Most but not all of Chicago's train system is above ground on steel structures running above the streets. Some of it is underground but people generally call the whole thing the L, for elevated.
People can get worn out by big city life and may drift off on their journey homeward. Some may stay alert, hunched up against a chilly evening like son Andy.
I apologize for leaving no comments for so long. Work is leaving me very little spare time. There is a particular reason that doesn't bear repeating. It will continue for a while longer, then ease off. Haven't forgotten you and your work.