_
racts
   U.S.Transportation Sector
   Greenhouse Gas Emissions
   1990-2010
  &EPA
United States
Environmental Protection
Agency
Office of Transportation and Air Quality
      EPA-420-F-12-063
      December 2012

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 Transportation Emissions of the United States
 The transportation end-use sector1 is one of the largest contributors to U.S. greenhouse gas
 (GHG) emissions. According to the Inventory of U.S. Greenhouse Gas Emissions and Sinks
 1990-2010, the national inventory that the U.S. prepares annually under the United Nations
 Framework Convention on Climate Change (UNFCCC), transportation represented 27% of
 total U.S. GHG emissions in 2010. Cars, trucks, commercial aircraft, and railroads, among other
 sources, all contribute to transportation end-use sector emissions. Within the sector, light-duty
 vehicles (including passenger cars and light-duty trucks) were by far the largest category, with
 62% of GHG emissions, while medium- and heavy-duty trucks made up the second largest
 category, with 22% of emissions. Between 1990 and 2010, GHG emissions in the transporta-
 tion end-use sector increased more in absolute terms than any other end-use sector (industrial,
 agriculture, residential, commercial).

 Greenhouse gas emissions from transportation sources include carbon dioxide (CO,), methane
 (CH4), nitrous oxide (N2O), and various hydrofluorocarbons (HFCs). CO2, CH4, and N2O
 are all emitted via the combustion of fuels, while HFCs are the result of leaks and end-of-life
 disposal from air conditioners used to cool people and/or freight.
Mobile Sources
Transportation
Highway Vehicles
Aircraft
Ships & Boats
Rail
Pipelines
Lubricants
Non-Transportation Mobile
Agricultural Equipment
Construction & Mining Equipment
Lawn & Garden Equipment
Logging Equipment
Recreational Equipment

                          When including emissions from non-transportation mobile sources2 such as agricultural, lawn and
                          garden, and construction equipment, mobile sources constituted nearly a third, or 30%, of total
                          U.S. GHG emissions in 2010. In addition, emissions have grown 20% since 1990 due in large
                          part to increased demand for travel.
U.S. Territories
Agriculture 8%
                                                                         AllOther
                                                                       Transportation
                                                                          Sources
                                                                        Medium- and
                                                                         Heavy-Duty
                                                                           Trucks
                              Ships and
                                Boats
                                 2%
                                                                                                     Passenger Cars
                                                                                                         43%
                                                                                   Light-Duty
                                                                                    Trucks
                                                                                     19%
                                                                                                             N20
                                                                                                             1.0%
          Share of U.S. GHG Emissions
          by End-Use Sector*
Share of U.S. Transportation End-Use
Sector GHG Emissions by Source*
* Note: Totals may not add to 100% due to rounding.
                                                                                                                                    Share of U.S. Transportation End-Use
                                                                                                                                    Sector GHG Emissions by Gas*
                                                                                                                                    * Note: Totals may not add to 100% due to rounding.
  End use sector emissions include (1) direct emissions and (2) emissions associated with electricity generation,
  as allocated to the sectors in which it is used.
                            C02 emissions from wood biomass and biofuel consumption are not included in this document. Data can be found
                            in the Land Use, Land-Use Change, and Forestry chapter of the Inventory. See page 4 for more information on the
                            Inventory.


