Editor’s note: This article is part of a series about sustainable cities. Read the other articles: "Sustaining our cities," "Room to grow," "Easing off the gas" and "A sustainable city is one that you love," "Sustainability – one building at a time" and "Nature by design."

Automobile. Spread-out. Sprawl. Download Full Image

These were just a few of the most common words used to describe Phoenix in a study conducted by Arizona State University’s Global Classroom. Students in the class interviewed local residents about how they perceive Phoenix. Participants were also asked to draw a map of the metro area from memory. The answers people gave and the maps they drew were analyzed to figure out how residents perceive Phoenix, and how that perception relates to the reality.

Some of the findings? Phoenix is big. But much of it is unmemorable, unconnected, blank space on the maps in peoples’ minds. This is the reality known as sprawl.

That Phoenix is dominated by its suburban sprawl is nothing new. The Valley’s economy started booming because of the housing market, on which – even after the recession – it still relies. But research shows that the spread-out-into-the-sunset model that many Western American cities have followed is unsustainable over the long term.

Because of this, city governments, urban planners and scholars are increasingly exploring an idea known as sprawl retrofitting. At Arizona State University, researchers have incorporated sprawl retrofitting into their toolkit for making cities more environmentally, socially and economically sustainable.

The story of sprawl

Emily Talen, a professor in ASU's School of Geographical Sciences and Urban Planning, says that the types of places being retrofitted are a “very failed urban form or urban condition,” which tend to be strongly automobile-centric. Rather than simply dismissing these areas, retrofitting seeks to build a more human-focused urbanism around them.

“This is really difficult, but you can’t just write these places off because they do define much of urban places in America,” says Talen, who is also a senior sustainability scientist in ASU’s Julie Ann Wrigley Global Institute of Sustainability. “You have to try to minimize your impact on the land by building more compactly.”

Sprawl development has been the dominant growth trend in the U.S. for the last 100 years, and has accelerated since the 1970s. It’s been spurred by a car-centered transportation network, economic incentives that favor single-family homes and a lingering cultural ideal of suburban-style living.

But sprawl has high environmental costs. In general, residents of sprawling cities generate more carbon emissions – or have a higher “carbon footprint” – than urban dwellers. This is due to the large amounts of driving such developments require and the prevalence of bigger, detached buildings. Since carbon dioxide is a greenhouse gas, it is a major contributor to global climate change.

Driving and the infrastructure it requires also create other types of pollutants. These include poisonous carbon monoxide; airborne particulates that can penetrate deep into human lungs; hydrocarbons and nitrogen oxides that create ground-level ozone and irritate the respiratory system; and sulfur dioxide, which causes acid rain.

Driving has additional negative effects on human health. Researchers have found correlations between obesity rate – and all of the health problems that go along with obesity – and sprawl development.

Even the roads themselves can cause problems. They absorb heat during the day and then release it during the night. This means that the city never has a chance to cool down, increasing the overall temperatures of urban areas compared to rural areas. This “urban heat island effect” exacerbates pollution, and can itself cause health problems.

Sprawl also has economic costs. For cities, public services and amenities are approximately 40 percent more expensive to provide in low-density areas, like suburbs, than in high-density areas. Additionally, suburban poverty has significantly increased over the past decade. This is particularly problematic because public services in the suburbs are difficult to access without a car. However, cars cost a lot of money to buy, gas up and keep up.

According to the Center for Housing Policy, after about 12-15 miles, the decreased cost of housing on the sprawling edges of suburbia is negated by the dramatically increasing cost of transportation. Families who live on the edges spend a disproportionate amount of their income just on transportation, and a majority of their income on the combined costs of housing and transportation.

What is sprawl retrofitting?

Sprawl retrofitting “involves the remaking of abandoned chain stores, dead malls, disconnected apartment complexes and segregated housing pods,” according to the Phoenix Urban Research Laboratory’s 2011 Annual Report.

The goal of retrofitting is to create a more sustainable urban environment within the context of the existing urban form. Sprawl retrofitting projects are centered around increasing density and diversity in a failed area.

