OCR providers usually suggest a minimum of 3 pixels per 1 cm to achieve high reliability rates (above 95%). Considering an European standard license plate with a character stroke of 1cm, to fully cover 4 meters of the road (3,5 meters lane width plus 0,5m overlapping) it would be required an image sensor with resolution of 400cm x 3pixel/cm = 1.200 pixel.
Additionally, vehicles changing lanes can be detected if a megapixel ANPR camera that fully covers 400 cm of the road (3,5 meters lane width plus 0,5m overlapping) is used.
Atalaya ANPR camera from Imagsa Technologies uses a 2048x1024 pixels sensor, to fully cover 7,5 meters of road width. Hence, it simultaneously detects multiple vehicles on 2 Lanes of traffic.