The Clean Air Act of 1970 produced a revolution in envi­ronmental law. From its unique approach to federalism to its technology forcing provisions, it remains an innovative statute to this day. In light of the growing threat posed by climate change, federal administrators have worked to adapt its text to deal with greenhouse gasses and carbon emissions. Global warming, though, is not the only context in which the Clean Air Act (CAA) can be used in ways not originally intended. Although not meant as an urban planning law, the CAA’s Trans­portation Control Plans (TCPs) offer an opportunity to promote smarter growth and sustainable cities on a national scale.

PDF: Monck,* Not Just Air Pollution

I. Background

Cities are not shaped by accident but are instead a product of statutes, codes, and judicial opinions. From transportation policy to racial discrimination to affordable housing programs, decisions by federal, state, and local policymakers have created the blueprint for the modern American city. This section re­views the history of urban planning in the United States to show that commonplace features of our municipal environ­ments, from the width of our streets to the size of residential lots, were not random occurrences but instead the product of reasoned decision-making. This section will also show that many of the policy choices that made sense ten, fifty, or a hun­dred years ago are now the source of many of the ills that affect contemporary cities.

Since New York City introduced zoning to North America in 1916, ¹ the power to regulate land use has remained almost exclusively with municipalities.² The legal framework for municipal zoning in America can be traced back to Village of Euclid v. Ambler Realty Co. where the Supreme Court specifically authorized use zoning, even when it substantially reduced a property owner’s land value.³ In 1922, Euclid, Ohio used the then-innovative practice of zoning to prevent Cleveland’s industrial growth from altering the primarily residential character of the village.⁴ Euclid created the outline for modern zoning when it divided the land within its borders across six uses, three height ranges, and four area classifications.⁵ Ambler Realty, a property owner that intended to develop sixty-eight acres for industrial uses, found that its land had been restricted to residential and community development.⁶ Holding for the village, the Court found zoning to be a constitutional exercise of a municipality’s police power.⁷ Applying the law of nuisance, the Court wrote, “[a] nuisance may be merely a right thing in the wrong place, like a pig in the parlor instead of the barnyard. If the validity of the legislative classification for zoning purposes be fairly debatable, the legislative judgment must be allowed to control.”⁸

Although the federal government took a hands-off approach to zoning, decisions made in Washington played an outsized role in shaping American cities. In 1938, the Federal National Mortgage Association (now called Fannie Mae)⁹ was created to subsidize new home construction during the depths of the Great Depression by providing loans to new buyers.¹⁰ But by prioritizing loans in suburban areas while refusing to grant them in downtown neighborhoods, Fannie Mae foreclosed the opportunity of homeownership in America’s cities.¹¹ Later, the Housing Act of 1949 made home ownership a national priority by providing federal support for urban slum clearance and increasing the Federal Housing Administration (FHA) budget for mortgage insurance.¹² Following World War II, Veteran Administration (VA) loans and the Servicemen’s Readjustment Act helped build 2.5 million new homes in three years in the nation’s fast growing suburbs.¹³ Eventually, the FHA and VA provided mortgages for eleven million new homes, often for less than the cost of paying rent.¹⁴ Until China’s rapid urban expansion in the early 2010s, the post-war period in the United States saw the fastest pace of new home construction in global history. ¹⁵

The federal policy that may have played the largest role in the development of urban sprawl, however, officially had nothing to do with housing.¹⁶ The 1956 National Interstate and Defense Highways Act authorized the construction, within ten years, of forty-one thousand miles of high-speed surface roadways connecting American cities.¹⁷ At the same time, rates of dependence on private cars for personal transportation exploded. ¹⁸From 1950 to 1990, the population of the fifty-eight largest U.S. metropolitan areas increased 80 percent while the geographic area of those cities increased 305 percent.¹⁹ Commuters began using the interstate highway system not only to travel between cities, but also to get between jobs in the city center and homes in outer suburbs.²⁰ By 1950, the suburban population was growing at a rate ten times that of city centers.²¹ Due to the emergence of the automobile as the country’s primary mode of transportation, “[b]etween one third and one half of urban America’s land is typically dedicated to the driving and parking of vehicles.”²² Two-thirds of Los Angeles is devoted to automobile use, and in Houston there is “the equivalent of 30 asphalt parking spaces per resident.”²³

