Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 0:00:25 GMT
I attended the LURS meeting, with the speaker being Jeff Ellis who is the General Manager of the Northern Line. He spoke mostly about the upgrade programme and the timetabling improvements recently introduced. Some interesting points: - If Stepping back is reintroduced at Morden, it would be done at South Wimbledon so that the problems of 3 platforms and stepping back are reduced.
- The 95ts has been extensively troubleshooted over the last few months with doors being the primary concern. He said that door failures due to bearings and seals (which couldn't cope with the dirt and grime that the Northern has (the same type of door system is used on the cleaner Jubilee Line!)
- The AC Motors are in good condition and don't need any attention (having been Central line chief before, I expect he's relieved he's on the Northern for this particular aspect!)
- The electronic proving devices to prove that equipment covers are closed (i.e. under seat equipment) has been changed. Fewer covers now have the Maglocks as the driver won't need to look under a lot of the seats. The covers only used in depots have been screwed down.
- A proposal to extend the Mill Hill East service to East Finchley and then to Highgate Depot as they need a staff train to convey staff to the new control centre.
- The new control centre has been built at Highgate (to nuclear bunker standards apparently!).
- TBTC conversions will commence with Brent Cross to Colindale soon which will be a Dual Fitted Area to test the equipment (though he was relieved that the Train Control system would be thoroughly tested by the Jubilee Line before it reaches the Northern!)
- The signalling desks at Coburg Street will be progressively transferred to Highgate Control Centre and eventually when enough of the line is converted the Line controllers will transfer to Highgate. This will leave Euston as a signal cabin essentially. (Apparently the Northern and Victoria are taking bets on who will turn out the lights at Coburg Street!)
- The timetables have been significantly improved lately. He was very pleased to show us the contrast between the two graphs showing train lateness and train sequences between the two timetables!
- The Regulators/Signallers at Coburg Street were told by an American consultant that they were doing everything wrong! (not well received by the signallers who had been there for decades!) The procedures have been changed so that regulation doesn't happen at Camden Town nor will it happen when the train is more than a third through its journey.
- New crew depots are to be constructed at High Barnet and Edgware. Edgware will absorb some operators from Golders Green and High Barnet is being built for the extra train operators required for the ATO.
- For the second Northern Line Upgrade (see below), there is a possibility that Highgate Depot may be converted back to a maintenance depot to increase flexibility.
- The TBTC will have a platform bias (unlike the Programme machines!). For example, if there are no trains at High Barnet and the train comes in, it will be signalled into platform 1, so that passengers don't have to go miles over the footbridge.
- Mr Ellis seemed to want to promote common sense. For example he wanted stock movements for maintenance to be done in passenger service. He has also implemented a protocol with Tubelines where the LU staff aren't so hostile to the contractors and vice versa. Apparently 200 contractors turned up at Camden Town and were refused entry as the weren't on a particular form! Another example is JNP demanding a suspension of the service in the morning peak for a signal fault. LU refused this and this started an argument between the infraco and LU. There are now ways that it will delay the service less. The infraco is required to check all equipment from the platform (in the relay room) and only after that will the Technical Officer be allowed to go onto the track. He is allowed to go in the front of the train and to have a few minutes at the signal. If he can't fix the fault then, he goes round until enough of the relevant managers are on the platform so that a suspension can be implemented to repair the fault.
- A technical officer has been allocated to Kennington at last. (There wasn't an officer before as LU couldn't find him an office!)
- He talked about the Northern Line Upgrade 2 and the proposal to split the line. He reckons that up to 36tph could be operated if the line was split. A new fleet of trains would be required. The split, as with most things relating to the Northern Line (and LUL !) would most probably be a political issue as well as an operational issue! (He had to fight the MPs to have the northbound split during the AM peak, but now he can boast the 98% miles operated figure!)
- Work has begun at Tottenham Court Road for the station expansion. The current stage is to divert services (he said that every telephone cable in London passes under Oxford Street and Tottenham Court Road!). Eventually the station will be prepared for current traffic and Crossrail.
