Originally Posted by
YVR Cockroach
I don't think you can do too much about steel on steel. Have a relatively-new (in it's 28th year or so now) light rail system in my town and any curve it goes around can be loud. I don't think the NYC subway is appreciably louder than some of the London Underground lines FWIW.
Skytrain has linear motors, which make most of the noise.