Splitting the Line

How you transfer stock from the jubilee to the northern line is there a crossover ?

Trackwise, leave Neasden to join the Metropolitan line up to Rayners Lane then reversal onto the Piccadilly line down to King's Cross then reversal onto either direction of the Northern line (Bank Branch) via the King's Cross Loop.

The resignalling upgrade only offered 24tph (the same as Picc Line before upgrade!), with 30tph south of Kennington. It struggled to meet demand south of Kennington, the most crowded section of tube line. Also struggles through Bank branch and inner area of Barnet branch. Demand growing at outer end of Edgware branch. With more trains could go to 30tph+ and 36tph south of Kennington, but more than 30tph apparently needs split of branches at Camden Town and therefore station reconstruction there. Although sub-surface lines promise 32tph over many flat junctions, so couldn't Camden grade separated junctions cope with more?

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I think it is more about junction conflicts at Camden Town since at the current configuration, Charing Cross branch trains will all go to High Barnet/Mill Hill East while Bank branch trains will all go to Edgware without clashing at that junction....

I think you will find the junction at Camden Town already allows the necessary flexibility for trains - look closely at the cutaway diagram here


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Yes for passengers there can be a scary moment if trains simultaneously approach Northbound to the separate branch platforms as they do appear to come awfully close - but thus far they have never touched.

The Camden Town problem is primarily about narrow cross platform connection tunnels and their (in)ability to handle an overnight doubling of the numbers of interchanging passengers and of course the related costs of updating the station to current safety standards.

Currently regular northern line passengers travelling through this junction on either branch/direction will tend to consult the platform departure board and make a decision on whether it is best to just wait for the next direct service to their destination or hop on the first service and change (mostly at Camden Town) although in the southbound direction some choose to change at Euston where they also have the option of adjacent Victoria line services. Inherently if passengers decide to wait a few minutes for a direct service they will do that on the platform they intend to board the Northern line so all those waiting people will be spread along much of the line.

In short this "passenger judgement" effect significantly lessens numbers of interchange passengers at Camden town as the waiting is spread along platforms on all the branches in all directions rather than concentrated at Camden Town.

Right now the pointwork at Camden Town Junction could already be set to completely separate the routes into the Mordware and Batternet branches.

The problem is that separating the two routes probably means that roughly 50% of passengers arriving at Camden Town will now need to change with obvious impact on platform dwell times as every arriving train is likely to see a rugby scrum as up to half the on-board passengers want to alight at the same time the platform will probably be thronged by equivalent numbers of interchanging passengers waiting to board.

This sort of flow would be challenging on a modern well designed spacious below-ground layout - and yes TFL do indeed have an almost shovel ready design complete with additional wide cross passageways and additional surface access but they do not have the cash, so it is probably not going to happen soon.



There is also the issue of passenger flows in/out the station which at times can be chaotic (think Camden Market) as people to struggle to get to/from escallators on the cross passange to the surface exit.

Camden Town can be set to separate the flows either way, but it is generally supposed that any split would be arranged so each line gets one of the two main depots, which are at Golders Green (on the Edgware branch) and at Morden. This would require Battersea-Edgware and Morden-High Barnet.

The split requires major works at Camden Town with a new entrance and lifts and escalators as well as cross passage improvements.

The split would also allow a big improvement in the service level on the Battersea extension.

I seem to recall the original Battersea construction plans showed they were intending to create quite long "over run" tunnels beyond the platforms at Battersea Power Station. Those plans showed the tunnels were far longer than the Battersea platform with the tunnels carefully oriented to allow future extension (seemingly towards Clapham Junction).

Obviously those ancient public plans may have since changed, but it does raise the question of whether at the end of the day a couple of trains could be safely parked overnight in those tunnels to reduce the number of early morning trains which need to be sent up the Charing Cross Branch from Morden?

I have no idea whether track has actually been installed almost through to the end wall or they are simply occupied by a super long sand drag, but from the size of the TBM used, it was obvious the Battersea extension tunnels were super wide compared with earlier Northern Line tunnels, so I guess there should be ample width in those tunnels to install a safe walking route from Batterseas station for drivers to enter/exit any trains parked up overnight. It may require lower approach speed control to Battersea whenever the over-run tunnels are occupied, but as this would be last thing at night it should not impact the final train service levels.

