Highways are quite controlled, compared to city driving. You have separated traffic directions, no traffic allowed below certain speed. Markings are usually in good conditions and any works on the highways are marked and secured long distance before actual work place. I was just driving new car couple months ago with lane assist, front sensors and cruise control. Only thing I needed was that it overtakes trucks on its own and that is it.

That said people do stupid things on highways, but one step is to allow only autonomous cars to drive there and we are done. In the cities and rural areas that is not going to happen because costs would be too high.

I would be happy enough if I could get self driving car only for highways. If someone expects fully autonomous vehicles that can go everywhere, that is not something I think it will going to be available in next 100 years.