Regular readers are aware that my hopes for sustainability are largely bound up with cities. By the simple act of bringing people together in close proximity, cities encourage diversity, health, innovation, and economic growth. They are the proving grounds where we will test new, more sustainable patterns of work, play, and mobility. I wrote a series of posts about this a while back called “Great Places.”

To me, one of the key barriers to truly green and enjoyable urbanism is the continued domination of urban spaces by cars (and parking). Cities, especially cities that grew up in the post-WWII era, are designed for cars; people scurry around on the margins, perpetually nervous about their safety. There’s really no way around this as long as car ownership is required to attain a convenient level of mobility, which it still is in the vast majority of cities.

Most public-transit alternatives to personal cars require a substantial investment of time and cognitive energy. Most people, like it or not, just want things to be easy. And so traffic congestion remains the rule in cities, even cities with robust public transit systems.