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Summary
Pages 1-14

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From page 1...
... 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)
From page 2...
... An additional factor, although less newsworthy, is the health risks resulting from transportation emissions and the difficulty being experienced by many regions in meeting federal clean air standards. At the same time, changing demographics -- an aging population, continued immigration -- and the possibility of sustained higher energy prices should lead to more opportunities for the kinds of development patterns that could reduce vehicular travel, thereby saving energy and reducing CO2 emissions.
From page 3...
... Nevertheless, at the low-density urban fringe, for example, simply reducing single-family lot sizes -- say, from 1 acre to a quarter acre -- should reduce vehicle trip distances by bringing origins and destinations closer together. In established moderate-density suburbs and along transportation corridors, smaller lots and multiunit housing can support public transit and encourage walking and bicycling, further reducing VMT.
From page 4...
... Likewise, demand management measures, such as reducing the supply and increasing the cost of parking, can complement efforts to reduce VMT. Evidence from the Literature Finding 2: The literature suggests that doubling residential density across a metropolitan area might lower household VMT by about 5 to 12 percent, and perhaps by as much as 25 percent, if coupled with higher employment concentrations, significant public transit improvements, mixed uses, and other supportive demand management measures.
From page 5...
... Effects on Energy and CO2 Emissions Finding 3: More compact, mixed-use development can produce reductions in energy consumption and CO2 emissions both directly and indirectly. To the extent that more compact development reduces VMT, it will directly reduce fuel use and CO2 emissions.
From page 6...
... or sustained higher fuel prices that encourage consumers to purchase more energy-efficient vehicles, the savings in fuel use and CO2 emissions from developing more compactly will be reduced, all else being equal. Additional, indirect savings in energy consumption and CO2 emissions from more compact, mixed-use development can accrue from higher ownership of smaller, more fuel-efficient vehicles; longer vehicle lifetimes due to driving less; smaller homes and more multifamily units, which are more energy efficient than the average single-family home; and more efficient urban truck travel and delivery patterns.
From page 7...
... In an upper-bound scenario that represents a significant departure from current conditions, the committee estimates that steering 75 percent of new and replacement housing units into more compact development and assuming that residents of compact communities will drive 25 percent less would reduce VMT and associated fuel use and CO2 emissions of new and existing households by about 7 to 8 percent relative to base case conditions by 2030, with the gap widening to between 8 and 11 percent less by 2050. A more moderate scenario, which assumes that 25 percent of new and replacement housing units will be built in more compact developments and that residents of those developments will drive 12 percent less, would result in reductions in fuel use and CO2 emissions of about 1 percent relative to base case conditions in 2030, growing to between 1.3 and 1.7 percent less than the base case in 2050.
From page 8...
... Macroeconomic trends -- likely higher energy prices and carbon taxes -- in combination with growing public support for strategic infill, investments in transit, and higher densities along rail corridors could result in considerably higher densities by 2050. Other members believe that the curbing of large-lot development at the urban fringe or substantial infill entailed in the upper-bound scenario requires such a significant departure from current housing trends, land use policies of jurisdictions on the urban fringe, and public preferences that those measures are unrealistic absent a strong state or regional role in growth management.
From page 9...
... In the near term, the biggest opportunities for more compact, mixed-use development are likely to lie in new housing construction and replacement units in areas already experiencing density increases, such as the inner suburbs and developments near transit stops and along major highway corridors or interchanges. Coordinated public infrastructure investments and development incentives can be used to encourage more compact development in these locations, and zoning regulations can be relaxed to steer this development to areas that can support transit and nonmotorized travel modes.
From page 10...
... Other Benefits and Costs Finding 6: C hanges in development patterns significant enough to substantially alter travel behavior and residential building efficiency entail other benefits and costs that have not been quantified in this study. On the benefit side, more compact, mixed-use development should reduce some infrastructure costs, increase the feasibility and costeffectiveness of public transit, and expand housing choices where compact developments are undersupplied.
From page 11...
... 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 GHGs. Compact development also promises benefits in the form of reduced pressure for highway construction due to lower growth in VMT.
From page 12...
... • Before-and-after studies of policy interventions to promote more compact, mixed-use development: Careful evaluations of pioneering efforts to promote more compact, mixed-used development would help determine what works and what does not. The landmark California legislation to reduce urban sprawl and automobile travel offers an obvious example; baseline data should be collected soon so before-andafter evaluations can be conducted.
From page 13...
... Similar threshold information is needed to determine what development densities and land use patterns are optimal to support walking and bicycling. • Studies of changing housing and travel preferences: Studies of the housing preferences and travel patterns of an aging population, new immigrant groups, and young adults are needed to help determine whether future trends will differ from those of the past.


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