I'm a lot in favour for something like this.
The issue currently are the circulars which serve two lines, rather than go to Dartford. Otherwise you could have 8-12tph Cannon St to Dartford via Greenwich pretty much isolated.
The Victoria to Dartford line is booming I've witnessed, and from Jan when it goes to midnight Mon-Sun (and becomes the only Bexleyheath line Sunday service, interestingly) use will increase a lot more. Connections at Denmark Hill for Clapham (avoiding zone 1!) and Peckham for the ELL core have no doubt helped this too.
If not 4tph via Bexleyheath, then the Sidcup line could easily feature from Victoria. It's slightly easier on the conflicts at Lewisham Junction too!
Anything that helps iron out conflicts is good. I think my thinking was to ease the number of changes that passengers from Hither Green to Sevenoaks would have to make to get to Charing Cross. Showing what a balancing act it is running SE!
Largely my thinking was based on pragatism, ie, what is possible given the context:
- no large scale tube extensions likely as these seem to have fallen from favour towards Crossrail type links.
- Further DLR extensions not that helpful as if they extend over a much greater distance there must be issues of distance versus speed/frequency of stops
- stuck with flat junctions and the nightmare layouts at Lewisham/Herne Hill - can't see how more lines or grade separation could be done with them both on viaducts and Lewisham increasingly surrounded by development
So with what we have I'd suggest:
- Short tube extensions to strategic hubs such as Peckham, Herne Hill, Lewisham, Tulse Hill to take pressure off the termini
- to interchange with a minimum of 4tph all day all week all routes (Vic-Orpington and Blackfriars-Catford Loop in addition to the routes into London Bridge). The routes have to be terminal specific or we lose the advantage of the frequency. For example, at present nice though it is for me to get to Charing X quickly, I have to plan to get that train because they're 30m apart, so if it's cancelled that's a proper pain. And it's non stop from Ladywell to London Bridge so if I want to get the DLR or LOROL at New Cross, I'm back to a 30 min spacing for the interchange stations. Turn up and go to interchange for other services that are also turn up and go seems far more useful.
I can't help think that this is the sort of thing that TfL had in mind ie they knew they couldn't give us a tube network down here but this was the best compromise. Speaking from experience I've watched demand rocket on the Vic-Orpington trains since they went 4tph - but of course it goes back to 2tph after 8pm and on Sundays and demand does not necessarily. Sunday trains can be horrendous - worse than rush hour services!
Thinking about what MIGHT happen:
If the Bakerloo does come to Hayes it should free up paths through Lewisham so maybe the TfL suggested New Cross to Bromley North link might happen. If they can get the cash to untangle the junction at Grove Park. Extend it all the way to Bromley South and you have another interchange.
Crossrail extending to a suitable destination beyond Dartford would be handy to remove further pressure from the termini and reduce journey times from those outer stops like Strood.
The Tonbridge line is suffering like the Brighton line. The only way forward that I can see is a tunnel from London Bridge to Sevenoaks to remove the long distance traffic from the inner areas entirely and that would be a big boost for SE Metro.
Long term I think TfL will get the Metro and then we should see a welcome change - I gather the Dartford and Sevenoaks lobby favours this - so it's a matter of convincing Kent proper that it doesn't affect them ie that the 4tph from London Bridge to Hayes we have now isn't going to make more Tunbridge Wells trains any more or less likely if they happen to run from 5am to 1am!
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They could tidy it up, but there is still a lot of demand for routes which clash there.
All Hayes trains fast would be one solution, but maybe unpopular and removes DLR access.
Hither Green trains via Nunhead would make sense in terms of Lewisham and the conflicts, but not where those folk want to go, currently.
Still, as mentioned above, Lewisham could become a big interchange point - but only if all services were 10tph at least and arrived at exact '50:50 intervals' if you see what I mean, meaning 3 minute connections.
Denmark Hill could be another mini-hub, changing for the Thameslink core (if that was improved through there). Also the London-bound trains at Denmark Hill seem to have some sort of PSR/TSR until the Loughborough curve which isn't the same on the down route.
The slowdown from Denmark Hill to the Loughborough Curve is a product of the signalling/junction speed. The speed falls from 60 to 20 from main line to junction; hence the signalling almost brings the train to a halt to bring its speed down before clearing for that route. Most of the trains from Denmark Hill will be starting from a station stop on a single yellow and as the junction signal is the next one this means they will crawl up to it until it clears. Coming the other way the speed is still 20 but the train will be slowing down from a higher speed as the last stop was some time ago (Elephant) so it won't crawl nearly so much.