Determining that a vehicle is speeding in violation of a speeding regulation. Capture a timed sequence of image frames of the target vehicle at known capture times of the vehicle, identify corresponding images of a license plate of the target vehicle in the image frames, recognize an alphanumeric character of the license plate in the corresponding images of the license plate, measure respective image dimensions of the alphanumeric character; and responsive to a change between the image dimensions of the alphanumeric character, compute a speed of the target vehicle relative to the camera. Font style and font size are stored of one or more standard vehicle license plate.