Earlier quoted context omitted.
Car oriented people seriously underestimate how many people that can be transported in a subway train and how much highway space it would take to transport the same number of people in cars. One subway line can transport more people than even the widest existing highway. https://en.wikipedia.org/wiki/File:Passenger_Capacity_of_dif... (edit: spelling)
How about if cities were built in such a way that you would just have buildings and podium being pedestrian and bike friendly with all transportation network being 1 level underground (or 2 levels) all as self driving EV pods. This may increase the no of possible 'roads' and does not sound as far fetched in terms of overall costs. Emergency vehicles can be given an exemption to operate on the podium
What you are describing is just a much less efficient, worse version of a subway.