- Camden Town can't happen until 2013 when money becomes available. The station would be in a JLE style.
- Clapham Common to Kennington is overloaded by 600%. He despairingly said that the Clapham's island platform would have to be done in similar style to Angel/Euston, and quoted the figure of £125million. Camden would probably cost £95million.
- He shook his head at the Battersea proposal! He knew nothing of it until last week. He cited the cost as prohibitive.
He finished by saying that although people have said that the Northern had operated 100 trains in the peak before, they rarely ever did. Anyway, that's just a few things that he went through during the talk. Sorry to go on but a lot of it is very interesting! |
|
mrfs42
71E25683904T 172E6538094T
Big Hair Day
Posts: 5,922
|
Post by mrfs42 on Jul 9, 2008 0:18:35 GMT
The procedures have been changed so that regulation doesn't happen at Camden Town nor will it happen when the train is more than a third through its journey. Was he talking in terms of time elapsed or distance travelled? The TBTC will have a platform bias (unlike the Programme machines!). Hmm. Either this is a reference to 'preferred routing' as in that used by NET (Nottingham Trams) or the information contained in the PM installation signalling notices is now plainly wrong. However, the point about terminal station platform bias is a useful one - and bears future interest with crossover clearance times. he goes round until enough of the relevant managers are on the platform so that a suspension can be implemented to repair the fault. Hmm. An interesting exposition. One to watch, I feel. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 8:01:41 GMT
Very interesting indeed. Especially more news about the split and the Mill Hill East extension.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 8:10:05 GMT
- Mr Ellis seemed to want to promote common sense. For example he wanted stock movements for maintenance to be done in passenger service.
Does that mean Antheas and the like? |
|
|
|
Post by ducatisti on Jul 9, 2008 8:11:34 GMT
Grrr... the split...
Wish I'd been to that.
Having struggled through Camden Town tube this am them all the High Barnet branch trains were going to the City and all the Edgeware ones to Charing X, the platform times are seriously slow. No-one's told me how they are going to manage to get x extra tph when each city train on Camden drops off c1/3rd capacity and takes on 2/3rds capacity and the CharingX ones do the opposite. You could add addtional cross-passages I assume, but you can't make the train doors any bigger or do anything about the peeps who got on at Barnet having to squeeze through the train to get off.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 8:35:20 GMT
If they still want to split in any way, to make it a 100% split is not good. Whenever there is a problem necessitating using Camden Town platforms and passages to overcome it, the station itself quickly becomes overloaded.
Perhaps, with a little improvement at intermediate terminating points, they could make it possible for people to reach the branch they want first, even if they then have to wait for the next through train.
|
|
|
|
Post by cetacean on Jul 9, 2008 9:07:31 GMT
Why would a split Camden Town be any different from any other interchange station on the network? There are no direct trains from, say Brixton to Bond Street, and Green Park seems to cope. Why is High Barnet to Charing Cross a special case?
|
|
|
|
Post by DrOne on Jul 9, 2008 9:09:04 GMT
- The timetables have been significantly improved lately. He was very pleased to show us the contrast between the two graphs showing train lateness and train sequences between the two timetables!
- He talked about the Northern Line Upgrade 2 and the proposal to split the line. He reckons that up to 36tph could be operated if the line was split. A new fleet of trains would be required. The split, as with most things relating to the Northern Line (and LUL !) would most probably be a political issue as well as an operational issue! (He had to fight the MPs to have the northbound split during the AM peak, but now he can boast the 98% miles operated figure!)
- Camden Town can't happen until 2013 when money becomes available. The station would be in a JLE style.
- Clapham Common to Kennington is overloaded by 600%. He despairingly said that the Clapham's island platform would have to be done in similar style to Angel/Euston, and quoted the figure of £125million. Camden would probably cost £95million.
