we had a switch which, when activated, allowed the signaller to route in and out of the sidings, but when deactivated, locked the points onto the mainline normal meaning a movement could pass the yellow dummy at will to access the headshunt. Obviously, there was communication between the shunter and the signaller so everyone was in the er... loop.
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| "Permissive" shunt signals 19/11/2015 at 14:01 #77897 | |
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Jersey_Mike
250 posts |
" said:I don't know what they are actually called but I'm referring to these:-The same concept is employed in North America in the form of something called a "drill signal". These are used in conjunction with a bi-directional route through the interlocking with two opposing signals each displaying a Restricting indication. For trains moving back and forth on yard tracks it's basically as if the interlocking wasn't there, but from a signaling perspective the movements have full route locking protection. I am unsure why a similar system is not employed in the UK, instead relying on the driver to observe points (which in and of itself presents a race condition with the signalman reversing the points). One lever would display the shunt signal in the trailing direction and lock the points and then allow the opposing shunt signal to be displayed. Both signals would be left displayed until the signalman would need to line a route onto the main track. Anyway, I wrote up a piece on drill signals for my blog. http://position-light.blogspot.com/2015/09/going-both-ways.html Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 14:13 #77898 | |
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mfcooper
707 posts |
" said:The signal aspect tells the driver the position of the points. If the signal is displaying Yellow, then the points are set towards the Headshunt. If the signal is displaying a Proceed (White), then the points are set towards the main line. I *guess* that there are instructions that the points cannot be moved towards the main line until the signal can show a Proceed aspect. See Also: Signals, handsignals, indicators and signs Handbook (Document page 17, labelled page 15) Last edited: 19/11/2015 at 14:16 by mfcooper Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 14:14 #77899 | |
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Stephen Fulcher
2028 posts |
" said:I don't know what they are actually called but I'm referring to these:-I believe these are banned for new installations. My understanding is that the driver is obliged to check the lie of the points before proceeding, and is deemed to have committed a SPAD if they are set for a route that is not permitted for passing the signal at yellow. I don't know of any accidents caused by the signal being passed and at the same moment the Signaller reversing the points, but I suppose it is theoretically possible. The points would become locked by the track circuits as soon as the train passed the signal, so the chances of it happening are fairly slim, but obviously not impossible. Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 14:30 #77900 | |
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Jersey_Mike
250 posts |
" said:The switch would have to be reversed before the signal could be displayed. Therefore you can have points reverse with a Stop* indication. Quote: I don't know of any accidents caused by the signal being passed and at the same moment the Signaller reversing the points, but I suppose it is theoretically possible. The points would become locked by the track circuits as soon as the train passed the signal, so the chances of it happening are fairly slim, but obviously not impossible.There are several seconds when a train is approaching a signal that the indication becomes either less visible or the driver becomes focused on the track ahead. A small chance yes, but still significant. This is why I am puzzled why this situation wasn't interlocked in the standard method with signals that could simply stay pulled up. Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 16:26 #77902 | |
Steamer
3925 posts |
" said:I'm not sure why the yellow signal was used in some locations, however the method you describe is used in the UK. It's featured in some simulations- Wetmore Sidings on the Derby simulation, for example. "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 |
| "Permissive" shunt signals 19/11/2015 at 17:39 #77904 | |
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Danny252
1461 posts |
" said:I don't know of any accidents caused by the signal being passed and at the same moment the Signaller reversing the points, but I suppose it is theoretically possible. The points would become locked by the track circuits as soon as the train passed the signal, so the chances of it happening are fairly slim, but obviously not impossible.Anecdotally I've heard of at least one, which was I believe due to the engine going through the points in the trailing direction, having gone into the headshunt and then returned without checking the route was still set. Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 17:45 #77905 | |
