Policy Options for Reducing Energy Use and Greenhouse Gas Emissions from U.S. Transportation Special Report 307 (2011) / Chapter Skim
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4 Factors Driving Modal Energy Use and Emissions
4 Factors Driving Modal Energy Use and Emissions
Pages 117-148
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From page 117... ...
The AEO 2010 projections imply that progress in curbing energy use and emissions from the fleet of light- and heavy-duty motor vehicles, and to a lesser extent commercial airplanes, will be central in making deep cuts in transportation energy use and emissions during the next half century. Accordingly, Chapter 4 examines some of the key factors that are likely to influence trends in the amount of energy used and GHGs emitted from these modes.
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From page 118... ...
How these two factors can influence trends in LDV energy use and emissions is described and illustrated, along with assumptions about changes in the carbon characteristics of the LDV fuel supply. role of changes in household travel According to the Federal Highway Administration's (FHWA's)
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From page 119... ...
Most of the nation's fleet of cars and light trucks consists of private vehicles that are owned and operated by households. Consequently, trends in household demographics and associated trip-making patterns will significantly influence total LDV travel.
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From page 120... ...
The result, 2.48 trillion vehicle miles, is divided by the Census Bureau forecast of 119.6 million households in 2010, which yields an average household VMT of 20,717. In the 2001 National Household Travel Survey, commuter, shopping, personal, family, and all other vehicle trips accounted for 27, 33, and 40 percent of household VMT, respectively.
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From page 121... ...
population, a reduction in total household VMT would likely require major changes in the number, structure, and size of households, which are outcomes that transportation policy making alone cannot bring about. Nevertheless, transportation policies that can help reduce VMT per household may be able to amplify the effect of fuel taxes and other policies in curbing growth in transportation energy use and emissions.
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From page 122... ...
12,000 10,000 8,000 6,000 4,000 2,000 0 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 06 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 Gasoline ICE vehicles TDI diesel ICE Ethanol-flex fuel ICE Electric vehicle Plug-in hybrid electric Hybrid electric Natural gas Fuel cell figure 4-1 Forecast new light-duty automobile sales by technology type, 2006–2030 (AEO 2010 reference case)
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From page 123... ...
Indeed, the projection of a 1.6 percent per year rate of growth in LDV travel in AEO 2010 implies that nearly all of the fuel savings from the annual 1.8 percent increase in vehicle efficiency will be countered by increased vehicle use. Table 4-3 illustrates how an average increase of 1.8 percent per year in the fuel economy of the fleet translates into changes in mpg for new vehicles (for all vehicles combined and for passenger cars and light trucks separately)
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From page 124... ...
resulting trends in ldv energy use and ghg emissions The factors affecting future LDV energy use and GHG emissions discussed in this section are household VMT and vehicle fuel economy. If trends in VMT and fuel economy were independent of one another, total LDV fuel consumption might be expected to fall by about 0.2 percent per year (the anticipated 1.6 percent annual growth in VMT would be more than offset by the 1.8 percent annual growth in fleet mpg resulting from current legislation)
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From page 125... ...
would cancel most of the fuel savings that would otherwise have been achieved from the higher vehicle fuel economy. Figure 4-3 shows the resulting trend line, which is similar to projections of LDV fuel use in the AEO 2009 reference case.8 In considering trends in GHG emissions, changes that may occur in the GHG characteristics of the energy used by the LDVs must be taken into account.
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From page 126... ...
remain the dominant fuel used by the LDV fleet for at least the next two decades, and probably for much longer, appears reasonable. Indeed, this assumption is consistent with Argonne National Laboratory's VISION model, whose reference case projections of the LDV energy supply are shown in Table 4-4.9 The VISION model assumes that in 2010 gasoline and ethanol will account for 94 and 5.4 percent, respectively, of LDV energy used, with the small remainder (<1 percent)
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From page 127... ...
Thus, the fuel consumption trends shown in Figure 4-3 assume that gasoline will remain the dominant energy source for LDVs until 2030. If such trends play out, CO2 emissions from the burning of fuel by LDVs will remain steady over the next 20 years, holding at about 1,125 million metric tons per year (19 pounds of CO2 per gallon × 130,000 billion gallons/ 2,200 pounds per metric ton)
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From page 128... ...
150 100 50 0 10 011 012 013 014 015 016 017 018 019 020 021 022 023 024 025 026 027 028 029 030 20 22 2 2 2 2 2 2 22 22 2 2 2 2 2 2 2 2 figure 4-4 FHWA truck freight forecasts for 2010–2030. from growth in freight demand to trends in truck payloads, average shipping distances, and vehicle efficiency characteristics.
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From page 129... ...
Table 4-6 shows how truck VMT would trend for the single-unit and combination fleets on the basis of these divisions and additional assumptions about the share of local, interstate, and intrastate traffic moved by single-unit versus combination trucks. On the basis of numerous simplifying assumptions, this scenario illustrates how changes in the nature and structure of freight markets and the trucking industry can affect trends in the overall energy performance of trucking, regardless of changes in the energy efficiency of the vehicles themselves.
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From page 130... ...
1.9 1.8 2.6 2.4 role of vehicle energy efficiency According to FHWA statistics for 2006,10 combination and single-unit trucks averaged 5.9 mpg of diesel fuel burned.11 In the AEO 2010 reference case, the mpg of the heavy-duty truck fleet is projected to reach 6.0 in 2010 and 6.9 by 2030, an improvement of 0.6 percent per year (Figure 4-5)
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From page 131... ...
