No, they don't. That's an abuse of their authority.
Cops who want to see why citizens increasingly hate cops should look in the mirror.
Posted speed limits are ridiculously low in order to entrap citizens and get them to pay fines that add to the town's coffers.
I usually drive signicantly over the posted speed limits when no cops are in the vicinity, because it is actually unsafe to drive at the speed limit. For you will have tailgaters every time.
Once in a while, I get caught in a speed trap, but the WAZE app is very good about warning you about those. But ironically you need to use your cell phone while driving to warn other drivers about the speed trap.