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

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
system delays, or air carrier delays (less than 6 percent were due to security or extreme
weather). Preliminary benefits analyses indicate that NextGen capacity increases could
yield economic growth of as much as $175 billion through 2025 (FAA, 2007).
Feasibility
Air transport features a challenging mixture of local, regional, national, and international
operations, management, and policy. Private operators (airlines) operate in publicly
managed airspace. Locally controlled airports may seek to reduce emissions in the
immediate area, but are constrained by competitive pressures and limited jurisdiction.
National governments also are constrained by concerns about placing their own carriers at
a competitive disadvantage, suggesting the need for an international framework for
addressing emissions from air transport (Hansen, Smirti, and Zou, 2008).
Despite these complexities, examples of many operational procedures already have
proven effective in the U.S. and other countries (see previous sidebar for examples of U.S.
implementation). For OPDs, the technology has ready been implemented at multiple
sites, but there is still concern over its impact and potential limitations on airspace
capacity at certain locations. To move towards more “free flight” technologies, pilots
would also have to be given training to decide on the most suitable and efficient routes
and altitudes during their flights. Furthermore, the cost of systems and operations
improvements will involve significant investment in air traffic management systems, both
on the ground and for avionics on aircraft. Progress on FAA’s NextGen initiative has
been challenged by factors, including its complexity, costs to FAA and airlines, technology
development, and interdependent government/industry implementation issues.(ATW,
2009).
Airport capacity expansion (runway extension, new runways, or even new airports)
continues to take place, but is often contentious as a result of local concerns regarding
aircraft noise, as well as other potential environmental impacts of expanding the airport’s
physical capacity. Airport design standards will likely change as part of NextGen, and
operations on closely spaced parallel runways may be permitted at separations much
closer than current standards. This would allow greater design flexibility, opening the
potential for new runways to be added within existing footprints of airport property and
allowing better use of existing runway layouts.
Other airport-specific operational practices, such as alternative-fuel GSE and GAV, gate
power, and single-engine taxiing, have been implemented at some airports with the
primary goal of reducing air pollutant emissions. Single-engine taxi can create some
engine operation and maintenance issues, and aircraft tugging may create safety concerns,
so care must be taken to determine when these procedures are appropriate to implement.
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