The vast majority of the U.S. population-some 80 percent-now lives in metropolitan areas, but population and employment continue to decentralize within regions, and density levels continue to decline at the urban fringe. Suburbanization is a long-standing trend that reflects the preference of many Americans for living in detached single-family homes, made possible largely through the mobility provided by the automobile and an extensive highway network. Yet these dispersed, automobile-dependent development patterns have come at a cost, consuming vast quantities of undeveloped land; increasing the nation's dependence on petroleum, particularly foreign imports; and increasing greenhouse gas (GHG) emissions that contribute to global warming. The primary purpose of this study is to examine the relationship between land development patterns, often referred to as the built environment, and motor vehicle travel in the United States and to assess whether petroleum use, and by extension GHG emissions, could be reduced through changes in the design of development patterns (see Appendix A for the full statement of task). A key question of interest is the extent to which developing more compactly would reduce vehicle miles traveled (VMT) and make alternative modes of travel (e.g., transit, walking) more feasible. The study is focused on metropolitan areasmore » and on personal travel, the primary vectors through which policy changes designed to encourage more compact development should have the greatest effect.« less
This paper examines some of the problems in estimating whether transportation users pay their way using five recent and widely cited studies in urban passenger transportation costs as illustrations. All studies cited find that automobile users do not pay their way, and the three of the five that consider public transit in detail find that its passengers also fail to pay their costs. While the broad conclusions of the studies are similar, the details are quite dissimilar. The paper provides an overview of the studies to help understand why the details differ.
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