Some incredible figures there. Too many passengers and not enough trains. I thought that the only thing that can be done to try and improve things is to run more tph through each branch, which requires a split and rebuilding the station. 36tph running through the bank branch would be a major step up from the current service level and might be enough to dissipate the crowds. It's a pain for people having to Change at Camden but what else can realistically be done to improve tph and reliability? It's not be the only station on the network where large numbers change from one line to another. |
|
|
|
Post by ducatisti on Jul 9, 2008 9:15:19 GMT
It's something that can be done, but will it actually improve matters? Will splitting the peak southbound services help the over-capacity on the southern end? I should imgaine by the time you get all the trains through to the southern end, the worst of the peak will be over?
Also, It's more than just a pain to change at Camden, it stands a good chance of preventing them delivering the tph improvement that they are claiming is on offer, whilst making it worse for the northbound.
Assuming there are gaps in the city loop service, and given that most southern-end peeps will be going to the central destinations, lots of Euston (and any other points that allow it) Reversers would seem the best way to get more trains back south quickly.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 9:56:38 GMT
Waht do you mean by the southern end, ducatisti? South of Kennington?
Running so many more trains would clearly improve matters, and making the lines much less complicated very much improves the reliability and possible speed. Those are very clear advantages.
If Camden Town is really re-built Jubilee style, I think this will be a great improvement to the current situation. I do wonder a bit about Kennington. How busy is that station at the moment with an effective split already?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 10:00:54 GMT
[/li][li] If Stepping back is reintroduced at Morden, it would be done at South Wimbledon so that the problems of 3 platforms and stepping back are reduced. [/quote] Pondering how this might work.......... [/li][li]The 95ts has been extensively troubleshooted over the last few months with doors being the primary concern. He said that door failures due to bearings and seals (which couldn't cope with the dirt and grime that the Northern has (the same type of door system is used on the cleaner Jubilee Line!) [/li][li]The AC Motors are in good condition and don't need any attention (having been Central line chief before, I expect he's relieved he's on the Northern for this particular aspect!) [/quote] Stock reliability does seem to be improving, however re. motors we're having quite a lot of problems with the PIMs (propulsion inverter module, part of the traction kit) going and it doesn't seem at this point that Alstom are entirely on top of this problem.... [/li][li]A proposal to extend the Mill Hill East service to East Finchley and then to Highgate Depot as they need a staff train to convey staff to the new control centre. [/li][li]The new control centre has been built at Highgate (to nuclear bunker standards apparently!). [/quote] This I have heard already. A lot of exisiting Northern line service control staff (of which I am one) are not keen on the move to Highgate because of its inconvenient location. So a staff shuttle might be one way to persuade people that the journey is feasible. Also I've heard (but haven't seen the building myself) that the new control room has no natural light. [/li][li]The signalling desks at Coburg Street will be progressively transferred to Highgate Control Centre and eventually when enough of the line is converted the Line controllers will transfer to Highgate. This will leave Euston as a signal cabin essentially. (Apparently the Northern and Victoria are taking bets on who will turn out the lights at Coburg Street!) [/quote] As I understand it (and I may be wrong) on the Vic the signalling function will first be transferred to the new control room while the controllers remain at Cobourg St, on the Northern I believe it will be the other way round, with the control function being the first part to move to Highgate. Also it looks likely that the Vic will go first. [/li][li] Mr Ellis seemed to want to promote common sense. For example he wanted stock movements for maintenance to be done in passenger service. [/quote] This is being done where possible - but it depends on 3 things, the move being done, the driver doing the move and also whether the train concerned is fit for passenger service. If we are moving a train from Highgate depot via Finchley Central/Euston & Kings Cross loops then across the main to Golders depot, any gain for running it in passenger service would be more than negated by the delays caused as the train has to be detrained at each reversing point. If the train is being moved by a depot driver then it wouldn't run passenger as (AFAIK) they are not licensed to run trains in passenger service, if it's being moved by a LU driver it could carry passengers. A lot of the time trains which are being stock moved are not fit for service anyway and were stopped at an out-stabling location (Edgware, High Barnet or Highgate) and are being moved back to a major depot for repair - in this case again the train could not carry passengers. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 10:02:46 GMT
Camden Town can't happen until 2013 when money becomes available. The station would be in a JLE style.
Interesting, does this mean some of the more futurist design they put out are going to be choosen then?