An often-overlooked element of urban planning is the role played by traffic engineers. “The desire for increased traffic volume—‘unimpeded flow’—has resulted in wider streets. While travel lanes on old streets are often only nine feet wide or less, new streets are usually required to have twelve-foot lanes.”²⁴ Intersection design, too, plays a major role in how people interact with their environment, and thus how urban planners design metropolitan and suburban areas. The availability of crosswalks, the presence of bicycle-specific signals, and the total number of lanes to cross all have an effect on an individual’s decision to walk, ride, or drive.²⁵ Modern intersections are a primary cause of congestion,²⁶ and they are designed mostly around the safety of automobile drivers as opposed to other types of users.²⁷Traffic engineers, who strive to maximize the flow of travelers, focus primarily on drivers as opposed to other types of users.²⁸

The politics of housing affordability and growth management has also long played a role in shaping American cities. Together, municipal zoning, building codes, and judicial opinions have been used to restrict new development, particularly denser types of housing. By forcing uniformity and homogeneity, these measures prevent diversity, not just in land use but in residences as well. The Mount Laurel doctrine, likely the high-water mark of judicial intervention into urban planning, created an affirmative mandate in New Jersey for municipalities to provide a realistic opportunity for residency by poor and moderate income families.²⁹ There, the New Jersey Supreme Court strongly criticized requirements for minimum home and lot sizes,³⁰ prohibitions on multifamily housing, and rules setting a maximum number of bedrooms a house may have.³¹ According to the court, such restrictions produced “an acute national housing shortage,” the brunt of which was “borne by persons with low or moderate incomes.”³² But the U.S. Supreme Court weighed in on housing regulations two years later in Village of Arlington Heights v. Metropolitan Housing Development Corp., where it held that the petitioner’s ban on multifamily housing in the center of the village was constitutional—even though it effectively barred minority and poor families from obtaining housing—because it had been uniformly applied and was not created with a “discriminatory purpose.”³³

Today, the provision of affordable housing remains controversial.³⁴ Although Mount Laurel remains good law in New Jersey, it has been limited to “growth areas” only.³⁵ Additionally, “[o]nce a municipality has satisfied its fair share,” the New Jersey Supreme Court held, “the Mount Laurel doctrine requires it to do no more.”³⁶

II. The Modern City Is Broken

Today, rules that once facilitated cheap home ownership in the suburbs now shackle millions of Americans to overpriced rental units in the city or long commutes on congested roads.³⁷ For too many, the simple task of buying a gallon of milk and some eggs requires a lengthy drive.³⁸ Parents have become semi-professional chauffeurs, spending more time driving to and from Little League games and band concerts than actually engaging with their children.³⁹ Acres of cities’ cores have been paved over for new road lanes and parking lots, with devastating impacts on natural spaces.⁴⁰ These consequences include destruction of the environment, harm to both young and old populations, and a failure to serve the desires of the millennial generation.

The environmental consequences of suburban sprawl have been well documented. Low density development takes up a significant amount of land.⁴¹ Reliance on private automobiles for transportation contributes significantly to global warming and air pollution.⁴² Single-family detached homes are energy inefficient, leading “suburban residents [to] spend huge amounts of energy heating and powering their larger homes.”⁴³ Sprawl can be disastrous for water quality by sealing topsoil beneath acres of asphalt, leading to chemical runoff into rivers, streams, and wetlands.⁴⁴

One-third of Americans are “too young, too old, or too poor to drive.”⁴⁵ These “stranded Americans” become isolated in the suburbs, unable to get to work, school, or a store by themselves. The low density and large geographic area of most American urban areas makes mass transit inefficient and makes walking or bicycling impossible for nearly all trips.⁴⁶ As a result, the average American household needs thirteen vehicle trips per day.⁴⁷ This affects not only people who are too young to drive, but also seniors who have given up (or lost) their licenses.⁴⁸ Unable to leave their houses, many suburban seniors are forced to spend their golden years relying on others for transportation, or living in retirement homes. ⁴⁹

