I actually am speaking from experience, I saw both of those things my first week in New York. It's really not uncommon, I find it hard to believe that you've never run into shit/barf, usually when a car pulls up that has nobody in it, that's what's in there.

And this is all to say nothing about the decrepit state of the stations and cars themselves.

I've also been to Japan and experienced their trains. It's in such a different league that it's almost comedy.