Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation's Role in Reducing U.S. Greenhouse Gas Emissions: Volume 1
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3.4 STRATEGY: INCREASE VEHICLE FUEL EFFICIENCY 68
Strategies to increase fuel efficiency are intended to reduce fuel consumption per
unit of travel by on-road vehicles, locomotives, aircraft, and marine vessels.
Although some retrofit options are available, energy efficiency improvements are
inherently a medium- to long-range strategy, as they apply primarily to new
vehicles and are dependent upon the rate of fleet turnover for the full affect on
reducing transportation GHG emissions. Examples that are market-ready, and
could be further incorporated in new vehicles in the near future, include:
efficiency improvements to internal combustion engines; hybrid-electric
powertrains and other efficiency improvements, such as weight reduction; and
aerodynamic improvements that reduce drag. Many of these technologies are
cost-effective, leading to net savings over the life of the vehicle, or even in a
much shorter period, from reduced fuel consumption. In the longer term,
entirely new propulsion systems relying on more efficient power conversion, and
low- or zero-carbon fuels (such as hydrogen fuel cells), may be developed.
Some improvements to energy efficiency already are incorporated into baseline
GHG projections, reflecting existing regulations and anticipated technological
trends. For example, the efficiency of new cars and light trucks is projected in
the AEO reference case to increase by 40 percent by 2030, as a result of expected
impacts of CAFE standards through 2020, and then continue to increase beyond
that time due to the effects of increasing fuel prices. Other sectors are not
currently regulated for efficiency, but nonetheless are expected to show
improvements (18 percent for aircraft, 14 percent for freight trucks, and 2 percent
for rail and domestic shipping), as a result of technological advancements and
market adoption. 69
Improvements beyond this baseline show strong potential for further GHG
reductions, with the largest potential in the light-duty vehicle sector. Estimates
suggest that there is considerable potential for improvement beyond what will be
achieved by the CAFE standards established under the 2007 EISA.
Potential GHG reduction benefits per vehicle (compared to the AEO baseline
projection for conventional gasoline vehicles) in 2030 and beyond range from 8 to
30 percent for advanced conventional gasoline vehicles; 0 to 16 percent for diesel
vehicles; 26 to 54 percent for hybrid-electric vehicles (HEVs); 46 to 70 percent for
plug-in hybrid electric vehicles (PHEVs); 40 to 84 percent for hydrogen fuel cell
vehicles; and 68 to 87 percent for battery-electric vehicles as shown in
68 Vol. 2 Chapter 3
69 The truck, air, rail, and marine efficiency measures are based on energy use per tonmile
(freight movement) and seat-mile (aircraft), and therefore may be affected by
utilization (load) factors as well as inherent vehicle efficiency. Source: AEO 2009
Reference case, April 2009 release.