This piece is part of the Sidewalk Talk series "15 Innovations That Shaped the Modern City."
Rules about how to build in a city are as old as civilization. In the modern era, zoning regulations---typically written by a municipality---have helped define the nature of our downtown neighborhoods and suburban developments. Following from a city plan, zones set the building types for a given area alongside details such as height, lot and setback dimensions, and required parking. The results can serve practical needs, such as keeping a noisy factory away from homes or schools, as well as more questionable ones, such as putting limits on the size of your neighbor's vegetable garden.
When early cities built walls to defend against outside invaders, they also made primitive zoning decisions by requiring businesses such as butcheries, with their foul smells and grisly tasks, to operate beyond the gates. As cities became more complex, civilizations including ancient China and the Vedas in India further divided their cities by use.
By the time of the Greek city-states, theorists had ideas that resembled modern zoning. Hippodamus---whom author Edward Glaeser calls the "father of European urban planning" in his book Triumph of the City---was the builder of the Piraeus, a carefully constructed port city that is still part of Athens today. Hippodamus planned a conceptual city whose primary purpose was to more efficiently separate uses and classes of people. "He divided the land into three parts," writes Aristotle in Politics. "One sacred, one public and one private: sacred land to supply the customary offerings to the gods, common land to provide the warrior class with food, and private land to be owned by the farmers."
During the Industrial Revolution, cities bulged with immigrants and workers, bringing about an anarchic arrangement of houses, tenements, factories, and markets. Administrators in Prussia and England came up with zoning to bring order to the chaos. "Zoning was very progressive, discovering that people could use the law to fashion the kinds of cities that they wanted," says Emily Talen, a professor of urbanism at the University of Chicago and author of City Rules: How Regulations Affect Urban Form. "These would be cities that were fair, equitable, keep noxious uses away from people, and be better organized."
The idea soon made the jump to America, where it spread like wildfire. New York City was first to enact comprehensive zoning, in 1916. A decade later, the Supreme Court sided with Euclid, Ohio, in halting a developer from using a parcel of land for industrial purposes. This decision enshrined the power of cities to control development and gave rise to "Euclidean zoning," which established the idea of single-use, such as residential, industrial, or commercial. Most cities soon followed in the footsteps of Euclid, although each municipality tended to define zones slightly differently.
During the 1950s, demand grew for homes in neighborhoods occupied by others of similar social and economic standing. City planners ensured that such suburbs existed by controlling lot size, building size, and even the number of dwelling rooms in homes. "Zoning is one of the classic ways to legally guarantee segregation," says Susan Henderson, a principal at the urban planning firm Placemakers. "Frequently there's such a differentiation of lot sizes in residential zones that there's absolutely no question that you're creating very distinct demographics."
During the same time period, car-ownership in the United States doubled. The interplay of zones and roads gave rise to suburban sprawl, significantly reduced walkability and influence of public places, and higher rents and the cost of living, since high-density buildings were restricted in most zones, leading to less housing supply.
In recent years, as people moved back downtown, there's been a rising demand for mixed-use communities with shops, work, and home all situated nearby. But zoning restrictions have contributed to severe housing shortages within the cores of high-demand cities. "The biggest problem zoning has had is the collective effect of keeping people out of good job markets," says David Schleicher, associate professor at Yale Law School specializing in land use and urban development. "There is a huge national economic effect when people can't live in cities like San Francisco."
The shortcomings of zoning have led to widespread interest in systems that favor mixed-use, walkable cities. Some experts support a system called form-based coding, which considers the form of buildings and spaces rather than how they're used, for instance allowing an unused house to be converted to a store selling food or clothing. Another alternative is performance-based code, which removes some use restrictions so long as the building performs to expected levels of public safety (such as pollution) or nuisance (such as noise)---sometimes called "pink" coding, word play for watering down the red tape.
Technological developments are likely to make performance-based codes more attractive in coming years. The Internet of Things has analogs outside: sensors for noise, artificial light, traffic, air quality, and other measurements. These are becoming cheap enough for widespread deployment, and data will likely also flow in from sources like self-driving vehicles. The ability to monitor these metrics could help make sure that cities are pleasant to live in without the layers of bureaucracy currently required.
Schleicher advocates safeguards at the state or federal levels, where more impartial bureaucrats would decide on allowed uses. But it's not easy to reclaim power from locals: take California Governor Jerry Brown's recent attempt to allow low-income housing projects to bypass a thicket of local fees and reviews that have driven up median home prices to nearly three times the national average. The attempt was smacked down by a coalition of interests including environmental groups, homeowners, and renter's unions. "Even if there are a bunch of journalists and academics saying things should change," says Schleichler, "people's interest in their house prices trumps my scribbling."