the_traveler
Engineer
There are not any subways where I live, so I only see them when I go to Boston, New York, Washington, etc...To the average person you often see railroad tracks for a brief moment in time, and usually there isn't a train on them. Perhaps they are abandoned or just see a few trains a day so you always a assume when you're on the tracks there probably won't be a train.
Even though I rarely see them, I would never think of crossing the tracks to get from the northbound side to the southbound side! I also feel the 90+% of the US population that does not have subways near them would feel the same way.