There is something called the Digital Recognition Network – which operates kind of like the fingerprint database the FBI maintains to keep track of criminals. The difference here is it's our cars that are being kept track of.
This is a distinction of no particular relevance in the "Homeland" (doesn't the eructation of that word make your right arm want to voluntarily snap outward and upward like a baton?) where the possibility that you might be guilty of something is sufficient to presume you are guilty.
The burden of innocence resting squarely – and perpetually – on our shoulders.
The DRN uses data gathered en masse, continuously and sans warrant or probable cause (two antiquarian ideas that just get in the way of things) by haltingly creepy devices called Automated Plate Readers – APLRs – which are cameras connected to government computers.
These APLRs are mounted by the side of the road – or fitted to the cars used by armed government workers to harass and collect.
They scan the license plate number of every passing vehicle – very much like a bar code reader at the supermarket – and cross-reference each number with DMV/government data about the vehicle wearing that particular ear tag, ostensibly to make sure its "papers" (e.g., registration, smog/safety certification, insurance) are in order.
It's like seine fishing; the trawler drags a huge net behind it that catches practically every fish and turtle and whatever else happens to be in the area; it's far more efficient from the point of view of the harassers and collectors because it's much less work and far more profitable.