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| "Five" aspect signalling 20/07/2015 at 07:32 #74373 | |
Mattyq
259 posts |
In a discussion in a different forum about consecutive double yellows.... " said: As stated, it's due to braking distances. The Great Eastern Main Line has loads of them too, up to three double yellows in sequence I believe.This begs the question..... In the Sydney metro area, the equivalent to a UK Double Yellow is Green over Yellow (called "Medium"). For the same reasons as Geoff mentioned, it is possible to get 2 or 3 consecutive G/Y signals in a row. In recent years the local rail authority introduced a fifth aspect to try and cut down on consecutive G/Y aspects. The new aspect is Green over *flashing Yellow (called "Preliminary Medium - see disclaimer below). To compare with UK signalling, this would be something between a Green and a Double Yellow aspect. This effectively means areas that have the "Preliminary Medium" aspect could be regarded, in UK terms, as having "five aspect signalling". I know a lot of development has occurred over the years in the UK with regard to lineside signalling, however, has introduction of a fifth aspect ever been looked at?. DISCLAIMER: Just to keep the NSW signalling people from spontaneously combusting :yikes  , the *correct* term is "Pulsating Yellow", so called because the lamp is bright for 640 milliseconds then dim for 200 milliseconds (as opposed to "flashing" which is on/off).
Not fat ..... fluffy!! (G Iglesias) Log in to reply |
| "Five" aspect signalling 20/07/2015 at 07:53 #74374 | |
kaiwhara
584 posts |
" said:In a discussion in a different forum about consecutive double yellows....I know what you are trying to achieve, and commend that, but at what point does it cease to be a Signal and become an advert for a Lighting Shop? :side: Sorry guys, I am in the business of making people wait! Log in to reply |
| "Five" aspect signalling 20/07/2015 at 08:08 #74375 | |
Danny252
1461 posts |
Somewhat different to what you asked is flashing green, which was briefly tested, though as far as I know never really used in anger. It indicated to a driver that he could proceed at enhanced speed, and was tested on the ECML to allow trains to run at 140mph rather than 125mph.
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| "Five" aspect signalling 20/07/2015 at 08:08 #74376 | |
headshot119
4869 posts |
The UK had "five" aspect signalling for a time on the ECML (unsure if it's still there) with a flashing green giving Class91+MK4 sets authority to go to 140mph. FG-G-YY-Y-R was the sequence.
"Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Log in to reply The following user said thank you: Mattyq |
| "Five" aspect signalling 20/07/2015 at 08:37 #74377 | |
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Mattyq
259 posts |
" said:I know what you are trying to achieve, and commend that, but at what point does it cease to be a Signal and become an advert for a Lighting Shop? :side:?????? Not fat ..... fluffy!! (G Iglesias) Log in to reply |
| "Five" aspect signalling 20/07/2015 at 09:18 #74378 | |
Peter Bennet
5360 posts |
" said:The UK had "five" aspect signalling for a time on the ECML (unsure if it's still there) with a flashing green giving Class91+MK4 sets authority to go to 140mph. FG-G-YY-Y-R was the sequence.It was between Grantham and Peterorough and it's still working, best viewed "backwards" as it were though there are a number of curves where you can see them if you press your head against the window. Peter I identify as half man half biscuit - crumbs! Log in to reply |
| "Five" aspect signalling 20/07/2015 at 09:24 #74379 | |
Steamer
3922 posts |
" said:The UK had "five" aspect signalling for a time on the ECML (unsure if it's still there) with a flashing green giving Class91+MK4 sets authority to go to 140mph. FG-G-YY-Y-R was the sequence.They're still there, but are treated as a normal green. Flashing greens are provided on the Down Fast between P487 and P615, and on the Up Fast between P610 and P494. "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: 20/07/2015 at 09:24 by Steamer Log in to reply |
| "Five" aspect signalling 20/07/2015 at 10:54 #74382 | |
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Mattyq
259 posts |
