The papers in this special issue of the Annals were first presented at the Transportation and Economic Development Conference held in Little Rock, Arkansas in March of 2006. The conference was attended by officials from U.S. Department of Transportation agencies, academic scholars and industry practitioners. This is the second of two conferences organized by the Transportation Research Board (TRB) Committee on Transportation and Economic Development that focused on the interface between these two important issues. The first conference, held in Portland in 1998, focused on estimating and explaining the effect of transportation investment on economic development. This responded to a burgeoning literature on the linkage between the two and the papers presented helped to sort out the complex interactions between transportation investment and economic development. The second conference, which is the topic of this volume, revisited this interaction, but also responded to the more demanding task of using these estimates to help make better policy and allocation decisions with respect to transportation investment. As the nation's transportation system has matured and competition for government funds has intensified, the issue is not simply whether transportation affects economic development. The questions are more complex. What mode of transportation is most cost-effective in meeting a region's transportation needs? How should a state department of transportation prioritize its transportation dollars to maximize economic growth? What are the spillover effects of building highways in one state on the economic development activities in another? What are the relative benefits of specific highway investment, such as adding lanes, building additional highway interchanges, or improving median strips in divided highways? Have tollways improved the efficiency of highways by reducing congestion? Policy makers are demanding answers to these questions, and the papers in this volume are an attempt to provide the framework if not the answer to these and other questions facing policy makers and practitioners.