5
Potential Effects of More Compact Development Patterns on Vehicle Miles Traveled, Energy Use, and CO2Emissions

In this chapter, estimates are developed of the potential magnitude of reductions in vehicle miles traveled (VMT), energy use, and carbon dioxide (CO2) emissions from more compact, mixed-use development, looking for ward to 2030 and to 2050. The chapter begins with a brief summary of two previous well-known estimates of the national-level impacts of more compact development. Then, the committee’s own development scenarios are elaborated, and results are summarized. The primary focus is on likely changes in travel behavior and related effects on VMT, energy use, and CO2 emissions. In addition, more compact development is likely to reduce energy use and CO2 emissions by improving the energy efficiency of buildings, a topic that is also briefly considered. The third section provides a more general discussion of other benefits and costs of more compact, mixed-use development patterns; no attempt is made to quantify these benefits and costs, which was beyond the scope of this study. The chapter ends with a series of findings.

PREVIOUS NATIONAL-LEVEL ESTIMATES OF REDUCTIONS IN TRAVEL, ENERGY USE, AND CO2EMISSIONS

Analysis Structure and Key Assumptions

Any estimate of the effect of compact, mixed-use development on future VMT, energy use, and CO2 emissions requires three sets of assumptions. The first concerns the quantity and characteristics of the new housing



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 144
5 | Potential Effects of More Compact Development Patterns on Vehicle Miles Traveled, Energy Use, and CO2 Emissions In this chapter, estimates are developed of the potential magnitude of reductions in vehicle miles traveled (VMT), energy use, and carbon dioxide (CO2) emissions from more compact, mixed-use development, looking forward to 2030 and to 2050. The chapter begins with a brief summary of two previous well-known estimates of the national-level impacts of more compact development. Then, the committee’s own development scenarios are elaborated, and results are summarized. The primary focus is on likely changes in travel behavior and related effects on VMT, energy use, and CO2 emissions. In addition, more compact development is likely to reduce energy use and CO2 emissions by improving the energy efficiency of buildings, a topic that is also briefly considered. The third section provides a more general discussion of other benefits and costs of more compact, mixed-use development patterns; no attempt is made to quantify these benefits and costs, which was beyond the scope of this study. The chapter ends with a series of findings. previous national-level estimates of reductions in travel, energy use, and co2 emissions Analysis Structure and Key Assumptions Any estimate of the effect of compact, mixed-use development on future VMT, energy use, and CO2 emissions requires three sets of assumptions. The first concerns the quantity and characteristics of the new housing 144

OCR for page 144
145 Potential Effects of More Compact Development Patterns and commercial developments that will be built between now and the end of the forecast period. How many new housing units are likely to be built, and how many of those new units will be in compact, mixed- use developments? The demographic, economic, and political factors that affect the quantity and character of new development were the subject of Chapter 4 of this report. The second set of assumptions concerns the number of vehicle miles driven by households in different types of developments. Will the number of vehicle miles driven by the average household in existing types of developments continue to increase as it has in the past, or will it slow down or stop? And how many fewer vehicle miles will households in the new compact, mixed-use developments travel? The empirical evidence on the reduction in VMT attributable to compact, mixed-use development was summarized in Chapter 3 of this report. The committee did not account for any behavioral feedback effects, but the sensitivity of key assumptions is tested. If estimates of reductions in VMT are to be translated into savings in energy use and CO2 emissions, one must make a further set of assump- tions about the fuels and fuel economy of future vehicles. Will cars continue to be powered by internal combustion engines or hybrids running on fossil fuels, or will all-electric, hydrogen, or other more novel forms of propulsion emerge to play a significant role? And whatever fuels are used, what will be their carbon content and CO2 emissions per VMT? The savings in energy and CO2 emissions from the use of vehicles that do not use fossil fuels will depend in part on the energy source. For example, the electricity to run an electric vehicle may be generated by a CO2-emitting, coal-fired electric plant. Ideally, the full life-cycle costs of alternative energy sources should be considered in computing energy and emissions savings. Previous National Estimates Two previous studies attempt to estimate the reduction in VMT that might result from more compact development. In Costs of Sprawl—2000,

