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| Bidirectional signalling in UK - main routes 13/10/2024 at 11:35 #158822 | |
Ignacio
17 posts |
Hi all, probably one of the UK experts can answer why in UK bidirectional signalling, also on main train routes, seems to be rather occasionally implemented. It came to my mind while using the busy Doncaster simulation where no bidirectional signalling for the main London to York line exists. Is it because of security reasons? Or cost implications? How is the train traffic organized when reconstruction work in a train section starts? There I assume a bidirectional signalling could ease maintaining (limited) train traffic using the second (parallel) track. In Austria and Switzerland bidir signals are usual, in Germany where I live also quite often. Simply interested in understanding the difference! Thanks a lot, Cheers Ignacio Log in to reply |
| Bidirectional signalling in UK - main routes 13/10/2024 at 16:13 #158833 | |
GeoffM
6367 posts |
Two common reasons: cost of installing and maintaining equipment which should rarely be used; and because capacity is so much lower that you're going to have to run buses or other alternate transportation anyway, so why run any train service at all? There are, of course, exceptions. Rugby's four track sections have two lines signalled in both directions, and simplified bi-directional signalling is installed in many places (often with 15 minute or worse headway; okay for Sunday services and an occasional "get out of a hole" situation, but not much more). SimSig Boss Log in to reply The following users said thank you: TUT, Ignacio, Farcical |
| Bidirectional signalling in UK - main routes 13/10/2024 at 16:35 #158834 | |
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kbarber
1736 posts |
As Geoff says, cost is a major driver. UK signalling tends to be rather more complex (overlaps are uncommon, for instance, in many other countries' systems) and UK signal engineers tend to be rather conservative. So the idea of BiDS was a long time coming. Somewhere in my father's papers is a paper written by one Chris Green, at the time an operations manager in the old Southern Region, describing the system used in Germany and proposing installation of a similar system (with some appropriate modifications) in the UK. (One of the modifications was that separate 'wrong-line' signals would be provided. Apparently in Germany when BiDS was in operation signals for the 'right line' would apply to the 'wrong line' when it was being used in the reverse direction. Which, to me, sounds like unduly complicated circuitry but maybe DB circuits allowed for signals to be switched across in that way. That particular feature suggests BiDS was for engineering work only and couldn't be used for traffic reasons, a major difference from UK BiDS.) Quite apart from cost, I have an idea there was a stage when Health & Safety considerations were cited as a reason for not using BiDS. Certainly the UK implementation, at least on the Western Region, had a 'patrolman's lockout' so engineers staff could bar use of BiDS while they conducted their regular examinations of the track. Given there was a period (late 1980s perhaps?) when the Health & Safety Executive was actively considering prohibiting Single Line Working during engineering works, that seems plausible. Beyond that, as Geoff says there are few locations now where BiDS would offer more than a marginal benefit - train services are much more intense than they were even 30 years ago. Log in to reply |
| Bidirectional signalling in UK - main routes 13/10/2024 at 17:04 #158836 | |
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Ignacio
17 posts |
Many thanks, GeoffM and kbarber! Seems to be really differently handled in UK versus Germany. I am not working as professional signaller at Deutsche Bahn, but would agree that BiDS is often not possible to use because of overbooked tracks...so it is not a proper means to increase resources...
