Here in Australia, especially Victoria the govt. rely on revenue from speeding fines, they actually budget for it. The coppers are specially trained and have quotas to fill or be replaced, same with the private camera operators who are very enthusiastic at their job, starting at 5AM in our area and go until 11PM sometimes.
A new toll way was just opened ( it was supposed to be free ) and they spent alot of time setting up speed cameras at regular intervals and kept the max. speed low knowing that people will speed.