" said:" said:Ah yes, forgot about them. I saw them in action on the excelent Video 125 fillum "The Flying Scotsman". :-)The UK had "five" aspect signalling for a time on the ECML (unsure if it's still there) with a flashing green giving Class91+MK4 sets authority to go to 140mph. FG-G-YY-Y-R was the sequence.They're still there, but are treated as a normal green. Flashing greens are provided on the Down Fast between P487 and P615, and on the Up Fast between P610 and P494. Not fat ..... fluffy!! (G Iglesias) Log in to reply |
| "Five" aspect signalling 20/07/2015 at 11:55 #74383 | |
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Jersey_Mike
250 posts |
" said:When I was doing research into Preliminary Medium it was mentioned that it is also used to give advance notice of diverging movements as well, specifically diverging movements to stop. It seems apparent that G/*Y* was implemented to clear up the confusion between G/Y as a preliminary caution and as an approach diverging indication. Use in 5 block signaling is a secondary benefit. Also you forgot the Low Speed indication which can act as a 6th main aspect in the NSW scheme. " said: In the UK a 5th main aspect would only be useful at the margins, allowing drivers to go slightly faster at a few places where consecutive double yellows to a stop are being employed. Without formal methods of explicit speed control, there really isn't a use case for adding more lower speed main signal aspects. Like I said NSW has a legitimate source of ambiguity when using G/Y -> G/R and G/Y -> Y/Y | Y/R, which appears to be the overriding factor. In the United States Amtrak utilized cab signals designed for higher speed turnouts (Cab Speed 60 and Cab Speed 80 denoted by *G* on a wayside signal) for a high density signaling system between Newark, NJ and Penn Station New York. The challenge was to allow speeds up to 100mph on a line with blocks as short as 1500 feet, a major junction and transfer station. The solution was a mostly in-cab system with speed steps of 100, 80, 60, 45, 30 and 15mph. The problem is that most of the commuter trains are 10-12 cars push-pull sets with an electric locomotive on one end and traditional air brakes along with an ATC system that requires a minimum brake application after cab signal drops. An engineer trying to follow the cab signals would cause too much passenger discomfort so they operate at speeds below those allowed. Last edited: 20/07/2015 at 11:56 by Jersey_Mike Log in to reply |
| "Five" aspect signalling 20/07/2015 at 14:44 #74387 | |
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Mattyq
259 posts |
" said:" said: When I was doing research into Preliminary Medium it was mentioned that it is also used to give advance notice of diverging movements as well, specifically diverging movements to stop. It seems apparent that G/*Y* was implemented to clear up the confusion between G/Y as a preliminary caution and as an approach diverging indication. Use in 5 block signaling is a secondary benefit.I'm sorry, Mike, but once again, you are very wrong. It is the Turnout Repeater that was implemented to rid the confusion of a Green over Yellow aspect.  As the picture above will show, a Turnout Repeater can be either a standard 5 lens UK "feather" (currently being phased out) or an LED banner (preferred). You are correct in saying that there was confusion with a Driver encountering a Green over Yellow and not knowing if the next aspect was going to be a "Caution" or one of the "Turnout" aspects. With the introduction of the Turnout Repeater, a Green over Yellow alone means the junction signal is at "Caution" (Green over Red) whereas a G/Y WITH a Turnout Repeater indeed means the junction signal will be displaying either "Caution Turnout" (Yellow over Red) or "Medium Turnout" (Yellow over Yellow). If a G/Y is preceded by one or more Green over Flashing Yellow "Preliminary Medium" aspects, they will also have a Turnout Repeater (TOR). So it is quite possible to have the following sequence:- G/G - G/FY(TOR) - G/FY(TOR) - G/Y(TOR) - Y/Y or Y/R. It is also possible to have a "Preliminary Medium" in a straight route sequence:- G/G - G/FY - G/Y - G/R - R/R. Therefore, the introduction of the "Preliminary Medium" is exactly what I said it was - the creation of an additional aspect. " said: Also you forgot the Low Speed indication which can act as a 6th main aspect in the NSW scheme.Agreed, the "Low Speed" can be used as a 6th aspect, as it does in the inner Sydney area. By the way, did you note who authored the animated gif at the bottom of Dave's (quite dated) page? :lol: " said: " said:That's exactly my point. Having said that, I will leave this part of the argument for the UK experts. Meantime, here's a (rather blurry) photo of a real signal with a banner type Turnout Repeater (Photo credit to "Woosang" (she knows who she is)).In the UK a 5th main aspect would only be useful at the margins, allowing drivers to go slightly faster at a few places where consecutive double yellows to a stop are being employed.  