Sudden slow downs. Why

Not necessarily. The radar is pretty fast, but it's being operated by a human being (who probably has slower reflexes than YOU do) and even at best it still takes a second or two to process, during which time it is still measuring your speed. If you slow quickly as soon as you see a cop, you can easily bleed off 5 - 10MPH or more before he actually gets a measurement of your speed. Oh, and that's buttuming that the cop doesn't estimate your speed first. That is, a cop can't use radar or lidar before he suspects that you are speeding. So buttuming you came around a blind corner and a cop measured your speed as soon as he could see your car (before your entire car was visible for at least a few seconds), then the ticket should be tossed by the judge, as there was no probable cause for the cop to use speed measuring equipment on your car until several seconds after the cop could clearly SEE your car.

What annoys me is when the cop parks out in plain view on a long straightaway and traffic flowing 20 over suddenly slows to 20 under. I mean, yeah, a cop is watching you, but 45 in a 65 is borderline illegal, also!!! -Dave