OCR for page 144
146 Driving and the Built Environment Burchell et al. (2002) produce comprehensive estimates of the various costs of sprawl in 2025 by developing scenarios of controlled growth and uncontrolled growth (business-as-usual sprawl) and then comparing the differences. One component of the cost of sprawl estimated in this study involves the extra travel costs associated with increased travel in spread-out areas, which are based on VMT estimates for the above two scenarios. The changes in land development in the study’s controlled-growth scenario are complex, which makes it difficult to compare this study with others. Controlled growth cuts sprawl in all nonurban counties by 25 percent compared with their historic trends. For intracounty sprawl, growth is directed toward more urbanized development within the county by increasing the density of this development by 20 percent. Shifting growth by 2025 from sprawling to controlled-growth counties moves 11 percent of new housing (2.6 million households) and 6 percent of jobs (3.1 million jobs). To estimate travel effects, Burchell et al. estimate a regression model that predicts personal miles of travel as a function of development type (urban, suburban, exurban, rural), income, gender, and household size. Separate models are developed for personally owned vehicles and transit. The models are calibrated by using individual data from the 1995 Nationwide Personal Transportation Survey, but the variables describing the built environment of households are limited, and there is no control for self-selection. (Perhaps as a result, these models explain a small share of the overall variance in the data: the models have an adjusted R2 of about 0.06.) The models predict that shifting residences and jobs from the sprawl to the controlled-growth scenario would reduce person miles of travel by about 4 percent overall. The 4 percent reduction results from combining a 5 percent reduction in travel in personally owned vehicles with a 19 percent increase in travel by transit by 2025. In a more recent study entitled Growing Cooler, Ewing et al. (2007) develop an estimate of the amount of CO2 that could be reduced by encouraging much greater compact development between 2005 and

OCR for page 144
147 Potential Effects of More Compact Development Patterns 2050. They estimate that 89 million additional dwelling units and 190 billion additional square feet of nonresidential space will be built between 2005 and 2050, or about a 70 percent increase over the existing residential stock. They then assume that between 60 and 90 percent of all new development will be compact. The authors further estimate that VMT per capita will be 30 percent less in compact than in conventional developments [primarily on the basis of the earlier Ewing and Cervero (2001) meta-analysis].1 They also project that VMT within urban areas will account for four-fifths of total VMT by 2050, noting that compact development will affect urban (not rural) VMT and that the United States will become more urbanized by 2050. Finally, the authors estimate that the CO2 emissions savings will be about 90 percent as large as the VMT reduction, attributing the difference to CO2 penalties associated with lower vehicle operat- ing speeds in more compact areas, among other reasons. By multiply- ing out these factors, the authors arrive at an overall reduction of 7 to 10 percent in future U.S. transportation-related CO2 emissions resulting from more compact development. Comparing the estimates of the above two studies would require limiting the Ewing et al. estimates to the VMT reduction resulting from compact development and ignoring the CO2 reduction factors described above. Doing so results in an estimated VMT reduction of 12.7 percent by 2050 from Ewing et al. compared with a 4 percent reduction in personal travel in private vehicles by 2025 from Burchell et al. The estimates were derived with totally different methods and apply to different time periods. That said, they appear to be in the same ballpark. If Burchell et al.’s estimates were extended another 25 years, they would presum- ably be of similar magnitude in 2050 to those of Ewing et al. 1 The Ewing and Cervero (2001) meta-analysis finds an elasticity of VMT with respect to accessibility of −0.20. Ewing et al. increase the elasticity estimate to −0.30 to account for the absence of compactness measures other than density (e.g., land use mix, availability of transit) that should also reduce VMT.

OCR for page 144
148 Driving and the Built Environment committee’s scenarios and results Assumptions and Scenarios This committee developed its own estimates of the potential savings in VMT, energy use, and CO2 emissions from more compact, mixed-use development, drawing on its review of the literature and the papers commissioned for this study. The committee’s estimates are focused on residential development patterns only.2 Two scenarios were developed relative to a base case. The base case assumes that current land use and travel patterns, which are heavily weighted toward suburban development and automobile-dependent travel, will continue into the future, producing a further decline in the overall average density of metropolitan areas, while the two alternative scenarios assume more compact, mixed-use development patterns. Two forecasting periods are analyzed: the first to 2030 and the second to 2050. The starting point selected was 2000 because firm data exist on the number of households (from the U.S. census) and their travel patterns [VMT per household from the 2001 National Household Travel Survey (NHTS)] (Hu and Reuscher 2004). Uncertainties grow over time. For example, the 2050 estimates are less certain than the 2030 estimates because of uncertainties as to the numbers of households,3 their demographic and socioeconomic composition, and technolog- ical innovations that could change the nature of travel (e.g., extent of 2 The committee recognized the importance of commercial development, in particular that in employment subcenters that are readily accessible to housing. More compact development would presumably create more demand for commercial space to serve such developments. Nevertheless, addressing the uncertainties with regard to both the amount and the location of new commercial development (in existing or new employment subcenters or in strip development) and performing the modeling required to estimate potential reductions in VMT from improved access to commercial space were beyond the resources of this study. 3 For 2030 the range of household projections is relatively small. As projections are extended further into the future, a growing proportion of those who will be of household-forming age are yet to be born, and their numbers depend on future fertility rates. As a result, the uncertainties multiply and cumulate, and the range of the household projections becomes wider (Pitkin and Myers 2008).

