This point is made in the book...
While fully fifty percent of children walked to school in 1969, fewer than thirteen percent do now. #walkablecity http://t.co/c5MBV5RvAJ
— Jeff Speck (@JeffSpeckAICP) July 29, 2013
At the end of Walkability, you are left with the feeling that only three things can save the world as we know it (a world that is known precisely because it is knowable—worlds can come and go without being known): the concentration of humans in cities, a sharp reduction in cars, and massive increase in trees.