A system in a moving surveillance vehicle operates in background mode to capture images of license plates of neighboring moving vehicles, which may occupy lanes other than the lane in which the surveillance vehicle is moving. The images are used to determine the license plate numbers of the moving vehicles, which are then checked against a database to determine whether there are any potential law enforcement-related problems that require the attention of the operator. If so, the system alerts the operator using an audible tone, visual prompt, vibration, or in some other suitable manner. The entire process, including generation of the alert can occur autonomously of the operator.