The cheapest thing to do is to build car-free city streets two stories up in the air. Running utilities in a 4m x 17m box that is completely free of dirt is pre

The cheapest thing to do is to build car-free city streets two stories up in the air. Running utilities in a 4m x 17m box that is completely free of dirt is pretty easy! You can even make the surface streets out of modular sections of prestressed concrete, which you could lift out of the way with a crane.