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| Bi-Directional Signaling 02/02/2015 at 23:02 #68685 | |
Jersey_Mike
250 posts |
I had a quick British signaling question that noticed while playing SimSig. It seems that up through the 20th century single direction ABS signaling is the norm in the UK. As more and more lines are re-signaled is bi-directional CTC replacing the ABS or is ABS still being installed / re-installed? Is there any reason why bi-directional signaling would not be installed everywhere? Anyway, here's your moment of Zen. Log in to reply |
| Bi-Directional Signaling 02/02/2015 at 23:32 #68687 | |
Steamer
3984 posts |
" said:I had a quick British signaling question that noticed while playing SimSig. It seems that up through the 20th century single direction ABS signaling is the norm in the UK. As more and more lines are re-signaled is bi-directional CTC replacing the ABS or is ABS still being installed / re-installed?The amount of bi-directional lines is increasing as lines are resignalled and control moved to the ROCs, but it's not being installed everywhere. Quote: Is there any reason why bi-directional signaling would not be installed everywhere?Money- adding extra infrastructure and putting more routes into the interlocking drives the design and test budget up. Quote: Anyway, here's your moment of Zen.Not sure that would work over here- generally, our traffic density is such that you couldn't get two trains running in parallel like that for a significant distance without delaying something coming the other way. Hence the prevalence of Fast/Slow lines in busy areas. That said, they do sometimes use it a Dawlish (see the Exeter simulation) when trains get delayed. Video. "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: 02/02/2015 at 23:33 by Steamer Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 07:26 #68700 | |
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kbarber
1742 posts |
" said:I had a quick British signaling question that noticed while playing SimSig. It seems that up through the 20th century single direction ABS signaling is the norm in the UK. As more and more lines are re-signaled is bi-directional CTC replacing the ABS or is ABS still being installed / re-installed? Traffic density. There's no BIDS between Barking & Fenchurch Street, even though it exists country side of Barking, simply because there's no way you could get any kind of sensible service in & out of Fenchurch over a single line. Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 09:09 #68703 | |
KymriskaDraken
963 posts |
Sometimes you get SIMBIDS (Simplified Bi-Directional Signalling) such as on the GWML between Swindon and Bristol TM (via Box). It has many shortcomings though, such as non-suppression of AWS for wrong direction moves, and an almost total lack of wrong direction signals (IIRC there was one wrong direction signal between Bath Goods and North Somerset Jn.. The signalmen at Bristol Panel called it CANBIDS (Cheap And Nasty Bi-Directional Signalling) as it was almost useless. Kev Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 10:54 #68707 | |
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Finger
220 posts |
" said:I had a quick British signaling question that noticed while playing SimSig. It seems that up through the 20th century single direction ABS signaling is the norm in the UK. As more and more lines are re-signaled is bi-directional CTC replacing the ABS or is ABS still being installed / re-installed?This is just a load of american buzzwords. If by ABS you mean automatic block system, that doesn't exist in the UK. The UK has AB (absolute block - signalmen pulling levers) and TCB (track circuit block - what you see in SimSig). CTC can mean almost anything, and surely PSBs and IECCs, some of them 50 years old. So your statement doesn't even make sense - ABS has never been in the UK, and CTC is not "replacing" it. And none of it has anything to do with bidirectionality. " said: Is there any reason why bi-directional signaling would not be installed everywhere?It is expensive (not only needs more signals, but also more track circuits), often results in poorer conditions for the right direction movements, needs loads more crossovers etc. and the usability except for traffic irregularities is debatable. Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 11:13 #68708 | |
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AndyG
1842 posts |
" said:Sometimes you get SIMBIDS (Simplified Bi-Directional Signalling) such as on the GWML between Swindon and Bristol TM (via Box). It has many shortcomings though, such as non-suppression of AWS for wrong direction moves, and an almost total lack of wrong direction signals (IIRC there was one wrong direction signal between Bath Goods and North Somerset Jn..Also on Swindon Panel, Wootton Bassett Jn to Chipping Sodbury via Hullavington, and Wantage Road to Swindon. As Kev says, restricted capacity, due to much longer sections and also lower speeds (85mph instead of 125mph). I can only help one person a day. Today's not your day. Tomorrow doesn't look too good either. Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 13:19 #68712 | |
