507485
research-article2013

JPEXXX10.1177/0739456X13507485Journal of Planning Education and ResearchKimball et al.

Article

Assessing the Potential for Reducing LifeCycle Environmental Impacts through
Transit-Oriented Development Infill along
Existing Light Rail in Phoenix

Journal of Planning Education and Research
33(4) 395­–410
© The Author(s) 2013
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DOI: 10.1177/0739456X13507485
jpe.sagepub.com

Mindy Kimball1, Mikhail Chester2, Christopher Gino2,
and Janet Reyna2

Abstract
There is significant interest in reducing urban growth impacts yet little information exists to comprehensively estimate the
energy and air quality tradeoffs. An integrated transportation and land-use life-cycle assessment framework is developed to
quantify the long-term impacts from residential infill, using the Phoenix light rail system as a case study. The results show
that (1) significant reductions in life-cycle energy use, greenhouse gas emissions, respiratory, and smog impacts are possible;
(2) building construction, vehicle manufacturing, and energy feedstock effects are significant; and (3) marginal benefits from
reduced automobile use and potential household behavior changes exceed marginal costs from new rail service.
Keywords
air quality, energy, environment, greenhouse gases, growth management, housing, land use, life-cycle assessment, sustainability,
transit-oriented development, transportation

As city and regional governments begin integrating sustainable practices into long-term planning, rigorous measures are
needed to understand the comprehensive impacts of land use
and transportation choices. One promising strategy, transitoriented development (TOD), seeks to synchronize the densification of land with new or improved public transportation
systems. Ideally, residents in TOD neighborhoods would
have easy access to public transportation and would be colocated with public and private services that meet a majority of
their social, physical, community, and economic needs
(Calthorpe 1993; Churchman 1999; Loukaitou-Sideris 2010;
Lund, Cervero, and Wilson 2004). Yet transportation policy
and land use policy often remain unsynchronized and narrowly focused, such as those aimed at raising transit ridership or increasing property values, and historically fail to
meet long-term expectations and goals (Bartholomew 2007;
Cervero, Ferrell, and Murphy 2002; TRB 2009). Decision
makers often use economic indicators to inform changes in
urban planning and transportation systems, while published
sustainability goals and regulatory compliance targets, like
those in Phoenix, Arizona, focus on more holistic social and
environmental goals (ADOT 2011; CCAG 2006; City of
Phoenix 2008). This paper henceforth refers to the Phoenix
metropolitan area as simply Phoenix, and distinguishes the
individual city as the City of Phoenix. Phoenix, with twentysix municipalities in Maricopa County, is one of the largest

metropolitan areas in the United States, where close to five
million people live in a region with few local natural
resources, few public transportation alternatives, and high
per capita energy footprints (City of Phoenix 2008; Gober
2005; Heim 2001; Rex 2000). As the global population shifts
toward cities, frameworks for assessing the energy and environmental effects of interdependent building and transportation infrastructure systems should be developed so that the
codependence and indirect effects are well understood.
This is particularly important in Phoenix, an area that has
incentivized auto-dominated travel and low-density sprawl
(Gober 2005; Heim 2001).
Life-cycle assessment (LCA) can be used to provide comprehensive measures of the land use and transportation infrastructure interdependencies. However, LCA has historically
Initial submission, September 2012; revised submissions, March and June
2013; final acceptance, August 2013
1

School of Sustainability, Arizona State University, Tempe, AZ, USA
School of Sustainable Engineering and the Built Environment, Arizona
State University, Tempe, AZ, USA
2

Corresponding Author:
Mikhail Chester, School of Sustainable Engineering and the Built
Environment, Arizona State University, 501 E Tyler Mall, Rm 252, PO Box
875306, Tempe, AZ 85287, USA.
Email: mchester@asu.edu

396
assessed building and transportation systems independently.
LCA is a framework for evaluating the raw material extraction, processing, use, maintenance, and end-of-life energy
and environmental impacts of products, processes, services,
activities, or the complex systems in which they reside.
While several building and transportation LCA studies exist,
they do not account for the full complexity of urban systems,
such as how neighborhood design affects transportation
mode choice and energy use in buildings. Phoenix has a
fledgling light rail transit (LRT) system and is trying to promote the development of city centers, yet physical growth is
largely unconstrained by geography and significant portions
of urban land area are vacant. An obvious solution for growth
that minimizes environmental impacts is placing TODs in
vacant lots near LRT stations. Denser neighborhoods can
have lower per-dwelling-unit energy and environmental
footprints (Norman, MacLean, and Kennedy 2006; TRB
2009), and increased use of public transportation can reduce
energy consumption and air pollutant emissions (Cervero,
Ferrell, and Murphy 2002; Chester, Horvath, and Madanat
2010a; Parker et al. 2002). However, the energy and environmental interplay between public transit, TODs, and auto use
has not been rigorously evaluated, and an LCA framework
should be developed to assess the environmental outcomes
of these interdependent systems.
This study assesses the interdependence of land use and
transportation infrastructure to evaluate how more efficient
and dense land use can accommodate population growth and
help meet regional sustainability goals. Densification can
reduce per-dwelling-unit energy consumption, improve
human health, reduce congestion and traffic, increase land
value, spur economic development, and grow local economies (Boarnet and Compin 1999; Cervero, Ferrell, and
Murphy 2002; Heim 2001; Kittrell 2009; Norman, MacLean,
and Kennedy 2006; TRB 2009). Densification and public
transportation strategies are both fundamental to achieving
urban sustainability goals (Churchman 1999; Lund, Cervero,
and Wilson 2004), but rather than optimizing existing systems, sustainability policies often focus on reducing energy
consumption and emissions through new growth initiatives
(Cooper, Ryley, and Smyth 2001; Echenique et al. 2012;
Norman, MacLean, and Kennedy 2006). If metropolitan
areas like Phoenix are to improve urban sustainability by
reducing energy use and air pollutant emissions while minimizing environmental tradeoffs, then policy makers, city
planners, engineers, and environmental agencies should
apply comprehensive assessment frameworks that evaluate
the interdependency between transportation and land use.
This study refers to this new approach as integrated transportation and land use LCA (ITLU-LCA).

