Wow, now that you say that it reminds me of this book I read "Haroun and the Sea of Stories" by Salman Rushdie (did The Satanic Verses as well), because it has those type of sayings on the signs on the roads (in the book). Here are a few:
IF YOU TRY TO RUSH OR ZOOM YOU ARE SURE TO MEET YOUR DOOM
LOOK OUT! SLOW DOWN! DON'T BE FUNNY! LIFE IS PRECIOUS! CARS COST MONEY!
IF FROM SPEED YOU GET YOUR THRILL TAKE PRECAUTION -- MAKE YOUR WILL