Abstract:Prepared for "New Urbanism and Smart Growth: A Research Symposium", National Center for Smart Growth Research and Education, University of Maryland, May 3, 2002

Several specific assumptions about the relationships between transportation and land use, some related to the causes of sprawl and some to its solutions, are commonly made by proponents of smart growth. These assumptions include (but are not limited to) the following:

• Building more highways will contribute to more sprawl.
• Building more highways will lead to more driving.
• Investing in light rail transit systems will increase densities.
• Adopting New Urbanism design strategies will reduce automobile use.

But are they right? This paper explores how well the available evidence supports these four assumptions. Although far from exhaustive, the review that follows provides an overview of the theory, research efforts, and current debates associated with each of these assumptions. Although the connections between transportation and land use at first brush seem both obvious and simple, our appreciation of the complexities of these connections increases as the research on these connections progresses: the more we know, the less we seem to know. Researchers have made more progress on some of these assumptions than others, but even in the best cases, our ability to predict the impact of different policies remains limited.