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clive
2789 posts |
" said:Sometimes you get SIMBIDS (Simplified Bi-Directional Signalling)There is, or used to be, SIMBIDS over Balcombe Viaduct on the Brighton Main line. In order to keep the equipment working and driver route knowledge up to date, one train each day ran "wrong line". There was a collision when the down train on the up line SPADed and hit the up train that was about to cross to the down line. Official report here - there's a signalling diagram at the back. Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 13:54 #68714 | |
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Jersey_Mike
250 posts |
" said:Usually capitol spending is a different pot of money and adding bi-directional capability would not significantly add to the cost and also justify spending money in the first place to increase your capabilities. If one is already going to let the contact, run new cables, install new appliances and establish line possessions, adding bi-directional signaling is like replacing your clutch plates when you already have the transmission out for repair. Quote: Traffic density. There's no BIDS between Barking & Fenchurch Street, even though it exists country side of Barking, simply because there's no way you could get any kind of sensible service in & out of Fenchurch over a single line.The ultimate reason for bi-directional signaling on high density lines is recovering from some sort of failure. When I'm playing whatever simulation and a train announces that it's going to be delayed for 40 minutes or an hour and I have a parade of trains stacking up behind it, the failure will not only destroy my score, but ruin a lot of commutes. Seeing how it won't let me cross trains over and run them against the current of traffic (I've tried that), I don't know what one is supposed to do in that situation. For the last 20 years "reverse signaling" projects have been the bread and butter of transit agencies winning government improvement money in the United States. They always have press releases that run along the lines of "now your commute won't be screwed up every couple of weeks". Quote: Automatic Block a fairly universal concept involving train detection, blocks and signals automatically reflecting block occupancy. For bi-directional operation you need some sort of Traffic Control system to prevent opposing train movements from becoming deadlocked. Since de-centralized traffic control isn't really installed any more, it's usually safe to assume that any traffic control system is of the centralized variety. Quote: It is expensive (not only needs more signals, but also more track circuits), often results in poorer conditions for the right direction movements, needs loads more crossovers etc. and the usability except for traffic irregularities is debatable.So yes it requires hardware, but if a train breaks down or you need to close a track for repair it doesn't completely hose your service (or require costly manual reverse running procedures). In the 21st century people's time (employees and passengers) is generally more valuable than capitol equipment. Last edited: 03/02/2015 at 13:54 by Jersey_Mike Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 15:04 #68715 | |
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KymriskaDraken
963 posts |
" said:Basset-Sodbury was proper BiDi rather than CANBIDS. The train describer even worked for that section, with proper wrong road berths. Kev Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 17:00 #68718 | |
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Steamer
3984 posts |
" said:" said:True, and hence why bi-directional signalling is becoming more common, especially where relay interlockings are changed to solid state. However, don't underestimate the penny-pinching and short sighted nature of our politicians. If they can see a way to trim the budget by a few million, they often will do, and I wouldn't be surprised if bi-directional signalling has been removed from schemes in the past to keep costs down. I'm not saying it's a good reason not to install it, but it's a reason nonetheless.Usually capitol spending is a different pot of money and adding bi-directional capability would not significantly add to the cost and also justify spending money in the first place to increase your capabilities. If one is already going to let the contact, run new cables, install new appliances and establish line possessions, adding bi-directional signaling is like replacing your clutch plates when you already have the transmission out for repair. Quote: Quote:Agreed, and I've seen bi-directional signalling used to work around a failureTraffic density. There's no BIDS between Barking & Fenchurch Street, even though it exists country side of Barking, simply because there's no way you could get any kind of sensible service in & out of Fenchurch over a single line.The ultimate reason for bi-directional signaling on high density lines is recovering from some sort of failure. When I'm playing whatever simulation and a train announces that it's going to be delayed for 40 minutes or an hour and I have a parade of trains stacking up behind it, the failure will not only destroy my score, but