Deleted
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Post by Deleted on Aug 1, 2011 21:50:17 GMT
Following on from a comment on the 'Closure from Edgware Rd to High St' thread, given that the various flat junctions seem such obvious bottlenecks for the SSR lines, have there been any serious projects to grade separate them (since the MDR did Earls Court)?
I would rather expect there to be such proposals in the 'things to do when there's some money' file.
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Colin
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Post by Colin on Aug 1, 2011 22:18:46 GMT
In most cases I would imagine the cost could never be justified.
All of the relevant junctions are underground and would thus require some serious engineering to create the required space needed.
As MetControl said in the aforementioned thread, the current junctions work so there's no need to fix what ain't broken!!
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Post by Harsig on Aug 2, 2011 8:32:21 GMT
In most cases I would imagine the cost could never be justified. To amplify that point, there was some very significant work carried out to the Aldgate Triangle before the second world war, to the extent of providing a new tunnel for the District side of the triangle, and yet they did not take the opportunity to provide any grade separated junctions. I cannot imagine they never considered the idea and so it must have been rejected on the grounds of cost and or complexity. |
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Post by citysig on Aug 2, 2011 9:04:57 GMT
The flat junctions - whilst not always ideal - don't cause as many problems as they used to. Careful timetabling has overcome many of the old conflicts, and we don't try and push as many trains into the tunnel as we used to (most northern Circle services are now every 5 minutes instead of every 4.)
The problem highlighted in the other thread was not really junction related - it was more to do with waiting to get into Edgware Road station.
To repeat what I said in the other thread, there is no plan, no money and very little space even if we had the money, to redesign any of our flat junctions into flying junctions. We're stuck with what we've got, and with careful and professional operation, we'll keep things moving.
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mrfs42
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Post by mrfs42 on Aug 2, 2011 10:43:36 GMT
We're stuck with what we've got, and with careful and professional operation, we'll keep things moving. The name of the game will change with resignalling (if/when it comes) taking a lot more of the decision making away from humans and allowing a faster, closer approach to a converging junction. |
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Post by citysig on Aug 2, 2011 13:52:33 GMT
With all due respect I couldn't disagree more  . Take what is the busiest 3-sided flat junction certainly in the country if not the world - Aldgate/Minories Junctions. They worked so much better under manual control. When they were put onto the computer the whole way in which the junctions were controlled changed, and not for the better. Even a software change (pushed through by yours truly) only slightly improved things. At the busiest times, especially following disruption, it takes a fair amount of manual intervention to keep things moving. Another is Baker Street junction. It copes well for the large majority of the time, but when it comes to making slightly different choices, often at the last minute, it needs human intervention. It is because although you can program a computer to do x,y,z it can only function as far as it is allowed/programmed to. A human can look much further ahead, and can alter decisions much more fluidly than a computer. So after the resignalling and with ATO you may be able to approach a junction at a higher speed - meaning each train spends less time actually carrying out the move - but you may not necessarily have a smooth passage of trains in the way we (mostly) do now. |
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Post by railtechnician on Aug 2, 2011 14:34:48 GMT
With all due respect I couldn't disagree more . Take what is the busiest 3-sided flat junction certainly in the country if not the world - Aldgate/Minories Junctions. They worked so much better under manual control. When they were put onto the computer the whole way in which the junctions were controlled changed, and not for the better. Even a software change (pushed through by yours truly) only slightly improved things. At the busiest times, especially following disruption, it takes a fair amount of manual intervention to keep things moving. Another is Baker Street junction. It copes well for the large majority of the time, but when it comes to making slightly different choices, often at the last minute, it needs human intervention. It is because although you can program a computer to do x,y,z it can only function as far as it is allowed/programmed to. A human can look much further ahead, and can alter decisions much more fluidly than a