I can only speak for myself, but I absolutely add any form of hidden speed traps to the list. Cops know they can perform "traffic calming" by parking a marked cruiser in an easily seen location, be it on a highway or a city street. People see the car and slow down. This works anywhere it's clear they can join traffic and pull you over. The officer effortlessly achieves a local bump in traffic safety just by sitting there, and cops don't need to do risky traffic stops unless someone is really not paying attention. So that's gotta be the preferred method, right?

Meanwhile, hidden traps and unmarked cars have only one purpose: generate ticket revenue. The only mass "calming" that happens is kinda/sorta in the area where a cop has someone pulled over - and that's after the car is clearly visible.

Edit: We can also solve speeding and reckless behavior by engineering calming measures into the road itself. The freaking DOT wrote a manual for it. IMO, it's hard to view speed traps as anything more than a band-aid fix with this in mind.