I'm going to get downvoted for this. But when I ride the train into work that time is used for extra sleep or video games.
The other trick is to keep your naps under 20 minutes. After 20 minutes you fall into a deep sleep, making it harder to wake up and leaving you feeling groggy after you do wake up.
I've certainly observed commuters set alarms on their watches/mobiles based on their expected arrival times. I find that a little rude, but nobody else every seems to comment..