ruin a lot of commutes. Seeing how it won't let me cross trains over and run them against the current of traffic (I've tried that), I don't know what one is supposed to do in that situation. I think you confused matters a bit with your video- in Britain we couldn't use bi-directional signalling in that manner, but can (and do) use it to run a reduced service around a failure. Quote: Automatic Block a fairly universal concept involving train detection, blocks and signals automatically reflecting block occupancy. For bi-directional operation you need some sort of Traffic Control system to prevent opposing train movements from becoming deadlocked. Since de-centralized traffic control isn't really installed any more, it's usually safe to assume that any traffic control system is of the centralized variety.We have automatic signals, which work in the way you describe, but they're all monitored by a signalbox somewhere- there's no grey areas where trains disappear and re-appear on the other side. As Finger said, in the UK it's all categorised as Track Circuit Block, which covers everything, including bi-directional working. There are plenty of smaller boxes ('Decentralised' to use your term) that work TCB to adjacent boxes- for example, there's a signalbox controlling each end of Stafford station. As train detection is provided throughout using track circuits, including the fringe between the two, it's classed as TCB. I think you're trying to crowbar a term used to describe an American system around the British system, when there a subtle differences between the two. "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: 03/02/2015 at 17:05 by Steamer Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 17:13 #68719 | |
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Forest Pines
525 posts |
" said:Sometimes you get SIMBIDS (Simplified Bi-Directional Signalling) such as on the GWML between Swindon and Bristol TM (via Box). It has many shortcomings though, such as non-suppression of AWS for wrong direction moves, and an almost total lack of wrong direction signals (IIRC there was one wrong direction signal between Bath Goods and North Somerset Jn..I'm a Bristol-Bath commuter, and was once (in the past 3 years of commuting) on a Down train that failed at Oldfield Park with a door that wouldn't shut. The following Down HST was run on the Up from Bath to North Somerset Jn so that it could get to Bristol in time to form its return service to London. Of course, that meant that no trains could leave Bristol towards Bath for about 25-30 minutes in total. Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 17:51 #68720 | |
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kbarber
1742 posts |
" said:
Do you have the Fenchurch Street sim Mike? That is the section I'm talking about. It may have thinned out a little since my day (1981/3), but the peak service out of Fencurch is not far off a 2.5 minute headway. (We'll draw a veil over the working at Fenchurch itself to manage that lot with 4 platforms.) Upminster line trains are a mix of 12-car (Shoebury and perhaps some Southends) and 8-car (Leigh-on-Sea and Laindon) trains. Tilbury line trains are all 8-car in the peak. The Shoeburys tend to be all-stations as do about half the Tilburys, the others have a variety of skip-stop patterns. This is designed to even out the loadings a little, otherwise every train would be absolutely packed to the gills as far as Barking (where there is interchange with the UndergrounD, whose Tower Hill station is about 150yards from Fenchurch). As it is, every train loads well - it's rare to see an empty seat on the down road between about 17:00 and 19:00 in the evening. If you had full BIDS you would be able to run a maximum of 6 or 8 trains in to Fenchurch before you had to get them all out again. (It's only 8 if you can stand a complete train clear of Christian St Junc at UR108 or UR512; if there isn't a full 12-car train length there it's 6 at a time). Running time from Barking to Fenchurch is about 14 minutes (16 if there's a Limehouse call). So for the sake of argument, if BIDS were provided, let's say you can get 8 trains up to Fenchurch in 15 minutes each. Once a train has left Barking, trains can't leave Fenchurch. So you start with a 20min window at Barking & send 8 trains up at 2.5 minute intervals. The first arrives at Fenchurch 15 minutes after the window opens. But it can't leave for another 20 minutes - there's still 5 minutes before the 8th train leaves Barking and it'll take the same 15 minutes to get clear at Christian St. You then get 20 minutes of madness at Fenchurch while 8 trains are got in, loaded to the gunwhales and got out again followed by a 30 minute gap before the first train of the next flight arrives. So you've managed 8 trains in 65 minutes rather than the 24 trains per hour of the normal timetable. Frankly, it's simply not useful to even try. Better by far to direct pax to the Underground for Barking, where you can reverse trains, or to Liverpool Street, where there's an alternative route to Southend (Victoria rather than Central station). (Of course that also means you can do things foul of the other running line that you wouldn't be able to do if you were using it in both directions.) Country side of Barking the service is thinner - that's where the Tilbury line diverges, taking approximately 1/3 of the trains and leaving just enough room to make BIDS useful. And BIDS - or at least SIMBIDS - there certainly is. (And I wish it had been there when I was station supervisor at Barking, it would've made a big difference at certain times when the service was up the wall.) Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 17:55 #68721 | |
