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| Bidirectional signalling in UK - main routes Today at 11:35 #158822 | |
Ignacio
14 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 Today at 16:13 #158833 | |
GeoffM
6364 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 user said thank you: Ignacio |
| Bidirectional signalling in UK - main routes Today at 16:35 #158834 | |
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kbarber
1732 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 Today at 17:04 #158836 | |
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Ignacio
14 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 Today at 19:22 #158837 | |
postal
5244 posts |
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 Today at 21:56 #158838 | |
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Jan
900 posts 
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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: Today at 21:57 by Jan Reason: None given Log in to reply |