_
racts
U.S.Transportation Sector
Greenhouse Gas Emissions
1990-2014
SEPA
United States
Environmental Protection
Agency
Office of Transportation and Air Quality
EPA-420-F-16-020
June 2016
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Transportation Emissions of the United States
The transportation sector 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 1990-2014
(the Inventory), the national inventory that the U.S. prepares annually under the United
Nations Framework Convention on Climate Change (UNFCCC), transportation represented
26% of total U.S. GHG emissions in 2014. 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 23% of emissions. Between 1990 and 2014, GHG emissions in
the transportation sector increased more in absolute terms than any other sector (i.e. electricity
generation, industry, agriculture, residential, or 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
Lubricants
Pipelines1
Non-Transportation Mobile
Agricultural Equipment
Construction & Mining Equipment
Lawn & Garden Equipment
Logging Equipment
Recreational Equipment
When including emissions from non-transportation mobile sources such as agricultural, lawn
and garden, and construction equipment, mobile sources constituted 29% of total U.S. GHG
emissions in 2014-2 Mobile source emissions have grown 21% since 1990 due in large part to
increased demand for travel.
Ships & Boats
2%v
Other
Medium- and
Heavy-Duty Trucks
23%
Share of U.S. GHG Emissions
by Sector3'4
Note: Totals may not add to 100% due to rounding.
Share of U.S. Transportation Sector
GHG Emissions by Source43
Note: Totals may not add to 100% due to rounding.
Share of U.S. Transportation Sector
GHG Emissions by Gas4
Note: Totals may not add to 100% due to rounding.
Pipeline emissions in the transportation sector include only C02 from the combustion of natural gas at compressor stations that power
natural gas pipelines, not emissions from electricity use, non-C02 gases, or other types of pipeline equipment. Note that natural gas pipe-
line compressor stations are stationary equipment that are included in the transportation sector, but are not considered mobile sources.
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.
For presentation purposes, emissions from territories which constitute less than 1% of the total U.S. GHG emissions, are not shown in
this chart although they are included in the total emissions used to calculate the percentage share of emissions from each sector. See
Table ES-6 in the Executive Summary of the Inventory for official data. See page 4 for more information on the Inventory.
4 "Transportation" emissions in these pie charts include C02, N20, CH4, and HFCs from transportation sources like highway vehicles,
aircraft, ships and boats, rail, pipelines and lubricants. They do not include emissions from non-transportation mobile sources such as
agriculture and construction equipment.
5 "Other" sources include buses, motorcycles, pipelines, and lubricants.
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U.S.Transportation GHG Emissions
(Tg C02 Equivalent)
Change from
1990 to 2014
Source 1990 1995 2000 2005 2010 2013 2014 Absolute Percent
On-Road Vehicles6
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
Pipelines7
Lubricants
Transportation Total
1,233.5
992.2
656.6
335.6
1.8
8.4
231.1
189.2
110.9
35.3
42.9
44.9
35.8
36.0
11.8
1,551.3
1,370.5
1 ,083.6
646.7
436.8
1.8
9.2
275.9
176.7
116.3
24.5
35.8
58.5
40.0
38.2
11.3
1,695.2
1,572.8
1,212.2
697.3
515.0
1.9
11.2
347.5
199.4
140.6
22.9
35.9
61.1
42.6
35.2
12.1
1,923.2
1,672.4
1 ,260.5
708.9
551.5
1.7
12.1
398.2
193.6
134.0
19.5
40.1
44.9
46.3
32.2
10.2
1,999.6
1,541.7
1,132.4
783.6
348.9
3.7
15.8
389.7
154.8
114.4
13.7
26.7
44.7
39.6
37.1
9.5
1,827.4
1 ,504.3
1 ,086.6
763.2
323.4
4.0
18.0
395.7
150.1
115.4
11.1
23.6
39.4
41.4
45.9
8.8
1,789.9
1,531.1
1,100.7
762.5
338.1
3.9
19.1
407.4
151.5
116.3
15.5
19.7
28.6
43.5
46.5
9.1
1,810.3
297.5
108.4
105.9
2.5
2.1
10.8
176.3
-37.7
