The technological barriers might only be minor, but, the legal barriers are a LOT stronger than I think you appreciate. Number one, most of those roads are not federal. They are state, or even county (provincial or county in Canada), meaning that the federal government has zero rights to monitor traffic cameras (for example) to track individuals. While I'm sure that traffic camera data is used for some purposes, I really, really doubt it would survive any challenge if you were actually tracking individuals. Remember, you cannot even require travel papers within the country. Police have zero right to ask you for identification without probably cause. Police, while they might be able to randomly check your license plate, would have a serious issue if they were surveilling you without a warrant or probable cause for any length of time.
I think the legal barriers are a lot grayer than you think.
New Jersey stores your plate information for 5 years every time you drive by one of their cameras, and they are one of the few states with a law that says they have to eventually delete it. Many states use data "pooled into regional sharing systems".
On the other side of the country, here's a video of officers in Denver literally pulling up personal info on every car that drives past an intentionally placed cruiser.
True, people like the ACLU are fighting this. But right now, there's nothing stopping police from simply putting a number of cars in strategic locations, taking the plate from every car that drives past, and giving that info to the feds. And this is without even bringing up the automatic tolling system.
The chance for abuse of this information is massive. The security you'd need around this information is incredible and you'd have to trust that, for effectively perpetuity, people in government positions would be free of any sort of improperiety. There are all sorts of business and governmental agencies that would pay all the monies for access to this information.
No disagreement with you on that point. It's a little scary.
Also, it's common for businesses to use the same tools and information.[/QUOTE][/QUOTE]