My opinion: replace all cars with self driving only, then you completely avoid the hard problem of interpreting other human drivers. And you can also let the cars communicate with each other, be centrally controlled and/or have assistance in the roads. Why would anyone want to have a non-self driving car. Maybe hard/unrealistic, but it would be super cool to see this as an experiment in a smaller city center to see what happens. It would bring so much opportunity for optimisations also around traffic flow, parking spaces etc.