Abstract:The connection between transportation and land use lies at the center of efforts in the United States to combat sprawl through smart growth strategies. Proponents of smart growth commonly make several specific propositions about the relationships between transportation and land use: (1) building more highways will contribute to more sprawl, (2) building more highways will lead to more driving, (3) investing in light rail transit systems will increase densities, and (4) adopting new urbanism design strategies will reduce automobile use. This article explores how well the available evidence supports these four propositions and provides an overview of the theory, research efforts, and current debates associated with each of these propositions. This overview shows that the four propositions have not yet been fully resolved: researchers have made more progress on some of these propositions than others, but even in the best cases, our ability to predict the impact of smart growth policies remains limited.