It's always puzzled me that we let old folks with their trolleys and fumbling for bus passes etc. on first, and mums/dads with buggies. Obviously it takes them longer to board, and the buggies, trolleys then inevitably clog things up. If they let me go first I'd be on, paid and out if their way in an upstairs seat before they've even got their money/pass/ticket out. I still always let them on first though. Manners innit?