Bob, I know people that have been "done". Its not how fast you are going at the point of the camera (though apparently they can be used as static speed traps too), its how long it takes to go between cameras. Do 60mph between and stop on the hard shoulder for a minute if you want...
So true, Al. A number of people think that the cameras compare your speed as you pass each one to get your average. They are supposed to measure the time you took from one camera to the next and then calculate "average" speed. Either way, a good revenue earner for the Government!!