OCR for page 144
149 Potential Effects of More Compact Development Patterns hybrid vehicles, introduction of new technologies such as fuel cells, use of alternative fuels with sharply reduced carbon content). Nevertheless, the longer time frame is shown to demonstrate that new development pat- terns (i.e., more compact, mixed-use development) can make a difference, and even the very small percentage changes by 2030 compound to more significant ones by 2050. At the same time, significant changes require decades to unfold because of the durability of the built environment. The base case and the two scenarios all assume the same growth in the number of housing units during the forecast periods but differ as to the proportion of new and replacement units that will be built in compact, mixed-use developments. The increase in total housing units is based on the projections provided by Pitkin and Myers (2008) in the paper commissioned for this study and is reported as a range, with a broader spread in 2050 than 2030 because of the greater uncertainties.4 The base case assumes that all new (and replacement) housing will be built at the average density of new development during the 1990s, which was about 30 percent below average density levels at the end of the decade.5 The two alternative scenarios channel some fraction of the new growth from new household formation and from replacement of existing housing units into more compact development.6 Scenario 1, 4 The growth in new households closely follows Nelson’s projections to 2030 (Nelson 2004; Nelson 2006) and extends them to 2050 (see Tables 4-3 and 4-4 in Chapter 4). Estimates of average annual replacement units are considerably lower than those of Nelson (2004) for the reasons noted in Chapter 4, with the result that 2030 total estimates of all new units with potential for more compact development are more conservative than Nelson’s. Nelson also believes that all new and replacement housing units will be more compactly developed (e.g., as attached or small-lot units) (see the discussion in Chapter 4). 5 See Appendix C for a more complete discussion of density trends in metropolitan areas. Table C-1 summarizes three ways in which the density of new and existing development can be computed from the two primary data sources—the National Resources Inventory and the U.S. Census of Population and Housing. The average of the three estimates of the density of new development is used here (i.e., new development is about 70 percent as dense as the average density at the end of the 1990s). 6 Where replacement units are involved, either the new unit could be built more compactly than the one it replaces (e.g., a single unit could be split into two) if zoning permits, or the homeowner could sell the replacement unit and move to a unit in a more compactly developed area.

OCR for page 144
150 Driving and the Built Environment the low-end estimate, assumes that only one-quarter of the new growth will be more compactly developed (i.e., density will be doubled from the baseline assumption of a continued decrease in density), similar to the shares assumed in Costs of Sprawl—2000.7 Scenario 2, the high- end estimate, assumes that three-quarters of the new growth will be more compactly developed, roughly the midpoint of the estimate in Growing Cooler. All three scenarios assume that the driving patterns of those who live in existing housing will remain unchanged at 21,187 miles per house- hold per year, the figure reported in the 2001 NHTS (Hu and Reuscher 2004). Between the 1990 Nationwide Personal Transportation Survey and the more recent 2001 NHTS, VMT per household rose by about 1.4 percent per year, but it appears reasonable to expect the growth to slow or stop given the aging of the population, the saturation of vehicle ownership (ownership levels nearing, on average, one vehicle for one licensed driver), and smaller household sizes.8 The sensitivity of the results to this assumption is tested later. Those living in new housing in more compact developments— with higher densities, more walkable neighborhoods, and good transit access—are assumed to drive less. Scenario 1 assumes a 12 percent reduction in household VMT for new housing built at double the aver- age density of existing housing. Scenario 2 assumes a 25 percent reduc- tion, which brackets the reductions at a regional scale found in the literature (see Table 3-1 in Chapter 3).9 A third scenario was considered, 7 The share assumptions are similar, but the methods for computing the effects are very different. Burchell et al. (2002) use a regression modeling approach to estimate travel effects. 8 The 1990 Nationwide Personal Transportation Survey reported annual VMT of 18,161 per household, implying an average annual growth rate of 1.41 percent between the 1990 and 2001 survey years (Hu and Reuscher 2004). 9 The 12 percent reduction comes from the Brownstone and Golob (2009) study, which cal- culates the reduction in VMT from a doubling of density. The larger “best case” 25 percent reduction comes from the Bento et al. (2005) study, which calculates the reduction in VMT from changes in population centrality, jobs–housing balance, supply of transit, and other built environment and transportation variables. See the discussion of both studies in Chapter 3.

