LOS ANGELES (AP) — 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. Such decisions come as a patchwork of local laws and regulations govern the use of such technology and the distribution of the information they collect, inflaming civil liberties advocates who see this as the next battleground in the fight over high-tech surveillance.