I earlier mentioned the positive feedback loops for “people-friendly” transportation modes, like walking and transit; in short, more people = better performance. Cars, on the other hand, have a negative feedback loop: one car makes life convenient, many result in congestion which inconveniences all.

Sometime-developer, sometime-think tank-er Chris Leinberger’s forthcoming book The Option of Urbanism extends this analogy to the built environment surrounding each mode:

[A]s you build more drivable sub-urban development, you get less quality of life, In other words, _more is less_. The more that is built, the more the very qualities that attract the households to suburbia are degraded or destroyed, setting the stage for further development on the ever-expanding fringe. The American Dream, based upon drivable sub-urbanism, is elusive if growth is assumed to continue; the more you build, the more the promise is denied…

He goes on to point out that this treadmill implicitly devalues existing suburbia, and that this “disposable cities” approach to growth lays to waste vast sums of capital tied up in the existing built environment.

In walkable urban places, when more development and activities are added into the stew, more people are attracted onto the street, thereby increasing safety with numbers. The restaurants are more crowded, encouraging more restaurants and other retail, increasing rents, making buildings more valuable, raising property taxes and on and on and on. In walkable urban places, more is better. Adding more density and uses makes life better and real estate values climb higher. It is an upward spiral of value creation. If a new housing development is built, this self-re-enforcing spiral creates value for the entire district.

Two completely different paradigms of urban development — but shifting from the NIMBY former to the YIMBY latter (and avoiding the equally extremist “skyscraper fan” position of BEAN: Build Everything, Anywhere, Now) seems either difficult or impossible.