computer. So after the resignalling and with ATO you may be able to approach a junction at a higher speed - meaning each train spends less time actually carrying out the move - but you may not necessarily have a smooth passage of trains in the way we (mostly) do now. While I fully understand your point of view I have to disagree with your analysis. When the Aldgate area resignalling was commissioned I was in Farrdingdon signal cabin commissioning the SPTs from Aldgate to King's Cross. It was a long night and even at Farringdon I could hear the Signal Engineer (Joe Kershaw) at Aldgate over the phone telling his supervisors what their futures might hold if they didn't get things sorted ASAP. Joe had a way with words! of course there wasn't a great deal that they could do because the problems were design and software issues. When the Aldagte area regulator at Farrindgon pushed a button to clear a route once trains were running in the morning he was querying why signals weren't clearing and then, when they had, why the trains were stationary. The reason was the way in which things were done, AIUI then the regulator pushed a button sending a command to Baker Street computer, which processed it and sent a command to Aldgate to clear the route. Basically it could take up to a full minute from route push to route clear. Computer control and manual control are effectively the same thing, what is different is the signal operator! The experienced signal operator able to operate a site efficiently was unfortunately not the computer programmer, had the computer been able to replicate the actions of an efficient signal operator the computer would win every time simply because it has a better attention span and faster processing. The Aldgate problem IMHO was two-fold, firstly the computer was programmed by a programmer interpreting what a signal operator would be expected to do and secondly a slow communications interface between sites. I believe that in any future resignalling neither of these problems will exist, it really all boils down to having the correct processing algorithms in place and at suitable locations. It is true to say that a human brain is a computer and still far cleverer than the manufactured item but the latter is simply so much faster and doesn't have to stop for lunch etc but it is only as good as its programmer so if you want a computer to do a better job than a human make it possible for the particular human to be able to programme it, at present AFAIAA this is still at the monkey see monkey do stage but over time it will progress, computers have for some years been doing things that humans simply cannot do or might be able to do if they lived long enough! |
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mrfs42
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Post by mrfs42 on Aug 2, 2011 16:07:35 GMT
With all due respect I couldn't disagree more . Take what is the busiest 3-sided flat junction certainly in the country if not the world - Aldgate/Minories Junctions. They worked so much better under manual control. When they were put onto the computer the whole way in which the junctions were controlled changed, and not for the better. Completely agree - and FWIW I'm none too keen on the move towards electric points, EP work so much quicker. All these little delays will build up; have you noticed the progressive 'padding-out' of stand time on your side of the Circle for some of the TTNs? |
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Post by railtechnician on Aug 2, 2011 16:52:22 GMT
With all due respect I couldn't disagree more . Take what is the busiest 3-sided flat junction certainly in the country if not the world - Aldgate/Minories Junctions. They worked so much better under manual control. When they were put onto the computer the whole way in which the junctions were controlled changed, and not for the better. Completely agree - and FWIW I'm none too keen on the move towards electric points, EP work so much quicker. All these little delays will build up; have you noticed the progressive 'padding-out' of stand time on your side of the Circle for some of the TTNs? Yep you just can't beat a decent set of EP points, even when the air pressure is quite low a good set will still throw fast. I've never had any dealings with electric points but my understanding is that they take time to 'wind' across. I suspect there may be more than one reason for a move towards them, not least of which will be the complaints from passengers and staff alike about the noise associated with air exhaust from the throw of EP points. I laughed my head off some years ago when we had to 'silence' a D valve at Acton Town because the exhaust from it frightened a member of staff walking the staff pathway from the station to Bollo House! |
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slugabed
Zu lang am schnuller.
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Post by slugabed on Aug 2, 2011 17:49:40 GMT
....But that "Psssssscht!!" is an intrinsic sound of the Underground!
Sometimes us passengers find it useful as it can let us know when a train is about to depart....