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U.S.Transportation GHG  Emissions
(Tg C02 Equivalent)
Change from
1990 to 2010
Source 1990 1995 2000 2005 2008 2009 2010 Absolute Percent
On-Road Vehicles
Light-Duty Vehicles 3
Passenger Cars
Light-Duty Trucks
Motorcycles
Buses
Medium- and Heavy-
Duty Trucks
Aircraft
Commercial Aviation
Military Aircraft
General Aviation
Ships and Boats
Rail
Pipelines
Lubricants
Transportation Total
1,235.2
993.9
657.4
336.6
1.8
8.4
231.1
181.2
136.8
34.8
9.6
45.1
39.0
36.0
11.8
1 ,548.3
1,371.3
1,082.5
646.0
436.6
1.8
9.2
277.8
175.4
143.1
24.1
8.2
58.6
43.7
38.2
11.3
1,698.5
1,575.1
1,207.4
695.3
512.1
1.9
11.2
354.6
204.4
170.9
21.3
12.1
61.0
48.1
35.2
12.1
1,935.8
1,683.0
1 ,260.8
709.6
551.3
1.7
12.0
408.5
198.7
162.8
18.3
17.5
45.2
53.0
32.2
10.2
2,022.3
1,603.0
1,154.0
807.0
347.0
4.5
17.5
427.1
158.6
123.4
16.4
18.8
37.1
50.7
35.6
9.5
1,894.6
1 ,558.4
1,148.2
798.7
349.5
4.3
16.6
389.3
142.9
112.5
14.3
16.1
34.0
43.4
36.6
8.5
1,823.9
1,556.8
1,134.3
787.9
346.4
3.8
16.5
402.3
143.9
115.2
12.6
16.1
43.3
46.3
38.8
9.5
1,838.6
321.6
140.3
130.5
9.8
2.0
8.1
171.1
-37.3
-21.6
-22.1
6.5
-1.8
7.3
2.7
-2.3
290.2
26.0
14.1
19.9
2.9
114.7
97.0
74.0
-20.6
-15.8
-63.7
67.2
-4.0
18.8
7.6
-19.8
18.7
U.S. Non-Transportation  Mobile GHG  Emissions
Change in GHG Emissions by Sector: 1990-2010
Non-Transportation
Mobile
Agricultural
Equipment
Construction
Equipment
Other Non-
Transportation Mobile
Non-Transportation +
Transportation Total
128.8
31.4
42.4
55.0
1,677.1
146.8
37.0
49.4
60.4
1 ,845.3
158.3
39.2
55.8
63.4
2,094.1
190.7
47.3
66.5
76.9
2,213.0
194.2
45.9
69.9
78.4
2,088.8
197.7
47.2
71.2
79.3
2,021.6
204.3
48.2
73.6
82.5
2,042.9
75.6
16.8
31.2
27.5
365.8
58.7
53.5
73.7
50.1
21.8
U.S.Transportation GHG  Emissions by Gas, 2010
(Tg C02 Equivalent)
Transportation Source CO2 CH4 N20 MFCs Total Percent
On-Road Vehicles
Light-Duty Vehicles
Passenger Cars
Light-Duty Trucks
Motorcycles
Buses
Medium- and Heavy-
Duty Trucks
Aircraft
Commercial Aviation
Military Aircraft
General Aviation
Ships and Boats
Rail
Pipelines
Lubricants
Transportation Total
1,482.6
1,073.5
757.5
316.0
3.7
16.0
389.3
142.4
114.0
12.5
15.9
42.6
43.5
38.8
9.5
1,759.5
1.4
1.2
0.9
0.3
0.0
0.0
0.2
0.1
0.1
0.0
0.0
0.0
0.1
0.0
0.0
1.6
16.7
15.5
10.9
4.7
0.0
0.0
1.1
1.3
1.1
0.1
0.1
0.6
0.3
0.0
0.0

56.1
44.1
18.6
25.4
0.0
0.4
11.6
0.0
0.0
0.0
0.0
0.0
2.3
0.0
0.0
58.4
1,556.8
1,134.3
787.9
346.4
3.8
16.5
402.3
143.9
115.2
12.6
16.1
43.3
46.3
38.8
9.5
1,838.5
76.2
55.5
38.6
17.0
0.2
0.8
19.7
7.0
5.6
0.6
0.8
2.1
2.3
1.9
0.5
90.0
                                                                                           U.S. Non-Transportation  Mobile GHG Emissions by Gas, 2010
Non-Transportation
Mobile
Agricultural
Equipment
Construction
Equipment
Other Non-
Transportation Mobile
Non-Transportation +
Transportation Total
202.4
47.6
73.0
81.8
1,961.9
0.3
0.1
0.1
0.1
1.9
1.6
0.4
0.6
0.6
20.6
0.0
0.0
0.0
0.0
58.4
204.3
48.2
73.6
82.5
2,042.9
10.0
2.4
3.6
4.0
100.0
                                                                                             FHWA has changed how vehicles are classified, moving from a system based on body-type to one that is based on wheelbase. This
                                                                                             change was incorporated for the 2010 Inventory and resulted in large changes in fuel consumption data by vehicle class, thus leading to
                                                                                             a shift in emissions among on-road vehicle classes in the 2007-2010 time period. FHWA changed from using designations of "Passenger
                                                                                             Cars" and "Other 2-Axle 4-Tire Vehicles" to "Light Duty Vehicles Short WB" (passenger cars, light trucks, vans, and sport utility vehicles
                                                                                             with a wheelbase equal to or less than 121 inches), and "Light Duty Vehicles Long WB" (large passenger cars, vans, pickup trucks, and
                                                                                             sport/utility vehicles with wheelbases larger than 121 inches).
                                                                                             Less than .05 Tg C02 Eq.
                                                                                            - Not calculated
                                                                                             Note that CH4 and N20 emissions are not calculated for pipelines in the (importation GHG Inventory.