He talked about the Northern Line Upgrade 2 and the proposal to split the line. He reckons that up to 36tph could be operated if the line was split. A new fleet of trains would be required.
New fleet? If Camden is rebuilt then in 2013 then does this mean a new fleet around that time? Hmmmm replace the Piccadilly and Norrthern lines at the same time?
Clapham Common to Kennington is overloaded by 600%. He despairingly said that the Clapham's island platform would have to be done in similar style to Angel/Euston, and quoted the figure of £125million. Camden would probably cost £95million.
Ouch, but is that for both of the Clapham's? If so thats not as bad. Tho it does mean that the Northern is going to require major civils and alot of money in the next decade to make it suitable for the currrent traffic levels.
And did someone say that the southern part of the Northern was over supplied?
If Stepping back is reintroduced at Morden, it would be done at South Wimbledon so that the problems of 3 platforms and stepping back are reduced.
Pondering how this might work..........
I think it means that they get a train back to South Wimbledon and get off there and walk to the back of the southbound platform and set up so that when the train gets to Morden there is a driver ready to take it out straight away.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 10:08:36 GMT
[/li][li] If Stepping back is reintroduced at Morden, it would be done at South Wimbledon so that the problems of 3 platforms and stepping back are reduced. [/quote] Pondering how this might work..........[/quote] The driver of the first train will pull into South Wimbledon. A driver on the platform would jump into the back cab. If there isn't a driver ready at South Wimbledon, a manager at Morden can deal with it with time to spare as the train hasn't arrived at Morden yet. The driver of the first train will then remain on the train as it pulls out of Morden (he said that 30-second turn arounds would be feasable), and then get out at South Wimbledon. The driver would then go to the southbound platform at South Wimbledon. He says that a team from Mitsubishi have come to assist Alstom, and that the problem has been identified. He showed us some pictures of the new control room. It has a six foot thick roof (which has grass on top!) and thick steel doors. Apparently there is a shutter that comes down at night so that the bats in the woods aren't disturbed. It looked a bit clinical in the pictures, but he said that they will put some pictures and plants in there to make it more lived in. The control room looked quite large as well. He seemed to make it sound like the control function will move to Highgate at around the half way point of the new train control being introduced. One of the problems currently is that there won't be enough signallers. The signallers are shared between the Northern and Victoria and so there are economies of scale. If one line moves out they will need to have more signallers (even though they will only be signalling for a couple of years!) |
|
|
|
Post by ducatisti on Jul 9, 2008 10:28:36 GMT
Quoting Sweek
I do mean South of Kennington.
Running more trains would only clearly improve matters if more trains can be run. My concern is that Camden Town will need to cater for some very large numbers of people trying to squash onto already crowded trains whilst a large number of people get off. I think this is comparatviely unusual as most peak-time flows are one-way. The result is (and I await to see what research has been done on this) that dwell times at Camden will go up very steeply in peak hours. So you won't get more trains (or at least nothing like as many as you'd hope).
In terms of Kennington, I've never had the pleasure in the rush hour, but again as it's splitting one feed into two outgoings, I should imagaine it's less bad.
Talk of how the station might be re-built doesn't really alter the key problem that there are fundamental limits on how many people you can get off and on the trains in a station stop, and until I see evidence that that has been properly factored in to calculations, I don't see how the proposed benefits will materialise, or outeigh the inconvenience caused
|
|
|
|
Post by tubeprune on Jul 9, 2008 10:45:56 GMT
Mr Ellis seemed to want to promote common sense.