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Post by mrjrt on Aug 2, 2011 21:08:39 GMT
Wasn't there a distant plan by the Met before nationalisation to tunnel down the western bay at Baker St to grade separate the northbound line north? I recall this because something I read mentioned that the new planned lift shafts would impinge on what the plans would have required. ...but with that, you could have a non-conflicting centre terminating road, and knocking through the other bay (and in all likelihood, turning the current pair of through roads into bays) would have made Baker Street a whole lot more efficient.
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Post by t697 on Aug 2, 2011 21:23:11 GMT
Wasn't there a distant plan by the Met before nationalisation to tunnel down the western bay at Baker St to grade separate the northbound line north? I recall this because something I read mentioned that the new planned lift shafts would impinge on what the plans would have required. ...but with that, you could have a non-conflicting centre terminating road, and knocking through the other bay (and in all likelihood, turning the current pair of through roads into bays) would have made Baker Street a whole lot more efficient. ISTR that one of the consortia that bid for the SSL contract under PPP included that one and one or more other flying/burrowing junctions to deal with the performance required at certain flat junctions. The consortium included at least one major Civil Engineering company of course.... |
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Deleted
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Post by Deleted on Aug 3, 2011 2:13:26 GMT
Wasn't there a distant plan by the Met before nationalisation The only plan I have read about was to eliminate the two-track bottleneck between Finchley Road and Baker Street by building a new line under ground from Finchley Road to west of Edgware Road. The Met got as far as rebuilding Edgware Road, but then was swallowed by LT which preferred to extend the Bakerloo. This plan is why Edgware Road has the extra platforms that are now used to turn District and Circle trains. |
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Ben
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Post by Ben on Aug 3, 2011 2:34:02 GMT
I thought the speed of electric points had improved massively over the past decade or so?
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mrfs42
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Post by mrfs42 on Aug 3, 2011 3:00:31 GMT
This plan is why Edgware Road has the extra platforms that are now used to turn District and Circle trains. I thought too it was to cater for the 'other' line up the Met. that appeared in the Railway Mag. article at the time of the resignalling. I thought the speed of electric points had improved massively over the past decade or so? Not really, AIUI. You've still got a motor and leadscrew effort - none of this big-piston-goes-whoosh-CLONK sort of speed. |
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Ben
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Post by Ben on Aug 3, 2011 3:19:59 GMT
Thanks for that, could of sworn I read possibly on here a while back about electric points being a more realistic replacement now than before.
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Post by citysig on Aug 3, 2011 8:40:27 GMT
The Aldgate problem IMHO was two-fold, firstly the computer was programmed by a programmer interpreting what a signal operator would be expected to do and secondly a slow communications interface between sites. I believe that in any future resignalling neither of these problems will exist, it really all boils down to having the correct processing algorithms in place and at suitable locations. Disagree again I'm afraid. First off, the communication to site is as fast as all the other sites, and as fast as you generally get anywhere when controlling remote equipment. There has never been a problem with any "lag." Second, the current programming (in terms of what it does and what it decides) has a great deal of input from me. A few years ago I, along with a couple of the people who wrote the software for the site, ripped the original design and routing specs apart. The site now does things slightly better than it used to, and makes certain decisions faster. Some of the decisions it makes have been re-written, so instead of it doing "x because y is happening" it now tends to do "y now, because y can happen now and will help x" if you see what I mean. But Aldgate has so many different scenarios, with so many different outcomes, you would need a pretty decent computer to be able to manage each and every decision as smoothly as a human. That kind of technology is not within the budget of our company, and as such will never been employed. Which leads us back to the original point that computer control - as far as we'll ever have it - being worse than human control at some locations. |
