Safety or Revenue?
Consider the "parking to close to a fire hydrant" or corner ticket for an answer. It it was for safety, the curb would be marked, so we were not guessing where the limit is at. There you simple answer. Revenue.
Photo Radar... Speed tax.
Interesting time we live in. The governments have become the highway men, robbing from the public traffic.
Other departments are just taxing to raise revenues for there wages. They produce little benefit. We live at a time of the acceleration of the decline of the western works try at democracy. Yes, I believe we have been in decline since about 1970. There is not a single date, as different parts or functions have different peaks. Communications, with the internet is changing the world fast.