OCR for page 144
151 Potential Effects of More Compact Development Patterns which assumes only a 5 percent reduction in VMT for households living in more compact developments, the lower bound of the elasticity estimates in the literature (see Table 3-1). Those living in new housing built at lower-than-average densities, continuing the recent trend, are assumed to drive more than existing households. The assumption is that the majority of this housing will be built at the urban fringe, with little access to transit and longer trip distances on average.10 The energy use estimates in the committee’s scenarios use data from a recent National Research Council (NRC) study (NRC 2008), which develops several scenarios to estimate the maximum practicable penetration rate for fuel cell vehicles and alternative technologies to reduce U.S. oil use and CO2 emissions to 2050. The committee uses the reference case from that NRC study.11 This scenario assumes improvements in gasoline internal combustion engine technology to meet the new cor porate average fuel economy (CAFE) standards by 2020, expected in compliance with the Energy Independence and Security Act of 2007.12 After 2020, fuel economy continues to 10 More specifically, Scenario 1 assumes that the annual household VMT of new housing built at lower densities would be 8.4 percent higher (12 percent 0.70) than the average for existing households, or 22,967 (21,187 1.084) VMT per household per year. In this scenario, households living in new housing built in compact developments would travel 12 percent less, or 20,211 (22,967 0.88) VMT per year. Similarly, Scenario 2 assumes that the annual household VMT of new housing built at lower densities would be 17.5 percent higher (25 percent 0.70) than the average for existing households, or 24,895 (21,187 1.175) VMT per household per year. In this scenario, those living in new housing built in compact developments would travel 25 percent less, or 18,671 (24,895 0.75) VMT per year. Both scenarios assume that the new housing built at lower densities would be 70 percent as dense as the average density at the end of the 1990s (see Footnote 5 for further detail). 11 The reference case is based on projections from the Annual Energy Outlook (high gasoline price scenario) to 2030 and from an adaptation of the Argonne National Laboratory’s VISION model for 2031 to 2050. The reference case assumes that gasoline prices rise to $3.19 per gallon in 2020, $3.54 per gallon in 2030, and $3.96 per gallon in 2050. 12 Achieving this target means raising the average miles per gallon (mpg) of new cars and light trucks to 35 mpg by 2020, or an on-road average of about 20 percent less, or 28 mpg. Since this report was completed, the Obama administration has proposed an accelerated schedule to reach the 2020 target by 2016.

OCR for page 144
152 Driving and the Built Environment grow but slowly, with some introduction of gasoline hybrid vehicles and some use of biofuels (blending up to 10 percent ethanol), but no introduction of hydrogen fuel cell vehicles or other advanced technologies. The sensitivity of the results is tested in a later section using a more aggressive fuel economy scenario. Estimates of CO2 emissions are derived from the fuel use projections on the basis of Environmental Protection Agency (EPA 2005) estimates of the carbon content of gasoline, the main fuel used by cars and light trucks.13 Changes in the mix of fuels used by the fleet, including the share and formulation of gasoline, will affect the level of CO2 emissions. The committee recognizes this potential but has not conducted an independent assessment or made its own expert judgment. Rather, it assumes that gasoline will remain the main transport fuel for the next 20 to 30 years at least and that using its carbon content for developing the scenario estimates makes the most sense. The committee recog- nizes, however, that if the carbon content of fuels falls in the future, which is certainly the intent of current and proposed federal policies, then the CO2 savings the committee estimates from reduced travel due to changes in urban form become smaller. The same relationship holds true for improvements in vehicle fuel economy generally. The committee’s scenarios assume that reductions in energy use and CO2 emissions are proportional to VMT. This assumption is a sim- plification in that density is likely to lead to changes in vehicle mix and driving conditions that could affect the relationship of VMT to energy use and CO2 emissions. For example, as discussed in Chapter 3, there is evidence that density will encourage the purchase of smaller and hence more fuel-efficient vehicles, so that the reduction in energy use may be more than proportionate to the reduction in VMT. Density may also increase stop-and-go driving and lower speeds under more congested conditions in higher-density areas, which would increase 13 The Environmental Protection Agency estimates that 1 gallon of gasoline produces 19.4 pounds, or 0.00879978 metric tons, of CO2 emissions.

OCR for page 144
153 Potential Effects of More Compact Development Patterns fuel consumption per VMT for conventional vehicles, though it would reduce fuel consumption per VMT sharply were hybrid vehicles to be widely adopted. The committee has not estimated differences in future energy use that might arise if hybrids are highly successful, rather assuming that conventional powertrains will dominate long into the future.14 Results Tables 5-1 and 5-2 summarize the results of the committee’s scenario analysis to 2030 and to 2050, respectively (Scenarios 1 and 2). Signi- ficant differences in magnitude are achieved only in Scenario 2 with its assumption of a doubling of density for 75 percent of new housing that is channeled to more compact development and an associated reduction in VMT of 25 percent for these households. Under these assumptions, reductions in VMT, energy use, and CO2 emissions of nearly 8 percent can be achieved by 2030. These savings cumulate and grow to more than 8 to 11 percent by 2050, illustrating on the one hand the longevity of the built environment and, on the other, the cumulative effect of land use changes (see Figures 5-1 to 5-3, which show how the reductions change both by scenario and over time).15 In Scenario 1, with its assump- tion of a doubling of density for 25 percent of new housing that is channeled to more compact development and an associated reduction in VMT of 12 percent for these households, reductions in VMT, energy use, and CO2 emissions of 1 to 1.2 percent can be achieved by 2030, growing 14 This assumption is tested in the sensitivity analysis in the section following the presenta- tion of results. 15 In all cases, only the scenarios assuming that 75 percent of the new growth will be in compact, mixed-use developments are shown. The differences between the scenarios and the baseline for the low-end estimates, which assume that only 25 percent of the new growth will be in more compact, mixed-use developments, are too small to illustrate graphically. The slight decline in fuel use after 2005 reflects the entry of a small number of high-mpg gasoline hybrid vehicles in the reference case fleet mix. The decline in fuel use after 2010 reflects the introduction of fuel economy improvements to meet the more stringent CAFE standards.