5.4
-19.8
-23.2
-16.3
7.7
10.5
-2.7
259.1
24.1
10.9
16.1
0.8
117.6
128.6
76.3
-19.9
4.8
-56.1
-54.1
-36.3
21.4
29.2
-22.7
16.7
U.S. Non-Transportation Mobile GHG Emissions
Change in GHG Emissions by Sector: 1990-2014
• Light-Duty Vehicles
I Medium-and Heavy-Duty Trucks •Aircraft
Non-Transportation Mobile Sources
Non-Transportation
Mobile
Agricultural
Equipment
Construction
Equipment
Other Non-
Transportation Mobile
Non-Transportation +
Transportation Total
128.8
31.4
42.4
55.0
1,680.0
146.8
37.0
49.4
60.4
1,842.0
159.6
39.8
56.6
63.2
2,082.9
191.9
47.9
67.4
76.6
2,191.6
204.2
48.7
74.6
80.9
2,031.6
214.9
51.0
82.9
81.0
2,004.8
215.3
51.7
81.1
82.5
2,025.6
86.5
20.4
38.7
27.5
345.6
657.2
64.9
91.3
49.9
20.2
U.S.Transportation GHG Emissions by Gas, 2014
(Tg C02 Equivalent)
Source CO2 CH4 N20 MFCs Total Percent
On-Road Vehicles6
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
Pipelines7
Lubricants
Transportation Total
Rail Electricity
1,471.3
1 ,046.9
737.6
309.2
3.8
18.6
402.0
150.1
115.2
15.4
19.5
28.0
41.7
46.5
9.1
1,746.7
4.05
1.5
1.3
1.0
0.3
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
1.6
0.00
12.5
11.5
8.0
3.6
0.0
0.1
0.9
1.4
1.1
0.1
0.2
0.5
0.3
0.0
0.0
14.7
0.04
45.8
40.9
16.0
25.0
0.0
0.4
4.4
0.0
0.0
0.0
0.0
0.0
1.4
0.0
0.0
47.2
0.00
1,531.1
1,100.7
762.5
338.1
3.9
19.1
407.4
151.5
116.3
15.5
19.7
28.6
43.5
46.5
9.1
1,810.3
4.09
75.6
54.3
37.6
16.7
0.2
0.9
20.1
7.5
5.7
0.8
1.0
1.4
2.1
2.3
0.5
89.4
NA
U.S. Non-Transportation Mobile GHG Emissions by Gas, 2014
Non-Transportation
Mobile
Agricultural
Equipment
Construction
Equipment
Other Non-
Transportation Mobile
Non-Transportation +
Transportation Total
213.3
51.2
80.4
81.7
1,960.0
0.4
0.2
0.1
0.1
2.0
1.6
0.4
0.6
0.6
16.3
0.0
0.0
0.0
0.0
47.2
215.3
51.7
81.1
82.5
2,025.6
10.6
2.6
4.0
4.1
100.0
All Other Transportation Sources
GHG emissions and vehicle miles traveled (VMT) estimates for on-road vehicles presented in the Inventory
are based on FHWA data. FHWAchanged its methods for estimating (VMT) and related data in 2011. 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-
14 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 vehicles short WB" and "other 2-axle 4-tire vehicles" has been replaced by "light duty vehicles long WB."
Includes only C02 from natural gas used to power natural gas pipelines, does not include emissions from
electricity use or non-CO gases.
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
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2014 Fuel Consumption
MOTOR GASOLINE
Volume
f billion gallons unless Energy (Tbtu)
otherwise specified)
129.5
16,073.7
Sfffil
1,146.5
Transportation8
Light-Duty Vehicles
Passenger Cars
Light-Duty Trucks
Medium- and Heavy-Duty Trucks
Motorcycles
Buses
Recreational Boats
115.8
82.7
33.1
4.5
0.4
0.1
1.4
14,395.2
10,281.6
4,113.7
560.2
53.1
12.4
171.1
1 ,026.9
733.5
293.5
40.0
3.8
0.9
12.2
Non-Transportation9
Agricultural Equipment
Construction Equipment
Other Non-Transportation Mobile
DISTILLATE FUEL
0.6
0.7
6.0
58.7
77.6
84.1
719.9
8,087.8
5.5
6.0
51.2
598.1
Transportation8
Light-Duty Vehicles
Passenger Cars
Light-Duty Trucks
Buses
Medium- and Heavy-Duty Trucks
Recreational Boats
Ships and Boats
Rail
1.8
0.4
1.4
1.6
35.5
0.4
0.6
4.1
243.6
56.1
187.6
224.5
4,885.2
51.7
83.4
563.7
18.0
4.1
13.9
16.6
361.3
3.8
6.2
41.7
Non-Transportation9
Agricultural Equipment
Construction Equipment
Other Non-Transportation Mobile
RESIDUAL FUEL OIL
Ships and Boats
JET FUEL
Commercial Aircraft
General Aviation Aircraft
Military Aircraft
4.5
7.3
3.0
0.5
0.5
15.2
12.1
1.7
1.4
617.2
1 ,005.6
412.8
77.4
77.4
2,057.0
1,637.7
226.2
193.1
45.6
74.4
30.5
5.8
5.8
148.6
115.2
18.0
15.4
AVIATION GASOLINE
General Aviation Aircraft
NATURAL GAS (million cubic feet)
Buses
Pipelines
LPG
Light-Duty Trucks
Medium- and Heavy-Duty Trucks
Buses
LUBRICANTS
Total"
0.2
0.2
871,036.8
20,029.5
851,007.3
0.5
0.4
0.2
0.0
0.9
213.1
Energy (Tbtu)
21.7
21.7
898.9
20.7
878.2
43.7
30.6
12.7
0.4
136.0
27,396.2
C02 (Tg)