Low-income residents often find themselves unwelcome in the modern American city. The affluent town of Huntington, New York, the subject of the Huntington Branch NAACP v. Huntington litigation, has been a microcosm of the difficulty of ensuring that affordable housing is available in many communities.⁵⁰ Though the town was explicitly ordered in 1988 “to rezone the 14.8 acre Matinecock Court site located at the corner of Elwood and Pulaski Roads in Huntington Township to [multifamily] status,”⁵¹ three decades later ground still has not been broken⁵² and 1,500 people have joined the “Stop Matinecock Court” Facebook group opposing affordable housing in their community. ⁵³

Millennials’ needs are especially unmet by the modern American city. Today’s young professionals have rejected the suburban model of single-family detached housing of yesteryear.⁵⁴ It is not exclusively an issue of affordability—millennials are spending more on rent,⁵⁵ renting for longer periods,⁵⁶ and saving larger amounts of money⁵⁷ than prior generations. Instead, millennials are looking for something they cannot find in the suburbs: the city.⁵⁸ The next generation of home, apartment, and condominium dwellers are seeking smaller homes in a more urban environment with public transportation options, but cities and towns have been slow to reform their building codes to accommodate contemporary demands.⁵⁹ Downtowns, from which older generations fled, have in the past. Forty-eight percent of respondents reported that they would prefer to live in communities containing houses with small yards but within easy walking distance of the community’s amenities, as opposed to living in communities with houses that have large yards, but they have to drive to all amenities. And while 60 percent of adults surveyed live in detached, single-family homes, 25 percent of those respondents said they would rather live in an attached home and have greater walkability.”). Downtowns, from which older generations fled, have been embraced by young people, more than 35 percent of whom now live in city centers.⁶⁰

America’s current approach to urban planning is failing. The environment, the young, the old, and the poor all bear the cost of current laws that encourage low-density development of land on cities’ fringes. Millennials with savings and a desire to purchase a home find themselves in a housing market with limited suitable supply.

III. A Path To Better Urban Planning

City planners should encourage mixed-use development by implementing zoning rules that permit buildings to contain both commercial and residential functions. Zones of differing, but compatible, functions should be located close to one another. Instead of maintaining strict separation between houses, businesses, offices, and clean industrial facilities, planners should encourage mixed-use development and consider the five-minute walk when drawing zoning maps. “Experience suggests that [a quarter mile] is a distance . . . most Americans simply feel dumb driving.”⁶¹ When shops, schools, and parks are located within a five-minute walk of someone’s home, that person is far more likely to choose to walk than to drive.⁶²

To maximize the number of people that live in that walk­ing range, cities should eliminate minimum square foot and maximum bedroom requirements. Denser construction, re­duced lot sizes, multifamily units, and smaller apartments will create the density necessary to ensure an adequate customer base for local retail. Larger shopping districts should also be integrated into housing developments instead of attached on peripheral arterial roads. Although such shopping districts may be further than a five-minute walk away for some resi­dents resi­dents, communities can make bicycling a viable alternative by placing these areas in neighborhoods (instead of along a busy highway), and by providing dedicated bike lanes or trail con­nections. ⁶³

Transportation Control Plans (TCPs), which were authorized by Section 110 of the CAA, provide a means for a national approach to improved urban planning. The provision created federally enforceable requirements that state governments impose land use and transportation controls to reduce air pollution.⁶⁴Although this program was greatly reduced in the face of public outcry,⁶⁵ its revival could lay the tracks for a unified national approach to more sustainable urban growth.⁶⁶

Intended to reduce air pollution emissions from mobile sources, TCPs formerly gave the Environmental Protection Agency (EPA) sweeping authority to mandate that cities take measures to reduce vehicle usage, such as subsidizing mass transit, creating vehicle free zones, and “prevent[ing] future urban growth from generating large volumes of traffic.”⁶⁷ Improvements to pedestrian and bike facilities, such as separate travel lanes and storage lockers, were also called for. ⁶⁸