OCR for page 144
154 Driving and the Built Environment TABLE 5-1 Scenario Analysis, 2000–2030, Assumptions and Results Year Base Case Scenario 1 Scenario 2 New Development Assumptions Percent growth in 36%–46% 36%–46% 36%–46% housing units Housing units 2000 105.2 105.2 105.2 (in millions) 2030 142.8–153.2 142.8–153.2 142.8–153.2 Percent of 2030 32%–37% 32%–37% 32%–37% units new and replacement New and 2030 45.8–56.7 45.8–56.7 45.8–56.7 replacement units (in millions) Percent of new and 0% 25% 75% replacement units compact New and replacement 2030 0.0–0.0 11.5–14.2 34.4–42.5 units compact (in millions) Changes in VMT Assumptions Percent change in 0% 0% 0% VMT/household in existing development VMT/household 2000 21,187 21,187 21,187 in existing 2030 21,187 21,187 21,187 development Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2030 new noncompact development −12% −25% Percent reduction in VMT/household in new compact development 20,211b 18,671b VMT/household in 2030 new compact development

OCR for page 144
189 Potential Effects of More Compact Development Patterns Year Base Case Scenario 1 Scenario 2 Fuel use (in billions 2000 114.3 114.3 2030 (1)c of gallons) 78.3–84.3 77.5–83.3 −29.6% to −23.8% −34.3% to −29.7% 2000 114.3 114.3 2030 (2)d 80.5–87.1 75.1–80.4 −1.0% to −1.2% −6.7% to −7.7% Percent change in fuel use in 2030 from base case −0.8 to −0.9 −6.9 to −6.7 Change in fuel use 2030 from base case (in billions of gallons) −31.5% to −26.2% −32.2% to −27.2% Percent change in CO2 emissions between 2000 and 2030 CO2 emissions 2000 1,006 1,006 2030 (1)c (millions of 689–742 682–733 −29.6% to −23.8% −34.3% to −29.7% metric tons) 2000 1,006 1,006 2030 (2)d 708–766 661–707 −1.0% to −1.2% −6.7% to −7.7% Percent change in CO2 emissions from base case −7 to −9 −47 to −59 Change in CO2 2030 emissions from base case (millions of metric tons) a In Scenario 1, VMT per household in new noncompact developments is assumed to be 8.4 percent higher (12 percent × .70) than the average for existing households, or 22,967 (21,187 × 1.084) VMT per household per year. In Scenario 2, VMT per household in new noncompact developments is assumed to be 17.5 percent higher (25 percent × .70) than the average for existing households, or 24,895 (21,187 × 1.175) VMT per household per year. b In Scenario 1, VMT per household in new compact developments is assumed to be 12 percent less than the baseline of new noncompact development households, or 20,211 (22,967 × .88). In Scenario 2, VMT per household in new compact developments is assumed to be 25 percent less than the baseline of new noncompact development households, or 18,671 (24,895 × .75). c The baseline projections for 2030 reflect the assumptions described in Footnote a. d The baseline projections for 2030 reflect the assumptions described in Footnote b.

OCR for page 144
190 Driving and the Built Environment ANNEX 5-1 TABLE 2 Sensitivity Analysis, 2000–2050, Changing Fuel Economy Assumptions Year Base Case Scenario 1 Scenario 2 New Development Assumptions Percent growth in 42.5%–82.5% 42.5%–82.5% 42.5%–82.5% housing units Housing units 2000 105.2 105.2 105.2 (in millions) 2050 152.8–192.0 152.8–192.0 152.8–192.0 Percent of 2050 40.8%–54.9% 40.8%–54.9% 40.8%–54.9% units new and replacement New and replacement 2050 62.4–105.4 62.4–105.4 62.4–105.4 units (in millions) Percent of new and 0% 25% 75% replacement units compact New and replacement 2050 0.0–0.0 15.6–25.8 46.8–78.4 units compact (in millions) Changes in VMT Assumptions Percent change in 0% 0% 0% VMT/household in existing development VMT/household in 2000 21,187 21,187 21,187 existing development 2050 21,187 21,187 21,187 Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2050 new noncompact development −12% −25% Percent reduction in VMT/household in new compact development