1.5
1.5
47.6
1.1
46.5
2.7
1.9
0.8
0.0
9.1
1,960.0
B/od/ese/11
EthanoP
1.4
12.9
180.8
1,092.8
0.0
0.0
8 Fuel consumption, energy, and C02 emissions from transportation sources exclude biofuels.
9 Non-transportation mobile fuel consumption, energy, and C02 are estimated based on the NONROAD component of EPA's
MOVES model (see epa.gov/otaq/nonrdmdl.htm). Because the fuel composition in the NONROAD model is intended to reflect
real-world usage, these estimates may include low-level ethanol blends. Note that these estimates are presented here and in
Annex 3.2 of the Inventory for informational purposes, but that non-transportation mobile sources are officially accounted for in
other energy sectors in the Inventory (e.g., the industrial sector) and the C02 estimates for those energy sectors do not include
emissions from biofuels.
10 Total Volume is the sum of physical (billion) gallons of fuel; because natural gas volumes are reported as million cubic feet,
natural gas volumes are converted to billion gallons of gasoline equivalent for the Total Volume (billion gallons) sum in
this table.
" Biofuels are presented as line items below the total for informational purposes only, in line with IPCC methodological guidance
and UNFCCC reporting obligations. C02 emissions from the combustion of biofuels are not directly included in the energy
sector contribution (which includes the contribution of transportation and non-transportation mobile sources) to U.S. totals in
the Inventory; instead, net carbon fluxes from changes in biogenic carbon reservoirs are accounted in the estimates for Land
Use, Land-Use Change, and Forestry in the Inventory. See page 4 for more information on the Inventory.
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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 1990-2014 (the Inventory) (EPA 2016). The U.S. Environmental Protection
Agency prepares the national emissions inventory annually to fulfill the U.S. 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 (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.
Inventory Definitions of Selected Transportation Categories12
Light-Duty Vehicles: passenger cars and light-duty trucks
Passenger Cars:13 automobiles used primarily to transport 12 people or less. In
2014, passenger cars traveled a total of 2,072,071 million vehicle miles.
Light-Duty Trucks:13 vehicles used primarily for transporting light-weight
cargo or which are equipped with special features such as four-wheel drive
for off-road operation. In the U.S., this category also includes many vehicles
that primarily transport passengers such as sport utility vehicles (SUVs) and
minivans. The gross vehicle weight rating (GVWR) normally ranges around
8,500 pounds or less. 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 2014, light-duty trucks traveled a total of 638,484 million
vehicle miles.
Medium- and Heavy-Duty Trucks:13 vehicles with GVWR of more than
around 8,500 pounds. In the Inventory, single unit trucks 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 2014, medium- and heavy-duty trucks traveled a
total of 295,130 million vehicle miles.
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 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 value14 or GWP of 25, which
means that releasing one ton of CH is equivalent to releasing 25 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) Fourth 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.
12 The data used to estimate emissions for specific transportation categories may not directly align with the Inventory's
definition of the categories; both the data and Inventory definitions may also differ from EPA's regulatory definitions
for the same categories.
13 GHG emissions and vehicle miles traveled (VMT) estimates for on-road vehicles presented in the Inventory
are based on FHWA data. FHWA changed its methods for estimating (VMT) and related data in 2011. 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-
14 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
vehicles short WB" and "other 2-axle 4-tire vehicles" has been replaced by "light duty vehicles long WB."
14 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-repo rt/ar4/syr/ar4_syr.pdf).
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