In the 1960s and 1970s, planned communities were created in response to concerns that typical subdivision regulations did not assure the presence of open, recreational space in residential areas. Today, they are the dominant form of development in several states, and cities and counties face a complex task in managing them.

In a planned community, architectural details, common open space, traffic circulation systems and building placement are defined to assure uniformity and compatibility with the surrounding area. The primary function of modern planned communities depends on the type of project, according to Daniel Mandelker, law professor at Washington University in St. Louis and author of “Planned Unit Developments,” a report for the Washington-based American Planning Association (APA) released in March 2007. Residential planned communities typically seek to preserve design quality and open space. A mixed-use planned unit development (PUD) combines residential with other uses to create a semi-autonomous community. Large planned communities may resemble incorporated cities. “They're building their own downtowns. They have commercial areas, industrial areas, residential areas,” Mandelker says. “They're going to look like a city pretty soon. Some of them already do.”

In 2006, the nation's 10 largest builders constructed 20 percent of the homes in the U.S. primarily in planned communities, according to Mandelker. In some areas of Florida and Colorado, planned communities make up 90 percent of all new development.

Irvine, Calif., started as a planned community in the early 1960s under the direction of The Irvine Co., which owned the 110,000-acre property that includes the city, and the University of California, which planned its design. The original plans were for a city of 50,000 people, with industrial, residential and recreational areas divided into semi-independent “villages.” In 1971, the city was incorporated, and today, its population exceeds 200,000 people and it covers more than 43 square miles.

Irvine Mayor Beth Krom says the city's land use planning makes it safer and more attractive to businesses and new residents, and it has influenced the development of other communities in Orange County. “I wouldn't say it's a matter of people saying, ‘It's a blueprint, we want to follow it,' but rather recognizing that a market has been created for a certain kind of housing product and a certain kind of community that people have, in some ways, sought to replicate,” she says.

According to Mandelker, because planned communities create small, self-contained communities in which residents can live close to where they work, they make better use of infrastructure and transportation facilities and reduce commuting time. They also encourage a variety of housing types.

Cities and counties that want planned communities need ordinances to make them best serve their area, Mandelker says in his report. The ordinance can define one type of PUD or allow different types. An agency must be selected to administer the ordinance, which can either supplement an existing zoning ordinance or establish an independent set of rules and regulations.

Manatee County, Fla., included planned development rules in its land development code, written in 1981 and expanded in 1990. Since then, hundreds of planned communities have located there, says Bob Pederson, the county's community planning administrator. Usually, a development that varies from the county's zoning ordinance, which was written in the early 1990s, is required to be approved as a planned community. “Almost all of the subdivisions of any size or scale in the last 10 or 12 years are done through planned development zoning,” he says.

The review process for a planned community is more time consuming, Pederson says, but he does not consider that a downside. “It's more work for county staff, but you see more detail, so you know what's going on,” he says. “The neighbors want to know what's going on in more detail. The commissioners want to know. The public wants to know.”