Why would you even want to?
Seems to me like porn should stay a private enterprise. It shouldn't branch out to places where every pervert can watch his favourite scene whilst dry humping the back of the seat on the bus.
But I'm just the Mary Whitehouse of the 21st century so you really shouldn't listen to me.
By all means dry hump if needs be, fuck it wet hump if you like. NO whip it out and cum over the other passengers shoes ... that's fine.