Modern urban car infrastructure is neither space- nor energy-efficient, but urban planning is long-term, and decisions shift all efficiency considerations in the long-term in a way that's hard to undo.
For example, transportation of people with the modern extensive net of streets would be most convenient and efficient if there was some kind of public transportation in small buses, available on demand and price being determined by regular market mechanisms. The difference between what I imagine and things like Uber would be a strong integration with existing train and bus lines, and public funding and legislation. Maybe self-driving will get us there, but there are also many political hurdles that make the less efficient option (high coefficient of cars pp) more attractive than the alternative that could provide better efficiency (and, ideally, also great user experience).
For example, transportation of people with the modern extensive net of streets would be most convenient and efficient if there was some kind of public transportation in small buses, available on demand and price being determined by regular market mechanisms. The difference between what I imagine and things like Uber would be a strong integration with existing train and bus lines, and public funding and legislation. Maybe self-driving will get us there, but there are also many political hurdles that make the less efficient option (high coefficient of cars pp) more attractive than the alternative that could provide better efficiency (and, ideally, also great user experience).