> If true self-driving cars ever become a reality, there's going to be a big demand spike for more and bigger roads

Why would there be a need for more roads? It seems like the opposite would be true: self-driving cars don't need safe following distance to each other. They could form a massive train (the more you look at self driving cars, the more they look like trains), with 1 inch of space between each vehicle. Highway lanes are so wide, that small self-driving vehicles could sit 2-across, with an inch of space between them. On-demand self-driving-cars could cut the total number of cars on the road by a big factor. Self-driving cars might never crash, so they won't need all those tons of safety equipment that each car lugs about, saving a pile of net energy.