The trick, these days, when building a large new city is to think small, or at least small-town.
In the wind-swept high desert of the Antelope Valley, developers hope to construct the largest planned community in Los Angeles County history -- the "new town" of Centennial, with 70,000 residents on the vast expanse of the Tejon Ranch.
Despite its giant scale -- Centennial would have 23,000 homes -- backers are promoting its seven so-called village centers, clusters of shops, restaurants and community services that divide the huge project into identifiable neighborhoods.
"We're creating a place in the tradition of small-town America," said Randy Jackson, whose Costa Mesa planning firm is putting the finishing touches on Centennial. "It's really about people wanting to get away from the sprawl of large-scale suburbia."
Yet critics say Centennial could add to that sprawl if plans for jobs and transit services in the far-flung development fall short. Those issues are sure to be examined when the project is considered by the regional planning commission this fall, and by the Board of Supervisors next year.
Centennial stands out, said county Planning Director James Hartl, not only because of its size, but because it is not an extension of a metropolitan area.
"The project is out there 30 miles by itself, so it will have to have all of its own infrastructure and services as a stand-alone town," he said.
While Centennial planners boast that the community would create 30,000 jobs for 23,000 households, Hartl notes that "you can't force people to live and work in the same location." And employment opportunities often lag years behind home and retail construction.
That means traffic on southbound Interstate 5 could snarl as it reaches Santa Clarita, Hartl said, especially when the nearly 21,000-home Newhall Ranch project, already approved by the county, is included in the mix.
"So when you add the Centennial traffic, we're going to be interested in how they propose to solve that," he said.
Greg Medeiros, project director for Centennial, said van pools and express buses would take the new community's residents to jobs in Santa Clarita and Lancaster.
And Medeiros said he's already talking with biomedical and light-industrial companies about relocating to Centennial. Sites have also been set aside for a college, hospital and civic center.
Planner Jackson said a large Eastern university has expressed interest in building a West Coast campus at the proposed town. Consider the economic jump-start UC Irvine gave that community, he said. "Here, they're starting Day One to recruit the jobs."
But even some of the nation's most renowned planned communities -- such as Reston, Va., and Columbia, Md. -- initially struggled to lure large employers. And it took the Newhall Land and Farming Co.'s developments in Valencia nearly two decades to bring many jobs. Now, its jobs-to-housing ratio is almost 3 to 1, and Los Angeles companies regularly relocate there, said company spokeswoman Marlee Lauffer.
Recognizing the importance of up-front employment, some local governments have begun to force new town developers to produce jobs with each phase of housing. But there are no guarantees.
Mountain House, a new town under construction 60 miles east of San Francisco, is about to begin the second phase of its 16,000-home project but has yet to lure a big employer. The project, though still in its early stages, is envisioned as a self-sustaining community with 22,000 jobs.
To keep a lid on sprawl, a development agreement prohibits any of the 700 acres zoned for business from being turned into housing if commercial tenants can't be found. San Joaquin County officials also will analyze the project every time 2,000 homes are built to ensure that it is living up to its promise of affordability and job creation.
Historically, communities have evolved step by step, with construction of thousands of homes finally producing enough customers to lure large retail centers. Then, after many years of growth, the cities are large enough to attract big private employers.
Berkeley-based planner Peter Calthorpe, a guru for self-sustaining "new urbanist" communities that promote pedestrian-friendly neighborhoods, said new towns should provide plenty of jobs up front, an efficient transit system and far more dwellings per acre than the typical suburban tract of single-family homes.
"I don't like projects that candy-coat what is essentially a bedroom community with the patina of urbanism without the reality of urbanism," Calthorpe said. "There has to be a true mix of uses, higher housing densities and a jobs-housing balance."
Centennial supporters say their project meets those criteria. Housing would be varied and affordable: About 10,000 of its dwellings would be condominiums or apartments. And its 14.2 million square feet of commercial space would support about 30,000 jobs in two decades, planners say.