Much has changed recently in how communities are designed. New urbanism has flourished, transitoriented
development (TOD) has become commonplace, and smart growth has gone national. All three
movements emphasize pedestrian- and transit-oriented design. The travel literature has expanded to
include literally hundreds of studies showing that the built environment, as measured by D variables
(density, diversity, and design), affect peopleÕs decisions to walk and use transit. Concerns over
AmericansÕ physical inactivity, obesity, and related chronic diseases have led to the active living
movement and a rich literature demonstrating how important the built environment is as an influence
on physical activity and weight status.