My personal opinion is they are really more of a revenue raising exercise and just a deterrent against speeding. They really should be putting more of their spending money into extra patrol cars to be present on the road. The bright "candy" stickered cars are by far a more effective method. How many people do you see slam on the brakes when they spot on of these. I would not mind one bit being physically pulled over for speeding by either a marked or unmarked police car, instead of finding out 2 weeks later you were snapped doing a few km's over by a vehicle hidden up a back road or behind a bush