Lastly, I'll clear up the confusion I've just created with all you British folk! :doh I can imagine now quite a few of you thinking "Hang on, if they use a feather for a Turnout Repeater, what do they use for the turnout"? The answer? Not a feather!! You can learn all about railway signalling in the Australian state of NSW here Post has attachments. Log in to view them. Not fat ..... fluffy!! (G Iglesias) Last edited: 20/07/2015 at 15:08 by Mattyq Log in to reply The following users said thank you: Gwasanaethau, TimTamToe |
| "Five" aspect signalling 20/07/2015 at 16:31 #74388 | |
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Jersey_Mike
250 posts |
" said:You might want to fix Wikipedia in that regard. " said: What came first, Preliminary Medium or the turnout repeaters? BTW how short are the signal blocks if 5-block signaling is necessary? Are there any extended lengths of 5-block or is this used more for special cases? This is where speed signaling can really come in handy because one doesn't need to distinguish between "blocks to stop" and "approach diverging move". Out west the big two railroads added two additional signals for higher speed turnouts, but the signals can do double duty as block signals. The rules read "pass next signal at X mph and prepared to enter diverging route at that speed". If the signal consultants felt like padding the contact the system supports 6-block signaling not counting the "low speed" situation. The progression would go G -> Y/*G* -> Y/G -> *Y* -> Y -> R with the speed step down of MAS -> 60 -> 50 -> 40 -> 30 -> Stop. Where one encounters "trivially short blocks" (blocks less than 1500 feet that arise from junction layout or station platform placement), sometimes in the United States (idk about Canada) the signal engineers will say F-it and have them act as a single logical block so you get things like G -> Y -short- Y -> R. At onterlockings were one has Slow speed signals available, one can get an Approach Slow to a Slow Approach to a short stop, however Slow speed signals are typically only used at interlockings, since the rules mention turnouts. In auto-signal territory I have seen Approach Slow to Approach to Stop. In this instance of a trivially short block, the presence of a movable bridge with a 30mph speed limit has trains pass no fewer than 5 signals at Y/*G* or Y/G in a row with speeds also enforced by a Y/G cab signal! " said: That won't clear up the confusion as Turnout Repeaters are covered in CNSG 604 and the normal signal indications being covered in CNSG 606! :blink: Log in to reply |
| "Five" aspect signalling 20/07/2015 at 19:05 #74389 | |
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clive
2738 posts |
" said:From the 1930s to the 1970s there was a signalling system on the lines around Mirfield, in Yorkshire, that had 5 aspects. On plain line the aspects were green, yellow-over-green, double yellow, single yellow, red. At crossovers between the two pairs of lines on the four-track core, the aspects were stacked: * straight ahead: aspect over red over red; * diverging to other pair: red over aspect over red; * turnout into siding: red over red over green if clear, red over red over yellow if occupied. (Junctions were the usual - for the time - side-by-side head arrangement.) Log in to reply The following user said thank you: Mattyq |
| "Five" aspect signalling 21/07/2015 at 12:38 #74397 | |
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Sparky
84 posts |