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Post by railtechnician on Aug 3, 2011 13:08:43 GMT
The Aldgate problem IMHO was two-fold, firstly the computer was programmed by a programmer interpreting what a signal operator would be expected to do and secondly a slow communications interface between sites. I believe that in any future resignalling neither of these problems will exist, it really all boils down to having the correct processing algorithms in place and at suitable locations. Disagree again I'm afraid. First off, the communication to site is as fast as all the other sites, and as fast as you generally get anywhere when controlling remote equipment. There has never been a problem with any "lag." Second, the current programming (in terms of what it does and what it decides) has a great deal of input from me. A few years ago I, along with a couple of the people who wrote the software for the site, ripped the original design and routing specs apart. The site now does things slightly better than it used to, and makes certain decisions faster. Some of the decisions it makes have been re-written, so instead of it doing "x because y is happening" it now tends to do "y now, because y can happen now and will help x" if you see what I mean. But Aldgate has so many different scenarios, with so many different outcomes, you would need a pretty decent computer to be able to manage each and every decision as smoothly as a human. That kind of technology is not within the budget of our company, and as such will never been employed. Which leads us back to the original point that computer control - as far as we'll ever have it - being worse than human control at some locations. My comment about Aldgate was about what was 25 years ago, I am sure that things have moved on considerably since then. Site communication as I'm sure you'll know is not just about the hardware but also the signalling protocol used. While I know little of the actual systems in use on the Met I have no doubt that just as on the Picc they have developed over time. My other comment regarding replication stands, if a computer could think as you do it would be able to do the job more efficiently because it would be faster, the problem is finding a programmer that understands how a signal operator's thought processes work and then being able to program the computer to do exactly the same. All the issues with computer control boil down to insufficient programming possibly as a result of a limited instruction set and possibly also insufficient memory. I am confident that computers will replace humans for such tasks in the future but it will require another revolution in terms of programming techniques to achieve it. LUL budgetting has always suffered from short sightedness but I can't help thinking that the current financial straits that all businesses find themselves in will pave the way for more long term forward thinking and innovation in order to cut the waste of financial resources. |
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mrfs42
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Post by mrfs42 on Aug 4, 2011 2:44:29 GMT
But Aldgate has so many different scenarios, with so many different outcomes Really? OTTOMH I can only think of 6 or so that really matter - of course it may look different to an operator rather than a designer. |
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Post by citysig on Aug 4, 2011 9:01:07 GMT
Well in terms of basically routing trains through the area, you're probably not far off, but I was thinking more in terms of marrying those basic decisions alongside further basic decisions for other services. I'm nearly confusing myself there, but I think I know what I mean.
There are a few sub-routes in and around Aldgate that, left to the computer, can really shut things down, but left to a human who can appreciate the whole picture, can speed journeys up. Maybe more indepth programming could have eased these examples, but even then you would never be able to "teach" the computer when to do one thing or when to do another.
I find it a little ironic that if you look back over my time here I've normally supported computer signalling - and indeed worked with it for 10 years. But maybe it's that time spent with such systems that has shown me that computers simply cannot do the job unaided. A terminus with 2 platforms - yes, the computer is more than capable. Such layouts as Aldgate with 3 busy junctions - then no.
