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Comment by chiph | Hacker News Reader

Not a New Yorker, but what I heard was that the tunnels only have two tracks, and both are needed for daily operations. So you can't replace one when it wears out because of the service interruption. If they had made the tunnels wide enough for three tracks, they'd have a spare for when they do repairs on one of them. And give them a place to do a rolling-upgrade of old middle-20th century signaling equipment.

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Actually, NY subway has 3 or even 4 tracks portions: https://en.wikipedia.org/wiki/List_of_New_York_City_Subway_l... I think that's the reason why the New York's subway can operate during all night, because maintenance operations can happen on the other set of tracks.

Two-track subways are the norm generally, at least in the US. In fact, New York's is unusual in that many trunk lines have more than two tracks, mostly separate express tracks so that express trains can pass locals stopped at a station.

(And it is possible to shut down one track of a two-track line for at least part of the way, if you're willing to run only one train through the affected stretch of track at a time. It may condemn you to fifteen or twenty minute waits between trains, but you can do it. The Washington, DC metro has been doing this a lot lately on weekends.)

Why not just do work on it at night like they do on the tube?

New York's subway system runs 24 hours, and many residents rely on late-night/early morning service.

Is that the official reason though? "The service cannot be stopped even for planned maintenance" doesn't sound like a reasonable constraint.

They have been doing shutdowns of particular lines for planned maintenance, but almost always with replacement service in place (either other nearby subway lines, or for more isolated lines, buses). And then there are major tunnel repairs, which can lead to shutdowns of over a year. (There's an upcoming shutdown on the L which a lot of people are dreading, as there is no good replacement service of anything like the same capacity.)

There is enough redundancy between portions of the 7th and 8th ave lines to permit partial shutdowns and yet five years in they still can't seem to finish their hurricane repairs.

Which is great but it sounds like they need to compromise. Does New York have night busses?

Yep. In fact they're ridden so infrequently at night, they have a request-a-stop program after late-night hours:

http://web.mta.info/nyct/bus/howto_bus.htm

Ha, that's how most busses in the world work, at least outside large cities.

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