" said:Preliminary Medium was introduced in 1993 with junction repeaters (JP) not appearing until 1997-98. The first turnout repeater was installed on ST407 @ Lidcombe. Ironically it has since been removed from this signal due to junction upgrades. Preliminary mediums were first installed on the Blue Mountains line which at the time had SLCL signalling. JP's were 1st installed to try and combat wrong roadings. The idea is the driver will see that the route is incorrectly set and will potentially have the distance to stop before the signal with the JP. this will speed up the release of approach locking and therefore getting trains moving to the right destinations quicker. HAHAHAHA The picture that mattyq posted is of SP42 on the up main @ Sefton. The diagram below shows the layout. SP42 JP. It repeats 211 points being set to the right. This shows the standard layout for JP's  In some instances there are 2 consecutive signals with JP's if the headway is to small for 1. Post has attachments. Log in to view them. I intend to live forever. So far so good Log in to reply |
| "Five" aspect signalling 21/07/2015 at 12:49 #74398 | |
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Jersey_Mike
250 posts |
" said:So the motivation could have been to remove some ambiguity over diverging movements as was suggested by some Wikipedia editor. Is 5-block signaling actually helpful otherwise? Log in to reply |
| "Five" aspect signalling 21/07/2015 at 15:39 #74399 | |
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Mattyq
259 posts |
" said:" said:Wikipedia? I've seen that entry and, dare I say it, it's a train wreck!! Full of unnecessary (and uncalled for) author opinion and full of errors, including the bit about how Preliminary Medium was introduced to mitigate confusion over the Medium (G/Y) aspect.You might want to fix Wikipedia in that regard. " said:
Obviously short enough that minimum braking distance is required to be spread over 3 signal block sections. This, of course, would be entirely dependent on the local conditions - line speed, type of traffic, gradients. This is like asking "How long is a piece of string"? " said: Are there any extended lengths of 5-block or is this used more for special cases?Yes. Moreover, there are extended lengths of straight line railway (IE: no junctions/turnouts) that uses Preliminary Medium as a 5th aspect. I cannot definitively state whether there are any locations that use both the Preliminary Medium AND the Low Speed, creating "6 aspect" signalling. Sparky will be able to comment on this. " said: " said:That won't clear up the confusion as Turnout Repeaters are covered in CNSG 604 and the normal signal indications being covered in CNSG 606! Ummm..... WHAT????? I was talking about the confusion that might be caused from a UK style Junction Indicator (feather) appearing on a signal that PRECEDES the actual junction signal. It has NOTHING to do with where the definitions are found. But since you brought it up..... Unlike any other state in Australia, NSW, in their rules and procedures, draw a distinct and separate definition between Signals and Indicators, even to the point where they are contained in their own separate manuals. A Signal provides a movement authority. There is nowhere in NSW where a Signal exists within an authority-based safeworking system (IE: Train Order). There are appliances within Train Order territory that LOOK like signals (IE: Main Line Indicators) but, as the name suggests, these are also only Indicators and do not provide a Movement Authority. An Indicator, on the other hand, provides information. A Turnout Repeater is an Indicator which provides supporting information about the signal it is fixed to. If the Indicator fails, the signal can still display the relevant aspect, however, the Driver will have to return to guessing what the next aspect will be (either "Caution" or "Turnout"). Either way, the worst that will happen is a wrong-routed train. " said: " said:NO!!!! It has nothing to do with diverging routes and everything to do with eliminating consecutive "Medium" aspects. The Wikipedia entry is wrong.So the motivation could have been to remove some ambiguity over diverging movements as was suggested by some Wikipedia editor. " said: Is 5-block signaling actually helpful otherwise?:doh Not fat ..... fluffy!! (G Iglesias) Last edited: 21/07/2015 at 15:47 by Mattyq Log in to reply |
| "Five" aspect signalling 21/07/2015 at 18:03 #74400 | |
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Jersey_Mike
250 posts |
