if there is a "no U" sign

i guess you can't get out of this. If the sign is not big or not clear or color faded, you can argue in a court(take picture. be prepared). usually the judge is very reasonable. If you really have a reason, you will be off the hook. I made two tickets go away :-). otherwise, just say you were in a hurry , did not see it. they will give you some break, not entirely.