Single unit 5.3 2 8.8 2 Combination 100.4 42 168.3 46 Total 237.1 100 365.9 100 2.2 Single unit 84.8 36 123.3 34 1.9 Combination 152.4 64 242.7 66 2.4 350 10 9 300 8 Miles per Gallon 250 VMT (billions) 7 6 200 5 150 4 3 100 2 50 1 0 0 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 2026 2028 2030 Medium-sized truck VMT Heavy-sized truck VMT Medium-sized truck average Heavy-sized truck average miles per gallon miles per gallon figure 4-5 Freight truck VMT and fuel economy forecasts, 2006–2030 (AEO 2010)
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From page 132... ...
The AEO assumption that the trucking industry, acting largely in its self-interest, will continue to pursue improvements in energy performance is based on the importance of diesel fuel costs to motor carrier operations and profitability. Figure 4-6 shows the major operating expenses from 2006 for the "truckload" segment of the trucking industry.
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From page 133... ...
Average annual improvement 1.1 The progress that will be made by the trucking industry in controlling fuel expenditures over the next two decades will almost certainly be driven by real and anticipated trends in the price of diesel fuel. Thus, some plausible scenarios for achieving energy savings in the trucking industry are considered below.
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From page 134... ...
On the other hand, the former trucks are more likely to benefit from improvements in vehicle aerodynamics and advances in auxiliary power units that can reduce engine idling in sleeper mode. The many fuel-saving design and technology opportunities shown in Table 4-7 suggest the potential for significant improvements in the energy efficiency of new combination trucks that enter the fleet from 2010 to 2030.
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From page 135... ...
Average annual 1.4 improvement trucks averaged 8.5 mpg in 2010, a 1.4 percent annual rate of increase would result in an average of 11.3 mpg by 2030. Implications for Fleetwide Fuel Efficiency The extent to which the improvements in new truck energy performance estimated above would translate into fleetwide mpg increases would
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From page 136... ...
. The fleetwide effects of increasing new-truck fuel economy will therefore occur more rapidly for combination trucks than for single-unit trucks, which average more years in service.
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From page 137... ...
trends in trucking energy use and ghg emissions The truck travel scenario in Table 4-6 assumes that VMT will increase by an average of 1.9 percent per year for single-unit trucks and 2.4 percent per year for combination trucks from 2010 to 2030. Additional scenarios assume that the average mpg of the single-unit and combination fleets will increase 1.4 percent and 1.7 percent per year, respectively.
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From page 138... ...
Combination Trucks Lower rolling resistance 3 60 1.8 replacement tires Trailer gap controls/ 2 20 0.4 vortex stabilizer Smart navigation 2 70 1.4 Driver training 4 50 2.0 Idle reduction or 6 75 4.5 elimination Road maximum speed 10 60 6.0 reduced about 7 mph (from assumed 65 mph) Trailer maintenance and 7 50 3.5 system compatibility with respect to tires, weight, aerodynamics (e.g., adding skirting and changes in trailer design)
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From page 139... ...
. If diesel remains the dominant fuel for trucking over this period, the effects on GHG emissions can be calculated by assuming the emission of 22 pounds of CO2 from the burning of each gallon of diesel fuel.
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From page 140... ...
11 percent increase in diesel fuel consumption, from 380 million metric tons in 2010 to 425 million metric tons in 2030. As in the calculations for the effects of LDV gasoline consumption on GHG emissions, these truck calculations do not include any upstream emissions of CO2 or other GHGs associated with diesel fuel production and distribution.
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From page 141... ...
Whereas 12 The Transportation Research Board's Airport Cooperative Research Program has completed a Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories (Kim et al.
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From page 142... ...
Because the taxi, takeoff, and climb phases of flight are the most fuel-intensive, shorter flights tend to consume more fuel per passenger mile than longer flights involving longer distances in cruise.13 Finally, newer aircraft tend to be more energy efficient than older aircraft because of technology improve 13 This relationship, in which larger aircraft and longer flight distances lead to reduced fuel consumption per passenger mile, can weaken for large aircraft flying very long distances because these trips will require more fuel storage that adds weight and leads to more fuel burn.
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From page 143... ...
Even with these assumptions of growth in travel, passenger airline fuel consumption is projected to grow by only 1.9 percent per year from 2010 to 2025, implying a reduction of 1 to 2 percent per year in the average amount of energy consumed per passenger mile. According to Lee et al.
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From page 144... ...
Barriers to faster deployment of energy- and emissions-saving technologies and operations in commercial aviation include the high capital costs of aircraft and the time-consuming processes for the safety certification of new designs, technologies, and operating procedures.
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From page 145... ...
Thus, focusing on these modes to achieve reductions in total transportation energy use and emissions will provide marginal gains at best. Collectively, for example, the nation's public transit systems -- buses and rail -- account for less than 1 percent of passenger miles and less than 1 percent of transport energy use and GHG emissions.
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From page 146... ...
Currently, passenger cars and light trucks (LDVs) account for about two-thirds of transportation energy use and emissions.
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From page 147... ...
For passenger airlines, the opportunities are likely to include aircraft that are more efficient in using energy and produce fewer emissions and of improved air traffic management procedures and systems. Policy approaches that seek to exploit these and other opportunities are considered in Chapter 5.
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From page 148... ...
2009. ACRP Report 11: Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories.
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