GeoffM
6288 posts |
" said:The same concept is employed in North America in the form of something called a "drill signal". These are used in conjunction with a bi-directional route through the interlocking with two opposing signals each displaying a Restricting indication. For trains moving back and forth on yard tracks it's basically as if the interlocking wasn't there, but from a signaling perspective the movements have full route locking protection.You're mixing two different things. What is called "drill" in North America is called "opposing locking omitted" in the UK. In both cases the signaller/dispatcher sets/lines routes in both directions and the signals show proceed towards each other. The track is route locked. What the OP is referring to is different. In its default/normal state, a yellow shunt signal is passable (subject to rules/point positions etc) without the signaller doing anything. The point is not locked, nor is there any route locking. However, once the train occupies the track circuit with the point on (if any) then the point will become deadlocked in its current position. Since there is no route locking, the entire track circuit (if any) would flood red (there might be exceptions to this if the signal designer was feeling clever). Attached is a screenshot showing opposing locking omitted - note the white shunt aspects facing towards each other. I'm struggling to find an example of a yellow shunt as they're not that common, but this (penultimate picture, SN201) shows a signal on the ground - to the left is the headshunt which does not require the signaller to set a route; to the right is the route onto the mainline which does require the signaller to set a route. PS. The last paragraph in your blog is wrong, per above! :P 
Post has attachments. Log in to view them. SimSig Boss Last edited: 19/11/2015 at 17:57 by GeoffM Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 17:50 #77907 | |
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Stephen Fulcher
2028 posts |
" said:" said:If it is in the trailing direction then the yellow shunt is completely irrelevant. You can get headshunts that do not have a signal protecting the exit irrespective of the colour of the ground signal that allows entry. It is a fairly common arrangement with conventional red GPLs.I don't know of any accidents caused by the signal being passed and at the same moment the Signaller reversing the points, but I suppose it is theoretically possible. The points would become locked by the track circuits as soon as the train passed the signal, so the chances of it happening are fairly slim, but obviously not impossible.Anecdotally I've heard of at least one, which was I believe due to the engine going through the points in the trailing direction, having gone into the headshunt and then returned without checking the route was still set. The driver concerned in the incident you mention probably should have phoned the box before returning, as the route back over the point appears to be unsignalled, whereas the yellow shunt to go in there is technically signalled, but the driver has authority to pass said signal under certain circumstances. The incident potential I was referring to, which I believe was the initial enquiry from MattyQ, was whether or not a derailment or train going the wrong way had ever occurred as a result of the points being moved AFTER the driver had used his own legitimate authority to pass the shunt signal at yellow. Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 19:20 #77916 | |
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clive
2738 posts |
" said:That sounds like what we call "opposing locking omitted". A normal shunt route is set from point A to point B, and then a normal shunt route is set from point B to point A. Both shunt signals clear and stay clear, not going back because there's a train in advance of them. This can be found in several sims. From memory there's a pair at Hitchin in the KX sim and some from the down sheds to the headshunts in the Euston sim. This system requires extra interlocking circuitry. The yellow shunt was something that could be installed very simply and cheaply, even in mechanical interlockings. As attitudes have changed, and as interlocking circuits change from "lots of extra relays" to "one line of code", the balance has swung from yellow shunt to OLO. Log in to reply |
| "Permissive" shunt signals 19/11/2015 at 19:23 #77917 | |
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clive
2738 posts |
" said:Probably nothing. In general it will rely on the fact that the signaller won't want to call it clear unless there's a train waiting to exit. Quote: Almost certainly. But it will have been a slow speed SPAD/derailment clear of any running line, so it would have been handled locally and not been reportable. Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 03:28 #77929 | |
BarryM
2158 posts |