On weekday mornings there is definitely more city branch northbound demand from the south end of the line than for Charing Cross Branch so it must be galling for Morden to have to send quite so many trains up the Charing Cross route first thing every day. Whilst a couple of extra trains may not sound much I suspect it would be well appreciated by the usual sardine hour commuters heading for the city.

Battersea was designed with two overrun tunnels for stabling defective trains, just like Walthamstow and Brixton. When five extra trains were to be obtained for the extension, three would have stabled overnight there, with only two more sidings required elsewhere. That means one train in each siding and one in a platform. That leaves one platform free because actually they would use the spare position to leave a different place vacant each night, platform or siding, to allow for track cleaning. Now the extra trains have not been obtained, this will not be necessary. To avoid running trains up from Morden to Charing Cross branch early morning, before crowding gets bad, they would have needed very long overrun tunnels, like those for four trains in each beyond Lewisham before the current plan to surface in the Council yard!

Current 24tph service uses 96 of 106 trains. NLU2 was to order 17 more trains for 30tph service. Feasibility study for 36tph split service table said 42 more trains, but subsequently revised in business case to 44 trains (see Aug 2016 Underground News). This would provide 55 for Edgware-Battersea and 77 for Barnet-Morden, remembering that 9 of Edgware branch trains are from Morden depot.

I don't see the need for a few trains CHX branch trains a day to start from Morden to preclude a split. Obviously the physical connections will remain, and there is precedent for this sort of service on the SSR with District line trains starting from Hammersmith or C&H trains beginning their journey at Upminster. Passengers cope without this being marked on the tube map, but Kennington-Morden could easily be marked as have a limited Edgware line service if desired (either as a dashed line or via a dagger or similar symbol).
Obviously this would mean either that Edgware line drivers would need route knowledge from Kennington to Morden or it would need to be worked south of Kennington by a High Barnet line driver. This would require coordination and thought about how to get drivers to the right place at the right time, but these are routine matters for the timetabling department as is so do not preclude a split.
A significant upgrade of the interchange capacity at Camden Town is an essential prerequisite of a split (although a split is not a necessary consequence of the upgrade). This was put in black and white in the publicity material about the Camden Town upgrade and is the single biggest reason (and maybe the only reason) why a split has not yet happened despite how long it has been proposed.

I can't see a way to do this without significant underground works as the two branches of the northern line are somewhat separated with the City branch having direct change with the Victoria, and the Charring Cross Branch being off to the Northwest and at a different height; customer flow/interchange with the Victoria Line I would imagine is also significant and additional flow from the other branch might overwhelm this?

There are the old tunnels linking them which could be brought back in to use but some of them are now used for ventilation so this would prove complex, they are also fairly narrow and sloped/stepped so not ideal for modern passenger use.

The sub-surface lines have many flat junctions, but there has been no push for the services to be separated in order to achieve 32tph planned with the new signalling. The Northern has grade separated junctions at Camden so beyond 30tph should be achievable. A progressive boost to 33tph would certainly be possible, and quite likely also to 36tph eventually. Current passenger travel plans are well embedded and any split would be disruptive. Camden station rebuilding for heavy interchange with a split service will be unaffordable. Kennington services are generally already separated, apart from the peak boost to Morden line service which would no longer be necessary if the boost continues via the Bank branch to the north. A split service would improve resilience, but at great cost and inconvenience to the travelling public.

Will more than 30tph be required on any line post covid?

I think more could be timetabled through Camden in theory, but the problem is that it would fall apart in practice when trains don’t present at exactly the right moment, or even worse not in the correct sequence. This then ends up with the junction not performing on the optimum way, which then pushes capacity down.

Even now it’s quite important to focus on getting the service in the right order - just one Edgware-Kennington train running around 4 minutes late all day can cause a surprising amount of reactionary delay. Battersea might make this worse as it introduces an extra opportunity for trains to run out of order if some trains still reverse at Kennington. In an ideal world with the current setup we’d have everything go to Battersea with crews stepping back several trains to give scope for righting minor issues.