This paper describes a cyber-physical system that we called autoBAHN as well as some economic and legal aspects for the realization of the vision of a driverless train operating on openly accessible existing railroads, particularly regional branch lines. Existing autonomous trains, for example in use on airports, do not need obstacle recognition because they operate on closed tracks that cannot be accessed by humans and have no intersections with roads. The vision is to economically offer a train frequency similar to urban public transport systems on regional branch lines. This requires more, but smaller trains. As it would not be economically feasible to operate them with human drivers, they need to be autonomous. As it would again not be economically feasible to change the infrastructure (from open to closed tracks), the autonomous trains need to recognize potential obstacles on or near tracks analogous to autonomous cars. First we describe how train intervals of ca. 10 minutes—comparable to urban public transport systems—can be achieved on single-track railroads. This aims at providing significantly improved economy and comfort for the passengers by dissolving the traditional schedule concept of trains. What kind and degree of changes in infrastructural equipment is necessary was validated with the help of a discrete event simulation. The focus of the paper is on the overall system architecture of the prototypical autonomous train that we have implemented and in particular on obstacle recognition based on a lean yet powerful algorithm for sensor fusion. Finally, the current legislation in German speaking countries is surveyed for the assessment of whether an autonomously operating railway system can become reality in the future.