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2010 Fuel Consumption
(Billion G^o Energy (Tbtu) CO2 (Tg)
MOTOR GASOLINE*
142.2 17,660.7 1,183.4
Transportation
Light-Duty Vehicles
Passenger Cars
Light-Duty Trucks
Medium- and Heavy-Duty Trucks
Motorcycles
Buses
Recreational Boats
127.3
90.9
36.4
5.2
0.5
0.1
1.6
15,813.4
11,288.3
4,525.2
650.5
56.0
11.2
196.1
1 ,056.0
753.8
302.2
43.4
3.7
0.7
13.1
Non-Transportation
Agricultural Equipment
Construction Equipment
Other Non-Transportation Mobile
DISTILLATE FUEL*
0.7
0.7
6.2
54.1
86.0
81.6
765.8
7,502.9
6.1
5.8
54.5
554.9
Transportation
Light-Duty Vehicles
Passenger Cars
Light-Duty Trucks
Buses
Medium- and Heavy-Duty Trucks
Recreational Boats
Ships and Boats
Rail
1.6
0.4
1.2
1.4
33.7
0.3
0.1
3.8
220.5
50.7
169.8
189.1
4,669.2
47.9
9.3
528.0
16.3
3.7
12.6
14.0
345.3
3.5
0.7
39.0
Non-Transportation
Agricultural Equipment
Construction Equipment
Other Non-Transportation Mobile
RESIDUAL FUEL OIL
Ships and Boats
JET FUEL
Commercial Aircraft
General Aviation Aircraft
Military Aircraft
AVIATION GASOLINE
General Aviation Aircraft
NATURAL GAS
Buses
Pipelines
4.0
6.5
2.7
2.3
2.3
14.4
11.7
1.4
1.3
0.2
0.2



561.2
908.0
369.8
337.2
337.2
1 ,945.4
1 ,579.0
193.4
173.0
27.7
27.7
668.7
22.0
646.7
41.5
67.2
27.3
25.3
25.3
140.5
114.0
14.0
12.5
1.9
1.9
40.1
1.3
38.8

LPG
Light-Duty Trucks
Medium- and Heavy-Duty Trucks
Buses
ELECTRICITY
Rail
LUBRICANTS
Total
(Billion GVS Energy (Tbtu) CO2 (Tg)







213.1
65.3
45.0
20.3
0.0
72.1
72.1
152
28,280.0
1.8
1.2
0.6
0.0
4.5
4.5
9.5
1,961.9
                                                                                                                  * Figures include ethanol blended in motor gasoline
                                                                                                                  + Less than .05 billion gallons or Tg C02 as appropriate
                                                                                                                   Not calculated
                                                                                                                  International Bunker  Fuels*
                                                                                                                  (Tg  CO Equivalent)
Change from
1990 to 2010
Source 1990 1995 2000 2005 2009 2010 Absolute Percent
Marine Residual Fuel Oil
Marine Distillate Fuel Oil
Aviation Jet Fuel
Total
53.7
11.7
46.4
111.8
39.3
9.3
51.2
99.8
33.0
6.3
58.8
99.0
43.6
9.4
56.8
109.8
45.4
8.3
68.6
122.3
46.5
8.8
72.5
127.8
-7.2
-2.9
26.1
16.0
-13.4
-25.1
56.3
14.3
                                                                                                                    This document includes international bunker fuels, fuels used for international transport activities by commercial aircraft and
                                                                                                                    ships, although they are not included in the Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1990-2010. See page
                                                                                                                    4 for more information on the Inventory. Fluctuations in emissions estimates from the combustion of residual fuel oil are
                                                                                                                    associated with fluctuations in reported fuel consumption and may reflect data collection problems.


