The Truth About Cars has followed the use of license plate recognition and storage technology by local law enforcement agencies, a practice that has raised alarms from civil liberties activists because of constitutional concerns over broad surveillance and the ability to reconstruct one’s movements from license plate data. Now it appears that United States Postal Inspection Service, the USPS’ own law enforcement agency has also, at least at one post office in Colorado, been collecting similar data from drivers. Though the device had apparently been operating for at least a few months, within an hour of Chris Halsne, of Denver’s...