Clive, I hope that this is not an impermanent question. Where were you when you posted your message today? Barry Sydney Australia Barry, Sydney, New South Wales, Australia Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 12:45 #77934 | |
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kbarber
1712 posts |
OLO was certainly present in the 1960-ish MV-GRS panel at Barking (both London End connections at East Ham Car Sheds). Likewise in the 1967 mechanical frame at Marylebone, where lever 8 worked a pair of discs reading in and out of the headshunt where No. 6 crossover led from the Down Slow (offically Down Siding) to the Down Main. Both were 'off' with 8 normal and returned to danger when the lever was pulled, but interestngly the lever was weighted so it would fly reverse when the catch was released. Even more interesting there was No. 2, which read over No. 4 points (Diesel Depot to Down Main). Again, normally 'off' with OLO but in this case there were three arms, one each from the 'Diesel Depot' (aka the fueling point) and the 'Short Coal Road' (an old name that survived) over handpoints into the headshunt (officially the 'Tunnel Siding' and one out of the headshunt that could read either way. (Actually, given the opposing arms were actually worked by the same lever, I suppose it isn't strictly OLO.)In times past, I believe there were no such thngs as yellow shunt signals. I have a couple of old diagrams of Hendon (MR) which show just a single disc before the points, no detail whether it's yellow or red but installed before yellow discs came in so it must have been a red disc at some point, but the MR way would be to treat them as yellow. As John Hinson said, only an idiot signalman would pull the points over with a train working... He went on to say "A lot of such working was informal in the old days - it was always done a certain way, nobody questioned it, and it worked. It did not necessary comply with a detailed interpretation of the Rules." Of course, that points to the real answer to all the questions. Yellow shunts were devised as a distinctive indication in the days when there would be a local (usually mechanical) signalbox and a signalman within sight keeping an eye on things, and usually a local shunter as well. Everybody knew the working, everybody knew the pitfalls and - because they talked direct to each other about a situation everybody could see with their own eyes - it was easy enough to avoid problems. Perhaps we also need to remember that a shunting derailment wasn't the big production number it has become these days (indeed had pretty much become even by the time I joined). A rerailing ramp and a bit of packing could sort out most problems. The senior man at my first box told a story of his younger days, when he was on the Goods Lines frame at St Pancras Junction (so before the 1957 power box). When he was still fairly new, a wagon came off the road outside the box (I don't recall whether it was a mistake on his part or just one of those things that happens when you shunt). He rang Control to report it and was told there was no derailment. When he protested, he was invited to look out of the window. There was the yard, already running normally (apart from the shunt waiting for him to finish on the phone)! Of course, phones weren't recorded in those days either :whistle: Log in to reply The following user said thank you: flabberdacks |
| "Permissive" shunt signals 20/11/2015 at 13:34 #77936 | |
lazzer
605 posts |
" said:I'm struggling to find an example of a yellow shunt as they're not that common]There's one in Thingley Yard, visible as you pass in the Up direction. At least it was there last time I went past a few weeks ago. Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 13:52 #77937 | |
Giantray
332 posts |
In the "Signals, Handsignals,Indicators and Signs Handbook RS/521", applicable to Network Rail, the following explains what you need. Position-light signals that display a yellow aspect Position-light shunting signals that display a yellow aspect are stop signals applying only to movements in the direction to which the signal can be cleared. Other movements can pass the signal without it being cleared. The signal identification plate may also have a direction arrow showing the line to which the signal applies. The driver may pass the signal in the‘stop’ position when the movement is being made towards the shunt neck or siding and not the running line. The driver must be prepared to stop short of any train, vehicle or obstruction. Retired Professional Railwayman (1981-2023); Pway & S&T (1981-88); Former Signalman/Signaller/ Signalling Trainer (1989-2023) [AB, TCB, Mechanical, NX, WestCad, Hitachi SARS]; Railway Historian (esp.SER, LCDR); Member of The Permanent Way Institution.. Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 13:55 #77938 | |
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JamesN
1577 posts |
" said:" said:SN201 is still a yellow shunt, and is set to remain so until Thingley is resignalled in the new year.I'm struggling to find an example of a yellow shunt as they're not that common]There's one in Thingley Yard, visible as you pass in the Up direction. At least it was there last time I went past a few weeks ago. Few Other examples I can recall on the GW are: SW6517 at Swindon Down Yard (former SN 232) B577 Bristol Kingsland Rd B604 at Weston s Mare Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 14:07 #77939 | |