LCA of Densification Strategies for
Urban Sustainability Goals
Previous studies have used the LCA framework to evaluate
the energy and environmental effects of buildings and

Journal of Planning Education and Research 33(4)
transportation independently, but no LCA studies were
identified that evaluate the future changes in energy and
environmental impacts from codependent land use and
transportation systems. There is an emerging body of LCA
research that evaluates transportation systems and the associated infrastructure including roadway construction, vehicle manufacturing, and fuel supply (Chester and Horvath
2009; Chester, Horvath, and Madanat 2010a; Cooney 2011;
Santero et al. 2011) and there are many LCAs of buildings
(Adalberth, Almgren, and Petersen 2001; Gustavsson and
Sathre 2006; Junnila and Horvath 2003; Masanet, Stadel,
and Gursel 2012). Typically building studies focus on comparisons of specific classifications (e.g., commercial office
building, multifamily residential building, or single-family
home) and rarely are the results expanded to the metropolitan scale that would be necessary for assessing the benefits
or costs of TODs.
Building LCA research to date has been limited in scope
and does not consider the secondary benefits and costs (i.e.,
transportation) of integrating these buildings into large-scale
urban systems. Building LCA studies evaluate either residential or commercial uses, and several focus on tradeoffs of
materials (Ramesh, Prakash, and Shukla 2010; Sartori and
Hestnes 2007). A small body of LCA literature considers
how building design affects neighborhoods, with the goal of
understanding densification effects (Adalberth, Almgren,
and Petersen 2001; Duffy 2009; Frijia, Guhathakurta, and
Williams 2012; Heinonen and Junnila 2011; Heinonen,
Kyrö, and Junnila 2011), but does not rigorously integrate
secondary impacts such as the travel behavior of those working or living in the buildings, particularly in response to the
addition of transit service. Norman, MacLean, and Kennedy
(2006) and Frijia, Guhathakurta, and Williams (2012) are
two of the more comprehensive neighborhood LCAs to date,
integrating transportation changes but extrapolating neighborhood impacts from data on individual buildings. In contrast, this study considers the energy and environmental
consequences from combined land use and transportation
changes, including upstream and nonlocal processes, when
new growth occurs in TOD locations as opposed to businessas-usual (BAU) automobile-oriented growth.
Phoenix has a history of supporting urban sprawl through
permissive residential zoning, agricultural land retirement,
and real estate development incentives (Gober 2005), but the
region is actively seeking solutions for sustainable growth in
the future (Maricopa Association of Governments 2011).
Sprawl has varied definitions but in this study refers to lowdensity, geographically dispersed development that separates residential from commercial land use (Bruegmann
2005; Galster et al. 2001). Since 1970, central Phoenix
experienced periods of reduced density and sprawl while
outlying land was developed (Rex 2000). City planners and
policy makers recently initiated densification strategies; the
region now has a widely used LRT and has received a
$2.9-million Sustainable Communities Grant from the U.S.
Department of Housing and Urban Development (HUD 2011)

397

Kimball et al.
to explore smart growth. The Local Initiatives Support
Coalition (LISC) has created a $20-million fund for development of near high-capacity transit (LISC 2013). The Cities of
Phoenix, Tempe, and Mesa (connected by the new LRT) promote mixed land use by limiting residential and commercial
growth (e.g., describing the intent of higher-density allowances in zoning regulations), and offering waivers and incentives for specific high-density construction near city centers.
While successful urban densification requires multiple physical, economic, and social preconditions (Cervero 1984;
Chatman 2013), this study evaluates the potential benefits
and costs of development strategies around existing LRT to
provide policy makers and planners with an understanding of
those energy and environmental effects.
In 2009, the Environmental Protection Agency (EPA), in
collaboration with the City of Phoenix, the City of Mesa, and
Valley Metro (Phoenix’s public transportation agency),
developed a “Strategic Package of Tools: Transit Oriented
Development in Metropolitan Phoenix” to chart a roadmap
for improving land use planning (EPA 2009). With this roadmap and the newly deployed LRT system, Phoenix will consider infill strategies where development takes advantage of
available land in urban areas rather than sprawling to the
periphery (Bruegmann 2005; Ellman 1997; Heim 2001).
Infill strategies use expedited permitting, permit fee waivers,
urban growth boundaries, reduced financing for suburban
infrastructure, and rezoning to dis-incentivize outward
growth (Bruegmann 2005; Ellman 1997). Phoenix faces a
projected 70–80 percent growth in population by 2040
(ADOT 2011; Morrison Institute for Public Policy 2011) and
is already battling poor air quality and escalating long-run
roadway costs. Infill strategies may hold potential for reducing future energy and environmental impacts.
Existing research has focused on the conditions that create healthy TODs (Cervero 1984; Cervero, Ferrell, and
Murphy 2002; FTA 2004) and has established that economic, social, and physical variables directly influence the
development potential and combined land use and transportation benefits from public transit. Unfavorable preconditions make future transit investments appear risky, such as
a weak local economy, zoning impediments, ample free
parking, and a low-density downtown (Cervero 1984).
While the economic downturn since 2007 has significantly
curbed Phoenix growth, the housing market is beginning to
rebound. New companies are moving to Phoenix, and several cities offer density bonus programs. Chatman (2013)
concludes that the automobile-related benefits of TOD are
not from transit access alone but from a combination of
travel changes that come with less parking availability and
greater access to jobs, destinations, and services. The
potential benefits from TOD infill in Phoenix are not just
about density but the policies and improved access that are
sometimes created with TOD. Parking fees and restrictions
are now in place in downtown locations, and the region is
actively encouraging TOD growth through grants, incentives, public–private partnerships, and planning initiatives

(HUD 2011; Kittrell 2009; LISC 2013; Maricopa Association
of Governments 2011).
Phoenix has significant unused urban land that can be
considered for TOD development, and developing an ITLULCA framework to comprehensively assess transportation
and land use coeffects can better inform decision makers of
upfront costs and long-term impacts. Within 0.5 mile of
LRT stations, there are 390 acres of vacant lots and another
340 acres of paved lots. These lots are zoned for both residential and commercial use and include neither historic
preservation areas nor restricted zoning that would prevent
residential infill. There is strong potential for Phoenix to
capitalize on the economic, social, and environmental benefits of TOD infill by maximizing the use of this land in a
form that minimizes future energy consumption and environmental impacts.

Methodology for Assessing TOD Strategies
An ITLU-LCA framework is developed to contrast densification around the existing LRT by utilizing vacant and parking lots against continued low-density automobile-centered
outlying development. Energy consumption and the potential environmental and human health impacts are determined
for increasing land use TOD commitment around the new
20-mile LRT system. For each TOD strategy, energy and
environmental indicators are determined for an equivalent
number of dwelling units (du) built in outlying areas that are
inaccessible to LRT.