Perhaps the most sweeping element of the TCPs, though, was a mandate that the EPA implement any “land-use and transportation controls” that “may be necessary” to meet air pollution limits.⁶⁹ No further specifications were provided, seemingly granting federal administrators unfettered authority to rewrite cities’ zoning and building codes.⁷⁰ The reaction was swift. By 1975, just five years after the CAA was passed, the District of Columbia Court of Appeals held that the bike and bus lane components of TCPs were outside the federal government’s constitutional authority.⁷¹ In 1977 the EPA was stripped of its power to use land use controls to fight air pollution, and Congress explicitly prohibited the agency from imposing urban growth controls.⁷²

In early 2001, the EPA instituted a program where cities with high levels of air pollution would receive federal credits for promoting sustainable growth principles.⁷³While nonbinding, these incentives could be a model for a larger federal role in land use control. The federal government could continue the incentive-based approach and encourage cities to implement specific zoning and land use rules in exchange for grants.⁷⁴Unfortunately, in the nearly two decades since these incentives have been offered, they have had minimal impact—suburbs have continued to grow, and public transit systems remain inadequate.⁷⁵

Alternatively, reauthorizing the TCP program would allow the EPA to require states to impose sustainable urban plan­ning techniques, and to create a federally enforceable mandate under the provisions of the CAA. To preserve local control, Congress may wish to give cities a first shot at implementing the ideals of sustainable urban planning. In this scenario, only a failure to meet the density requirements or the predetermin­ed goals of increased public transit and nonmotorized travel would trigger federal intervention. The constitutionality of the original TCPs was never decided by the Supreme Court.⁷⁶ Since the 1970s, the Court has shown a willingness to allow the federal government to promulgate land-use regulations for environmental protection. ⁷⁷

Independently of the federal government, cities could do much to improve their urban environments. Counterintuitively, more (not fewer) roads should be built, but those roads should be narrow and difficult to navigate. Far from being safer, “wide streets lead to an increased number of traffic accidents, since people drive faster on them.”⁷⁸ Data suggest that this increase in accidents is exponential: a thirty-six-foot-wide street is four times more dangerous than a twenty-four-feet-wide street.⁷⁹ “Posting speed limits to slow traffic on high-speed roads is futile, because people drive at the speed at which they feel safe,” not the speed that is permitted.⁸⁰ Pedestrians and bikers are less likely to use a street where people regularly drive over the speed limit, particularly if they are travelling in automotive traffic lanes. ⁸¹

There are two obvious solutions. The first is to narrow streets and design unusual intersections, which would force drivers to pay more attention while driving. Narrower streets feel more dangerous, which naturally cause drivers to slow down. ⁸² Not including a passing lane, or even room to get around a slow-moving vehicle, may cause temporary annoyance, but also produces slower traffic. ⁸³ A review of the research on the relationship between road width and safety concluded that narrower roads were better for all travelers: drivers, cyclists, and pedestrians. Narrow streets not only produce more consistent vehicle traffic speeds, but they also reduced the number and severity of crashes. ⁸⁴ Designing unusual intersections has also been shown to have a positive effect on road safety.⁸⁵ Roundabouts, for example, “are often safer, more efficient, less costly and more aesthetically appealing than conventional intersection designs . . . [and] are designed to improve safety for all users, including pedestrians and bicycles.”⁸⁶Or consider the “Confusion Corner” in Stuart, Florida, maybe the safest intersection in the entire United States.⁸⁷ Despite the fact that seven streets and an at-grade railroad all converge, the intersection has recorded only a single accident in decades because drivers are forced to slow down and pay particular attention as they approach. ⁸⁸

Second, cities should segregate traffic types. This can be done by creating separate lanes for drivers, bicyclists, and pedestrians. These lanes should be far enough apart to create both actual and apparent separation—simply putting lines with a picture of a bike in the center of a freeway lane is unlikely to inspire someone to start pedaling there. Colorado’s U.S. 36 corridor is a good example. Connecting Boulder to Denver, the roadway is a busy six-lane expressway.⁸⁹ A twelve-foot-wide bike path parallels the expressway for most of the distance, giving commuters the option to bike between the cities.⁹⁰ The bike path crosses the road in several places but is always separated via an aerial bridge or under-roadway tunnel. Throughout the length of the bike path a fence and median protect cyclists from automobiles.

