very cool idea. they will counter with RFID or turn the plate into the equiv of a qrcode. store a cryptographically secure hash of the plate number and you pretty much put an end to that, no?. if I cant get a crypto signed version of your plate, flag the the car as a scofflaw (or worse) and track it as it travels in other ways. I think we are pretty much screwed without a change in laws.
with anti-women laws in some of these states, this is terrifying.
plate number is tied to a VIN which describes the make/model. (sir, this is a
wendystoyota. where is the honda?)replies not required from the plate - plate has a specialized qrcode printed across the entire plate (infrared reflector?) with an identifier (lic + other public info?) and signed with an RSA keypair - reader can authenticate the information and a qrcode read counts as a verifiably good read
…or just ship RFID tags in the yearly inspection stickers - same cryptographic concept
none of this is hard or costly. only impediment is public rejection and we all know that can be managed.