Urban sprawl defines unsustainable cities, but it can be undone

Analysis paralysis—being so overwhelmed by options you can’t pick a path—has new meaning thanks to climate change. Making the “right” choice has never been more complicated, but we’re here to help. This is Impact, a new sustainability series from PopSci.

In 2020, during her re-election campaign, Paris mayor Anne Hidalgo set out plans to make the French capital a “15-minute” city. 

The goal: to offer city dwellers easy walking or biking access to most of their daily activities, from shops and leisure activities to schools and even workplaces. The plan came complete with promises for more pedestrianization, the creation of bike lanes on every street, and the elimination of 60,000 parking spaces across Paris.

The 15-minute city concept is one of many ideas popping up among rising interest in the benefits of making cities denser, healthier, lower-carbon-emitting, and easier to get around. It is the latest catchphrase to describe the “new urbanism” movement which first arrived in the United States around 1990, says Reid Ewing, professor of city and metropolitan planning at the University of Utah. “The new urbanism promotes towns and suburban cities that are built the way we used to build them back around 1900, where we had corner stores and neighborhood schools, and we had higher [housing] density and connected street networks.”

It’s a picture that contrasts many cities around the world today, especially in the US, where decades of city-planning policies have supported huge areas of urban sprawl and sparsely populated neighborhoods. The towns we know today often lock residents into lengthy car journeys to go about their daily lives, leading to congestion, air pollution, long commutes, and a lack of exercise. As the world struggles to undo unsustainable systems, as well as the growing inequality between the rich and the poor, cities are making their way back into the spotlight as potential solutions—and missteps.

Defining urban sprawl is tricky, but in his research Ewing characterizes it with four components: low-density housing, segregated land uses (meaning housing is separated from shops, workplaces, schools and leisure activities), a lack of local town centers, and limited street connectivity. Atlanta is the classic example of urban sprawl in the US, says Jenny Schuetz, an expert in urban economics and housing policy at Brookings Metro. “It’s grown in population, but it’s grown in land area by much more, because the houses get bigger and bigger and farther and farther away,” she says. 

All this means high car traffic and low public transport use, which racks up a significant amount of carbon emissions. Ewing and his colleagues have estimated that more compact development in the US would lead to a 7 to 10 percent reduction in total transportation carbon dioxide emissions (the largest source of emissions by sector in the US) by 2050, compared to continuing urban sprawl. “If anything can be stated with certainty in urban planning, it is that concentrated development produces less in the way of vehicle emissions,” says Ewing. Transportation makes up the largest portion of emissions in the US, a huge emitter globally, so improved urban planning stateside would have a significant impact on global greenhouse gas emissions. 

What’s more, urban sprawl lends itself to big, detached houses, notes Schuetz. Each home in itself sucks up considerably more energy than compact apartments and homes. Separate, spread-out homes tend to need more energy for heating and cooling than the smaller houses found in inner cities because they don’t share common walls. As of 2015, a single-family detached home in the US used around three times as much energy as an apartment in a building of five or more different units. They also mean less land for everything else—like public parks and city green belts.

“Both our housing patterns and transportation patterns push people towards having very large carbon footprints per household,” says Schuetz. “So we drive a lot; we drive long distance; we live in large houses that use lots of energy; and we have policies now that bake in these choices.”

It’s not just the climate that is impacted by this model of development. “In sprawling areas, there are more traffic fatalities, prevalence of obesity, and worse air quality,” says Reid.

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And this car-dependent transport system also fails to provide mobility to people who are too poor to afford a car, or cannot operate a car for other reasons such as age or disability, says Basav Sen, director of the climate policy project at American think tank Institute for Policy Studies. 

Low-income families who own vehicles also use a far larger portion of their budget on them compared to wealthier counterparts, adds Sen. Rising house prices can force them to move ever further away from workplaces, adding even more to these costs. “Greater access to affordable and reliable public transportation options would go a long way towards providing much needed relief to lower-income households,” he says.

There are racial dynamics too when it comes to car use and urban sprawl in the US. “Lower-income Black households are much more likely to live in the central city, not own cars, and rely on public transportation, which is often not that reliable,” says Schuetz. Low-income Latino households are much more likely to live in the exurbs, or a semi rural area even further out from the city center than the suburbs, she says, which means people must own cars and drive very long distances.

Meanwhile, high-income white households live in low-density neighborhoods closer to the city, can afford cars, drive most places, and take up more space. In a sense, they get the best of both worlds—close proximity to everything urban centers have to offer, while still overusing emissions-heavy personal modes of transit. 

Before drawing up solutions, it’s useful to determine how the US got here in the first place. Urban sprawl wasn’t always seen with the disfavor it is today—it was the ideal, says Ewing. “If you went back to 1950 and talked to an urban planner, the urban planner would say, ‘Using zoning, we should hold down densities, and we should separate land uses, we should build cul de sacs, and we should have linear corridors of commercial development’.” 