OCR for page 144
191 Potential Effects of More Compact Development Patterns Year Base Case Scenario 1 Scenario 2 20,211b 18,671b VMT/household in 2050 new compact development Results Percent change in 50.2%–90.9% 48.3%–87.7% VMT between 2000 and 2050 VMT (in billions of miles) 2000 2,228.9 2,228.9 2050 (1)c 3,348.5–4,255.4 3,305.5–4,182.8 55.6%–100% 42.6%–78% 2000 2,228.9 2,228.9 2050 (2)d 3,468.9–4,458.6 3,177.4–3,966.8 −1.3% to −1.7% −8.4% to −11.0% Percent change in VMT in 2050 from base case −43.0 to −72.6 −291.5 to −491.8 Change in VMT from 2050 base case (in billions of miles) Changes in Energy Use and CO2 Emissions Assumptions Percent change in fleet 193.8% 193.8% 193.8% mpg by 2050 Fleet mpg 2000 19.5 19.5 19.5 57.3e 57.3e 57.3e 2050 Percent change in 0% 0% 0% carbon content of fuel between 2000 and 2050 Results −48.9% to −35% −49.5% to −36.1% Percent change in fuel use between 2000 and 2050 Fuel use (in billions 2000 114.3 114.3 2050 (1)c of gallons) 58.4–74.3 57.7–72.9 −47% to −31.9% −51.5% to −39.4% 2000 114.3 114.3 2050 (2)d 60.5–77.8 55.4–69.2 (continued on next page)

OCR for page 144
192 Driving and the Built Environment ANNEX 5-1 TABLE 2 (continued) Sensitivity Analysis, 2000–2050, Changing Fuel Economy Assumptions Year Base Case Scenario 1 Scenario 2 −1.3% to −1.7% −8.4% to −11.0% Percent change in fuel use in 2050 from base case −0.8 to −1.3 −5.1 to −8.6 Change in fuel use from 2050 base case (in billions of gallons) −48.9% to −35% −49.5% to −36.1% Percent change in CO2 emissions between 2000 and 2050 CO2 emissions (millions 2000 1,006 1,006 2050 (1)c of metric tons) 514–654 508–642 −47% to −31.9% −51.5% to −39.4% 2000 1,006 1,006 2050 (2)d 533–685 488–609 −1.3% to −1.7% −8.4% to −11.0% Percent change in CO2 emissions from base case −7 to −11 −45 to −76 Change in CO2 2050 emissions from base case (millions of metric tons) a In Scenario 1, VMT per household in new noncompact developments is assumed to be 8.4 percent higher (12 percent × .70) than the average for existing households, or 22,967 (21,187 × 1.084) VMT per household per year. In Scenario 2, VMT per household in new noncompact developments is assumed to be 17.5 percent higher (25 percent × .70) than the average for existing households, or 24,895 (21,187 × 1.175) VMT per household per year. b In Scenario 1, VMT per household in new compact developments is assumed to be 12 percent less than the baseline of new noncompact development households, or 20,211 (22,967 × .88). In Scenario 2, VMT per household in new compact developments is assumed to be 25 percent less than the baseline of new noncompact development households, or 18,671 (24,895 × .75). c The baseline projections for 2050 reflect the assumptions described in Footnote a. d The baseline projections for 2050 reflect the assumptions described in Footnote b. e Assumes more aggressive fuel economy improvements. Average fleetwide on-road fuel economy reaches 57.3 mpg by 2050 rather than 32.9 mpg, an increase of 193.8 percent versus 68.7 percent over mpg in 2000 (see text and NRC 2008 for discussion of high-efficiency fuel assumptions).

OCR for page 144
193 Potential Effects of More Compact Development Patterns ANNEX 5-1 TABLE 3 Sensitivity Analysis, 2000–2030, Changing VMT Assumptions Year Base Case Scenario 1 Scenario 2 New Development Assumptions Percent growth in 36%–46% 36%–46% 36%–46% housing units Housing units 2000 105.2 105.2 105.2 (in millions) 2030 142.8–153.2 142.8–153.2 142.8–153.2 Percent of 32%–37% 32%–37% 32%–37% 2030 units new and replacement New and replacement 2030 45.8–56.7 45.8–56.7 45.8–56.7 units (in millions) Percent of new and 0% 25% 75% replacement units compact New and replacement 2030 0.0–0.0 11.5–14.2 34.4–42.5 units compact (in millions) Changes in VMT Assumptions Percent change in 7.8% 7.8% 7.8% VMT/household in existing development VMT/household 2000 21,187 21,187 21,187 in existing 2030 22,835 22,835 22,835 development Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2000 new noncompact 2030 24,753 26,831 development −12% −25% Percent reduction in VMT/household in new compact development (continued on next page)

