When I took my very excited daughter (aged 4) on the DART for the first time, we had a serious discussion about staying in your seat, not bumping into other people, speaking in a quiet voice, and ... explaining why 'seats are not for feet.'
Almost on cue, a sulk of crater-faced callow teens flopped down beside us and put their enormous trainers up on the seats.
"Mum! Muuuuuuuummmmmmm! They've their feeeeeet on the seat! Tell them they're bold, Mum!"