While law enforcement has been using license plate readers to track vehicles for a while, they never formed into a unified network. In fact, the Department of Homeland Security posited a 29-page document about a vehicle-tracking network, but the idea didn't go any further. Until now, that is. The Justice Department has apparently crafted a nationwide database to track vehicle movement across states. While the main aim of license plate tracking is to assist the Drug Enforcement Administration (DEA) in seizing cars and other assets while tackling drug trafficking, according to a government document seen by the WSJ, this will expand to encompass the search for vehicles that have been associated with other crimes, including killings and rape cases.