OCR for page 144
194 Driving and the Built Environment ANNEX 5-1 TABLE 3 (continued) Sensitivity Analysis, 2000–2030, Changing VMT Assumptions Year Base Case Scenario 1 Scenario 2 20,211b 18,671b VMT/household in 2000 new compact 2030 21,783 20,123 development Results Percent change in VMT 39.4%–61.8% 38.0%–59.9% between 2000 and 2030 VMT (in billions 2000 2,228.9 2,228.9 2030 (1)c of miles) 3,106.9–3,607.1 3,075.4–3,565.0 54.5%–67.1% 44.2%–54.1% 2000 2,228.9 2,228.9 2030 (2)d 3,443.6–3,724.9 3,213.5–3,439.6 −1.0% to −1.2% −6.7% to −7.7% Percent change in VMT in 2030 from base case −31.5 to −42.1 −230.1 to −285.3 Change in VMT from 2030 base case (in billions of miles) Changes in Energy Use and CO2 Emissions Assumptions Percent change in 58.5% 58.5% 58.5% fleet mpg by 2030 Fleet mpg 2000 19.5 19.5 19.5 2030 30.9 30.9 30.9 Percent change in 0% 0% 0% carbon content of fuel between 2000 and 2030 Results −12.0% to +2.1% −12.9% to +0.9% Percent change in fuel use between 2000 and 2030 Fuel use (in billions 2000 114.3 114.3 2030 (1)c of gallons) 100.5–116.7 99.5–115.4 −2.5% to +5.5% −9.0% to −2.6% 2000 114.3 114.3 2030 (2)d 111.4–120.5 104.0–111.3

OCR for page 144
195 Potential Effects of More Compact Development Patterns Year Base Case Scenario 1 Scenario 2 −1.0% to −1.2% −6.7% to −7.7% Percent change in fuel use in 2030 from base case −1.0 to −1.3 −7.4 to −9.2 Change in fuel use 2030 from base case (in billions of gallons) −12.0% to +2.1% −12.9% to +0.9% Percent change in CO2 emissions between 2000 and 2030 CO2 emissions 2000 1,006 1,006 2030 (1)c (millions of metric 885–1,027 876–1,015 −2.5% to +5.5% −9.0% to −2.6% tons) 2000 1,006 1,006 2030 (2)d 981–1,061 915–980 −1.0% to −1.2% −6.7% to −7.7% Percent change in CO2 emissions from base case −8.9 to −12 −66 to −81 Change in CO2 2030 emissions from base case (millions of metric tons) a In Scenario 1, VMT per household in new noncompact developments is assumed to be 8.4 percent higher (12 percent × .70) than the average for existing households, or 22,967 (21,187 × 1.084) VMT per household per year. In Scenario 2, VMT per household in new noncompact developments is assumed to be 17.5 percent higher (25 percent × .70) than the average for existing households, or 24,895 (21,187 × 1.175) VMT per household per year. b In Scenario 1, VMT per household in new compact developments is assumed to be 12 percent less than the baseline of new noncompact development households, or 20,211 (22,967 × .88). In Scenario 2, VMT per household in new compact developments is assumed to be 25 percent less than the baseline of new noncompact development households, or 18,671 (24,895 × .75). c The baseline projections for 2030 reflect the assumptions described in Footnote a. d The baseline projections for 2030 reflect the assumptions described in Footnote b.

OCR for page 144
196 Driving and the Built Environment ANNEX 5-1 TABLE 4 Sensitivity Analysis, 2000–2050, Changing VMT Assumptions Year Base Case Scenario 1 Scenario 2 New Development Assumptions Percent growth 42.5%–82.5% 42.5%–82.5% 42.5%–82.5% in housing units Housing units 2000 105.2 105.2 105.2 (in millions) 2050 152.8–192.0 152.8–192.0 152.8–192.0 Percent of 2050 40.8–54.9% 40.8–54.9% 40.8–54.9% units new and replacement New and 2050 62.4–105.4 62.4–105.4 62.4–105.4 replacement units (in millions) Percent of new and 0% 25% 75% replacement units compact New and replacement 2050 0.0–0.0 15.6–25.8 46.8–78.4 units compact (in millions) Changes in VMT Assumptions Percent change in 13.3% 13.3% 13.3% VMT/household in existing development VMT/household 2000 21,187 21,187 21,187 in existing 2050 24,004 24,004 24,004 development Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2000 new noncompact 2050 26,021 28,205 development −12% −25% Percent reduction in VMT/household in new compact development

