On Wed, 2 Mar 2016 03:26:31 +0000 (UTC), John Levine
wrote:

Hi from New York, where the unde, excuse me, subway has run 24/7 since
1904. Some services stop running after midnight, but every station
has service all night, most with 3tph or better.

How is maintenance handled? I know many sections have more than two
tracks, but surely not all of the network? Is the frequency low enough
to allow single track running?

--
jhk