> Ultimately, retrofitting the suburbs is the great challenge of the 21st century. We need more walkability and density in their cores. Basically, we need to bring back streetcar suburbs (which is what my town is, and after going through decades of losing density, it has been transformed).

> And then cities need to become better designed for more people, especially people with families and retirees.

Ultimately, it all boils down to work. Walkability is great, being able to bike is great, but if you don't have industry in your walkable suburb, it's just there and nice and everyone still has to drive or take a train to work in the city. As long as work centralizes in cities, we will have problems like this.