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> I'd be interested to know if any US cities have deeper tunnels

Some NYC subway stations and lines were built with boring as opposed to cut and cover. 90% of the new 2nd Avenue line, for example, is planned to be bored[1]. Here[2] is an article with more details about the tunnel boring machine used -- the comments also have a lot of good discussion. Also, Los Angeles has done some boring for its new subway lines[3].

1: https://en.wikipedia.org/wiki/Second_Avenue_Subway#Construct...

2: http://secondavenuesagas.com/2010/05/14/down-the-rabbit-hole...

3: https://www.metro.net/projects/tunnel-boring-machine-tbm/

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That 2nd Avenue line looks awesome! Also, one BIG thing the NYC subway has over on the London Underground...extensive Air Conditioning! hat-tip

Only in the handful of most recently constructed stations (like the 2nd Ave line, or the new Hudson Yards extension of the 7 line). The overwhelming majority of the station network is 80+ years old and has no climate control.

DC's certainly seems bored—and some are extremely deep and therefore must be. Stations might be cut and cover but are arched to match.

The Washington Post has a good graphic [1] on which stations were cut-and-cover and which stations were bored.

You will find that most stations were actually cut-and-cover, with only the Red Line having bored segments: one starting from after Farragut North [2] and running until shortly after the Medical Center [3], and another starting as soon as it leaves the CSX Metropolitan Sub northwest of Silver Spring and continues until the terminus at Glenmont, although that station itself was built from the surface [4].

Also highly recommend the book 'The Great Society Subway: A History of the Washington Metro' [5]

[1] https://www.washingtonpost.com/graphics/local/wmata-metro-de... [2] http://www.johnreilly.us/washington-metro-transit-design-and... [3] http://www.roadstothefuture.com/Metro_Glenmont_Route.html [4] http://www.nycsubway.org/wiki/Washington,_D.C. [5] https://books.google.com/books?id=beDoAwAAQBAJ

That makes sense. DuPont and Rosslyn are insanely deep; the rest of the orange line, not so much. Thanks for the info!

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