Application of the Environmental LCA Framework
The LCA framework is used to evaluate the cradle-to-use
energy consumption and impact potentials of the combined
land use and transportation changes. The analytical system
boundary (see Figure 1) includes building construction,
building energy feedstock (primary fuel extraction and processing combined with transmission and distribution for
electricity and natural gas), building end-use energy (emissions and energy associated with electricity generation at the
power plant as well as natural gas used within the household), vehicle manufacturing, gasoline feedstock (crude oil
extraction and processing), and vehicle operation. For each
life-cycle component in Figure 1, end-use energy (not primary energy) inputs are determined as well as emissions of
greenhouse gases (CO2, CH4, and N2O), nitrogen oxides
(NOx), sulfur oxides (SOx), carbon monoxide (CO), particulate matter less than 10 microns (PM10), particulate matter
less than 2.5 microns (PM2.5), and volatile organic compounds (VOCs). NOX, SO2, CO, PM10, PM2.5, and VOCs are
either directly emitted or are precursors to the Criteria Air
Pollutants regulated by the EPA’s Clean Air Act and
Amendments. Greenhouse gas (GHG) emissions are reported
as CO2 equivalence (CO2e) using radiative forcing multipliers of 25 for CH4 and 298 for N2O for a hundred-year horizon (IPCC 2007). The Tool for the Reduction and Assessment

398

Journal of Planning Education and Research 33(4)

Figure 1. Life-cycle system boundary.

Note: Life-cycle groupings: B1: Building Construction (Athena Sustainable Materials Institute 2011); B2: Electricity Feedstock for Building Electricity Use
(ANL 2012); B3: Building Energy Use (Electricity Generation Emissions) (Ochsendorf et al. 2011; ANL 2012); T1: Vehicle Manufacturing (Chester, Pincetl,
et al. 2013; ANL 2012); T2: Gasoline Feedstock (Crude Oil Extraction and Processing) (ANL 2012); T3: Vehicle Operation Tailpipe (ANL 2012).

of Chemical and Other Environmental Impacts (TRACI) is
used to determine midpoint characterization factors that
quantify the potential for photochemical smog formation and
human health respiratory impacts (inhalation of particle pollutants) from air emissions (Bare 2011), and the specific
normalization factors used in this study are included in
the Supplementary Information (SI; available online at
http://jper.sagepub.com/supplemental). Phoenix experiences
chronic smog and respiratory issues, and the inclusion of
these measures, in addition to energy consumption and GHG
emissions, will provide a broader understanding of the interdependent environmental effects. By evaluating a broad suite
of environmental impacts in addition to GHG emissions (i.e.,
global warming potential), the potential for unintended tradeoffs (i.e., trading a reduction in one environmental impact
for an increase in another) will be reduced and the cobenefits
(e.g., decreasing GHG emissions and the potential for human
health respiratory impacts) will be clearer.
The functional unit in this prospective LCA is the LRT
corridor over the sixty-year building lifetime. The components included in the analysis are those that will change
between BAU and TOD scenarios. While many behavioral
changes may occur when people move to TOD neighborhoods, we focus on buildings and transportation effects
exclusively (as shown in Figure 1).
The building and transportation effects modeled in this
study are only a portion of the total changes that may occur
from shifts to TOD. Existing research has quantified the
housing and transportation fractions of an individual’s total
environmental footprint (Heinonen and Junnila 2011;
Heinonen, Kyrö, and Junnila 2011; Weber and Matthews
2008). As residents move to TODs, there may be changes in
their consumption of goods and services that are outside the
scope of this analysis. The LCA framework developed here
can serve as a foundation for future studies to assess these
lifestyle changes.

Urban Infill Potential
Five TOD densification strategies are developed to evaluate the life-cycle footprint of varying levels of residential
urban infill along the LRT corridor. For each TOD strategy, the number of dwelling units is used to compute the
life-cycle footprint of a corresponding BAU strategy. The
BAU strategies evaluate the same number of dwelling
units built in outlying areas where residents commute only
by automobile. Table 1 summarizes the development
potential of the TOD and BAU strategies. In the results,
each TOD strategy is directly compared to its BAU counterpart, and each strategy increases the aggressiveness of
residential densification.
Commercial building changes are not included because of
the dearth of data on the heterogeneous configurations of
retail, leisure, and office space; however, changes in nonwork travel capture some of the nonresidential TOD lifecycle effects. Commercial properties exhibit many different
configurations making assessment of TOD changes challenging. While this is also true for residential properties,
there has been significant research of and tools developed for
residential buildings (EIA 2008, 2012; Norman, MacLean,
and Kennedy 2006; RSMeans 2009a). A survey of resources
revealed significant challenges in assessing commercial
building energy use and design changes for TODs and was
therefore excluded from the study, ultimately producing a
conservative assessment of TOD environmental benefits.
Research results using the ITLU-LCA methodology that
include commercial buildings and associated travel indicate
that commercial-based energy consumption and travel
generate significantly more benefits in TODs than residential-based benefits (Chester, Nahlik, et al. 2013).
The scenarios demonstrate successively aggressive residential infill and the potential for increased land use around
LRT stations. All scenarios evaluate some configuration of

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Kimball et al.
TOD around every existing LRT station. It is possible that
TOD deployment would occur at a subset of stations and the
assessment is structured as a bounding analysis to show the
maximum potential benefits that could be achieved. The first
three scenarios (TOD1, TOD2, and TOD3) only consider infill
of vacant lots while the more aggressive TOD4 and TOD5
consider vacant and dedicated surface parking lots. TOD1
evaluates a future where vacant lots have been replaced with
single-family homes and avoid the equivalent development in
outlying areas. TOD2 evaluates infilling multifamily apartments where current zoning and land area allows, and singlefamily homes in the remaining vacant lots. TOD3 evaluates
rezoning all vacant lots for multifamily apartments, and only
places single-family homes where parcels are too small for
large buildings. TOD4 increases the available infill land area
by including paved lots and applies the same approach as
TOD2. TOD5 is the most aggressive strategy, evaluating the
construction of multifamily apartment buildings at the highest
allowable city densities (du/acre) on both vacant and parking
lots. For each of the five TOD scenarios, the counter scenario
(BAU) considers the equivalent number of dwelling units constructed in outlying areas as single-family homes. TOD strategies assume that policy mechanisms such as fee reductions,
expedited permitting, and zoning waivers will incentivize residential infill around the LRT stations. The strategies use densities of 6 du/acre for single-family homes and 46, 30, and 43
du/acre for City of Phoenix, Tempe, and Mesa multifamily
apartments respectively, consistent with the current zoning
codes (City of Mesa 2011; City of Phoenix 2011; City of
Tempe 2005). While many social, technical, political, community, and economic factors dictate how vacant and parking
lots are used, the scenarios are designed to illustrate environmental benefits and costs that could be achieved at a confluence of these exogenous factors.
The land area and residential densities are determined
from Phoenix assessor data. A generally accepted walking
distance of one-half mile (FTA 2004; Guerra, Cervero, and
Tischler 2012) is used for determining the number of potential TOD locations with access to the twenty-eight Phoenix
LRT stations. Potential land areas are tallied from zoning
maps and satellite imagery (City of Mesa 2011; City of
Phoenix 2004; City of Tempe 2005; Google Earth 2012) as
shown in Figure 2 for the 12th/Washington and 24th/
Washington stations. The assessment of available land across
the system is detailed and illustrated in the SI.
The conservative scenarios (TOD1, TOD2, and TOD3)
evaluate 390 acres of undeveloped vacant lots and the aggressive scenarios (TOD4 and TOD5) increase the available land
area to 730 acres by including paved dedicated surface parking lots. Each city’s zoning codes specify residential density
by du/acre. Observed densities for existing single-family
residences around light rail stations range from 1 to 9 du/acre
for City of Phoenix, Tempe, and Mesa, and the multifamily
densities range from 10 to 46 du/acre for City of Phoenix, 10
to 30 du/acre for Tempe, and 14 to 43 du/acre for Mesa (City

of Mesa 2011; City of Phoenix 2004; City of Tempe 2005;
Google Earth 2012).

