Washington, D.C. Has a particular speed camera that generates $10,000,000 in revenue ( I mean safety) annually. The speed limit drops 20mph in 30 feet with no notice. $150 fine. I may ultimately pay it but I’m going to make them earn it.
I think in Wisconsin that would be considered a speed trap and illegal. There is an intersection where I use to live that dropped from 35 to 25 as a result police only pulled people over if they were speeding going from the 25 to the 35 zone, not the other way.