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

Transportation's Role in Reducing U.S. Greenhouse Gas Emissions: Volume 1
3.0 Greenhouse Gas Reduction
Strategies and Impacts
3.1 STRATEGIES
Transportation greenhouse gas (GHG) emissions from fuel combustion and
vehicle air conditioning systems account for 29 percent of total U.S. GHG
emissions. In light of the aggressive national GHG reduction goals currently
under discussion, which seek to reduce U.S. GHG emissions by as much as 80
percent from 2005 levels by 2050, the transportation sector could play a large
role. The technical report for this study examines dozens of proposed strategies,
and assesses their potential to reduce transportation GHG emissions. These
assessments are based on published scientific literature, current policy studies,
and best professional estimates. This section presents an overview and
comparative summary of the technical report findings.
The strategies to reduce transportation GHG emissions discussed in the technical
report are organized into four major groups. They include strategies to:
• Introduce low-carbon fuels Petroleum-based fuels account for 97 percent of
U.S. transportation energy use. 61 The objective of this group of strategies is to
develop and introduce alternative fuels that have lower carbon content and
therefore generate fewer transportation GHG emissions. These alternative
fuels include ethanol, biodiesel, natural gas, liquefied petroleum gas, lowcarbon
synthetic fuels (such as biomass-to-liquids), hydrogen, and electricity.
• Increase vehicle fuel efficiency. The objective of this group of strategies is to
reduce GHG emissions by using less fuel per mile traveled. Fuel efficiency
improvements include advanced engine and transmission designs, lighterweight
materials, improved aerodynamics, and reduced rolling resistance.
• Improve transportation system efficiency. These strategies seek to improve
the operation of the transportation system through reduced vehicle travel
time, improved traffic flow, decreased idling, and other efficiency of
operations; improvements that can also result in lower energy use and GHG
emissions. The strategies range from truck-idle reduction, to reducing
congestion through Intelligent Transportation Systems (ITS) and other
innovative forms of traffic management, to air traffic control systems that
route aircraft more efficiently and reduce delays. Efficiency can also be
61 U.S. Department of Energy, Annual Energy Outlook 2009.
3-1