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Jersey_Mike
250 posts |
" said:[It seems fairly simple to set up on a mechanical frame. Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 14:34 #77941 | |
pedroathome
891 posts |
" said:" said:Don't know if it still is or not, but the shunt signal coming out of Bristol Barrow road certainly looks yellow, although in realiaty is this siding not connected via a ground frame?" said:SN201 is still a yellow shunt, and is set to remain so until Thingley is resignalled in the new year.I'm struggling to find an example of a yellow shunt as they're not that common]There's one in Thingley Yard, visible as you pass in the Up direction. At least it was there last time I went past a few weeks ago. Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 15:11 #77943 | |
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jeffh16
40 posts |
" said:" said:All the remaining ground frames in the bristol area where a headshunt exists have yellow GPLs. I suppose it was considered that shunting could carry on regardless over these points until such a time as a train needed to enter/leave the sidings." said:Don't know if it still is or not, but the shunt signal coming out of Bristol Barrow road certainly looks yellow, although in realiaty is this siding not connected via a ground frame?" said:SN201 is still a yellow shunt, and is set to remain so until Thingley is resignalled in the new year.I'm struggling to find an example of a yellow shunt as they're not that common]There's one in Thingley Yard, visible as you pass in the Up direction. At least it was there last time I went past a few weeks ago. Another example of yellow shunts on the WR, although not the mainline would be at Bishops Bridge on the South Devon Railway, where there are two. One in the dock siding, and one in station sidings Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 15:55 #77944 | |
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kbarber
1712 posts |
" said:" said:[It seems fairly simple to set up on a mechanical frame. Easiest of all on a frame: simply omit a bar and a couple of dogs. But there aren't that many of them going in at the moment so it's a bit academic. And with the loss of wagonload traffic and the move to fixed-formation trains, there's less shunting generally than there used to be, hence less need for any signalling in & out of headshunts (and, as Clive says, just a line of code - perhaps pretty standard so it goes in as a template to fill in the numbers? - in any case). The really big change is attitudinal - a move away from local arrangements operated using the knowledge and skill of the staff to complete signalling of everything (including numbering stop blocks in the signalling system and proving the red lights) so there's a complete signal sequence to put down on paper for every move going. Along with that is the change to methods of communication, with phonetic alphabets and suchlike. I'm sure there are benefits - maybe one day we will even authorise unsignalled wrong-road moves through sections by radio (on the rare occasions there's anything to gain by doing so). But I still find it quite peculiar at meets to hear people referring to 'two alpha so-and-so' rather than 'the up parly'. Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 16:09 #77945 | |
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RainbowNines
272 posts |
I recall (from my single visit some 3 years ago) there was one from the unused platform line at Chessington onto the line beyond which I understand from a bit of googling was once some sort of yard. EDIT: Ah I've just seen the pic on Wiki from 2008 which looks like a normal red GPL. I must be mixing it up with elsewhere. Last edited: 20/11/2015 at 16:10 by RainbowNines Log in to reply |
| "Permissive" shunt signals 20/11/2015 at 16:14 #77946 | |
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GeoffM
6288 posts |
" said:" said:Sorry, I meant "in a sim". SN120 was the example I linked to earlier, but the sim shows it as a red shunt." said:SN201 is still a yellow shunt, and is set to remain so until Thingley is resignalled in the new year.I'm struggling to find an example of a yellow shunt as they're not that common]There's one in Thingley Yard, visible as you pass in the Up direction. At least it was there last time I went past a few weeks ago. " said: As attitudes have changed, and as interlocking circuits change from "lots of extra relays" to "one line of code", the balance has swung from yellow shunt to OLO.Actually OLO requires more data than normal opposing locking. You'd think the "omitted" part would cut down on something but no, it changes route release (to none) and adds extra conditions before even setting the route - for example, OLO moves blocked in by red signals at either end of the movement. SimSig Boss Log in to reply |