License plate scanner networks capture millions of vehicles' movements across the US
A rapidly expanding digital network that uses cameras mounted to traffic signals and police cruisers captures the movements of millions of vehicles across the U.S., regardless of whether the drivers are being investigated by law enforcement. The license plate scanning systems have multiplied across the U.S. over the last decade, funded largely by Homeland Security grants, and judges recently have upheld authorities' rights to keep details from hundreds of millions of scans a secret from the public.