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Post by railtechnician on Aug 4, 2011 10:41:12 GMT
Well in terms of basically routing trains through the area, you're probably not far off, but I was thinking more in terms of marrying those basic decisions alongside further basic decisions for other services. I'm nearly confusing myself there, but I think I know what I mean. There are a few sub-routes in and around Aldgate that, left to the computer, can really shut things down, but left to a human who can appreciate the whole picture, can speed journeys up. Maybe more indepth programming could have eased these examples, but even then you would never be able to "teach" the computer when to do one thing or when to do another. I find it a little ironic that if you look back over my time here I've normally supported computer signalling - and indeed worked with it for 10 years. But maybe it's that time spent with such systems that has shown me that computers simply cannot do the job unaided. A terminus with 2 platforms - yes, the computer is more than capable. Such layouts as Aldgate with 3 busy junctions - then no. Mmm! Looking back over 28 years I would suggest that the performance of signal operators varied greatly. As in all things no two are exactly alike and like controllers some are definitely a cut above the rest when it matters. I never had the opportunity to work on the signal computer section but I did maintain the computer controlled signalling at the east end of the Picc and the computer programme machines at Heathrow. IMO perhaps the biggest problem in computer control of LT signalling is the method of operation. Even with a decent signal operator entering commands at the terminal the time taken to move a lever always seemed inordinately slow. I suspect that was due to the way in which everything was proved before clearing the route. Programme machines did not suffer the same problem so one might be forgiven for thinking that 1950s/60s discrete electronic technology was better than 1970s/1980s/1990s computer technology but this is like mixing apples and oranges. The P/MC is just running a timetable with fixed programme and a very limited and finite amount of decision making, i.e. storage, whereas the computer is supposed to be doing much more. The P/Mc relies upon both safety and non-safety interlocking but AFAIAA the computer also relies upon software interlocking. This is a fundamental difference, the P/Mc actually being closer in nature to a signal operator than a signalling computer, the signal operator relying only upon the safety and non-safety interlocking to inhibit bad decision making. If the signalling computer was programmed only to issue commands and to respond to events as a signal operator does and leave the interlocking to the safety and non-safety signalling equipment it would no doubt give a much better performance. My understanding is that to date LT/LU signalling computers have also become much of the non-safety circuitry and if that is so then perhaps what is required is a 'division of labour' using true parallel processing. |
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Deleted
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Post by Deleted on Nov 21, 2011 1:48:08 GMT
Wasn't there a distant plan by the Met before nationalisation to tunnel down the western bay at Baker St to grade separate the northbound line north? I recall this because something I read mentioned that the new planned lift shafts would impinge on what the plans would have required. ...but with that, you could have a non-conflicting centre terminating road, and knocking through the other bay (and in all likelihood, turning the current pair of through roads into bays) would have made Baker Street a whole lot more efficient. Even just taking the Eastern bay at Baker Street through to the circle (can't be far) would provide some benefit to the Met line, but this would be pretty much in the basement of Madame Tussauds which could be a problem. The western bay is much more challenging due to the concourse immediately underneath and the listed circle platforms it would need to pass under. The engineering required to keep the listed platforms in place whilst a new tunnel is created immediately below them - and not forgetting the busy Marylebone Road above - would be incredible. Personally, if we're talking the fantasy of grade separation at Baker Street, I think the workable scheme would be to lower the line from Edgware Road, with the listed platforms at Baker Street becoming a kind of mezzanine to new platforms below, kind of like St Pancras. If the lower tunnel(s) continued almost to Great Portland Street, the open area around Regent's Park station (Crescent Gardens and Park Sq Gardens) could be used as a work site to separate the east/west circle into new tunnels and ramp up the lines from EWR in between. Having gone this far, one may as well also continue the "lowered lines" at the other end to beyond Praed Street junction, thus forever separating the circle/hammersmith at EWR between the terminating "upper" lines and the through "lower" lines. Obviously this scheme would probably require a closure lasting years between Paddington and Great Portland Street to allow downward excavation of the existing tunnels, plus Finsbury Circus-style blockades of Crescent Gardens and Park Sq Gardens and likely closure of Regents' Park station for the same period, perhaps with an opportunity to install escalators and link it to Great Portland street (might seem pointless as an extra interchange but could relieve some of the capacity pressure on Baker Street). All seems in the "flying pigs" category though. Hard to see the cost benefit ratio stacking up, though the elimination of Praed St junction as well as the grade separation of Baker Street could do a lot for capacity. |
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Post by nickf on Nov 21, 2011 12:07:42 GMT
I thought the speed of electric points had improved massively over the past decade or so? FWIW, the electric points at Alton on the Mid Hants Railway throw, lock and prove in under three seconds. |
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Post by mrjrt on Nov 21, 2011 14:00:19 GMT
Obviously this scheme would probably require a closure lasting years between Paddington and Great Portland Street to allow downward excavation of the existing tunnels ...or you using the solution they used moving/lowering Aldgate East. |
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