Automobile and Light Rail Transportation
Automobile and LRT use, vehicle manufacturing, and energy
feedstock production are inventoried. In TOD strategies, it is
assumed that households will reduce, but not eliminate, automobile travel and switch to LRT (Cervero, Ferrell, and
Murphy 2002; Hankey and Marshall 2010; TRB 2009).
Work and nonwork travel distances are inventoried, assuming that one worker in each TOD household will use the LRT
for commuting (by biking or walking to the station) while all
other work and nonwork travel will occur by automobile.
Phoenix averages 1.8 workers per household (DOT 2011).
The BAU strategies assume that all workers will drive an
automobile for both work and nonwork travel, since new
outlying developments are unlikely to have access to bus,
biking, or walking routes.
Automobile commute distances vary within the scenarios, generally with shorter work trips for those living in
TOD neighborhoods (see Table 1). In TOD strategies, an
11-mile one-way work distance is used and is based on
current commute distances for the highest density neighborhoods in Phoenix (DOT 2011). According to the
National Household Travel Survey data, average annual
mileage per Phoenix household is 32,000 miles. This value
is used as a baseline for BAU1 and TOD1 travel, and the
nonwork travel is subtracted from the total. The nonwork
automobile travel is kept constant in all BAU strategies,
while the TOD strategies assume that higher-density living
will generate less nonwork automobile travel. Because the
BAU strategies evaluate more single-family homes constructed in outlying areas, successive BAU strategies
incrementally increase the work commute distance. Most
auto transportation is assumed to occur in BAU5, where
22,000 dwelling units would generate nearly 860 million
miles of auto travel per year. A summary of the calculations is provided in the SI.
The Greenhouse Gases, Regulated Emissions, and Energy
Use in Transportation (GREET) model (ANL 2012) is used
to evaluate energy consumption and emissions of a typical
future automobile through its life-cycle phases: crude oil
extraction and processing; vehicle manufacturing including
raw material extraction and processing; and vehicle operation. Changes in automobile travel are evaluated over the
sixty-year building lifetime. New fuel economy standards
require that cars achieve 55 miles per gallon (mpg) by 2025
(NHTSA 2012). Assuming a ten-year fleet turnover, a
weighted average future gasoline automobile is developed
for the next sixty years with a resulting fuel economy of 50
mpg. A higher-fuel-economy future vehicle (e.g., a gasoline
or hybrid vehicle with a fuel economy greater than 50 mpg)
is considered conservative in that it reduces the benefits of
TODs because shifting auto trips will have less energy and

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Journal of Planning Education and Research 33(4)

Figure 2. Land development assessment for the 12th and Washington and 24th and Washington stations.

Note: The light rail line is shown as bold black lines (note that there is a separated right-of-way for each direction of travel) and stations are dark shaded
(purple in the online version of this article, available at http://jper.sagepub.com) square icons. Around stations are heavy one-quarter mile and light onehalf mile circle boundaries. Vacant lots (conservative) are light shaded (orange in the online version) and surface lots (aggressive) are dark shaded (purple
in the online version).

air emissions benefits than a lower fuel economy vehicle.
This would also be true of electric vehicles being charged in
a greening electricity mix. The GREET 2 model (ANL 2012)
was used to develop energy and emissions inventories for
vehicle manufacturing based on the number of vehicles a
household would need over the sixty-year time span (given a
160,000-mile vehicle lifetime). It is assumed that lightweighting must occur (decreasing vehicle weight to 1,800
lbs) to achieve the 50-mpg fuel economy.
Additional light rail service is needed to meet the new
demand generated by TOD households in strategies 4 and 5.
In TOD1–3 it is estimated that the system already has the
capacity for the additional riders (National Transit Database
2011). The existing Valley Metro LRT system has an average capacity of slightly more than 66,000 passengers per day
and a maximum capacity of 91,800 passengers per day based
on train seats (Kinkisharyo International LLC 2008; National
Transit Database 2011). In TOD4 and TOD5, the new TOD
riders will exceed the available seats and standing room so
new trains must be put into service. In addition to the energy
consumption, manufacturing of the vehicles will also occur.
Train manufacturing was modeled with SimaPro and is consistent with the results of Chester, Nahlik, et al. (2013)
(PRé Consultants 2008).
It is anticipated that TOD residents will be more likely to
travel by bus in addition to rail; however, changes in bus
service are not obvious. As residents shift from fringe areas
to TODs, it is unclear if existing bus service will be reduced.
It is also unclear if an influx of new residents near light rail

will be large enough to justify increases in bus service that
hubs at LRT stations. However, if TOD residents commute
by bus to light rail stations and these trips are met by new bus
service then additional impacts will be produced.

Low- and High-Density Residential Buildings
The assessment of TOD infill around light rail stations is
based on a single-family home and a multifamily apartment
building model. The single-family home is 1,600 ft2, the
average house size in the light rail corridor (Maricopa County
Assessor’s Office 2012), and the multifamily apartment
building is 34,000 ft2 (approximately 1,100 ft2 each for 32
du), typical to the designs that are currently being used by
developers near light rail (DOE 2012; Michael J. Lafferty,
personal communication, September 19, 2012). Many different building designs could be used in the development of this
land, and the design chosen in this study is intended to serve
as a reasonable middle estimate, between a high-rise and
low-rise apartment building. As building designs change, the
per-dwelling-unit energy use may change and this is considered in the uncertainty assessment in the SI. The life span of
these buildings is assumed to be sixty years, consistent with
building LCA literature (Aktas and Bilec 2011; Athena
Sustainable Materials Institute 2011; Ochsendorf et al.
2011), and the results are normalized to this time period.
A materials-based life-cycle inventory (LCI) of energy
consumption and air emissions is developed for the construction of each building type. RSMeans (2009b) is used to

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Kimball et al.
Table 1. BAU and TOD Strategy Summary.

