High Speed Rail - Center for Neighborhood Technology

High Speed Rail and Greenhouse Gas Emissions – CCAP & CNT
vehicle occupancy to develop vehicle emissions factors as well. By using these same average occupancy
figures in the vehicle trip calculations, we are generating the same results as if we had used emissions per
passenger mile estimates. We felt that using vehicle emissions rather than passenger emissions was
valuable enough to future research to make this extra step worthwhile.
Emissions Factors
Automobiles
We developed estimated emissions factors for automobiles using the U.S. Department of Energy’s
Annual Energy Outlook projection of average on-road efficiency of 23.08 miles per gallon in 2025. 8 This
translates to 0.85 pounds of CO2 per vehicle mile if all vehicles use gasoline as fuel 9 (we did not model
diesel passenger cars or alternative fuels such as biodiesel). The Annual Energy Outlook’s projection is
less efficient than many others—for example, that of the midsize car value used by the Greenhouse Gas
(GHG) Protocol 10 —because their model assumes relatively low fuel prices and a continuing trend of
drivers switching to sport utility vehicles and other light trucks. Assuming 1.6 passengers per vehicle—
the average vehicle occupancy for intercity travel in the National Household Travel Survey 11 —the Annual
Energy Outlook’s fuel efficiency value translates to an emissions factor of 0.53 pounds of CO2 per
passenger mile.
Airplanes
We used the Annual Energy Outlook’s projection of 48.3 seat miles per gallon for 2025 regional aircraft
stock 12 to develop an emissions factor of 48 pounds of CO2 per mile 13 for a regional jet with 110 seats.
Assuming 70 percent occupancy, this translates this to an emissions factor of 0.62 pounds of CO2 per
passenger mile.
Buses
The Annual Energy Outlook and the GHG protocol both incorporate bus energy use data from the U.S.
Department of Energy’s Transportation Energy Data Book, 14 which cites the ENO Transportation
Foundation's Transportation in America 2001 and reports an energy use factor of 932 BTUs per
passenger mile in the year 2000. We used this value as well and assumed that efficiency improvements
follows recent trends of 0.3 percent improvement per year. Our derived emissions factor for 2025 is thus
8 U.S. Department of Energy, Energy Information Administration. “Annual Energy Outlook 2005.” by Stacy C. Davis and Susan
W. Diegel of Oak Ridge National Laboratory January 2005. http://www.eia.doe.gov/oiaf/aeo/index.html
9 A gallon of gasoline produces 19.564 pounds of CO2 when combusted according to the U.S. Department of
Energy, Energy Information Administration, Voluntary Reporting of Greenhouse Gases Program. “Fuel and Energy
Source Codes and Emission Coefficients.” http://www.eia.doe.gov/oiaf/1605/factors.html
10 See GHG Protocol Calculation Tools: http://www.ghgprotocol.org/
11 U.S. Department of Transportation, Bureau of Transportation Statistics. “National Household Travel Survey
2001.” http://www.bts.gov/programs/national_household_travel_survey/
12 U.S. Department of Energy, Energy Information Administration. “Annual Energy Outlook 2005.”
13 A gallon of jet fuel produces 21.095 pounds of CO2 when combusted according to the U.S. Department of Energy,
Energy Information Administration, Voluntary Reporting of Greenhouse Gases Program. “Fuel and Energy Source
Codes and Emission Coefficients.” http://www.eia.doe.gov/oiaf/1605/factors.html
14
U.S. Department of Energy, Energy Efficiency and Renewable Energy. “Transportation Energy Data Book, Edition 24.”
December 2004. http://cta.ornl.gov/data/index.shtml
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