years back I read an interesting article about unfounded/justified/etc. radar setups and one was used by a town that the interstate passed through. the town fuzz would set up radar, write a few tickets, which incidentally was a large percentage of the town's budget.
it seems that this was challenged and forced to end because there wasn't even an exit for the town. :)
but there is some interesting reading in the radar speed trap web site. there does seem to be a mix/confusion with a speed trap and strict enforcement.
bumpy