Strategy

Characteristics

1

Single-family homes, mixed
LRT/automobile commute
Single-family homes,
automobile commute

TOD
BAU

2

TOD

BAU
3

TOD

BAU
4

TOD

BAU
5

TOD

BAU

Dwelling
Units (n)

SingleFamily
(%)

Multifamily
(%)

2,200

100

–

390

100

–

370

6

94

390

100

–

1,800

4

96

390

100

–

2,000

5

95

730

100

–

3,500

4

96

730

100

–

3,600

Multifamily apartments,
limited single-family
homes, mixed LRT/
automobile commute
Single-family homes,
automobile commute

11,000

Rezoning, multifamily
apartments, single-family
homes where lot is
too small, mixed LRT/
automobile commute
Single-family homes,
automobile commute

12,000

Include paved lots,
21,000
multifamily apartments,
limited single-family, mixed
LRT/automobile commute
Single-family homes,
automobile commute
Rezoning, include
paved lots, multifamily
apartments, single-family
homes where lot is
too small, mixed LRT/
automobile commute
Single-family homes,
automobile commute

22,000

Land Area Land Savings Ratio
Demand
(acres saved per One-way Commute
(acres)
acre used)
Distance (miles)
0.94

11
13

3.6

11

15
4.0

11

17
3.7

11

19
4.0

11

21

Note: Summary of BAU and TOD strategies with number of dwelling units (du), proportion of housing structure type (single-family vs. multifamily), and
commute distance. Each TOD strategy fills the vacant lots within a half-mile of LRT stations, whereas each BAU strategy builds new homes that are
automobile-centric and inaccessible to LRT. The land savings ratio is the acres of development avoided (i.e., BAU minus TOD) per acre of land consumed
in the TOD scenario. TOD = transit-oriented development; BAU = business-as-usual; LRT = light rail transit.

determine the material profile of an average one-story home
and four-story apartment building, assuming typical assemblies for Phoenix (e.g., foundation, roof, framing). The buildings are then modeled in the Athena building LCA tool to
develop estimates of construction energy use and impacts
(Athena 2012). Materials listings for each building type as
well as the impact estimator results are reported in the SI.
Parking effects are also considered. For the single-family
home, a two-car garage is included, and for the apartment
building it is assumed that a parking garage is built with 1.5
spaces/du using existing parking garage LCA results to
model the structure (Chester, Horvath, and Madanat 2010b).
Building energy use and resulting emissions are determined from existing databases for each building type.
Multifamily structures tend to have lower per-dwelling unit

energy footprints than single-family homes because of a confluence of factors (including smaller dwelling unit sizes) that
may be affected by the demographics of inhabitants and efficiency gains in shared walls and HVAC systems (TRB
2009). Phoenix-specific estimates from the American
Housing Survey (U.S. Census Bureau 2012) are adopted for
both single- and multifamily building types and are validated
against results from other literature (see SI). Utility bills
from homes built in the last decade are used with average
electricity prices (EIA 2011) to estimate energy consumption. A Phoenix single-family home consumes 58 TJ/year in
combined electricity and natural gas, and a multifamily
apartment dwelling unit consumes 45 TJ/year of energy in
electricity only (EIA 2011; U.S. Census Bureau 2012). A
typical Arizona home consumes roughly 63 percent of their

402
total energy as electricity with the remainder natural gas
(EIA 2008, 2012, 2013), but the American Housing Survey
data suggest that multifamily apartments built in the last two
decades are transitioning away from natural gas use (U.S.
Census Bureau 2012). Given the uncertainty in the final
design of apartment buildings, the energy consumption associated with public spaces (e.g., elevators, common area lighting, and HVAC) is not included. Since construction of these
BAU or TOD strategies is likely to happen over decades,
energy consumption is evaluated with a forecasted 2025
region-specific electricity mix that incorporates renewable
portfolio standards (DSIRE 2012), and energy delivery is
assumed to be electric in apartments and electric and gas in
single-family homes. Electricity feedstock and generation
emissions are determined with the GREET Fuel Cycle Model
(ANL 2012). Natural gas use feedstock effects are also determined using laboratory-tested combustion values (EPA
1998) and GREET modeling (ANL 2012; EPA 2011;
Traynor, Apte, and Chang 1996). The SI validates residential
energy consumption estimates against several other sources
and also lists electricity generation mixes for 2009 and projected to 2025.

Energy and Environmental Effects of
TOD Strategies
The results show that the energy and environmental footprints associated with land use and transportation are heavily interdependent and reveal the potential for significant
human health and environmental savings from smart growth
strategies (Figure 3). There are increasing GHG emissions,
respiratory, and ozone impact reductions from the building
and transportation life cycles with each increasing densification strategy. TODs lower the life-cycle footprint in all
five strategies, largely the result of reduced automobile use.
Building life-cycle energy consumption and GHG emissions decrease by 9–25 percent while the potential respiratory impacts increase by up to 21 percent and smog up to 10
percent. In the case of respiratory and smog impact potentials, the transition to larger shares of electricity use (replacing natural gas use in households for electricity from a
heavy coal mix) combined with heavier material in multifamily buildings produces increases in impacts that are offset by transportation reductions. Buildings and transportation
combined decrease the total effects by as much as 36 percent for GHG emissions, 8.4 percent for respiratory impacts,
and 25 percent for smog formation potential. This is the
result of lower building energy demands paired with access
to LRT, reducing work and nonwork automobile use for the
households. Should residents access and egress light rail stations through new linked bus service then transportation
emissions in TOD scenarios will increase. Using natural gas
bus emission profiles from Chester, Pincetl, et al. (2013)
and assuming that all light rail commuters from the TODs
connect to/from light rail by bus, then over the sixty years
GHG emissions would increase between 0.15 and 0.18

Journal of Planning Education and Research 33(4)
percent for TOD scenarios and would have negligible
impacts on the results. The smaller TOD footprints would
not be possible without the existing LRT infrastructure, and
the results show that by utilizing the excess infrastructure
capacity there is a significant opportunity to lower the corridor’s GHG emissions footprint through infill strategies.
The energy consumption and environmental impacts from
expanding LRT operations will enable the reduction in automobile use that over sixty years decreases impacts from residents by as much as 44 percent, as seen in the energy
consumption results for scenario TOD5. In TOD4 and
TOD5, LRT capacity is exceeded and new trains must be put
into operation. However, the additional life-cycle impacts
are negligible when joined with the avoided effects from
denser living and reduced automobile demands. Small marginal costs that utilize the existing transportation infrastructure (in this case adding LRT trains) can lead to as much as
hundredfold marginal benefits in avoided automobile travel
and building energy. Figure 3 shows a blowout of the LRT
effects (green sidebar) since they are nearly invisible when
graphed together with the building and automobile phases.
The reduced automobile effects seen in the TOD strategies
would not be possible without residents using the 26,000
trips per weekday excess capacity of light rail (National
Transit Database 2011).
The results suggest that previous studies, by only considering use phases (e.g., building energy use or tailpipe emissions), fail to account for as much as 25 percent of total
energy consumption savings and up to 30 percent of GHG
emissions savings. Building end-use energy and vehicle
operation life-cycle components together account for 70–76
percent of energy consumption and GHG emissions in all
BAU and TOD strategies. The reductions seen in the TOD
strategies are largely the result of reduced automobile travel.
Previous TOD studies have typically considered building
energy use (the darkest red in Figure 3) and auto operation
(the darkest blue) exclusively (Adalberth, Almgren, and
Petersen 2001; Echenique et al. 2012; Norman, MacLean,
and Kennedy 2006). While these two components do account
for the majority of the life-cycle footprint of every strategy,
there are significant contributions from building construction
and energy (electricity and natural gas) feedstock (accounting for 7–11 percent of the total energy consumption and
11–18 percent of the total GHG emissions), and from vehicle
manufacturing and gasoline feedstock (accounting for 13–18
percent of the total energy consumption and GHG emissions). This reveals the importance of expanding analytical
system boundaries beyond operational (use) phases. Policy
makers and planners who only consider use phase effects
will underestimate the benefits and costs of their strategies
(see SI for a comparison of use-only phases vs. all LCA
phases). Even in the most conservative TOD1 strategy,
Phoenix can place the next two thousand homes near stations
and achieve 6.8–13 percent life-cycle impact reductions. By
rezoning all vacant lots and maximizing the use of multifamily apartments in TOD3, twelve thousand new dwelling units

