Even though self-driving cars are being focused, there are limitations to deploying selfdriving cars on real roads due to technical and legal issues. To cope with these issues, this paper describes the co-pilot system for cooperative driving with a driver through highly automated driving. According to the driver????s status and driving situations, the control authority is transferred to between a driver and the system. This paper also shows function tests of the copilot system by using PreScan simulation software and a vehicle simulator. Demonstration videos of the in-vehicle tests can be viewed at http://www.youtube.com/watch?v=cjLcUdGg1j0&list=UUgJtilxc9kY0UqaNj2jgxXg&index=2
and http://www.youtube.com/watch?v=qJ_33kQOlho&list=UUgJtilxc9kY0UqaNj2jgxXg

Keywords: Co-pilot, cooperative driving, autonomous driving, driving control authority, PreScan