In all the postings and blogs regarding self driving cars and automatic driving systems I have not seen discussion about an obvious solution. For highways ( and I really mean the Interstates) would it not be an easy solution albeit expensive to embed guidance systems in the road infrastructure? Something the car could use to reliably position itself. It seems like this would be much easier to design than the complex array of cameras, gps and radar being utilized now. I guess forward sensing to stop would still be needed but the system could be designed to provide position information.