Why are they called "speed traps"? If you're driving over the speed limit and get a citation, it isn't a trap. This isn't like a sting operation for vehicle the

Why are they called "speed traps"? If you're driving over the speed limit and get a citation, it isn't a trap. This isn't like a sting operation for vehicle theft with a car left parked and running with keys in the ignition. There are some states where it was found illegal to have someone slow down too fast, i.e. you can't have a 70 mph zone followed by a 30 mph zone. That would in fact constitute a speed trap of kinds, since no one can safely slow down 50 mph in an instant. The practical effect of this is 3 or 4 series of signs spaced exactly 100 ft or so, each one lowering the speed limit no more than 15 mph. It's the equivalent of a 'braking zone' on a race track, but on the street.