In which case, it's not the Police then, Howard..!
The word 'speed trap' harks back to the days when motor cars were still new. I hardly think a fluorescent yellow box on a pole is a 'trap' nor indeed is a white van with livery on..
Just to come back to the Enid Blyton character for a moment, the term refers to that person and that person only. To use the term in a generic way, usually with some sort of emphasis is lampooning anyone that is in the Police and, as many have said, disrespectful.
Why don't you simply say 'the Police'..? You don't have to describe them in any other way unless (a) you have an axe to grind, or (b) you have a baseball cap on backwards and wear a hoodie..!