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| Bidirectional signalling in UK - main routes 13/10/2024 at 19:22 #158837 | |
postal
5256 posts 
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Ignacio in post 158836 said:Many thanks, GeoffM and kbarber! Seems to be really differently handled in UK versus Germany. I am not working as professional signaller at Deutsche Bahn, but would agree that BiDS is often not possible to use because of overbooked tracks...so it is not a proper means to increase resources...The SimBids (Simplified Bi-Directional Signalling) was used on the twin-track ECML between Morpeth and Newcastle recently due to the closure of one of the two running lines because of the collapse of a bridge parapet. That stretch of line is not the most intensively used on the network but even so an emergency timetable had to be introduced which I believe had less than half of the normal trains running. “In life, there is always someone out there, who won’t like you, for whatever reason, don’t let the insecurities in their lives affect yours.” – Rashida Rowe Log in to reply |
| Bidirectional signalling in UK - main routes 13/10/2024 at 21:56 #158838 | |
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Jan
903 posts |
kbarber in post 158834 said:Apparently in Germany when BiDS was in operation signals for the 'right line' would apply to the 'wrong line' when it was being used in the reverse direction. Which, to me, sounds like unduly complicated circuitry but maybe DB circuits allowed for signals to be switched across in that way. That particular feature suggests BiDS was for engineering work only and couldn't be used for traffic reasons, a major difference from UK BiDS. That system rings a bell ("Zeitweise eingleisiger Betrieb", i.e. "temporary signal-track operations"), but it was (maybe still is, no idea? Though if so, then certainly under a different name…) indeed only ever used for major engineering works due to the need to rewire the signalling for the temporary single-track operation. (Though supposedly in some cases that mode of operation could also be dynamically switched-in and switched-out again, but that was still only used in conjunction with construction works which e.g. might only take place over the weekend.) However Germany has had true bi-directional signalling, too, with the first installation having been taken into service in 1951, so I'm a bit curious why that paper you mentioned would focus so much on the very limited ZEB-system. Another German particularity in that regard was the West German so-called "Signalisierter Falschfahrbetrieb", i.e. "signalised wrong-line running" (I think East German DR had a similar system, but with a differing name and using regular-scale signals instead of dwarf signals). What that system amounted to was basically that stations and intermediate junctions were provided with simplified dwarf signals which could only display a subsidiary or shunting aspect and the corresponding routes in the interlocking for entering/exiting a station respectively traversing a junction on the wrong line, but crucially no block system was provided for the plain line between those stations and/or junctions. Compared to the UK distinction of full bi-directional signalling vs. SIMBIDS, in Germany regular bi-directional signalling often includes the increased signal spacing/reduced capacity aspect for wrong-line movements in order to economise on costs, however there was no need to compromise on train protection because PZB inductors are inherently unidrectional anyway, whereas in the UK AWS magnets always require extra suppressing for reverse direction movements. Two million people attempt to use Birmingham's magnificent rail network every year, with just over a million of them managing to get further than Smethwick. Last edited: 13/10/2024 at 21:57 by Jan Reason: None given Log in to reply |
| Bidirectional signalling in UK - main routes 14/10/2024 at 09:40 #158840 | |
Splodge
716 posts
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Even on Manchester South, where the 'wrong direction' signalling mirrors the normal direction signalling, with full AWS and TPWS provision, we're limited to 60 in the wrong direction with slower speed crossovers and restrictive signalling on approach to them. It can be used pretty effectively in times of disruption, and can also be used for regulation but the low speed approaches mean its often easier to keep the slower train running as booked and utilise a loop
There's the right way, the wrong way and the railway. Log in to reply |
| Bidirectional signalling in UK - main routes 14/10/2024 at 10:55 #158841 | |
flabberdacks
630 posts |
It's a shame that the vision for bidirectional signalling seems to have been so narrow. There's at least one Swiss cabride on youtube where you're cruising on double track, cross to the other line for seemingly no reason, only to go past a clearly planned worksite (multiple track machines present) and then cross back at the next junction. Being able to isolate small sections of line like that for maintenance while still running a full service seems to be a massive advantage in regional areas. Not so useful where traffic is heaviest though, of course. Log in to reply The following user said thank you: sunocske |
| Bidirectional signalling in UK - main routes 14/10/2024 at 12:50 #158843 | |
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sunocske
120 posts |
