Clarification, please
Are you saying that those caught chose to speed? Or that there is some little-known quirk of the law that says you don't have to pay the fine?
If (as I assume) you're saying that people are free to not speed, you must not have heard of the red light monitoring cameras. Studies by citizen groups have proved that when they go up, the length of the yellow goes down. And the ones that are for speeding are typically located on highways where the posted limit is significantly lower than local Department of Transportation studies have recommended.
