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

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
• Buildings – All transportation agencies have buildings for housing office staff and
keeping equipment and supplies in a sheltered environment. A number of strategies
can be implemented to increase the energy efficiency of these buildings, such as
pursuing LEED certification or the EPA ENERGY STAR label for a building certification,
or implementing energy efficiency measures separately such as energy efficient heating
and air conditioning, fluorescent lighting, and energy efficient appliances.
• Traffic Impacts of Work Zones – When work zones are created to perform
maintenance activities on roadways or to rebuild them a common side-effect is the
creation of traffic congestion due to lane closures and speed reductions. This traffic
congestion lowers the fuel efficiency of vehicles and often requires vehicles to idle,
both of which increase GHG emissions. Strategies to prevent traffic congestion in
work zones include scheduling activities at night or on weekends, scheduling
simultaneous activities along a roadway where a bottleneck already is created, traveler
information, variable speed limits, temporary contraflow lanes, and dynamic lane
merging. Many of these strategies also are discussed earlier in this section as general
traffic management and traveler information strategies.
Magnitude and Timing of GHG Reduction
Very limited data is available on the potential nationwide GHG benefits of transportation
agency practices. A recent EPA report examined the potential for GHG reduction
practices in the construction sector as a whole. The study noted a general lack of data on
both total activity and the potential for emission reductions in this sector, but did provide
some aspirational estimates for three practices: reduced idling, maintenance and driver
training practices to increase fuel economy of heavy-duty equipment, and replacement of
diesel with a 20 percent biodiesel blend (B20). The combined estimate was a reduction of
2.4 mmt CO2e annually in the entire construction sector (U.S. EPA 2009), which, if
allocated 16 percent to the transportation subsector (in proportion to transportation
subsector’s contribution to construction emissions), would imply a potential reduction of
0.37 mmt CO2e annually from transportation construction activities. 39
A recent NCHRP study examined the contribution of State DOTs to reducing GHG
emissions (Cambridge Systematics, 2009b). This study estimated that about 19 percent of
State DOTs’ current vehicle fleet is powered by alternative fuels, saving 0.03 mmt CO2
annually. If 100 percent of State DOT vehicles were alternative fuel vehicles using these
39 The EPA study assumed a 10 percent reduction in idling from all off-road diesel equipment, a 3
percent increase in fuel economy due to improved maintenance and driver training, and a 10
percent replacement of diesel with biodiesel.
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