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15 FIGURE 9 New York MTA GHG emissions by source, 2007 (draft) (Source : Greening Mass Transit & Metro Regions: A Synopsis of the Final Report of the Blue Ribbon Commission on Sustainability and the MTA , Metropolitan Transportation Authority, State of New York, Feb. 2009, p. 22). While transit vehicles account for the majority of energy are attributed to nonrevenue vehicles (see Figure 9). Many used by a typical transit agency, buildings are also important employees of transit agencies emit GHG emissions from consumers of energy. Of the 2.7 MMtCO2e emitted by the their own vehicles as they commute to and from their jobs, New York Metropolitan Transportation Authority (NYMTA) although these emissions may or may not be attributed to in 2007, 18% are attributed to electricity and heating in the the agencies themselves. agency's facilities, stations, and maintenance yards. Figure 9 illustrates the sources of the agency's emissions. Traction energy, or energy used to propel transit vehicles, accounts for NET IMPACT OF U.S. TRANSIT ON GREENHOUSE GAS EMISSIONS 79% of emissions. All other energy is considered nontrac- tion. NYMTA's inventory does not include embodied emis- sions related to the agency's vehicles and infrastructure. Four recent studies have estimated the net amount of GHG emissions that U.S. transit services save each year. All have Construction and Maintenance found that American public transit significantly reduces GHG emissions from the transportation sector. Each of the Depending on the modes used, transit systems may require studies accounted for the travel mode shift effect of tran- significant construction efforts. Rail systems are the most sit and for transit vehicles' emissions. Some of the studies construction intensive, often requiring that miles of new track also accounted for the compact development and conges- and new stations be constructed as systems are initiated or tion mitigation effects of transit. Reductions range between expanded. Transit agencies also construct and maintain bus 6.9 MMtCO2 and 36.6 MMtCO2, depending on the scope of stations, bus shelters, and park-and-ride lots. Construction displaced emissions considered. For comparison, emissions and maintenance of all transit offices, facilities, and infra- from all on-road transportation in the state of Washington in structure use energy and produce GHG emissions: 2005 totaled 32.3 MMtCO2e (15). · From on-road transportation of materials, construction Table 2 provides the results of individual studies. Esti- workers, and waste; mates of mode shift and congestion reduction impact are · From construction equipment; and similar across the studies. Of the two studies that estimated · Emissions embodied in any materials used. the impact of compact development, the study by ICF Inter- national calculates the greatest reduction. The statistical Other Emissions technique used by ICF to capture land use effects of transit is more comprehensive than that used in the California's Public Transit agencies also maintain nonrevenue vehicle fleets Interest Research Group (CALPIRG) study (see chapter five, used for maintenance and local travel. These vehicles Compact Development for more information). The results of emit GHGs as well. At NYMTA, 3% of GHG emissions the CALPIRG study are buoyed by two other factors:
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16 TABLE 2 AGGREGATE GHG REDUCTIONS FROM PUBLIC TRANSIT IN THE UNITED STATES Emissions Impact (MMtCO2) Congestion Compact Transit Study Author Study Date Mode Shift Net Reduction Development Emissions ICF Intl. 2008 -15.8 -3.0 -29.9 12.1 -36.6 CALPIRG 2008 -- -- -- -- -25.8 Shapiro et al. 2002 -16.5 N/A N/A 9.1 -7.4 SAIC 2007 -16.2 -3.0 N/A 12.3 -6.9 Sources: Bailey et al., The Broader Connection between Public Transportation, Energy Conservation and Greenhouse Gas Reduction, ICF International, 2008 (10); Davis and Hale, Public Transportation's Contribution to U.S. Greenhouse Gas Reduction, Science Appli- cations International Corporation, 2007 (4); Baxandall et al., A Better Way to Go: Meeting America's 21st Century Transportation Challenges with Modern Public Transit, California's Public Interest Research Group Education Fund, 2008 (16); Shapiro et al., Con- serving Energy and Preserving the Environment: The Role of Public Transportation, 2002 (7). Note: Figures from the ICF study are calculated from figures in Tables 2 and 3 in that report using a conversion of 1 billion gallons of gasoline = 8.8 MMtCO2. A dash (--) indicates that separate figures were not provided. N/A indicates that the effect was not included in the calculation. 1. CALPIRG did not include demand response services, on analysis of a sample of 503 U.S. transit systems, the which tend to be inefficient in GHG emissions, in its CALPIRG study concluded the following: estimate. The authors reasoned that including demand response in the estimate would mask the benefit of · Rail transit systems reduce emissions the most, in large fixed-route services. part because of the land use impacts of rail in dense urban settings, and because of the use of electricity as 2. CALPIRG estimated lower emissions from electric a transportation fuel. transit vehicles in some regions, because it accounted · Bus systems have smaller, but still important impacts for regional variations in sources of electricity. The to reduce GHG emissions. other studies assumed an average national mix of · Vanpool programs provide relatively high savings on a electricity generation. per passenger basis. · Even most small transit agencies also provide GHG Results also vary between the studies depending on the savings (16 ). year of data used and modes included. For example, the Sha- piro study (7 ) used older data than the other studies, and From a sample of 50 of the largest transit agencies, the study included only bus and rail modes. found that agencies' impacts ranged from a net reduction of 10.5 MMtCO2 per year to a net increase of 0.07 MMtCO2 per Individual transit agencies have different net impacts on year. Only one agency produced a net increase in GHG emis- GHG emissions, depending on their sizes, types of service, sions. Appendix C provides estimates from CALPIRG of the fleets, sources of energy, and operating parameters. Based impact of individual transit agencies on GHG emissions.