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Forest Pines
525 posts |
" said:In a high-density situation - London Underground or Barking-London are good examples - you'd turn back some or all of the services that couldn't reach their destination, so that they can make up for services that would otherwise be running late in the opposite direction. Passengers would get across the gap using buses or other trains (in the Barking situation for example you could potentially put passengers onto the parallel Underground service) Quote: Two countries separated by a common language and rather different railway concepts. It's well over 100 years since Britain's first centralised Traffic Control opened - but it didn't have anything to do with signalling! As other people have said, "Automatic Block Signalling" isn't really a separate concept here - some TCB signals are automatic and some are controlled (and some are in-between). I don't know if it was ever used to describe the early installations like York-Thirsk that used American-style hardware. Log in to reply |
| Bi-Directional Signaling 03/02/2015 at 21:36 #68729 | |
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Hooverman
306 posts |
" said:" said:The SIMBIDs between Balcombe Tunnel Jcn and Copyhold Jcn is due to be decommissioned over the weekend of March 28th/29th and to be replaced with full BIDS which will allow 12tph (6 trains in each direction in flights of 3). the SIIMBIDS between Haywards Heath & Keymer Jcn and Keymer Jcn & Preston Park will still remain. But in all cases we are not permitted to run trains in parallel in the same direction.Sometimes you get SIMBIDS (Simplified Bi-Directional Signalling)There is, or used to be, SIMBIDS over Balcombe Viaduct on the Brighton Main line. In order to keep the equipment working and driver route knowledge up to date, one train each day ran "wrong line". Last edited: 03/02/2015 at 21:37 by Hooverman Log in to reply The following user said thank you: TimTamToe |
| Bi-Directional Signaling 03/02/2015 at 23:39 #68730 | |
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Muzer
718 posts |
Not permitted to? Why not?
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| Bi-Directional Signaling 04/02/2015 at 00:01 #68731 | |
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JamesN
1607 posts |
" said:Not permitted to? Why not?Because that's what the rule book says... As eluded to twice already it's a get out of difficult situations tool. If you can run trains on the normal line you shouldn't be using the SIMBIDS Log in to reply |
| Bi-Directional Signaling 04/02/2015 at 00:24 #68732 | |
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Hooverman
306 posts |
" said:Not permitted to? Why not?In fact while using SIMBIDS no train on the other line is allowed to be moving in any direction as per our "SBIs". Log in to reply |
| Bi-Directional Signaling 04/02/2015 at 00:55 #68734 | |
BarryM
2158 posts |
" said:" said:In other words, it is there for emergency use only.Not permitted to? Why not?In fact while using SIMBIDS no train on the other line is allowed to be moving in any direction as per our "SBIs". Barry Barry, Sydney, New South Wales, Australia Log in to reply |
| Bi-Directional Signaling 04/02/2015 at 09:57 #68749 | |
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Hooverman
306 posts |
" said:" said:Not really emergency, more like a get out of jail free card (failed train or infrastructure)." said:In other words, it is there for emergency use only.Not permitted to? Why not?In fact while using SIMBIDS no train on the other line is allowed to be moving in any direction as per our "SBIs". Log in to reply |
| Bi-Directional Signaling 04/02/2015 at 10:05 #68751 | |
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KymriskaDraken
963 posts |
" said:" said:Free, as long as you can get hold of the patrolman that has locked out the CANBIDS..." said:Not really emergency, more like a get out of jail free card (failed train or infrastructure)." said:In other words, it is there for emergency use only.Not permitted to? Why not?In fact while using SIMBIDS no train on the other line is allowed to be moving in any direction as per our "SBIs". Log in to reply |
| Bi-Directional Signaling 04/02/2015 at 10:25 #68755 | |
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Hooverman
306 posts |
" said:" said:That's why you have to test communications before granting. The biggest problem is when the direction of flow arrows get stuck in the wrong direction when it's time to go back to mormal working." said:Free, as long as you can get hold of the patrolman that has locked out the CANBIDS..." said:Not really emergency, more like a get out of jail free card (failed train or infrastructure)." said:In other words, it is there for emergency use only.Not permitted to? Why not?In fact while using SIMBIDS no train on the other line is allowed to be moving in any direction as per our "SBIs". Log in to reply |
