Un.tud SwtL-s          Office of Transportation                               EPA420-F-05-003
    AuoncC""""1''' P'"tl>rt ""  and Air Quality                                     February 2005

                     77?e L/.S. Environmental Protection Agency (EPA) developed this series
                     of four fact sheets to facilitate consistency of assumptions and practices
                     in the calculation of emissions of greenhouse gases from transportation
                     and mobile sources. They are intended as a reference for anyone
                     estimating emissions benefits of mobile sources air pollution control
                     Average Fuel Economy
                     EPA and the Federal Highway Administration (FHWA) use two different
                     methodologies for calculating the average fuel economy of a passenger
                     vehicle. Although MOBILE6 (EPA's computer model for estimating
                     emissions for highway vehicles) estimates are more current, EPA uses
                     the FHWA numbers in developing the greenhouse gas inventory because
                     they are consistent with the methodology used to estimate carbon diox-
                     ide emissions.
                     Fuel Economy             from MOBILES
                     (in miles per gallon [mpg])

                     Passenger car                                  23.9 mpg
                     Light duty truck                               17.4 mpg
                     Passenger vehicle (cars and light trucks combined)  20.3 mpg

Source: MOBILE6 model run conducted in 2003, based on fuel economy
test data from EPA's annual Fuel Economy Trends Reports. Estimates
are in-use fleet averages for 2003 vehicles and earlier. Estimates include
all vehicles up to 25 years old. Note: These estimates do not include
vehicles over 8500 pounds.
 Fuel Economy              from FHWA
 Passenger car        22.1mpg
 Light duty truck      17.6mpg

 Source: FHWA "Highway Statistics, 2001. "Estimates are in-use fleet
 estimates obtained by dividing fleet total Vehicles Miles Traveled (VMT)
 by fuel sales in each category.
Vehicle        Traveled Per Year
Typical passenger vehicle (cars and trucks combined)      12,000 miles

Source: Approximation from several sources. This estimate can be used
for rough calculations. MOBILE6 can also provide annual milage
accumulation estimates for specific ages and classes of vehicles. VMT
estimates can vary, and for purposes other than rough estimates, you
should obtain estimates specific to your needs.
 Greenhouse      Emissions
 Passenger vehicle - 5.5 metric tons carbon dioxide (CO2) annually (=1.5
 metric tons carbon equivalent)

 Source: Approximation for a typical passenger vehicle based on EPA
 calculation - see fact sheet #EPA420-F-05-004 on greenhouse gas
 (GHG) emissions from a passenger vehicle. This value includes
 emissions of carbon dioxide, methane, nitrous oxide, and hydro-
fluorocarbons. The estimate is of vehicle emissions only (i.e., it does not
 include lifecycle emissions from fuel processing or distribution). Note:
 This estimate does not include vehicles over 8500 pounds (Ibs).

 CO2 emissions from a gallon of gasoline          19.4 Ibs
 CO  emissions from a gallon of diesel fuel         22.2 Ibs

Source: Calculation based on 40 CFR 600.113 and Intergovernmental Panel
on Climate Change (IPCC) methodology - see fact sheet #EPA420-F-05-

Note: All estimates above are single point estimates, and have associated
variation and uncertainty. In some cases it may be appropriate to use other
values, or a range of values.
 Global Warming Potentials
 CO9         1
 HFC-134a    1,300 (HFC-134a is used in mobile source air conditioning)
Source: IPCC "Second Assessment Report" (1996)
 1 metric ton of carbon equivalent = 3.667 metric tons CO2 eq.
 1 metric ton of CO2 eq. = 0.2727 metric tons of carbon eq.
 1 teragram = 1 million metric tons
 1 kilogram = 2.205 pounds
 metric ton = 1.102 tons
      New Personal Vehicle Fuel Economy
                    at 22-Year Low
          ("Real World" fuel economy, 15% lower than CAFE value)



mpg  21



                        Model Year
           2003 Trends Report data - combined cars and trucks

Putting Transportation Greenhouse       Emissions
into Perspective
    2002 U.S. Greenhouse Gas Emissions by Sector
  Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 - 2002
              Commercial   xv|  \^^^ 30%
                18%   ^
                                ^ Transportation
       2002 U.S. Transportation Sector by Category
    Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2002

                        Source             mmt CO2e
                        Other nonroad        100.2
                        Rail                 33.9
                        Boats               52.9
                        Aircraft              179.4
                        Mobile MFCs         40.3
                        Lubricants           10.8
                        Buses              8.5
                        Heavy Trucks         296.7
                        Passenger Cars,      1153
                        Light Trucks and
                        Motorcycles (62% of transp. GHGs)
                        mmt = million metric tons

            Vehicle Miles Traveled Since 1970
                    (Trillions of Miles)
              Source: FHWA Traffic Volume Trends, December, 2002
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For More information
You can access documents on greenhouse gas emissions on the Office
of Transportation and Air Quality Web site at:


For further information on calculating emissions of greenhouse gases,
please contact Ed Coe at:

    U. S. Environmental Protection Agency
    Office of Transportation and Air Quality
    1200 Pennsylvania Ave., NW (6406J)
    Washington, DC 20460
    E-mail: coe.edmund@epa.gov