[barneybooroo]

It is amazing how what might seem like fairly routine engineering jobs become completely nightmarish once you do it underground.

I used to commute via Goodge Street every day. A few years ago they replaced the four lifts (in twos so that two were still in service) which ultimately took two years. I could never really fathom what it was that specifically slowed that down so much but hey the lift congestion every morning was fun

[jaclaz]

From experience in construction (both open air and underground) the key difference is not about something being underground, but rather with something being "in use" while the building site is doing the whatever work is needed.

Particularly when it is something of public use, be it a highway or a railway, the amount of precautions, limitations and safety risks (in some cases for both the public and the workers) grows incredibly, slowing down considerably any intervention.

[bartread]

This happens in software too.

Over the last 4 years our team has achieved a lot: huge numbers of valuable changes and improvements to our platform. But it's been much harder than it might otherwise have been because we've had to make those changes with the systems in use. Had we started from scratch, or been able to take downtime, there are a lot of projects we could have done much more quickly, but we had to keep the business running - it is, after all, what was and is paying all of our salaries.

[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.

[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.

[lbriner]

Underground does present challenges but there are many reasons why these seemingly straight-forward jobs take time. You need qualified/certified workers, a load of up-front work related to ventilation, noise, structural movement, surveys etc. Some of this can only be done in engineering hours.

You have issues around the lack of space in central london for work vehicles, the need for removal of rubbish which can't block up emergency staircases, exits.

Then add in the challenges of unknown unknowns and needing to be able to revert any change quickly that can't be done to plan so you don't end up with a closed station and you start to get there.

I assume they had to do them 1 at a time to completion as well?

[ljm]

I like taking the stairs at those stations. I think Russell Square is the station with a particularly long staircase; 200 or more steps.

If you like epic spiral staircases you can't go wrong in London.