Originally Posted by Jared
Does the Northern Line "reattatch" up north, or does it simply fork permanantly at Kennington station?
Anyways, I wasnt refering to either Circle (well, sort of, but differently) or Northern (the Circle Line especially is a different situation, its timing a bunch of different lines to use the same track, not timing one line to share a bunch of different sets of tracks), but rather just a line which interlines with two other seperate lines at different points. For example, Metropolitan interlining with Picadilly, and then by itself, then later 3 other lines at the Circle Line. Or the Hammersmith and City line sharing tracks with District and then by itself, before with the other three "circle lines".
I wonder if the issues with the Circle Line are simply due to such a high number of lines to co-ordinate all on the same stretch (4 lines), plus some of them must be acoomodated with other lines as well (i.e. Hammersmith+City joining with District), rather than issues like the one that would be present for the Millenium Line once Evergreen is built. There are several other cities which do the same thing the Millenium Line would. For example, in Washington DC, the Yellow Line has a (share with blue-by itself-share with orange) setup. The Blue Line also has a (share with yellow-by itself-share with green) setup. San Fransisco's BART also does something fairly similar in Oakland (actually its even more complicated, it would be equivalent to then also interlining Evergreen with Expo).
Good points. I'm sure it can be done - especially with a automated system. However, I still think from a customer service and reliability point of view, it's better to separate. Another advantage to separating at Lougheed is, if the "evergreen" extension is P3, maybe a operating concession for the entire UBC-Coquitlam line could be given out. Just a thought.
Another example in interleaving trains is on the Docklands Light Railway - but even there, the branches only run through trains on a 10 minute schedule, with every other train terminating at the junction station.
The Northern Line rejoins.
From Morden: Line splits at Kennington with trains alternating route - every seond via City, every other via Charing Cross
Just before Camden Town there is a complicated deep-level junction to allow trains from City branch or Charing Cross branch to access either Edgeware or High Barnett branch platforms at Camden Town - trains arriving via Charing Cross will alternate Edgeware/High Barnett - ditto for trains arriving via City Branch. Note the city branch takes 2 minutes longer to travel, adding to scheduling nightmare.
This system has operated without benefit of computer on a first train in system - if they get out out of turn, trains find themselves re-routed, sometimes up the wrong branch.
Here's a diagramme of the Camden Town deep-level tube junction on the Northern Line - it was built around 1924. A bit of trivia, the Northern Line carries over 204 millions people per year (more than any other line on the Underground, which collectively carries over 1 billion people per year).
Sit at Earls Court on the District line (where two branches of the District enter from the east, and 4 branches leave from the west. It's complicated and sometimes the signalmen and the station dispatcher don't always agree on where the train is going; opening the door for some amusing situations such as the famous, "this train is not going to Parson's Green"
This train is not going to Parsons Green
District Line, hometime, me and several hundred other passengers and indeed the station announcer at Earl's Court were thoroughly confused by the signal men. I hopped on the tube at Victoria thinking that I was on a Richmond bound train. At Earl's Court, the platforn indicator said Parsons Green. I ignored this as ...well, when did you last believe what the indicator at Earl's Court said? Anyway, there were several loud announcements and it turned out that the train was going to Parson's Green. Unfortunately the carriage was packed with Italian students who didn't get off. Now maybe they knew something I didn't, because they all carried on to Parsons Green, which is completely in the wrong direction to Richmond. Perhaps I should have been public spirited and said "Are you sure you all want to go to Parson's Green", but my Italian is non existent, so I didn't!
Anyway on the platform of Earl's Court, the female announcer was beginning to get a bit harrassed and apologises for the boards and enthusiastically tells us that the next Richmond train is just leaving South Kensington and will be with us in four minutes time. She then gave us minute by minute updates apologising for the confusion.
Four minutes later and the train appears with 'Richmond' on the platform indicator. We're all about to pile on the train, when lo and behold it changed to 'Parsons Green' again.
"I am sorry," the announcer says "I was told this train was going to Richmond and the signal men have changed their mind and this train is now going to Parsons Green".
The same thing happened with a train that was supposed to be going to Ealing Broadway and ended up going to Wimbledon instead.
Another four minutes and a Richmond train appeared. The announcer was now in full swing "The train at platform three is not going to Parsons Green but to Richmond. The train approaching platform two is also not going to Parsons Green but to Ealing Broadway. These trains are not going to Parsons Green despite what the signal men think."