The committee’s own scenarios suggest that compact development will generate only modest reductions in energy use and carbon emissions in the near term, although these savings will grow over time. By 2050, the committee’s scenarios show that reductions in VMT, energy use, and CO2 emissions resulting from compact, mixed-use development would be in the range of less than 1 percent to 11 percent, although the committee members disagreed about whether the changes in development patterns and public policies necessary to achieve the high end of these findings are plausible. Increasing densities and mixing land uses may be more achievable in some metropolitan areas than others. The examples of Portland, Oregon, and Phoenix show that concerted public policies to control and steer growth and strategic infrastructure investment can reverse current trends toward low-density new development. Without a strong state or regional role in growth management, however, the replication of these outcomes in other metropolitan areas is unlikely. Metropolitan areas differ widely in their geographic characteristics, land area, historical growth patterns, economic conditions, and local zoning and land use controls.
Nevertheless, climate change is a problem that is likely to be more easily dealt with sooner rather than later, and more energy-efficient development patterns may have to be part of the strategy if the nation sets ambitious goals to move toward greater energy efficiency and reduced production of greenhouse gases. Compact, mixed-use development also promises additional benefits in the form of increased energy efficiency of residential buildings and reduced pressure for highway construction thanks to lower growth in VMT, among other benefits. Moreover, such development need not entail the demise of single-family housing and could, if implemented carefully, reduce housing costs while increasing housing choices. The committee, however, has not examined the other benefits and costs of compact, mixed-use development or how the trade-offs among these benefits and costs might