If flashing your lights does the job and slows the driver down then the job is done. No need for a fine! I dated a guy who did stats for the police and he said it is known that the police don't target accident prone areas and that the stats were mostly about working out good areas to raise high $$$ amounts. If they wanted to really reduce speeding there would be more fixed cameras, speed humps, circles and traffic lights. The hand held movable cameras are there primarily to raise revenue!