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Additional Information
Data Sources for This Document
The source for all data in this document is the Inventory of U.S. Greenhouse Gas Emissions
and Sinks 1990-2010 (EPA 2012). The U.S. Environmental Protection Agency prepares the
national emissions inventory annually to fulfill our commitment under the United Nations
Framework Convention on Climate Change (UNFCCC), using calculation methods that are
consistent with guidelines from the Intergovernmental Panel on Climate Change (IPPC).
Complete information on this inventory is available at: www.epa.gov/climatechange/
ghgemissions/usinventoryreport.html. The inventory methods and assumptions related to
transportation and non-transportation mobile sources are available in the main body of the
Inventory and Annex 3.2.

Definitions of Selected Transportation Categories
              Passenger Cars:4 Automobiles used primarily to transport less than 10 passen-
              gers. In 2010, the average fuel economy for passenger cars was  23.49 miles per
              gallon (mpg), and passenger cars traveled a total of 2,025,396 million vehicle
              miles.
              Light-Duty Trucks:4 Pick-up trucks, sport utility vehicles (SUVs), minivans,
              and similar vehicles that have a gross vehicle weight rating (GVWR) of less
              than 8,500 pounds. GVWR is the maximum weight a vehicle is designed to
              carry when passengers, fuel, cargo, and any other additions to the vehicle are
              accounted for. In this document, trucks with 2 axles and 4 tires (that are not
              otherwise categorized as passenger cars) represent the light duty truck category.

              Medium- and Heavy-Duty Trucks: Vehicles with a gross vehicle weight rating
              (GVWR) of more than 8,500 pounds. For medium- and heavy-duty trucks,
              GVWR is the sum of the weight of the vehicle plus the maximum weight of
              the cargo that the vehicle can carry. In this document, single unit trucks (with
              at least 2 axles and 6 tires) and combination trucks represent the  medium- and
              heavy-duty truck category, including tractor-trailers and box trucks used for
              freight transportation. In addition, this category includes some  vehicles that are
              not typically used for freight movement such as service and utility trucks.

              Pipelines: Systems that transport liquids, gases, or slurries through either above or
              below ground pipes. In the Inventory, the pipelines category includes emissions
              from the combustion of natural gas used to power pumps and other  distribution
              equipment, while leaks and other emission sources from pipelines are assigned to
              the natural gas systems category.
Emissions Metrics
A Teragram (Tg) is equal to 1 million metric tons.

Greenhouse gas (GHG) emissions are measured in this document in terms of Teragrams of
"carbon dioxide equivalent" (CO2 Eq); an "equivalent" refers to the Global Warming Potential
(GWP) of a greenhouse gas. GWP values are determined based on the chosen time horizon and
properties of the gas, such as the ability to absorb radiation and its atmospheric lifetime. CO2
has a GWP of "1"; all other greenhouse gases have GWP values relative to that of CO2. For
example, methane (CH ) has a radiative forcing value5 or GWP of 21, which means that releasing
one ton of CH is equivalent to releasing 21 tons of CO2.

The data in this document is based on the 100-year time horizon GWP values from the Inter-
governmental Panel on Climate Change's (IPCC's) Second Assessment Report, in accordance
with UNFCCC reporting guidelines for national GHG inventories. More information on green-
house gases, radiative forcing, and GWPs can be found in the sources listed below.

Additional GWP Information Sources
www.epa.gov/climatechange/index.html
www.global-greenhouse-warming.com/global-warming-potential.html
www.epa.gov/highgwp/



                                                                                                      FHWA has changed how vehicles are classified, moving from a system based on body-type to one that is based
                                                                                                      on wheelbase. This change was incorporated for the 2010 Inventory and resulted in large changes in fuel
                                                                                                      consumption data by vehicle class, thus leading to a shift in emissions among on-road vehicle classes in the 2007-
                                                                                                      2010 time period. FHWA changed from using designations of "Passenger Cars" and "Other 2-Axle 4-Tire Vehicles"
                                                                                                      to "Light Duty Vehicles Short WB" (passenger cars, light trucks, vans, and sport utility vehicles with a wheelbase
                                                                                                      equal to or less than 121 inches), and "Light Duty Vehicles Long WB" (large passenger cars, vans, pickup trucks,
                                                                                                      and sport/utility vehicles with wheelbases larger than 121 inches).
                                                                                                      Radiative forcing is a measure of the influence a factor has in altering the balance of incoming and outgoing
                                                                                                      energy in the Earth-atmosphere system and is an index of the importance of the factor as a potential climate
                                                                                                      change mechanism (www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf)

                                                                                          4

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