Onesome: No Bicycles-- on the Freeway? Ya' think? Do you have a better 'sign of the times' for the gang? I'm thinking along the lines of "Coffee is Hot", if you catch my drift...
Hm, I'm not sure if this counts: designing multiple choice quizzes with the occasional Really Obvious Wrong Option, yet having students mark that one anyway.
Twosome: on the-- flip side, how about a sign you think needs to be in place? ...maybe something like one that lights up and says, "Get out" after you pull the fire alarm in a building?
It's not necessarily a sign, but I think people should stop wearing dark clothes when walking outside after dark. Or at the very least, they should plaster on some reflectors.
Threesome: Freeway--, friend or foe? Utility or necessary evil? Extra points if you have to use the Pennsylvania Turnpike or happen to live in Los Angeles!
It depends on the situation and especially the other drivers around you. I don't have to use the freeway to go to work, so this isn't exactly applicable--but I also live in a fairly out of way place so there isn't very much traffic to make driving too much of a headache.