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

Transportation's Role in Reducing U.S. Greenhouse Gas Emissions: Volume 1
Improvements to aviation efficiency, such as more direct routing and more
efficient takeoff and landing profiles, show the potential to increase air traffic
operational efficiency by 2.5 to 6 percent by 2035. Many of these improvements
already are being implemented through the FAA’s NextGen program. Other
operational improvements at airports (e.g., single-engine taxi, electric gate
power) show very modest potential GHG benefits, although they may have
significant co-benefits in the form of reductions in local air pollution and airline
cost savings. Aviation efficiency improvements that reduce the cost of air travel
could potentially result in offsetting increases in GHG emissions as more people
travel, but this effect has not been reliably quantified and is not included in the
estimates presented here. 85
Transportation infrastructure construction is a significant contributor to GHG
emissions. These emissions are discussed under life-cycle emissions in
Section 2.3, since only tailpipe emissions are included as transportation
emissions in the U.S. GHG inventory for accounting reasons. Perhaps the most
significant and currently available strategy to reduce GHG emissions from
construction is the use of fly ash in cement, which uses a recycled material to
reduce the amount of cement needed by up to 50 percent (cement production
produces large amounts of GHGs). Already in use in a few places, this strategy
could be implemented much more widely as State DOTs become more
comfortable with the technology. Greater widespread use of warm- and coldmix
asphalt also has the potential to reduce GHGs generated to produce and
laydown these asphalt materials, but further research and demonstration under a
variety of conditions in the U.S. is needed. Together these strategies have the
potential to reduce GHG emissions by roughly 0.8 percent, relative to the
transportation sector baseline in 2030. 86
3.6 STRATEGY: REDUCE CARBON-INTENSIVE TRAVEL
ACTIVITY
Strategies to reduce carbon-intensive travel activity seek to influence travelers’
patterns in order to shift travel to more efficient modes, increase vehicle
occupancy, reduce the need for travel, or otherwise take actions that reduce
energy use and GHG emissions associated with personal travel. The collective
impact of these strategies on transportation GHG emissions could range from 5
to as high as 17 percent in 2030; or 6 to 21 percent in 2050. 87 The greatest near-
85 Vol. 2 Sec. 4.5.
86 Vol. 2 Sec. 4.6.
87 Vol. 2 Sec. 5.1. Some of the benefit estimates for a number of travel activity strategies,
including transit, nonmotorized improvements, land use, and commuter strategies,
incorporate “induced demand” effects. As some travelers shift to other modes or reduce
Footnote continued
3-17