In Hungary, we have a very few uni-directional double track routes, the majority is fully bi-directional and it comes very handy quite often. There is no extra speed restriction when you send a train on the "wrong line" (it is the term in Hungarian for it), and on busier routes it is quite common to see trains passing each other between two stations (and stations are quite frequent, too, 10+ km long sections without crossovers are very rare). Re single line working vs. substitution buses. In Hungary, we prefer to maintain a limited train service during engineering works or emergencies. Works are usually timed to nights or weekends, when the capacity of a single line section is enough for the limited service - maybe some trains need to be retimed to wait at the ends of the temporary single line sections for their slot, but these are usually not more than 5 to 10 minutes. When major works take place, they're withdrawing some of the trains, but add extra capacity to the others on the same route. Sadly, trains often hit pedestrians or cars nowadays in Hungary, and single line working with fully bi-directional signalling comes extremely handy when dealing this type of emergencies (only if the incident site allows that so there is enough clearance or something), with emergency speed restriction in the vicinity of the site. Requesting buses for this types of ad-hoc vis-maior events are impossible (the first buses would arrive to the stations after the problem is solved and everything is ready to carry on). Not sending trains at all for two or three hours on a main line is no-go, too. Planned substitutions buses are a different piece of cake, it is usually well planned in advance and operated seamless. Log in to reply |
| Bidirectional signalling in UK - main routes 14/10/2024 at 13:31 #158845 | |
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broodje
184 posts |
As far as I could find out most mainland countries have some form of bidi working on mainlines. Either limited with a bigger headway, or fully signalled. But then again, the UK has a somewhat unique way of signalling. It is route based, there is a concept of overlaps, but also a different philosophy in the way signal boxes worked in the mechanical era and thus a different way at looking at signalling on a whole. I think all that combined makes designing and maintaining a fully BIDI signalled track in the UK a lot more expensive. In the Netherlands most lines are fully signalled in both ways. This is also used a lot in the evening hours especially for 4 track railways. I live close to the mainline between Leiden and The Hague (4 IC per hour and 4 stopping trains in both directions). It has 4 tracks, fully signalled in both ways and they are combined as 2 up, 2 down next to each other. In the evening either the down, or the up goes out of service and the other bundle is used, and in effect 1 of the tracks is used in the opposing direction as during the day. This way, smaller maintenance can be carried out without completely closing the line. I wonder if introducing ERTMS on the mainlines in the UK will change the situation? Will the design of the signalling change? You could do away with the concept of overlaps, and you will loose the concept of route based signalling. Maybe the price difference to install 2 way working won’t be as high as it is now? Log in to reply The following user said thank you: sunocske |
| Bidirectional signalling in UK - main routes 14/10/2024 at 16:57 #158851 | |
Steamer
3976 posts |
There's another side to the coin, namely that funding limitations and associated short-sightedness can lead to descoping of elements that would be very good to have in normal operation, let alone bi-di. There's also the fact that the NR safety ratchet is progressively eliminating any form of access by staff to the track without a line block, so the opportunities for wrong line running are increasingly limited. "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 |
| Bidirectional signalling in UK - main routes 15/10/2024 at 08:15 #158868 | |
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kbarber
1736 posts |
flabberdacks in post 158841 said:It's a shame that the vision for bidirectional signalling seems to have been so narrow. There's at least one Swiss cabride on youtube where you're cruising on double track, cross to the other line for seemingly no reason, only to go past a clearly planned worksite (multiple track machines present) and then cross back at the next junction.Ah yes, Switzerland. On the Gotthard and Loetschberg classic routes, the most heavily graded mountain sections have a linespeed of 75kmh. Crossovers can therefore very easily be 'linespeed' and most of them are, which facilitates bi-di working no end; at that point, if you have a preponderance of traffic in one direction at peak times, it becomes worthwhile using the BiDS for traffic regulation. It also makes working past engineering very easy, with little or no time penalty. I rather assume what I used to see at Kandersteg would be typical of Swiss signalling practice. Kandersteg, certainly until 2015, controlled the long loops down the valley to Frutigen; both lines had full bi-di with crossovers at every signal(!!) Swiss practice seems to use approach control as a default in those 'out-of-station' sections. What I noticed was that, in normal working, all main line routes were called in both directions. As a train entered the section in rear (or perhaps even before), it would 'claim' the section, a white direction of flow indicator would illuminate and the signal (and its associated vorsignal) through that section would clear. There would then come a point when it