Kimball et al.

403

Figure 3. Net impact potentials over sixty years.

Note: The figure shows the sixty-year life-cycle energy consumption, greenhouse gas emissions, respiratory impact potential, and smog formation potential for the decision to infill vacant lots with transit-oriented development (TOD) vs. low-density single-family home construction (business-as-usual [BAU]
growth) on the fringe. The building (shades of red in the online version of this article, available at http://jper.sagepub.com), automobile (shades of blue in
the online version), and light rail transit (LRT; shades of green in the online version) life-cycle effects are shown together. The LRT effects are not visible
against auto and building effects and as such are blown out separately on the sidebar. For each system (i.e., automobile, building, and LRT), operation,
feedstock, and manufacturing/construction results are shown in the vertical order that appears in the legend. Local impacts are indicated by white vertical
lines on the left side of the bar and remote impacts are indicated by dark vertical lines on the right side.

can be moved near stations and achieve 3.5 and 3.1 times the
reduction over TOD1 for life-cycle energy and GHG emissions. By including paved surface lots in TOD5, nearly
22,000 dwelling units can be infilled and achieve 4.0 and 3.6
times the reductions of TOD1.
Respiratory and smog impact potentials are dominated by
building energy use and feedstock production, as well as
auto manufacturing and gasoline feedstock production. The
inclusion of life-cycle components increases the respiratory
footprint calculations by as much as 290 percent and smog
potential as much as 119 percent. Respiratory impacts are
largely the result of surface mining operations that provide
coal to Arizona power plants (ANL 2012). These mining
operations generate significant PM10 emissions that create
the potential for respiratory impacts. Furthermore, the

shifting of building energy use from a mixture of electricity
and natural gas in single-family homes to only electricity in
apartment buildings increases the feedstock impacts for
TODs. Production of steel for building materials and vehicle
components also contributes to building construction and
vehicle manufacturing components (ANL 2012; Athena
2012). The smog impact potentials primarily result from
NOx emissions from ocean tanker transport of crude oil to
U.S. refineries and from coal electricity used in the supply
chain for concrete and steel building materials and vehicle
parts (ANL 2012; Athena Sustainable Materials Institute
2011). The construction and electricity feedstock respiratory
and smog impacts for apartment buildings are higher per
dwelling unit than single-family homes. However, these
upfront costs make possible significantly larger reductions in

404
reduced automobile travel life-cycle effects. At the very
least, Phoenix could add two thousand dwelling units in
TOD1 and enable 6.8 percent respiratory and 10 percent
smog impact reductions through reduced automobile use.
With rezoning, TOD3 will achieve a 1.0 and 2.3 times reduction over TOD1 for respiratory and smog impacts, and in
TOD5 a 1.3 and 2.8 times reduction.
LCA calls for the analysis of direct and supply chain
effects and captures both local and remote impacts. The LCA
framework transcends geopolitical boundaries in the assessment of large and complex systems, and urban sustainability
policies and decisions should develop accounting protocols
for assessing supply chain networks. For example, the building construction life-cycle component captures material production and its associated emissions outside of Phoenix, and
gasoline refining also does not occur locally. Furthermore,
impact potentials do not distinguish between upstream
effects that may occur in remote low-risk areas versus those
that may occur in heavily populated Phoenix neighborhoods.
A majority of the energy consumption and GHG emissions
occur locally (75 and 70 percent roughly for each strategy),
whereas the majority of the respiratory and smog formation
impact potentials occur outside of Phoenix (74 and 54 percent). The local and remote effects show that new methods
are needed for urban sustainability policies and decisions
that (1) include strategies for greening supply chains, (2)
improve environmental inventorying and develop allocation
models for upstream effects, and (3) identify upstream market and regulatory signals that incentivize local and remote
actors to reduce the impacts that are ultimately realized in
Phoenix.
The inclusion of commercial infrastructure changes
would likely increase the benefits of TOD due to additional
building energy efficiency gains (Chester, Nahlik, et al.
2013). Including commercial space would increase TOD
building construction impacts but could offset current big
box retail trends (FTA 2004). Mixed-use TODs are also
likely to have lower building energy use and feedstock
effects for commercial activities (Cervero, Ferrell, and
Murphy 2002; Guggemos and Horvath 2006). The counter
case would be if TODs induce new commercial infill but do
not offset BAU growth. Regardless, these results demonstrate the significant benefits in transportation effects from
reduced nonwork travel when TOD residents utilize more
local and transit-oriented commercial infrastructure. Research
in this area is ongoing and emerging methodologies will
facilitate the assessment of the benefits and costs from retail
and office infill with specific TOD typologies and both the
building and transportation (shopping and work travel)
effects (Chester, Nahlik, et al. 2013).

