51
Getting There Greener
1
Coach seats with more legroom—sometimes called
“economy-plus”—are responsible for an average of 20 percent
more carbon than standard coach seats.
2
U.S. Department of Transportation. 1997. 1995 American travel
survey. Washington, DC. These statistics are the most recent
available, as the department does not update them routinely.
3
U.S. Department of Transportation. National household travel
survey: Summer travel quick facts, 2001–2002. Washington,
DC. Online at www.bts.gov/programs/national_household_
travel_survey/summer_travel.html.
4
Travel Industry Association (TIA). 2007. New study identifies
travelers’ ideal vacation trip. Washington, DC.
5
TIA 2007.
6
U.S. Department of Transportation 1997.
7
See Appendices A through E for more on our research
methods and how we calculated our results.
8
TIA 2007.
9
NBC News. 2007. Escape work: Get the most out of your
vacations. Online at http://today.msnbc.msn.com/id/
18897063/.
10
U.S. Department of Transportation. National household travel
survey: Summer travel quick facts, 2001–2002.
11
This calculation is based on: U.S. Environmental Protection
Agency (EPA). 2006. Greenhouse gas emissions from the U.S.
transportation sector: 1990–2003. And: Energy Information
Administration. 2007. Emissions of greenhouse gases in
the United States, 2006. The 40 percent figure includes
“upstream” emissions associated with extracting, refining, and
transporting fuel from the wellhead to the fuel pump.
12
For more information, see www.ucsusa.org/global_warming/
global_warming_101/.
13
Oak Ridge National Laboratory (ORNL). 2008. Transportation
energy data book, 27
th
edition, Table 9.2. Oak Ridge, TN.
14
Federal Aviation Administration (FAA). March 15, 2007. Press
release no. AOC-8-07. Washington, DC.
15
U.S. Department of Transportation, Bureau of Transportation
Statistics, Research and Innovation Technology Administration
(RITA). 2008. Transtats database. Online at www.transtats.
bts.gov. Washington, DC.
16
Although the aircraft and its fuel account for most of the
weight on a flight, the “payload” (crew, supplies, passengers,
luggage, and air freight) does affect the flight’s carbon
footprint. The industry attributes 100 kilograms (220 pounds)
to each passenger and their luggage, although experts now
believe this estimate is too low. Because most large airlines
accrue additional revenues from carrying cargo, they add air
freight to an underoccupied plane whenever possible. The
emission factors used in this report do not consider air freight.
Instead, all emissions stem from an assumed passenger
load of 80 percent (the industry average). See Appendix B
for more details.
17
See endnote 1.
18
For aircraft with multiple classes of seats, we calculated the
area that each seat class occupies by dividing the pitch (in
inches) by the number of seats across the aircraft, multiplied
by the percent of overhead space devoted to each class. We
then converted this area to an economy-equivalent number of
seats. The same aircraft can have different seat configurations,
and thus varying numbers of economy-equivalent seats. For
example, Delta configures its Boeing 777s with 381 economy-
equivalent seats, while United’s 777s have 402 economy-
equivalent seats.
19
See www.seatguru.com for seating configurations for the
planes each airline has in service.
20
The type of engine in an aircraft does affect its carbon
emissions. If a manufacturer decides to use different engines
in various aircraft of the same model, estimates of carbon
emissions for that model will be less accurate.
21
Direct emissions alone are 21 pounds of CO
2
per gallon of jet
fuel. See: Energy Information Administration. 2007. Voluntary
reporting of greenhouse gases. Online at www.eia.doe.gov/
oiaf/1605/coefficients.html. Indirect emissions add 20 percent
to this amount. See: EPA 2006, Appendix B.
22
U.S. Senate Joint Economic Committee. 2008. Your flight has
been delayed again. Figure 2. This number includes indirect
emissions, as estimated in EPA 2006.
23
Domestic commercial air operations are responsible for
emitting a total of 144 million metric tons of CO
2
according
to: EPA. Forthcoming. Greenhouse gas emissions from U.S.
transportation and other mobile sources. Washington, DC. This
figure includes both direct and indirect carbon emissions.
24
Bureau of Transportation Statistics. 2004. National household
travel survey. Online at www.bts.gov/programs/national_
household_travel_survey/summer_travel.html.
25
Throughout this report we use fuel cycle emission factors.
That is, we include emissions from the extraction, shipment,
refining, and distribution of fuel, in addition to the direct
emissions from each vehicle’s tailpipe. See: EPA 2006. For
up-to-date fuel economy ratings for any vehicle, see www.
fueleconomy.gov.
26
The sole exception is first-class air travel covering distances of
500 miles or fewer, which has a slightly larger carbon footprint
than driving a typical (23 mpg) car that distance.
Endnotes