South Kensington station's escalator replacement project

Smoking on the escalators, wooden steps, and build-up of trash in the inaccessible area underneath them all contributed.

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.

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.)

This is one of the big missunderstandings about the HS2 line. Politicians focus on the shorter journey times, but the big win is actually increased capacity. HS2 will take the express trains off the normal line. With just HS trains on that line you can run more of them than you can if you have stopping trains sharing the track. In addition you should actually be able to run more stopping trains faster since they don't need to be fitted in around the expresses with no extended stops waiting for a delayed express to pass at a station or passing place.

> just like in any other number of countries around the world

Other cities had extra benefit of hindsight, being able to design around the problems identified in older systems (particularly London's).

> They could have used the same rails, no need for a separate line

You at least need passing places around stations in practise. In theory* you could have many extra points and pass trains between the existing two lines to work around each other instead of keeping one line dedicated for each direction (as is the case for most of the track length) even at stopping points like stations but that gets complex to manage, has more moving parts (which are difficult to maintain in the confined space), would considerably slow down flow at busy periods as the trains can't move as fast over the points (particularly if they may need to switch line at them) and will spend time waiting for an opposing train ahead to switch out of the way, the tunnel around each change point needs to be wider (for the train partly, unless you redesign them too, for maintenance even more so), … It might work for a small number of non-stop trains worming their way through the system around the majority stop-start services, but that number of services would be so small to the point where the investment would not be nearly worth the small overall gain in reduced journey times.

[†] only about 45% of the line distance of the current tube is actually underground[‡] [‡] though that includes large overground sections in the outer zones if you are only considering central London I suspected that %age is considerably higher

I think it might be worth increasing the line speed through signaling upgrades and more automation.

I guess they used a lot of water from wells, lowering the water table ?

I think they move them to sidings in central London very late in the evening, so that after the last passenger train has departed (00:30-01:00) the equipment/materials can be where they're needed in just a few minutes.

[1] https://en.wikipedia.org/wiki/London_Underground_engineering...

[2] A web search for "London Underground engineering train".

[3] http://cartometro.com/cartes/metro-tram-london/ (detailed map, showing sidings etc)

(based on TfL's draft budget for 2018-19)

Yes, the income via transportation fees are usually similar to operating expenses, but like it's the case with roads, no one should expect for it to cover the full cost of building the infraestructure, much like roads.

The tube is not a part of a closed system and delivers thousands of other societal and economic benefits that are not reflected in the fees paid by their direct users.

Also, this infraestructure can last for more than one century, as I understand is the case of London's tube.

I see this with for example the public transport in Zürich, Switzerland. Some of the light rail is very old but they are maintenance revisions done on them and things are continuously improved or replaced. Same goes for the tracks which have to be pulled out of the streets every few years and replaced. How this is done has improved tremendously over the years and materials of the track have also changed.

Another example are the electric busses that used to have a gasoline backup generator. These have now all been replaced with batteries as they became small and efficient enough to replace the generator.

Letting the bus run until it's dead will end up costing more than keeping it in good working condition.