TOD Policy for Phoenix Environmental
Goals
Planners and policy makers should incorporate the contribution of environmental effects to the total benefits and costs of

Journal of Planning Education and Research 33(4)
urban infill strategies, including the interdependence of land
use and transportation systems, when developing urban
renewal and sustainability strategies. Currently, TOD and
transit strategy decisions “get driven more by political and
ideological considerations than by objective research” (FTA
2004, 133), and many of the assumed benefits are not rigorously quantified (TRB 2009). The results show that basic
infill strategies have significant environmental benefits.
Figure 4 shows the per-dwelling-unit avoidable energy consumption and environmental impacts from choosing TOD
infill over BAU growth. The benefits of TOD infill increase
with each strategy, with one exception, TOD4. TOD4
includes paved lots, and many of these parcels are too small
for multifamily apartment buildings. As a result, TOD4 has a
higher proportion of single-family homes than TOD3. This
tradeoff suggests that planners might seek to deploy TODs to
areas with sufficient land for higher density buildings to optimize the environmental benefits of infill.
The greatest environmental benefits occur when land-use
policies trigger the greatest reduction in personal automobile
travel, which are enabled by the use of the existing LRT system. The results are heavily influenced by the vehicle travel
characteristics of the new residents, and Figure 4 shows the
effect of an over- or underestimate of TOD household auto
vehicle miles traveled (VMT). The upper bound of the uncertainty bars show the effect of more household travel by LRT
(i.e., more than one worker per household commutes on LRT)
and the lower bound shows less (i.e., people move to TODs
but continue driving autos for the majority of their travel). The
upper bound is one standard deviation from the average and
the lower bound is 100 percent of TOD travel by automobile.
Where previous studies have only calculated the use phases, or
have not linked land use with transportation, the interdependent results show that transportation changes from land use
policy should be considered if the decision maker aims to
more accurately assess the benefits of TOD strategies. Phoenix
already has some TOD initiatives and mixed-use land development in progress and has even rezoned parcels for densification. Prior to TOD project selection, planners can use the
ITLU-LCA framework and results to understand how utilization of existing sunk transit infrastructure can position projects
to achieve enhanced public health and mobility benefits.
Planners and policy makers should recognize that TOD
deployment will produce upfront environmental impacts during construction that will enable long-term environmental
benefits that are 1.1 to 130 times greater than the initial environmental investment. In TOD2 through TOD5, the majority
of upfront impacts are the result of heavier building construction materials (specifically, concrete and steel). In TOD4 and
TOD5, new trains must be manufactured. Over time, however,
strategies that favor land reuse at maximum density (TOD3
and TOD5) have the potential for benefits that are three to four
times greater than single-family home infill (TOD1). The
upfront impacts should not be viewed as an uncontrollable
outcome of TOD development but should instead be targeted
for mitigation. LCA provides policy makers and planners

405

Kimball et al.

Figure 4. Impact potential savings per dwelling unit (BAU minus TOD).

Note: The figure shows the difference, per dwelling unit, between business-as-usual (BAU) growth and transit-oriented development (TOD) infill in each
strategy when considering the life-cycle energy consumption, greenhouse gas emissions, respiratory impact potentials, and smog formation potentials
sixty years after new dwelling units have been constructed. In the online version of this article (available at http://jper.sagepub.com), the red bars are
building life-cycle effects, the blue bars are automobile effects, and the green bars are new light rail transit (LRT) effects. The life-cycle processes that
are below zero are phases where the TOD strategy has a greater impact than the BAU strategy. The negative bar segments in greenhouse gas emissions
and smog potential are building construction and LRT operation (the other LRT phases are not visible at this scale and are detailed in the Supplementary
Information [SI]). The negative bar segments in respiratory potential are all three building phases, with LRT feedstock and operation below (see SI for
detailed results). The uncertainty bars are the difference in automobile life-cycle savings if all new TOD households still commute by automobile (lower
bound) and multiple TOD household workers shift to transit (upper bound).

insight into the outcomes of their decisions and provides
opportunity for mitigating those impacts through intelligent
planning and project incentives. Strategies for deploying TOD
should include mitigation requirements to minimize life-cycle
impacts. This could include requirements to use low-impact or
recycled materials, the use of Tier 4 construction equipment to
minimize air pollution, or the production of materials in locations that will have minimal human health or environmental
exposures. Furthermore, any incentives to shift TOD buildings
off of coal electricity (e.g., through rooftop solar incentives)
will have large air emissions benefits.
Future behavior is a critical element in the environmental
outcomes of TOD strategies and incentives can be offered to
ensure that maximum benefits are achieved. Residential sorting and self-selection might attract new TOD residents who
are already LRT riders and/or previous high-density dwellers;
therefore, the smaller TOD home energy or automobile footprints may be overestimated (Cervero, Ferrell, and Murphy
2002). However, regional policies and incentives might be
tailored to recognize the potential for long-term benefits, such
as modifying employer trip reduction programs or behaviorbased electricity rates, both of which are already active in
Phoenix. Furthermore, LRT ridership may depend on job
prospects near rail stations, so attracting employers to TODs
is likely to be an important component of urban growth initiatives. It is possible that the people who live in Phoenix TODs
are self-selected, that is, younger, willing to make longer

commute trips by transit to avoid auto travel, and likely to live
in higher-density buildings for short periods of time (Gober
2005; Cervero, Ferrell, and Murphy 2002). In deploying
TODs, Phoenix should consider developing long-term programs to assess the characteristics of inhabitants and develop
intelligent and adaptive incentive systems to ensure environmental benefits are maximized.
Regional planners and policy makers can prioritize direct
and indirect residential impacts from sustainability initiatives by identifying the benefits and costs of environmental
mitigation efforts. Several impacts occur in similar quantities
regardless of the BAU or TOD scenario. For example, electricity generation emissions for building end-use energy
make up 23–31 percent of the total life-cycle footprint for
smog formation in all TOD and BAU scenarios, yet the
building energy savings in smog formation emissions from
deploying TOD5 instead of BAU5 represent only 0.59 percent of the total smog reductions. In this case, more significant reductions can be achieved in the building energy use
phase by reducing high-emitting electricity sources in conjunction with the TOD initiatives. Similarly, technological
improvements that reduce automobile particle emissions
could be promoted based on the fact that the automobile
operation phase is 76 percent of the TOD5 respiratory savings but only 6–12 percent of the total life-cycle respiratory
impact footprint. Efforts to reduce smog and respiratory
impacts will produce the largest benefits by focusing on