Jeff is an eminently sensible person. He and I were motormen on the same shift at Baker St (Met.) in the early 70s. He knows what goes on and he is very experienced. I'm sorry I missed the talk. Thanks for your summary Rob.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 11:09:15 GMT
Being able to get to either northern branch under normal circumstances from either central branch would be good, even if the Bank trains not going to HB terminated at GG or Colindale, and the CX trains not going to Edgware at East Finchley or MHE. Still, if the only way capacity can reasonably be improved is the split, I guess I will have to seriously consider moving to Finchley.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 11:29:24 GMT
Thanks for filling us in on the presentation Rob. I miss being able to attend LURS meetings. If Stepping back is reintroduced at Morden, it would be done at South Wimbledon so that the problems of 3 platforms and stepping back are reduced. This seems like a very sensible idea. It would also allow for late running trains to be turned very quickly at Morden in the crossover movements allow. Would toilet facilities be provided at platform level at South Wimbledon? If these trains are using up slots on the main line, then it would reduce the overall line capacity. If 36tph (see below) were to be run via Bank & Highgate, then trains would have to short turned south of East Finchley to allow this to happen. Of course this can only happen in Archway siding, which means tipping out is needed, which makes 36tph rather difficult. Since when did Americans know anything about how to run an efficient metro system? Maybe a French, Russian or Japanese consultant may be a better choice? The program machine method works well as long as trains arrive at the terminus on time and in the correct order, this makes maximum efficiency of the three track terminus layout's 2/3 parallel movements. However when trains are delayed or running out of order, then terminus operations become less efficient. I would assume that the platform bias would have the bias towards the tracks closer to the city bound tracks (sorry I don't know the exact platform numbers here). This would reduce the number of conflicting movements for when those trains depart the terminus. I think 36tph may be pushing it. Morden would have to operated with very little operating margin (although saying that, it's already operated with very little operating margin). If the operations were changed to reversing beyond the platforms using the outside tracks, and reversing in the platform in the middle track then 36tph would be more achievable. If the 36tph were to go via Bank and Highgate, then where would you do the short turns without tipping out? Maybe a change of track layout at East Finchley to allow trains to reverse N-S in the centre tracks would be a good idea? I doubt that the Charing X and Edgware branches require more than 30tph. Golders Green having a middle track should make short turning much easier. Where did this figure come from? The industry standard for overcrowding figures is that 100% capacity is all seats occupied plus 1/3 of seating capacity standing. (Thus a train with 300 seats will be 100% full with 400 passengers). I would estimate the figure as being around or just over 200%. It's also only extremely heavily loaded between the Clapham Common and Stockwell, where a lot of passengers disembark to join the Victoria Line. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 11:37:55 GMT
Where did this figure come from? The industry standard for overcrowding figures is that 100% capacity is all seats occupied plus 1/3 of seating capacity standing. (Thus a train with 300 seats will be 100% full with 400 passengers). I would estimate the figure as being around or just over 200%. It's also only extremely heavily loaded between the Clapham Common and Stockwell, where a lot of passengers disembark to join the Victoria Line. Apologies, he did say Stockwell rather than Kennington. I think he may have said oversubscribed, but in any case the figure of 600% wass used. |
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 13:58:27 GMT
Being able to get to either northern branch under normal circumstances from either central branch would be good, even if the Bank trains not going to HB terminated at GG or Colindale, and the CX trains not going to Edgware at East Finchley or MHE. Still, if the only way capacity can reasonably be improved is the split, I guess I will have to seriously consider moving to Finchley. That wouldn't improve the capacity through Camden Town though. The point of the split would be that if all the trains off the Cross run up the Edgware side and all trains off the City run up the Barnet side then more trains could be pushed through Camden. As for reversing trains at East Finchley - eeeek! I don't use East Finchley unless I have absolutely no alternative (or unless the train is double ended with 2 drivers to reverse it quickly) it causes far too much delay! Did you mean Finchley Central? |
|
Chris M
Global Moderator
Forum Quizmaster
Always happy to receive quiz ideas and pictures by email or PM
Posts: 19,440
|
Post by Chris M on Jul 9, 2008 16:26:33 GMT
I don't understand how the split would increase capacity - aren't the junctions designed so that all moves are non-conflicting?
If you run trains from both central branches to both northern branches you will get fewer interchanges at Camden, which should be better for dwell times (e.g. a person travelling from Goodge Street to Archway would be just as likely to wait for a Barnet train at Goodge Street as to change at Camden. If you send all Charing Cross trains to Edgware, the passenger has no option but to change at Camden).