If a city cannot achieve this degree of separation, whether because of limited space or constrained budgets, regulations could call for some other form of barrier between vehicle and other travelers, like bollards.⁹¹ On-street parking is one particularly effective barrier because it constructs a physical and visual wall between a sidewalk and traffic lane, and it forces drivers to slow down and focus on driving. ⁹²

IV. Negative Implications and Mitigation Measures

These reforms are not a panacea. Municipal zoning and land-use requirements drive up costs to develop new housing, and additional greenspace and parks reduce the amount of developable land in a city. Compare Houston’s absence of zoning to Boulder or Portland’s restrictive rules, for example. Houston is famous for its lack of zoning rules and restrictions on land use.⁹³ This has resulted in a complete free-for-all of development, with housing and businesses sharing a block and skyscrapers towering over single-family homes.⁹⁴ Thanks to Houston’s seemingly limitless growth, Zillow’s chief economist classified it as “one of the most affordable housing markets in the country.”⁹⁵ While Houston was the nation’s fastest growing city between 2000 and 2010, the median home price was only $144,900.⁹⁶ In contrast, Boulder and Portland, two cities noted for their restrictions on new development and protection of greenspace, are seen as increasingly unaffordable. ⁹⁷

To help solve the affordability problems associated with extreme land use regulation, cities should encourage “granny flats,” backyard cottages, and basement units, each of which can increase the number of households on a lot without changing a neighborhood’s character.⁹⁸ Alternatively, municipalities can follow New York City’s lead and incentivize private developers to include affordable housing in new residential buildings. The Big Apple allows larger buildings and provides tax abatements and bond financing to builders who agree to set aside approximately 20 percent of their units for low- and moderate-income residents.⁹⁹ If rezoning will “substantially increase potential housing capacity in strong markets, the City will require a portion of the new housing developed to be permanently affordable to low- or moderate-income households in order to ensure diverse and inclusive communities.”¹⁰⁰ Further, the elimination of multifamily housing bans, large lot mandates, and minimum square foot requirements should facilitate more affordable housing in areas that have traditionally been associated with urban sprawl.

The displacement of longtime, often poor and minority residents must also be considered with any urban planning project. Cities should take measures to blunt some of the worst impacts of gentrification. The New York City approach of requiring developers to set aside a certain percentage of new apartments as rent-controlled in new buildings offers one solution.¹⁰¹ Local dynamics might change that percentage in different cities, or even in different neighborhoods within a city.

Even if a city implements some of these measures, it is possible that new development will force some longtime residents to move; but affordable housing would remain available in the same area, preventing historic communities from being completely displaced. Planning commissions should also be proactive in communicating with residents who would be affected by a development project. Understanding their needs and incorporating them into the site approval process can maintain the historic character of urban communities. ¹⁰²

Conclusion

America’s zoning policies and building codes are broken. Rules once intended to promote home ownership among the rapidly expanding post-war middle class have created cities that fail their residents. Sprawl has left children, the elderly, and the poor stranded on cul-de-sacs and dead-end roads, while minority populations remain segregated in the inner-city. Huge areas of land are paved over, and millennials who want to live in walkable neighborhoods with a sense of community are forced to pay inflated rents, or follow the path laid out by Monica and Chandler from the television sitcom Friends and move to the suburbs.¹⁰³

It does not need to be this way. Tools like the Clean Air Act can help urban planners develop new regulations to facilitate more sustainable city growth and provide better options to stranded Americans on a national scale. Decisions made now will dictate the shape tomorrow’s cities take: whether they will be filled with identical houses cut off from each other by a pri­vacy fence and acres of asphalt, and segregated along racial and class lines; or whether they will be a diverse mix of homes, businesses, and offices. The federal government, states, and municipalities must work together to build more vibrant and more sustainable urban environments. By rewriting zoning rules, narrowing roads, and promoting denser construction, cities across the county can become the kinds of places where Americans want to live, work, and play.

*J.D. Candidate, 2019, University of Colorado Law School; Associate Editor, University of Colorado Law Review; President, Student Bar Association. I would like to express my deepest appreciation to the many Law Review members who assisted with this Comment.