" said:Instead of complaining about the article you could fix it, especially since you seem to have the necessary graphics. " said: Well how long in feet...or if you must...meters. " said: I'm surprised they found that necessary. Adding blocks is a method to ease congestion and a six-track trunk in a modestly populated country would seem to be enough What's the line speed for MU's...around 60mph?" said: Logical, but I just guess I was used to the practice in Australia North where anything that's a sign or signal are all lumped into the same section of the rulebook. I'd say it makes it easier to look things up, but it's probably to save on printing costs re: graphics. I am surprised that Junction Repeaters are not treated as signals along the lines of a Y/Y or Y/R signal since those also convey route information. " said: Do you know that or are you making an assumption? The answer can be determined from how the first Preliminary Medium signals were employed in 1993. Log in to reply |
| "Five" aspect signalling 21/07/2015 at 18:59 #74401 | |
KymriskaDraken
963 posts |
" said:If something is wrong on Wikipedia you can correct it yourself, providing appropriate sources of course. Kev Log in to reply |
| "Five" aspect signalling 22/07/2015 at 01:55 #74409 | |
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Sparky
84 posts |
" said:If The junction repeater fails the signal that it is on will drop down to a caution. This is regardless of the aspect of the next signal. That way the driver will take action accordingly and not assume the next signal is set for the non diverging route. Also some people seem to be under the assumption that preliminary caution indications and junction repeaters are mutually exclusive. This is wrong. There are cases where JP's are fitted without the ability to display a preliminary caution, and in turn signals that can display a preliminary caution without a JP being fitted. As for a signal with low speed and preliminary caution, that does not happen. It is a case of 1 or the other. I intend to live forever. So far so good Log in to reply The following user said thank you: Mattyq |
| "Five" aspect signalling 22/07/2015 at 05:29 #74413 | |
flabberdacks
579 posts |
" said:Some signal-to-signal blocks between Illawarra Junction and Strathfield on the main west line are not much more than an eight-car train length plus overlap (approx 250-300 metres). Track speed in this area is between 60 and 100 kph. These areas see a thousand trains a day, at 3 minute intervals during peak. Drivers are given the earliest reasonable indication that they need to slow down, considering track speed, curvature of the line (signal sighting distance) and braking performance of trains which use that corridor. Last edited: 22/07/2015 at 05:30 by flabberdacks Log in to reply The following user said thank you: Mattyq |
| "Five" aspect signalling 22/07/2015 at 07:46 #74415 | |
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Muzer
718 posts |
" said:" said::doh :doh :doh :doh :doh Do you... do you understand the meaning of that expression?Well how long in feet...or if you must...meters. Log in to reply |
| "Five" aspect signalling 22/07/2015 at 12:44 #74417 | |
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Mattyq
259 posts |
" said:" said:Someone less qualified than you told me otherwise, Damo. Thanks for the correction.If The junction repeater fails the signal that it is on will drop down to a caution. This is regardless of the aspect of the next signal. That way the driver will take action accordingly and not assume the next signal is set for the non diverging route. " said: " said:Signal blocks on the City Underground and Eastern Suburbs Railway are as close as 74 metres. Signal spacing here is styled on the London Underground "Multi-Home" strategy. Track speed is 50 to 60km/h.Some signal-to-signal blocks between Illawarra Junction and Strathfield on the main west line are not much more than an eight-car train length plus overlap (approx 250-300 metres). On the other hand, looking out towards St Mary's - Penrith way, signals are up to 1,500 metres apart with a line speed of 115km/h and 4,000 tonne freighters up to 1,400m long mixing it up with MU commuter, inter-regional and interstate passenger traffic. Not fat ..... fluffy!! (G Iglesias) Log in to reply |
| "Five" aspect signalling 22/07/2015 at 13:39 #74418 | |
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Jersey_Mike
250 posts |
" said:Ah gotcha. I see it's sort of a hybrid metro system instead of pure commuter rail. Log in to reply |