Higher densities and compact urban forms minimize the need for energy, allow for non-motorized types of transportation and increase the efficiency with which cities can deliver utilities and services. And that's just in the realm of environmental sustainability. Reducing sprawl can also benefit social sustainability.

“You want to try to make sure that there is some level of interaction – social interaction – possibly leading to things like sense of community, sense of identity, concern for place, concern for neighborhood,” says Talen.

She adds that these can help “people feel responsible for the places that they live in.” Making sure that the population within an area is diverse is important to social sustainability, as well. Diversity helps foster good social interactions and equalizes access to resources. Conversely, when groups are trying to separate from each other, the city ends up spreading out.

How to retrofit a city

The main approaches to retrofitting are called reinhabitation and redevelopment.

Reinhabitation involves tweaking existing places to create new community spaces. It is useful in areas that cannot afford a lot of new construction. An example of this is mall retrofitting. Many struggling suburban malls, dead big-box stores and strip malls have been repurposed for use by community groups, artist studios, classrooms, offices, libraries or theater groups.

One goal of reinhabitation is taking spaces and turning them into “third places.” These are places that are neither home nor work, where the community can come together. Essentially, a third place is a local hangout that can serve to improve social capital among community members.

Redevelopment, on the other hand, is a total transformation. The underlying structures of a failed area are changed. Redevelopment strategies include building parks, increasing connectivity between streets and between residential and commercial areas, and increasing density and mixed-use capabilities. Reducing block size is another example of redevelopment. Smaller blocks increase the ease and appeal of walking, and correlate with reduced greenhouse gas emissions.

Another redevelopment strategy is known as a “road diet.” A road – typically a large, busy and potentially dangerous one – is transformed into a more pedestrian- and bike-friendly path. This can be done by narrowing the road and reducing the speed of traffic while adding or widening sidewalks and bike lanes.

Road diets are one of the more popular forms of retrofitting because roads are owned by cities. In the case of parking lots, strip malls or cul-de-sacs, multiple private owners can make implementing changes difficult. Mall retrofitting is simpler because it involves a large space with a single owner.

Retrofitting in Action

Aaron Golub, an assistant professor in ASU’s School of Sustainability and School of Geographical Sciences and Urban Planning, designed a retrofitting plan for the ubiquitous cul-de-sac. He co-led the project with assistant professor Milagros Zingoni from ASU's Design School."

“We took a cul-de-sac, and we asked, 'What are the needs of people?’” he explains.

One need his team identified was a focus on relationships. As a result, the cul-de-sac's houses were redesigned as multi-family dwellings, increasing the residential density and decreasing the private living spaces of residents. The greatest number of apartments were designed for singles or couples, but the team also included some apartments for families with children, and some ground-floor apartments aimed at seniors. This promotes diversity.

“Rather than having families with children in one area of the city, older people in another area of the city, young people living in a different area – why can't they all live together? Because older people could do daycare for the young, for the infants, it's a natural synergy. The older people could read to the young people. There’s so many areas where you could have this kind of intergenerational relationship. That's important,” says Golub, who is also a senior sustainability scientist.

Social interaction and walkability were encouraged by creating mixed-use spaces that were flexible enough to be transformed into whatever the residents might need. These transformations could include “food production, learning on-site, teaching on-site, energy production on-site and sharing space more,” says Golub. “We just questioned everything as best we could within the confines of a single cul-de-sac.”

Although the project was not implemented, Golub says, “it allows us to ask some questions about where we could go with what we have on the ground right now.”

Several other retrofitting projects have actually occurred or are occurring throughout the Phoenix Metro Area. Parts of Central Avenue in Phoenix also underwent such treatment. And in the Fiesta Mall district of Mesa, Southern Avenue is currently undergoing a road diet to go along with a district-wide retrofitting plan.

Talen, however, believes we still have a long way to go.

“What's actually been happening, in terms of sprawl retrofit, is very minimal, and at the very beginning stages,” she says.

Other than a few road diets, not many retrofitting projects have gone past the idea stage. Although more action is desirable, Talen says that ideas should still be encouraged.

“It’s good to just keep the dialogue going, get people’s interest in this topic and allow them to see the possibilities,” she says.

Written by Erin Barton, Office of Knowledge Enterprise Development