_
racts
U.S.Transportation Sector
Greenhouse Gas Emissions
1990-2011
&EPA
United States
Environmental Protection
Agency
Office of Transportation and Air Quality
EPA-420-F-13-033
August 2013
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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
1990-2011 (the Inventory), 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 2011. 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 61% of GHG emissions, while medium- and heavy-duty trucks made up
the second largest category, with 22% of emissions. Between 1990 and 2011, GHG emissions in
the transportation end-use sector increased more in absolute terms than any other end-use sec-
tor (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
Pipelines2
Lubricants
Non-Transportation Mobile
Agricultural Equipment
Construction & Mining Equipment
Lawn & Garden Equipment
Logging Equipment
Recreational Equipment
When including emissions from non-transportation mobile sources3 such as agricultural, lawn and
garden, and construction equipment, mobile sources constituted nearly a third, or 30%, of total
U.S. GHG emissions in 2011. In addition, mobile source emissions have grown 21% since 1990
due in large part to increased demand for travel.
U.S. Territories
Ships and Boats
3% \
AllOther
Transportation
Sources
Residential
17%
Transportation
27%
Commercial
17%
22%
.1%
Share of U.S. GHG Emissions
by End-Use Sector*
* Note: Totals may not add to 100% due to rounding.
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.
Includes only C02 from natural gas used to power natural gas pipelines, does not include emissions from electricity
use or non-C02 gases.
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.
1
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U.S.Transportation GHG Emissions
(Tg C02 Equivalent)
Change from
1990 to 2011
Source 1990 1995 2000 2005 2009 2010 2011 Absolute Percent
On-Road Vehicles4
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
1,235.2
993.9
657.4
336.6
1.8
8.4
231.1
189.2
110.9
35.3
43.0
45.1
39.0
36.0
11.8
1,556.3
1,371.3
1,082.5
646.0
436.6
1.8
9.2
277.8
176.7
116.4
24.5
35.8
58.6
43.7
38.2
11.3
1,699.8
1,575.1
1,207.4
695.3
512.1
1.9
11.2
354.6
199.4
140.7
22.9
35.9
61.0
48.1
35.2
12.1
1,930.9
1,682.9
1 ,260.8
709.5
551.3
1.7
12.1
408.4
193.7
134.0
19.5
40.1
45.2
53.0
32.2
10.2
2,017.2
1,558.2
1,148.2
798.7
349.5
4.3
16.5
389.2
157.5
120.7
15.6
21.2
40.8
43.4
36.7
8.5
1 ,845.2
1,565.1
1,142.1
794.1
348.0
3.8
16.3
402.9
154.8
114.4
13.7
26.7
44.1
46.3
37.1
9.5
1,856.9
1,540.9
1,118.8
787.4
331.4
3.7
17.4
401.1
149.9
115.7
12.7
21.5
48.2
48.0
37.7
9.0
1,833.7
305.7
124.9
130.1
-5.2
1.9
9.0
169.9
-39.4
4.8
-22.6
-21.5
3.1
9.1
1.7
-2.8
277.4
24.8
12.6
19.8
-1.5
109.5
107.5
73.5
-20.8
4.3
-64.1
-50.0
6.8
23.3
4.7
-23.9
17.8
U.S. Non-Transportation Mobile GHG Emissions
Change in GHG Emissions by Sector: 1990-2011
assenger Cars • Light-Duty Trucks Medium- and Heavy-Duty Trucks • Aircraft Non Transportation Mobile Sources All Other Transportation Sources * Ships and Boats
Non-Transportation
Mobile
Agricultural
Equipment
Construction
Equipment
Other Non-
Transportation Mobile
Non-Transportation +
Transportation Total
128.8
31.4
42.4
55.0
1,685.1
146.8
37.0
49.4
60.4
1,846.6
158.3
39.2
55.8
63.4
2,089.2
190.7
47.3
66.5
76.9
2,207.9
197.7
47.2
71.2
79.3
2,042.9
204.3
48.2
73.6
82.5
2,061.2
207.0
50.0
74.8
82.3
2,040.7
78.3
18.6
32.4
27.3
355.6
60.8
59.2
76.3
49.7
21.1
1990 1991 1993 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 3008 2009 2010 2011
U.S.Transportation GHG Emissions by Gas, 2011
(Tg C02 Equivalent)
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
1,470.4
1,061.6
759.0
302.6
3.6
16.9
388.3
148.4
114.6
12.6
21.2
47.4
45.3
37.7
9.0
1,758.3
1.3
1.1
0.8
0.3
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
1.4
14.5
13.4
9.4
4.0
0.0
0.0
1.0
1.4
1.1
0.1
0.2
0.7
0.4
0.0
0.0
16.9
54.8
42.7
18.3
24.5
0.0
0.4
11.7
0.0
0.0
0.0
0.0
0.0
2.3
0.0
0.0
57.1
1,540.9
1,118.8
787.4
331.4
3.7
17.4
401.1
149.9
115.7
12.7
21.5
48.2
48.0
37.7
9.0
1,833.7
75.5
54.8
38.6
16.2
0.2
0.9
19.7
7.3
5.7
0.6
1.1
2.4
2.4
1.8
0.4
89.9
U.S. Non-Transportation Mobile GHG Emissions by Gas, 2011
Non-Transportation
Mobile
Agricultural
Equipment
Construction
Equipment
Other Non-
Transportation Mobile
Non-Transportation +
Transportation Total
205.1
49.4
74.1
81.6
1,963.4
0.3
0.1
0.1
0.1
1.7
1.6
0.4
0.6
0.6
18.5
0.0
0.0
0.0
0.0
57.1
207.0
50.0
74.8
82.3
2,040.7
10.1
2.4
3.7
4.0
100.0
4 FHWA changed its methods for estimated vehicle miles traveled (VMT) and related data. These methodological changes
included how vehicles are classified, moving from a system based on body-type to one that is based on wheelbase. These
changes were first incorporated for the 2010 Inventory and apply to the 2007-11 time period. This resulted in large changes
in VMT and fuel consumption data by vehicle class, thus leading to a shift in emissions among on-road vehicle classes.
