Facts: Some departments or rather the cities go, it seems out of their way to generate ticket income.. Such things as placing a sign directly behind an obstruction so you can not see it, And as noted in at least one post above, Rigging the radar so it shows a higher speed than the target was traveling.
MOST honest departments give you a bit of "Grace" shall we say, this is because the speedometer in your car is NOT calibrated and certified like the police officers, and the officer can easily see from the sticker how far off HIS speedo is at 55mph (Can be off a bit).
Add to that the TV shows which have Radared a fan or a Stop sign or other "Fixed" object and found it to be speeding.. Of course a properly trained operator knows how to tell those from a legit "Target vehicle" (Heck I know a couple of ways) but it is very possible for a non-speeder to get tagged.
Thus if the town gets a rep for that king of thing, AAA will underline them in RED and your best options is... Avoid
When they see profits from tourists going around them.. They change, or they join Detroit in Federal bankruptcy court.