locked in the route and a second, red direction of flow indicator would illuminate. (I imagine before the red illuminated it would be possible to 'pull up' the route buttons and the approach locking would time out in the normal way, whereas something more involved would be necessary if the red indicator had illuminated.) When the train entered the section the white DoF would extinguish but the red would remain alight until the train cleared the section. In many ways these DoF indications may be taken as mimicking UK block indications, I would say. The really clever thing was that similar working was possible when using the crossovers during engineering work. With all routes in and out of the affected section called, signals would remain red until 'claimed'. At which point the route would set (including swinging points if the previous movement had been in the opposite direction) and the signal into the affected section would clear. If a train approached from the opposite direction, the DoF locking would prevent it claiming its route until the oncoming train had run clear, at which point it would take the section and the route would clear for it. So the whole single line working operation ran itself quite happily without needing any intervention at all by the Fahrdienstleiter! We should be so lucky on this side of the water! Log in to reply The following user said thank you: mldaureol |
| Bidirectional signalling in UK - main routes 15/10/2024 at 18:13 #158881 | |
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Ignacio
17 posts |
Thanks all for very good explanations! Meanwhile Tyneside added to my shop...did I say that bidi is not useful :-) Post has attachments. Log in to view them. Log in to reply |
| Bidirectional signalling in UK - main routes 15/10/2024 at 19:48 #158882 | |
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postal
5256 posts
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Ignacio in post 158881 said:Thanks all for very good explanations! Meanwhile Tyneside added to my shop...did I say that bidi is not useful :-)The real world SimBids was operated between Plessey at the North end of the sim and Morpeth which is off sim. The Southbound line was closed. The crossover at Morpeth is within the platform limits which does make it less than helpful. The blockage lasted for about a month. There was another SimBids intrusion at about the same time following a landslip at Aycliffe so single line working was in place between Darlington Station and Aycliffe IIRC with the Northbound line closed but that only lasted about a week. “In life, there is always someone out there, who won’t like you, for whatever reason, don’t let the insecurities in their lives affect yours.” – Rashida Rowe Log in to reply |
| Bidirectional signalling in UK - main routes 15/10/2024 at 23:28 #158885 | |
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bill_gensheet
1394 posts |
Edinburgh sim also has a stretch of bi-di, fully on the up line and SimBIDS on the down, installed apparently to allow overtaking on a two track line. The idea was that slow freight (coal to Yorkshire) going up the hill Innerwick to Grantshouse could be overtaken by sending passenger trains on the down line. Might have worked with only 1 train an hour north... but I do not think ever used at WTT level Bill Log in to reply |
| Bidirectional signalling in UK - main routes 16/10/2024 at 00:43 #158887 | |
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postal
5256 posts
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bill_gensheet in post 158885 said:Edinburgh sim also has a stretch of bi-di, fully on the up line and SimBIDS on the down, installed apparently to allow overtaking on a two track line.There is an oddity with the working of that stretch which is modelled in the Edinburgh sim. Rather than the signals having to be physically cleared to work an Up train on the Down line the "wrong line" signals are auto-working. Instead of the "wrong line" signals showing R until such time as an Up train is booked on the Down they show a proceed aspect if the TC following is clear. As a Down train approaches the "wrong line" signal you can watch it drop back from G to Y then R then revert to G after the train has passed. I have some rather blurry photos from 2010 showing the sequence if anyone is desperately interested. “In life, there is always someone out there, who won’t like you, for whatever reason, don’t let the insecurities in their lives affect yours.” – Rashida Rowe Log in to reply |
| Bidirectional signalling in UK - main routes 17/10/2024 at 16:50 #158903 | |
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Ron_J
331 posts |
bill_gensheet in post 158885 said:Edinburgh sim also has a stretch of bi-di, fully on the up line and SimBIDS on the down, installed apparently to allow overtaking on a two track line.There are a couple of booked overtaking moves utilising this. Log in to reply The following user said thank you: bill_gensheet |
| Bidirectional signalling in UK - main routes 17/10/2024 at 18:07 #158907 | |
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flabberdacks
630 posts |
postal in post 158887 said:As a Down train approaches the "wrong line" signal you can watch it drop back from G to Y then R then revert to G after the train has passed.Have also heard of this happening on lines in North America - signals protecting entrance to the section are direction locked but block signals in the section aren't, and they just drop down as a train approaches them from the other direction Log in to reply |