I'm a great sleeper. I can fall asleep more or less anywhere and stay asleep with no problem. I sleep on the metro all the time and never sleep through my stop. I halfway wake up at most stops, figure out more or less how much farther I have to go, then fall asleep again. This is made easy by visual clues in both directions - on the way home, everything's aboveground so I can always tell where I am; going to work, the doors at my station open on one side after three stops in a row of opening on the other side, so I can tell when we get there.
Or that's how it used to work. In the last month or so, I've slept through my stop twice. One night I was coming home and decided it would be a good idea to doze off a stop and a half before my stop; when I woke up again, the doors were closing at my stop. Then this morning I fell asleep and woke up when the train was *three* stops past work, the doors were already closed, and the driver was announcing the next stop.
I think I need to brush up my sleeping skills. (Or I could stay awake, but, I mean, cmon now. That's just silly.)