To be effective in lane positioning, automated vehicle cameras must be able to detect the road making lines, even if the road marking is very old. Several studies have attempted to define detection threshold for various physical indicators characterizing markings, but the results are not unanimous. A specific instrumentation was carried out on a test track to generate several types of road marking lines (from very good to extremely worn). Experiments were conducted by day and night to study the detection performance of a Machine Vision (MV) system on a dry road. The road markings lines were characterized by physical indicators expressing their state of wear and their contrast with the surrounding road. The MV system was always able to detect the marking lines, including the most severe case of wear. This result raises the question of the relevance of the threshold values to be ensured for good detection by automated vehicles.