406
power plant or vehicle technology, and those efforts will
require nonlocal industry partnerships. Since these effects
may be outside of the influence of city government, local
resources might focus on enabling and incentivizing TOD
infill whereas state and federal funding, or possibly national
lobbying and advocacy, could aim to produce technologic
solutions that reduce impacts from life-cycle processes.
By structuring the environmental assessment around the
decision to deploy TODs, the benefits of policies that utilize
existing infrastructure are shown. The impacts from expanding LRT service in TOD4 and TOD5 are dwarfed by the land
use benefits and automobile reductions that are enabled,
highlighting the advantages of synchronizing land use with
existing transportation infrastructure, as well as the massive
marginal benefits from small marginal LRT expansion costs.
While infill benefits have been discussed for some time
(Boarnet and Compin 1999; Calthorpe 1993; Churchman
1999; Ellman 1997), the results in this study show a distinct
advantage of TOD strategies for reducing environmental
impacts and only a small subset of interdependent infrastructure services have been considered. It is possible that TOD
will achieve environmental impact reduction cobenefits
through processes not included in these results such as
reduced water use, wastewater generation, greater impervious surfaces, and heat island creation. However, there is also
the question of how changes in lifestyle affect a household’s
consumption of goods and service (Heinonen and Junnila
2011). Given Phoenix’s historic path dependence toward
automobile-oriented sprawl, policies and initiatives that capitalize on existing infrastructure may promise enough benefits to break the automobile lock-in and low-density behavior.
Had it not been for Phoenix’s history of leapfrogging and
sprawl, this infill opportunity would not exist.
Energy and environmental benefits are just two dimensions of the total potential benefits of land-use densification
policies, and may increase as additional factors are included.
Technology advancements in manufacturing, construction,
and operation of cars, trains, and buildings are likely to alter
the benefits achieved from TOD infill, but not likely to change
the relative comparison between TOD infill and BAU growth
(i.e. advancements in housing construction will be joined
with advancements in apartment building construction).
Uncertainty in electricity generation, building energy use
efficiency, and automobile fuel efficiency are assessed in
the SI, and the combined worst-case uncertainty still demonstrates significant savings from TOD infill. As more city
residents live closer to public transportation options or their
place of work, multimodal travel becomes more attractive
(Cervero, Ferrell, and Murphy 2002; Parker et al. 2002).
Walking, biking, and public transit use may increase, leading
to greater reductions in energy use and emissions. Rezoning
is both time and cost intensive because of bureaucratic rezoning practices and regulatory procedures within cities.
However, if underutilized parking lots and vacant commercial lots become less valuable than land occupied with TOD,

Journal of Planning Education and Research 33(4)
the energy and environmental benefits could be enlarged significantly. Furthermore, economic and social benefits may be
realized, making a stronger case for TOD infill. Economic
benefits include increased economic activity, increased land
values, more efficient use of existing infrastructure, increased
employment, and increased transit ridership (Cervero, Ferrell,
and Murphy 2002; Ellman 1997; Golub, Guhathakurta, and
Sollapuram 2012; Parker et al. 2002). Social benefits include
increased accessibility to transit and public services, clean air,
greater conservation of open lands, increased social interaction, and better accommodation of projected population
increases (Cervero, Ferrell, and Murphy 2002; Ellman 1997;
Parker et al. 2002). The environmental results combined with
existing research on the economic and social benefits of TOD
produce a strong justification for Phoenix to maximize the
use of the light rail infrastructure that has already been
deployed.

Conclusion
The ITLU-LCA framework can be used to inform city leadership as they develop strategies to meet environmental and
sustainability goals. Furthermore, the cobenefits of land use
and transportation activity can be calculated with consistent
methods that satisfy the critical eyes of stakeholders at all
levels. TOD densification produces benefits across a broad
suite of environmental indicators, and the few short-term
negative impacts are far outweighed by long-term benefits.
In Phoenix, GHG emissions can be reduced by as much as
370 mt CO2e/du and energy consumption can be reduced by
nearly 5.7 TJ/du (the equivalent of 1.2 million households
each driving 460 fewer annual miles, or turning off all BAU
households for 3 days of the year). By transitioning the next
residential developments from outlying areas to TODs, the
potential for human health respiratory effects will be
reduced by 8.4 percent and photochemical smog formation
by 25 percent. The Arizona Climate Change Advisory
Group (CCAG) projects that the state’s GHG emissions
footprint will reach 147 mmt CO2e (148 percent increase
from 1990 levels) by the year 2020 (CCAG 2006). TOD
densification provides one solution, and at most (in TOD5
with 22,000 dwelling units) accounts for only 0.17 percent
of this future footprint. The 22,000 new dwelling units are
1.8 percent of the current 1.2 million residential properties
in Maricopa County (Maricopa County Assessor’s Office
2012). By expanding the opportunity for high-density walk,
bike, and transit-oriented neighborhoods to other regions of
the city (assuming non-automobile travel options exist and
are competitive), Phoenix could meet 7 percent of the
Arizona GHG emissions reduction goals by targeting
200,000 dwelling units for TODs instead of allowing continued low-density auto-oriented construction of outlying
regions.
This study is specific to Phoenix and shows that planners
can consider and justify land use strategies that require

Kimball et al.
capacity expansion of the existing transit infrastructure to
enable long-term impact reductions. During this research, and
subsequent expansion of this work (Chester, Nahlik, et al.
2013), local stakeholders both contributed to the design of the
study and showed enthusiasm for learning about the results
(see SI for a discussion of these interactions). Replicating this
study may not result in the same conclusions for a city with
less vacant space or without an existing light rail or other
transit system. Nevertheless, the ITLU-LCA framework can
be applied to other cities to assess the environmental benefits
and costs of urban revitalization strategies.
In each of the five TOD strategies, the combined land use
and transportation environmental benefits from densification
are greater than the benefits gained through disjointed planning efforts. In land use planning literature, TODs appear to
meet many of the demands for more affordable housing, economic growth, increased “livability,” curbing sprawl, and the
revitalization of aging downtown areas (Boarnet and Compin
1999; Cervero, Ferrell, and Murphy 2002; Golub,
Guhathakurta, and Sollapuram 2012; Loukaitou-Sideris
2010). In transportation planning literature, TODs seem to
be an antidote for congestion problems, low public transit
ridership, and increasing gaps between infrastructure maintenance costs and revenue streams (Echenique et al. 2012;
Hankey and Marshall 2010; Mashayekh, Hendrickson, and
Matthews 2012; TRB 2009). Dense TOD districts can be
successful without significant gains in transportation efficiency, while campaigns to increase transit ridership can be
marginally successful without changes to building energy
use at the rider’s home. However, coupling land use and
transportation policies by promoting residential infill near
light rail stations would reduce the energy and environmental impacts of population growth, providing benefits to residents in the neighborhoods and across the city.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to
the research, authorship, and/or publication of this article.

Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.

Supplemental Material
Supplementary material for this article is available online at http://
jper.sagepub.com/supplemental.

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Author Biographies
Mindy Kimball is a doctoral candidate in the School of Sustainability
at Arizona State University and a Lieutenant Colonel in the United
States Army. Her research interests include sustainable transportation, life-cycle assessment, and the national security implications of
climate change.
Mikhail Chester is an assistant professor with a joint appointment
in the School of Sustainable Engineering and the Built Environment
and the School of Sustainability at Arizona State University. His
research interests include the energy and environmental life-cycle

Journal of Planning Education and Research 33(4)
assessment of transportation systems including infrastructure
interdependencies.
Christopher Gino is a recent graduate of Arizona State University
with a Master’s of Science and Engineering in Civil, Environmental,
and Sustainable Engineering. His research interests include transportation systems and travel behavior modeling.
Janet Reyna is a doctoral student in the School of Sustainable
Engineering and the Built Environment at Arizona State University. Her
research interests include life-cycle assessment of infrastructure systems,
complex systems analysis, and interdisciplinary sustainability solutions.