| Bi-Directional Signaling 04/02/2015 at 10:29 #68757 | |
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KymriskaDraken
963 posts |
" said:" said:I can't remember how we used to get hold of the patrolman - this was 1993 - but I suspect it was radiopagers rather than mobile phones." said:That's why you have to test communications before granting. The biggest problem is when the direction of flow arrows get stuck in the wrong direction when it's time to go back to mormal working." said:Free, as long as you can get hold of the patrolman that has locked out the CANBIDS..." said:Not really emergency, more like a get out of jail free card (failed train or infrastructure)." said:In other words, it is there for emergency use only.Not permitted to? Why not?In fact while using SIMBIDS no train on the other line is allowed to be moving in any direction as per our "SBIs". Log in to reply |
| Bi-Directional Signaling 04/02/2015 at 12:38 #68769 | |
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Jersey_Mike
250 posts |
One use case for bi-directional operation outside of emergencies is having reversible tracks on 3+ track lines to handle peak traffic flows. For example a 4 track line can be run as 3+1 with three tracks in the peak direction at peak times. With highly unbalanced flows they can save the expense of building an additional track. The New York City Subway was big into three track elevated lines with reversible center tracks and don't forget the Chicago Racetrack. " said: The key idea is that of traffic control. One's interlocking logic is a lot simpler if routes are single direction. The flavors of CTC between US and UK are certainly different since we use so many true automatics, but in either case there is logic to prevent a signaler from sending two trains towards each other on the same track section so that one will eventually have to back up. Where every signal is controlled and can act like a holdout, the idea of setting traffic flow on a section of track becomes a bit muddy, but one doesn't need to implement the logic that way since there is almost zero need for two trains to approach each other on the same track without some intervening switch or station. Quote: However, don't underestimate the penny-pinching and short sighted nature of our politicians. If they can see a way to trim the budget by a few million, they often will do, and I wouldn't be surprised if bi-directional signalling has been removed from schemes in the past to keep costs down. I'm not saying it's a good reason not to install it, but it's a reason nonetheless.That is one of the drawbacks to having an independent operator in charge of the infrastructure. The cost of service disruptions falls to the train operating companies (and/or their passengers). In the United States where the operators own the tracks, bi-directional signaling is always implemented as soon as the money becomes available because having to employ manual reverse running procedures drives the operations people nuts and also increases the risk of accident. That being said, CTC can be implemented very inexpensively if one is willing to use true automatic signals and put them back to back like this. There is an issue with having to electrically lock every hand operated set of points because under single direction operation trailing points do not present a derailment risk, where under bi-directional operation there are no more "trailing" points. I know one example where one track of a double track line was left as single direction ABS simply so that a frequently used hand throw switch could be left unlocked (and thus not require the crew to wait 8-13 minutes to obtain a release). Log in to reply |
| Bi-Directional Signaling 04/02/2015 at 13:14 #68775 | |
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Ron_J
331 posts |
We don't have hand points on passenger running lines here... Look, railway/railroad operations in the UK and the US are fundamentally different. We approach problems from different angles and come up with different solutions. Most of your questions here and elsewhere seem to really be asking why we in the UK don't do things the superior American way. The answer is simply that we just don't. The UK railway system has matured in a different way and taken a different path, particularly when it comes to signalling and operating practices. That's just how it is and you need to accept that. Log in to reply |
| Bi-Directional Signaling 04/02/2015 at 13:21 #68776 | |
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Firefly
521 posts |
Quote:That's why you have to test communications before granting. The biggest problem is when the direction of flow arrows get stuck in the wrong direction when it's time to go back to mormal working.Ah, the Three Bridges direction of flow arrows. Now there's a mysterious bit of circuitry design. I think it was Purley that I managed to get both Arrows Up when testing some alterations. FF Log in to reply |