Transforming Transportation Demand

AuthorTrip Pollard
Page 328 Legal Pathways to Deep Decarbonization in the United States
I. Introduction
Transportation is central to the economy and quality of
life in the United States. It also is the largest source of
greenhouse gas (GHG) emissions. Transforming current
transportation patterns could generate deep reductions in
GHG pollution by 2050 and play a major role in limiting
the magnitude of climate change.
Eorts to cut transportation emissions have tended to
focus on lowering the amount of pollution per mile trav-
eled by seeking to improve fuel eciency and by promot-
ing cleaner fuels and vehicles. ese eorts are essential,
but this chapter examines a complementary approach that
should also be a critical component of eorts to decarbon-
ize transportation—curbing the number of miles travelled
by reducing the demand for motorized transportation. A
cornerstone of this eort is ensuring that practical, con-
venient, and appealing alternatives to driving are widely
available. Addressing demand is pa rticularly importa nt in
light of projected population and economic growth that
is forecast to further increase personal and freight travel.
Later chapters will exa mine other aspects of transportation
emissions reduction, including cleaner light-duty passen-
ger vehicles (Chapter 14), heavy-duty vehicles and freight
(Chapter 15), aviation (Chapter 16), and shipping (Chap-
ter 17).
is chapter begins with an overview of transporta-
tion’s contribution to climate change and the role of travel
demand in driving GHG pollution. It then reviews the
decision of the Deep Decarbonization Pathways Project
(DDPP) to assume, but not discuss, a modest reduction
in per capita driving in developing scenarios for reducing
U.S. GHG emissions by 80% from 1990 levels by 2050,
and summarizes other analyses that more thoroughly
assess potential GHG reductions by addressing demand.
e second part of the chapter identies laws, policies,
and programs at all levels of government, as well a s pri-
vate-sector actions, which can help achieve these poten-
tial emissions reductions. ese abundant opportunities
for change include steps to eliminate unnecessary travel;
Chapter 13
Transforming Transportation Demand
by Trip Pollard
Transportation is the leading source of carbon pollution in the United States, and transportation demand is a
key determinant of emissions levels. Although the Deep Decarbonization Pathways Project reports provide valu-
able analysis of a number of alternatives to slash greenhouse gas emissions, they do not investigate transportation
demand in any depth. Opportunities to transform transportation are plentiful and could dramatically reduce
greenhouse gas pollution and check the spread of roads, parking lots, and other aspects of our transportation sys-
tem that can destroy carbon sinks. Steps should be taken at the federal, state, regional, and local levels to remove
subsidies for driving; send better price signals to help internalize the costs of driving; remove barriers to low- and
zero-carbon transportation alternatives and provide meaningful rail, transit, bicycling, and walking options;
and promote more compact, mixed-use development patterns that can shorten or eliminate trips. ese steps
often complement each other and are most eective if implemented together. e pressing question is whether
the enormous potential to decarbonize transportation will be realized in time to help avoid the worst impacts of
climate change. Rapid technological innovation, demographic changes, public support for cleaner transporta-
tion choices, and the multiple co-benets these changes can bring—including health, economic, scal, national
security, and equity co-benets—can all help overcome barriers to decarbonizing transportation.
Page 329
to reduce miles driven when still using motor vehicles; to
switch travel to low- or zero-carbon alternatives such as
rail, transit, bicycling, and walking ; and to promote more
compact, mixed-use development that can shorten or
eliminate vehicle trips.
Althoug h innovative approaches to address trans-
portation demand are readily avai lable, shifting travel
behavior can be challenging, particularly in light of
the numerous factors that inuence individual deci-
sions—such as whether to drive or use less-polluting
alternatives like mass transit, how frequently to drive,
and where to live. (Individual a nd household behav-
ior are discussed fur ther in Chapter 3.) ere also will
be substantial political a nd institutional opposition to
some measures that oer the greatest potential to cur-
tail pollution.1 However, as the nal part of this chapter
highlights, addressing transportation demand in concert
with other carbon reduction eorts and recognizing the
signicant additional benets that demand reduction
oers—i ncluding i mproved health, economic de velop-
ment, community revitalization, decreased dependence
on foreign oil, and better access to jobs—can help over-
come barriers to decarbonizing transportation. And as
declining driving rates per capita and increasing use
of cleaner travel modes between 2004 a nd 2013 show,
travel behavior can shift. Of course, behavior can also
shift in ways that will increase GHG pollution, as the
increase in driving in 2014-2017 indicates. Steps to
shape the impacts of demographic, technological, policy,
and cultural cha nges on driving rates and to promote
innovation can enhance the prospects for making major
transformations that slash the climate impacts of trans-
portation—getting u s to where we need to go.
II. The Challenge: What Needs to Be
Achieved by 2050
A. Transportation: The Largest Source of
GHG Pollution
Transportation is the leading source of carbon dioxide
(CO2) emissions in the United States, and the level of
1. It has been observed that “[t]he more urgent the need to make deep cuts in
energy use and emissions from transportation, the more likely are required
policy actions to be disruptive to households and commerce and to present
policy makers at all levels of government with dicult choices.” T-
 R B, S R 307, P O 
R E U  G G E F U.S.
T 17 (2011).
transportation demand is likely to be a major determinant
of future GHG emissions.
As a report from the U.S. Department of Transporta-
tion (DOT) to Congress noted, “[O]ur historic approach
to transportation and land use has created an energy-
intensive system dependent on carbon-based fuels and
automobiles.”2 America ns’ personal travel totaled approxi-
mately 5.6 trillion miles in 2015, with almost 70% of that
total in cars and other persona l vehicles.3 Freig ht tr ans -
portation totaled over 5.25 billion ton-miles in 2015.4 As
a result, transportation requires enormous amounts of
energy, consuming an average of over 14 million barrels
of petroleum per day in the United States in 2017.5 is
makes transpor tation the largest source of oil consumption
in the country, accounting for 71% of total demand.6
Not surprisingly, burning that much fossil fuel makes
transportation a major source of GHG pollution. Annual
CO2 emissions from transportation increased steadily
from 1990 to 2005, rising from 1470.6 to 1860.5 million
metric tons of CO2-equivalent (MMT CO2-eq), declined
to 1665.8 MMT CO2-eq in 2012, but are rising again and
reached 1786.1 MMT CO2-eq in 2016.7 Transportation is
the largest single end-use source of GHG emissions in the
United States, accounting for about one-third of total CO2
produced by fossil fuel combustion.8 It surpassed electric-
ity generation in 2016 to also become the largest source
when ranking emissions by sector,9 and transportation has
been labeled “Climate Enemy #1.10
2. DOT, T’ R  R U.S. G G E-
—V 1: S R  C ES-10 (2010), available
3. B  T S, DOT, T S
A R 2017, at 2-2 (2017), available atles/docs/TSAR_2016.pdf
4. B  T S, DOT, N T-
 S 2018, tbl. 1-50,
5. U.S. E I A, M E R—
J 2018, at 69 tbl. 3.7c (2018) (DOE/EIA-0035(2018/6)), available at
6. Id. at 66 g. 3.7.
7. U.S. E P A, I  U.S. G-
 G E  S: 1990-2016, at 2-12 tbl. 2-5 (2018) (EPA
8. Id. at 2-13 g. 2-8.
9. U.S. E I A, supra note 5, at 186 tbl. 12.5
and 187 tbl. 12.6.
10. T D, F G, 50 S T C-F T-
: R U.S. T P  F G
W 1 (2016), available atles/

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