You can compress a lot, but you can't compress away all the space currently used as roads. The space is important for allowing sunlight and fresh air to enter b

You can compress a lot, but you can't compress away all the space currently used as roads. The space is important for allowing sunlight and fresh air to enter buildings and also acts as a noise damper in a community. Not to mention, some amount of visual privacy from neighbors. There is also the problem of emergency services (ambulances, fire trucks, police etc) being able to move around quickly. Finally, you should probably have some amount of bus/train transit in the city. Good reasons for it are bad weather, night time safety, tired or sick people, people with disabilities or long-term health problems and children. I think the best you can do is that every building is next to one one-way car lane (shared with bikes going the same way) and one bike lane (for going in the opposite direction). The road should not be asphalt but some softer, less conductive material. No street parking. If you want to own a car, you can't externalize the cost to society but build a garage for yourself. Of course, there is a maximum size on the cars that you can buy and 30 km/h speed limit on most roads. You can have mini-buses (20ish people) and subways to take people around. I think this is already a massive improvement on car centric cities. With the right distribution of retail and housing, you can have people enjoying a really nice life.