First off, to get the slight snarky out of the way, octagon is exclusively a stop sign shape. The shape of SLOW DOWN could be a diamond or a rectangle, and I would be cool with yellow or orange. But a yellow octagon is right out. Unless the sign is actually some kind of Zen koan meant to induce spiritual awakening: STOP(shape) SLOW DOWN(text), especially if you are already going about 10 mph, which most of these drivers (and cyclists) are--should I slow down even further? Stop? If I stop, do I still need to slow down? What is the speed of one stopped bicycle slowing? Should I stop slowingly? Slow stoppingly? Or some kind of nightmarish driver's license test question in the making: a school bus, two bicycles, cars from both directions, and children getting ready to cross in the crosswalk (as pictured). A woman walking by carries a yellow SLOW DOWN sign octagonal in shape within the school zone. A horse and rider approach: who has the right of way? I also wonder if this sign in motion has any sensible application to cars that are also in motion--I know drivers get what is meant in this case, generally, but specifically, what are you supposed to do when you see an octagonal sign moving down the street? Stop, wait, stop, wait, stop, wait....Since one generally stops AT a particular location, I mean. OK, hungry and sleep-deprived now. Time for the weekend. Time for bike. Get up. Go ride.