http://www.wired.com/politics/security/news/2005/08/68429

" The British government is preparing to test new high-tech license
plates containing microchips capable of transmitting unique vehicle
identification numbers and other data to readers more than 300 feet
away.

Officials in the United States say they'll be closely watching the
British trial as they contemplate initiating their own tests of the
plates, which incorporate radio frequency identification, or RFID,
tags to make vehicles electronically trackable.

"We definitely have an interest in testing an RFID-tagged license
plate," said Jerry *****, chairman of the American Association of Motor
Vehicle Administrators and director of the Vehicle Titles and
Registration Division of the Texas Department of Transportation.

So-called "active" RFID tags, like the one in the e-Plate made by the
U.K. firm Hills Numberplates, have built-in batteries, allowing them
to broadcast data much farther than the small passive tags used to
track inventory at retail stores.

Active RFID is already enjoying limited use on U.S. roadways. Under a
new program, the U.S. Department of Homeland Security is issuing RFID
tags to foreign freight and passenger vehicles as they enter the
country.

The technology is also used in electronic toll-collection systems in
the United States to automatically charge participating drivers as
they breeze past unstaffed toll booths. In the San Francisco Bay Area,
FasTrak toll transponders are also polled at readers away from the
toll booths, to determine how quickly traffic is moving through
particular areas.

...

Civil libertarians don't object to an RFID automatic toll-collection
system that "anonymizes" vehicles in databases once a transaction is
completed. But they doubt the government -- given its thirst for
intelligence -- will use such privacy-protection measures. From a
law-enforcement perspective, "there is no reason to have privacy for
anything," said Lee Tien, senior staff attorney at the Electronic
Frontier Foundation."