A radio receiver is a cheap interface to implement and doesn't have the same line of sight requirements. Such a system would offer a bigger speed trap monitoring range, easier installation, and much more location flexibility.

Put one in every police vehicle. Get on a few interstate-adjacent radio towers. Roadside battery-powered installations that can easily be moved on a regular basis.

I wasn't trying to make a moral claim about the good/badness of speed traps. Just that a broadcast vehicle position system that allows the state to easily identify the vehicle will eventually be used for enforcing traffic law.