This paper presents the vision system used by the ARGO autonomous vehicle to sense the surrounding environment. Based on a pair of low-cost b/w cameras, the system is able to detect lane markings and to localize obstacles in real-time and, thanks to an electric engine mounted on the steering column, it can autonomously steer the vehicle. This paper also presents a discussion and a critical analysis of the 'MilleMiglia in Automatico', an extensive test of the ARGO vehicle that took place in the first week of June 98, when ARGO drove autonomously for about 2000 km on Italian public roads in real traffic conditions. The experience gained during this trip is described and the main problems of the vision system discussed.