Here is a great TED talk by Jeff Speck about the economic, health and environmental benefits of having a more walkable and less car dependant city. It is described as:
How do we solve the problem of the suburbs? Urbanist Jeff Speck shows how we can free ourselves from dependence on the car — which he calls “a gas-belching, time-wasting, life-threatening prosthetic device” — by making our cities more walkable and more pleasant for more people.
If you don’t know who he is then here is his bio
Jeff Speck is a city planner and architectural designer who, through writing, lectures, and built work, advocates internationally for smart growth and sustainable design. As Director of Design at the National Endowment for the Arts from 2003 through 2007, he oversaw the Mayors’ Institute on City Design and created the Governors’ Institute on Community Design, a federal program that helps state governors fight suburban sprawl. Prior to joining the Endowment, Mr. Speck spent ten years as Director of Town Planning at Duany Plater-Zyberk and Co., a leading practitioner of the New Urbanism, where he led or managed more than forty of the firm’s projects. He is the co-author of Suburban Nation: The Rise of Sprawl and the Decline of the American Dream as well as The Smart Growth Manual. He serves as a Contributing Editor to Metropolis Magazine, and on the Sustainability Task Force of the U.S. Department of Homeland Security. His new book, Walkable City: How Downtown Can Save America, One Step at a Time, is now available in print, digital, and audio format.