Comment by TuringNYC

>> I wouldn't say thin air, exactly.

Fair but have you seen how long things take in the US? The original proposal for the 2nd ave line was in 1920 and they have only managed to deploy four stops. I read about it in the news when I was in 5th grade and still read about it now, 40yrs later. https://en.wikipedia.org/wiki/Second_Avenue_Subway

Similar for the Hudson tunnel which is supposed to allow commuter trains to function w/o the current madness...