Read the links I posted to LawDog's blog (he's a west Texas deputy sheriff). He mentions, and links to sources, putting readers in squad cars so they can scan automatically while on patrol:Simple solution all the illegals will know.......back into your parking spot so the tag is not visible.
Remember, that article is better than ten years old; technology has advanced since then.What you may not have been aware of -- I wasn't -- is the new designs which are intended for mobile use. In other words, they are mounted in/on patrol cars.
Impressive technology. The infra-red cameras are capable of reading license plates at triple digit speeds AND across up to four lanes of traffic AND at angles which I would not have believed capable, at up to 1,500 different license plates per minute per eight hour shift. Automatically.
Now, imagine those queries including not just a plate number, but a GPS location. And stuff the whole query into a database.
Feel like being tracked in your every movement? It's coming...with all the attendant potential for abuse (see above).