[ddek]

Compound that with the depth work too.

Unlike most metro systems, many London Underground (tube) lines are bored, and at a much greater depth. The Northern, Victoria, Bakerloo and Jubilee lines go under the river; while most systems route trains over bridges.

The history of the tube is fascinating. The most recent lines (Victoria, Jubilee, CrossRail/Elizabeth) were built by a centralised authority. The older lines were built by various railway companies wanting to extend their lines into London. Over the years, railway companies dissolved and merged, leaving the fairly awkward map (the two branches of the Northern line share a platform at Camden, a stations at Euston and Kennington, and usually nothing else).

Because of the depth and lack of foresight when building anything, changing the network is nigh on impossible without major disruption.

For example, a new terminal is being built at Bank, meaning the Northern Line platform is no longer a ’bridge’ between Bank and Monument. Most of the work is done, but a substantial amount of the line will close for 3 months to finish it off. (Unfortunately, this is my commute. It’s annoying but I’m ok with it.)

[asdff]

As dramatic as line closures are, the impact to commuters can be minimized if the transit agency supplies shuttlebusses servicing the line in its place. When LA metro closed substantial sections of the Expo and Blue lines a few years ago, the shuttle routing only added a few extra minutes to commuters trips along those corridors.

[gsnedders]

You need 187 buses per hour to have the same capacity as the Piccadilly Line has on-peak (using the capacity of the New Routemaster), or, alternatively, three buses per minute. It's hard to imagine any way in which that is practically workable. I think the most frequent bus service in London currently is scheduled for 30 buses per hour, by way of comparison.

Add to this the fact that average road speed in Central London is about a third of average Underground speed, hence you're quite possibly looking at making journeys three times as long, even ignoring the extra congestion that all those buses would cause.

[ddek]

Nice idea, but no chance it works in London. It’s faster for me to go the long way round the northern than anything overground, even a taxi.

[andrewaylett]

Unfortunately, that's unlikely to work in London where there are already more people on public transport than private transport [0]. The London Underground has roughly twice the overall capacity of the London Bus network [1].

[0]: Specifically inner London, ref Page 67 of https://content.tfl.gov.uk/travel-in-london-report-13.pdf

[1]: By spaces-times-distance, ref Page 101 ibid.

[ljm]

It's like Passeig de Gracia in Barcelona, going from the green line down to the more central yellow and purple lines.

It's sometimes quicker, or at least nicer, to walk above ground than it is to take the gigantic tunnel (spanning maybe 3 blocks) between the two.