Interesting thread to read.
My son got caught in one of the "non-existent" speed traps that don't exist (as some seem to think). I may have posted about this awhile ago - in a Maryland "construction zone" (some people may already be sadly nodding their heads). Turns out that in Maryland, when they are thinking about doing highway work, they can put up "construction ahead" signs in that area months before anything is started, and lower the speed limit by 10-25mph seemingly depending on the mood of whoever decides these things.
Son was using cruise control right around 68mph in a 65mph zone (YES! He was speeding!! 3mph over!!!). Little traffic, and as he said no construction cones, flashing lights, nothing. NO police cars. He got a mailed traffic citation (from a camera) for "speeding in a construction zone". Turns out there was a "construction ahead" sign somewhere that he passed without seeing it, and the speed limit dropped - again, without him realizing it.
I told him to just pay it (it wasn't that much), because in today's world of computerized records you want to make sure it doesn't come back to bite you in the future to have that on your record.
I looked it up on the internet, turns out Maryland is notorious for doing this. Put up construction ahead signs in an area that might have construction sometime in the future, lower the speed limit (with little signage, and nothing like traffic cones or construction trucks / equipment), use cameras to enforce it. Later, when no construction actually is going to be done in that area, take all the signage down and move to another possible future construction area.
But, of course, it isn't a speed trap.