Overreaching unions. Layers of consultants. Squabbling jurisdictions. And as the article mentions, the fact that they build so infrequently that they essentially have to skill up from scratch every time and can never optimise or learn from previous mistakes.
There's a lot of information about this out there but that about covers it I think. Here's a nice quote from a nytimes article:
"Trade unions, which have closely aligned themselves with Gov. Andrew M. Cuomo and other politicians, have secured deals requiring underground construction work to be staffed by as many as four times more laborers than elsewhere in the world, documents show."
https://www.nytimes.com/2017/12/28/nyregion/new-york-subway-...
The major issue seems to be that construction unions do not negotiate with the public authorities paying for it, but the construction contractors, and the contractors are more than happy to just pass along the cost and pad their margins. https://www.nytimes.com/2017/12/28/nyregion/new-york-subway-...
It's taken so long that projected peak system congestion _with_ the extra line is predicted to be worse than it was without the line when it was funded, even though its capacity is about 10 passengers per second through the core. The lines it's "relieving" are hopelessly over-capacity, so it will fill immediately when it opens AND it's expected to increase total usage because hey, there's this line from outside London right into the core, why not live there and commute...
But certainly it's a comparable problem, in the sense that e.g. Crossrail had to "thread the needle" fitting the new tunnels between existing escalators and the Northern Line underground rail tunnel that both remained in use during construction.
This seems pretty reasonable to me, to be honest. And most of it is done ahead of schedule isn't it?
How quickly do you think it should take from zero to a 21 km tunnel underneath London? It seems insanely fast now I think about it.
It's the biggest civil engineering project in Europe, or so they say. And a big part of that is because you don't just massively increase transport capacity into the core of a major metro area. That would just overload all the other infrastructure.
The BBC's documentaries on the Crossrail are great at showing all of the complexity of building the thing and dealing with historic buildings, super-hard brickwork, archaeological discoveries, concert halls and more.
Plenty of other cities worldwide use tunnel boring and get far better cost per mile than in the states. That's not the issue.