ANNAPOLIS, Md. (AP) — The American Civil Liberties Union is asking police agencies nationwide for details on how they store data captured by automatic license plate readers, which authorities say help fight crime and terrorism and are not used to stockpile information on all drivers.

A top concern, the ACLU says, is how long the location and movements of people are kept on file after cameras mounted on patrol cars or along roads on telephone poles and bridges photograph license plates. ACLU affiliates in 38 states and the District of Columbia have joined in asking for the information.