If you've been on skytrain lately, you may have noticed they have started to make random announcements telling people to make sure they are holding on to a handrail at all times while on the train. Now let me tell you why this is important. It's because sometimes you'll be just outside a station and a track intrusion alarm (not audible btw, so you don't know it's coming) will go off causing your train to slam on its emergency brakes. The train will stop very suddenly. You will probably go flying forward or sideways and practically crush the hand of the poor girl next to you despite holding on to the rail (my apologies to that girl). If you weren't hanging on, well then her whole body may have been crushed.
Added bonus: when the transit officials come to check the track and make sure it is safe to send your train on its way, if you are lucky, there will be a guy on the train with a bike during rush hour who will be informed that this is not allowed and that the train will not be allowed to leave until he gets off. He will say he's not getting off and that he's only got one stop left. No one will care if he stays because the train is far from full, except of course the angry transit lady who will not let the train go until he takes the bike off the train.
Now I'm certainly all about having rules on transit, but the spirit of the "no bikes in rush hour" rule is hardly being broken when the train is not full.