For instance, passenger car has been replaced by "Light duty vehicle, short WB" and other 4 axle-2 tire has been replaced
by "Light duty vehicle, long WB."
* CH4 and N20 emissions from pipelines are not included in transportation end-use sector totals.
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2011 Fuel Consumption
(Billion G^o™ Energy (Tbtu) CO2 (Tg)
MOTOR GASOLINE*
140.0 17,395.3 1,166.4
Transportation
Light-Duty Vehicles
Passenger Cars
Light-Duty Trucks
Medium- and Heavy-Duty Trucks
Motorcycles
Buses
Recreational Boats
125.6
90.9
34.7
4.8
0.4
0.1
1.6
15,608.2
11,295.9
4,312.3
597.7
54.5
11.3
194.7
1 ,043.0
754.8
288.2
39.9
3.6
0.8
13.0
Non-Transportation
Agricultural Equipment
Construction Equipment
Other Non-Transportation Mobile
DIESEL FUEL"
0.8
0.6
6.1
56.0
99.3
76.3
753.3
7,767.1
7.1
5.4
53.6
574.4
Transportation
Light-Duty Vehicles
Passenger Cars
Light-Duty Trucks
Buses
Medium- and Heavy-Duty Trucks
Recreational Boats
Ships and Boats
Rail
1.7
0.4
1.3
1.5
33.9
0.4
1.0
4.0
232.9
55.6
177.4
204.3
4,702.3
49.0
144.3
554.5
17.2
4.1
13.1
15.1
347.8
3.6
10.7
41.0
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
4.1
6.7
2.7
1.8
1.8
15.0
12.1
1.8
1.2
0.2
0.2
—
—
—
572.6
928.3
378.8
268.1
268.1
2,029.0
1 ,629.0
242.6
157.4
27.1
27.1
720.4
19.6
700.8
42.4
68.7
28.0
20.1
20.1
146.5
114.6
19.4
12.6
1.9
1.9
38.8
1.1
37.7
LPG
Light-Duty Trucks
Medium- and Heavy-Duty Trucks
Buses
ELECTRICITY
Rail
LUBRICANTS
Total
(Billion GVS Energy (Tbtu) CO2 (Tg)
—
—
—
—
—
—
—
213.1
67.5
47.0
20.5
0.0
71.2
71.2
152
28,345.7
1.9
1.3
0.6
0.0
4.3
4.3
9.0
1,963.4
* Figures include ethanol blended in motor gasoline.
** Figures include biodiesel blended into diesel fuel.
— Not calculated.
International Bunker Fuels5
(Tg CO Equivalent)
Change from
1990 to 2011
Source 1990 1995 2000 2005 2009 2010 2011 Absolute Percent
Marine Residual Fuel Oil
Marine Distillate Fuel Oil
Aviation Jet Fuel
Total
53.7
11.7
38.0
103.5
39.3
9.3
49.9
98.5
33.3
6.3
62.0
101.7
43.6
9.4
60.1
113.1
45.4
8.2
52.8
106.4
46.5
9.5
61.0
117.0
38.9
7.5
64.9
111.3
-14.8
-4.2
26.8
7.9
-27.6
-35.5
70.5
7.6
International bunker fuels are fuels used for international transport activities by commercial aircraft and ships. They are not
included in Transportation or Non-Transportation Mobile Sector totals.
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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 1990-2011 (the Inventory) (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 calcu-
lation methods that are consistent with guidelines from the Intergovernmental Panel on
Climate Change (IPCC). 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 as well as Annex 3.2 of the Inventory.
Definitions of Selected Transportation Categories
Passenger Cars:6 Automobiles used primarily to transport less than 10 passen-
gers. In 2011, passenger cars traveled a total of 2,043,409 million vehicle miles.
Light-Duty Trucks:6 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, light-duty vehicles with long wheelbases
represent the light duty truck category. In 2011, light-duty trucks traveled a
total of 603,232 million vehicle miles.
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.
In 2011, medium- and heavy-duty trucks traveled a total of 280,990 million
vehicle miles.
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 its 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 value7 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
greenhouse gases and GWP is available at: www.epa.gov/climatechange/ghgemissions/gases.html.
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.
FHWA changed its methods for estimating vehicle miles traveled (VMT) and related data. These methodological
changes included how vehicles are classified, moving from a system based on body-type to one that is based on
wheelbase. These changes were first incorporated for the 2010 Inventory and apply to the 2007-11 time period.
This resulted in large changes in VMT and fuel consumption data by vehicle class, thus leading to a shift in
emissions among on-road vehicle classes. For instance, passenger car has been replaced by "Light duty vehicle,
short WB" and other 4 axle-2 tire has been replaced by "Light duty vehicle, long WB."
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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