The zoning laws of the 1900s and 1920s separated houses from industry for understandable reasons, says Schuetz: It made sense to keep polluting factories or smelly slaughterhouses away from residential areas. Forcing grocery stores and coffee shops far apart from homes, though, is harder to justify on health and safety grounds, she says. Instead, today’s zoning patterns are more about protecting the property values of high-income neighborhoods.

But the period when suburban sprawl really took off in the US was after the Second World War. This was also fueled by deep legacies of racism, says Sen. “Many of the new suburbs were exclusively white,” he explains. Neighborhood covenant restricted which buyers homeowners could sell to. Meanwhile, discriminatory lending policies of banks, which were condoned or even outright supported by the government, amped the inequity up to a nationwide scale, says Sen. 

As history has gone on, wealthier folks tend to spread to the outskirts of town. And transportation funding mirrored this—specifically emphasizing roads and highways for cars to get into the city, versus public transit to get closer-packed homes from here to there.

For decades, some 80 percent of America’s transportation spending has gone to roads and car-related infrastructure, with a max of 20 percent going to public transit, sidewalks, and bike lanes. This leads to a negative feedback loop, where low investment in accessible, clean, and timely buses means people don’t take them, leading city planners to invest in them even less, says Schuetz. “We’re subsidizing the costs of building new roads and widening existing roads to benefit the suburbs, and essentially starving our public transportation systems. We have made public transit slow, inefficient and unreliable,” she says. “And then we’re shocked when nobody wants to ride it.”

At the end of the day, individuals confined to car-dependent neighborhoods can be seriously limited in how much they can cut their personal carbon footprints–even if they want to. Solving this issue might require overhauling some people’s notions of an ideal urban living, and traveling, environment.

But changing the system as a whole would require bringing down scores of barriers. Oil billionaires such as the Koch brothers lobby against local governments investing in better public transit, all while older home-owning generations in comfortable places resist changes for social good, says Schuetz.

Additionally, investing in certain transport initiatives like subway systems always ends up being expensive due to the huge infrastructure changes involved. The global median cost for new subway lines is around $220 million per kilometer, but prices can be much higher in richer countries: New York City’s recent subway extensions added up to a whopping $1.3-1.6 billion per kilometer, according to a New York University report.

But not all the needed policy changes are so dramatic, says Schuetz. Ensuring streets have protected bike lanes, sidewalks, crosswalks, and stop signs to make it safe for people to walk are just a few low-cost ideas. Dedicated bus lanes could also allow mass transit vehicles to skirt traffic on major roads. And changing zoning laws to allow services like schools, shops, and cafes to be built closer to where people live is essentially free, as are changes to construct denser housing where it is currently not permitted.

Salt Lake City, another city known for its urban sprawl, is one place where these kinds of changes are being seen in action, says Ewing. In the Sugar House area, for example, zoning laws were changed to admit mixed and high build development. In addition, a streetcar line opened in 2013; as of 2019, ridership has increased 60 percent. “What we’re seeing in the city of Salt Lake is redevelopment plans and phenomenal amounts of development in centers,” Ewing notes. “The combination of the two–rezoning and transit–has made the biggest difference.”

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Some may argue that the advent of electric cars will help with transportation-related emissions. But they are unlikely to completely solve the many issues that grow out of burgeoning suburbs. 

“Even if you electrified everything, that’s not in fact going to get our carbon emissions down to where we need,” says Schuetz. Even the fairly conservative International Energy Agency has called for behavioral changes like walking, moving to public transport, or taking less flights for countries and communities to reach net zero by 2050. What’s more, the US government’s long-term climate strategy notes the importance of alternatives to cars like public transit, trains, and bikes. “We have to nudge people toward energy efficiency, which probably means smaller homes that are packed closely together in the urban core and then easier to serve with these transportation systems,” says Schuetz.

Another giant problem to tackle is affordable housing. Increasing rent and home ownership prices can cause two effects, Ewing says: They can push those who still long for a single-family dwelling out edges of cities, or lead people who want to have a more “urban experience” to take over affordable multifamily housing in the inner cities, causing a host of other gentrification problems.

Still, Ewing says that the US is seeing a move away from urban sprawl, such as the redevelopment of old commercial areas for mixed use. “It’s happening all over the country,” he says. Zoning code changes are helping to allow this more compact development, he adds; his research has shown that development around public transit stations can cut car trips in half. “We’ve added the ability to mix land uses a la the 15-minute city, which wasn’t the case early on in the 1950s.”

Since the COVID-19 pandemic hit, Paris has taken steps to get their walk-more, ride-more plan rolling by looking down miles and miles of streets from cars, banning cars entirely from the first four arrondissements of the glamorous city, and initiating what some have called the “largest public transit project in Europe.” 

Still, Paris is just one example. Sen says that meaningful investment in public transit, a shift of resources away from highway expansion, and a change in land use and street design are all still needed to break the “vicious cycle” of sprawl.

“There’s nothing inevitable about a highway-centric transportation system,” he says. “What was done through misguided public policy favoring oil companies, road builders, and car manufacturers can be undone through policy that puts people and planet over greed.”