I didn't need to take mine on the train when I was in NYC, so I can't help you there. But if you don't want a whole bag, you can buy a small cover for them that slips over and lets the seat poke through for carrying. I have both for my Boardwalk just in case, I prefer to bag it for long transits. Oh yeah, you might want to put a tennis ball or something on the bottom of the seat post, mine quickly started to wear its way through the Dahon bag, you can just throw it in the bag when the bike isn't in there.