OCR for page 144
197 Potential Effects of More Compact Development Patterns Year Base Case Scenario 1 Scenario 2 20,211b 18,671b VMT/household in 2000 new compact 2050 22,898 21,154 development Results Percent change in VMT between 2000 and 2050 70.2%–116.3% 68.0%–112.6% VMT (in billions 2000 2,228.9 2,228.9 2050 (1)c of miles) 3,793.7–4,821.3 3,745.0–4,739.0 76.3%–126.6% 61.5%–101.6% 2000 2,228.9 2,228.9 2050 (2)d 3,930.1–5,051.4 3,599.9–4,494.2 −1.3% to −1.7% −8.4% to −11.0% Percent change in VMT in 2050 from base case −48.7 to −82.3 −330.2 to −557.2 Change in VMT from 2050 base case (in billions of miles) Changes in Energy Use and CO2 Emissions Assumptions Percent change in 68.7% 68.7% 68.7% fleet mpg by 2050 Fleet mpg 2000 19.5 19.5 19.5 2050 32.9 32.9 32.9 Percent change in 0% 0% 0% carbon content of fuel between 2000 and 2050 Results +0.9% to +28.2% −0.4% to +26% Percent change in fuel use between 2000 and 2050 Fuel use (in billions 2000 114.3 114.3 2050 (1)c of gallons) 115.3–146.5 113.8–144 +4.5% to +34.3% −4.3% to +19.5% 2000 114.3 119.5 2050 (2)d 119.4–153.5 109.4–136.6 (continued on next page)

OCR for page 144
198 Driving and the Built Environment ANNEX 5-1 TABLE 4 (continued) Sensitivity Analysis, 2000–2050, Changing VMT Assumptions Year Base Case Scenario 1 Scenario 2 −1.3% to −1.7% −8.4% to −11.0% Percent change in fuel use in 2050 from base case −1.5 to −2.5 −10 to −16.9 Change in fuel use 2050 from base case (in billions of gallons) +0.9% to +28.2% −0.4% to +26% Percent change in CO2 emissions between 2000 and 2050 CO2 emissions 2000 1,006 1,006 2050 (1)c (millions of metric 1,015–1,290 1,002–1,268 +4.5% to +34.3% −4.3% to +19.5% tons) 2000 1,006 1,006 2050 (2)d 1,051–1,351 963–1,202 −1.3% to −1.7% −8.4% to −11.0% Percent change in CO2 emissions from base case −13 to −22 −88 to −149 Change in CO2 2050 emissions from base case (millions of metric tons) a In Scenario 1, VMT per household in new noncompact developments is assumed to be 8.4 percent higher (12 percent × .70) than the average for existing households, or 22,967 (21,187 × 1.084) VMT per household per year. In Scenario 2, VMT per household in new noncompact developments is assumed to be 17.5 percent higher (25 percent × .70) than the average for existing households, or 24,895 (21,187 × 1.175) VMT per household per year. b In Scenario 1, VMT per household in new compact developments is assumed to be 12 percent less than the baseline of new noncompact development households, or 20,211 (22,967 × .88). In Scenario 2, VMT per household in new compact developments is assumed to be 25 percent less than the baseline of new noncompact development households, or 18,671 (24,895 × .75). c The baseline projections for 2050 reflect the assumptions described in Footnote a. d The baseline projections for 2050 reflect the assumptions described in Footnote b.

OCR for page 144
199 Potential Effects of More Compact Development Patterns ANNEX 5-1 TABLE 5 Savings Calculations in Energy Use and CO2 Emissions from Improved Residential Energy Efficiency with More Compact Growth Scenario Base Case: Move to Move to 2,400-ft2 SFDU 2,000-ft2 SFDU 2,000-ft2 MFDU Energy use 14,980 kW-h per unit 14,660 kW-h per unit 11,308 kW-h per unit per year (51.1 million per year (50 million per year (38.6 million Btu per unit per year) Btu per unit per year) Btu per unit per year) 395.9 ccf ng per unit 366.7 ccf ng per unit 186.1 ccf ng per unit per year (40.7 million per year (37.7 million per year (19.1 million Btu per unit per year) Btu per unit per year) Btu per unit per year) Subtotal 92.8 million Btu per 87.7 million Btu per 57.7 million Btu per unit energy use unit per year unit per year per year Energy savings — 320 kW-h (1.1 million 3,671 kW-h (12.5 million Btu) per unit per year Btu) per unit per year — 29.2 ccf ng (3.0 million 209.8 ccf ng Btu) per unit per year (21.6 million Btu) per unit per year Subtotal 4.1 million Btu per unit 34.1 million Btu per unit energy per year per year savings CO2 emissions 24,705 lb per unit per 23,935 lb per unit per 17,330 lb per unit per year (11.2 metric tons year (10.9 metric tons year (7.9 metric tons per unit per year) per unit per year) per unit per year) CO2 emissions — 770 lb (0.35 metric tons) 7,376 lb (3.3 metric tons) savings per unit per year per unit per year Note: Btu = British thermal units; ccf ng = hundred cubic feet of natural gas; kW-h = kilowatt-hours; MFDU = multifamily dwelling unit; SFDU = single-family dwelling unit. Factors for converting energy figures to Btu: 1 kW-h of electricity = 3, 412 Btu; 1 cf of natural gas = 1,028 Btu; 1 ccf of natural gas = 102,800 Btu; 1 gallon of gasoline = 124,000 Btu. Factor for converting CO2 emissions to metric tons: 1 metric ton of CO2 emissions = 2,204.6 lb.