What am I missing?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 16:40:39 GMT
I was thinking maybe when they say JLE style do they mean like Canary Wharf? Wide passanger area between the running lines? Expensive but maybe the only way to ensure people can change trains easily in large numbers?
|
|
|
|
Post by ducatisti on Jul 9, 2008 16:51:20 GMT
i'm with Chris M on this.
The JLE platforms can get a lot of people getting off *or* getting on. But they can't do anything about the size of the trains themselves, which is going to be the big issue at Camdn as you get both-way changes.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 19:11:23 GMT
I don't understand how the split would increase capacity - aren't the junctions designed so that all moves are non-conflicting? If you run trains from both central branches to both northern branches you will get fewer interchanges at Camden, which should be better for dwell times (e.g. a person travelling from Goodge Street to Archway would be just as likely to wait for a Barnet train at Goodge Street as to change at Camden. If you send all Charing Cross trains to Edgware, the passenger has no option but to change at Camden). What am I missing? Um, if you have 2 trains approaching on the 2 branches both of which are supposed to go to Edgware, one will have to wait to run behind the other. Then the Barnet train behind that gets held. Etc, etc............... |
|
Chris M
Global Moderator
Forum Quizmaster
Always happy to receive quiz ideas and pictures by email or PM
Posts: 19,440
|
Post by Chris M on Jul 9, 2008 20:26:58 GMT
Ah yes, that makes sense.
I guess that the timetable is designed so this doesn't happen when things are running to plan?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 20:59:55 GMT
Ah yes, that makes sense. I guess that the timetable is designed so this doesn't happen when things are running to plan? However we're talking about the Northern line here ;D |
|
|
|
Post by cetacean on Jul 9, 2008 21:50:19 GMT
Even when things are running to plan, you're not going to be able to time trains to arrive at exactly the same second. Every second of variability needs to be accounted for with extra padding in the timetable. And padding in the timetable means less tph.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 9, 2008 22:21:58 GMT
If there is sufficient lateral space and sufficient soil conditions to allow for load-bearing structures to be constructed, would it be possible to grandfather in side platforms for all four platform tunnels at Camden? You could then completely segregate passenger flows, with the current "inner" platforms used for Way In traffic and the new "outer" platforms used for Way Out traffic. With such segregation in place you would be able to eliminate a LOT of the problems that Camden experiences right now with Way In and Way Out traffic fighting for space in the passenger tunnels.
|
|
|
|
Post by amershamsi on Jul 9, 2008 23:36:31 GMT
With such segregation in place you would be able to eliminate a LOT of the problems that Camden experiences right now with Way In and Way Out traffic fighting for space in the passenger tunnels. but bang goes the cross platform interchange... |
|
mrfs42
71E25683904T 172E6538094T
Big Hair Day
Posts: 5,922
|
Post by mrfs42 on Jul 10, 2008 0:20:41 GMT
Ah yes, that makes sense. I guess that the timetable is designed so this doesn't happen when things are running to plan? However we're talking about the Northern line here ;D I So true - it's still not completely workable - so many timetable changes. Even though others have a better working knowledge/selection of timetables than I can lay my hands on (a fair selection of the past 70[just] years); I'm of the opinion that the trouble centres around two locations - Morden and Camden. If Morden were just a terminal, then the turnaround would be so much slicker. With Camden I'd critically examine E233/4 and E122 with relation to the blockjoints and control lengths. (I'm not utterly sure of where they are, having never seen a dimensioned diagram of Camden, so my opinion is subjective) Having said that the Northern (I'm fairly sure) holds the record for the longest WTT in force - 47 - I think I've got at least 4 editions of that TT - no major revisons, just minor tweaks and reprinting in different sizes. Not even the 'Drain' with it's long-lived TTs can match '47.  |
|
|
|
Post by cetacean on Jul 10, 2008 0:30:01 GMT
Structurally I think grafting anything larger than cross passages onto the side of a circular tunnel is a non-starter. You'd either need to replace the rings with much larger ones or do it all by cut and cover.
But as I said earlier in the thread, there are plenty of other interchanges on the network that cope without any such measures.
|
|
