I took this photo last week while on Mackinac Island, Michigan and thought it was too funny. No cars are allowed on the Island--only bikes or horses--so there are lots of bikes, so you can begin to understand why the sign was posted, but still!! I wouldn't want to try it!
West Des Moines, Iowa
(I don't care how many bikes there are, you'd have to be an idiot to try and go UP or DOWN these stairs on a bike. But if there's a sign, somebody must have tried it! Ami)