«*EPA
Un.tud SwtL-s Office of Transportation EPA420-F-05-003
AuoncC""""1''' P'"tl>rt "" and Air Quality February 2005
Of
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
programs.
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
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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
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Source: Calculation based on 40 CFR 600.113 and Intergovernmental Panel
on Climate Change (IPCC) methodology - see fact sheet #EPA420-F-05-
001.
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
21
310
HFC-134a 1,300 (HFC-134a is used in mobile source air conditioning)
CH4
NO
Source: IPCC "Second Assessment Report" (1996)
Conversions
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)
24
23
22
mpg 21
20
19
18
Model Year
2003 Trends Report data - combined cars and trucks
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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
Agriculture
8%
Industry
Commercial xv| \^^^ 30%
18% ^
Residential
17%
^ Transportation
27%
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
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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:
www.epa.gov/otaq/greenhousegases.htm
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
202-343-9629
E-mail: coe.edmund@epa.gov
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