They danced the tango in Portland, Ore., they're doing the samba in New York, and by the end of this month, they'll be dancing in the streets of San Francisco. It's urban planning with a Latin twist, a simple idea imported from South America for transforming the cityscape. Temporary street closures, or ciclovias, are sweeping across the US, as cities take a new look at alternative uses for their streets.

It all started in Bogota, Colombia, about 30 years ago. The ciclovia – which means "cycle way," or bike path, in Spanish – was designed as a relatively inexpensive way to promote walking and bicycling, and to encourage the mingling of people from all backgrounds in the city's streets.

It worked. Every Sunday Bogota draws nearly one-fourth of its population of 7 million out to walk and cycle 81 miles of car-free streets.

In the early years of the event, residents from the poorer sections of town, many of them of Indian descent, and those from more affluent neighborhoods, of European descent, would halt at one another's boundaries. After a while, though, those invisible lines began to melt, and now people from all over the city mingle freely.

Gil Penalosa supervised Bogota's ciclovias when he was the city's parks and recreation commissioner from 1995-97. He expanded the program from eight to 70 miles of closed streets and now promotes ciclovias all over the world from his Toronto-based nonprofit, Walk & Bike For Life. Mr. Penalosa likes to quote Central Park designer Frederick Law Olmsted on the positive benefits of public spaces. Penalosa notes that Bogota's ciclovia "is one of the few places where the owners of large corporations share activities out on the streets with their own employees."

Some US cities are hoping for similar social benefits. When it launches its first ciclovia Aug. 31, San Francisco is hoping to help connect a currently isolated, low-income neighborhood, the Bayview, with other parts of the city on a six-mile route. Portland's June 22 event linked an African-American neighborhood with newer, gentrified neighborhoods on the city's north side.

For some public space advocates, this is just the beginning: "London, Paris, and other cities have taken this idea much further, but they started with temporary street closures," notes Wiley Norvell, whose organization, Transportation Alternatives, is participating in the New York event. "Once you get out of the mind-set of 'all cars all the time,' all sorts of possibilities open up."

Every summer Paris closes a portion of one of its major expressways and creates a temporary beachfront and promenade – complete with sand and palm trees – along the Seine. Starting with the closure of one street more than 40 years ago, Copenhagen has gradually developed a central city that prioritizes walking and cycling.

With the encouragement of Mayor Michael Bloomberg and the city's transportation czar, Janette Sadik-Khan, New York is becoming an open-air laboratory for alternative uses of public space. On three Saturdays this month, seven miles of streets in Manhattan, including a long stretch of Park Avenue, will be closed to traffic for six hours each day. Vehicular traffic has been permenantly removed from two lanes of Broadway in midtown Manhattan to make room for pedestrians and cyclists. As part of this transformation, people will soon be sitting at cafe tables on what used to be one of Broadway's busy southbound lanes.

Barbara Randall is in the thick of this latest experiment. She heads an association of property owners in midtown Manhattan's Fashion Center. Both she and her organization are fully in support of the new project. Ms. Randall points out that New York City's population is expected to grow by 1 million in the next 20 years and asks: "How do we accommodate them as they move around the city? The obvious answer is to use our limited space more efficiently by freeing up more of it for pedestrians and cyclists. And if you transform a crowded, traffic-choked environment to one that's more beautiful, more user-friendly, it becomes a destination, and that's good for neighborhood merchants."

For some time now, New York has been temporarily closing some neighborhood streets in the summertime and turning them into "play streets" for children. Its Department of Transportation has just launched a Public Plaza Initiative convert underused streets to public plazas throughout the city's five boroughs.

Not surprisingly, with all these plans to limit auto access to city streets, there's been some squawking from businesses. It's helped somewhat that the weekend ciclovia events occur on days when deliveries are usually minimal. And the approach has generally been to avoid turning them into street fairs, where vendors often compete with established merchants. Instead, the emphasis is on free activities such as yoga, bike repair lessons, dancing and, as Mr. Norvell puts it, "just letting open space be open space" for people to enjoy as they choose.

Before Brooklyn Heights closed a major boulevard to cars for four Sundays in July, organizers soothed merchants' concerns with a survey that found that 91 percent of their customers arrived by foot, bike, or public transportation.

Still, it isn't an easy sell, this idea of car-free streets in cities that have long catered to the automobile. Portland helped ease concerns with a "soft closing" of streets on its six-mile route. Police were on hand to direct traffic through major intersections. On other blocks, volunteers escorted drivers to and from homes on the route.

Portland is already making plans to expand to three or four ciclovias next summer. In New York, supporters envision a regular event on the scale of Bogota's that goes through all five boroughs. Chicago plans two ciclovias for October; Baltimore, one next April.

"It's part of a sea change in how we're viewing city streets," says Susan King, the coordinator of San Francisco's event. "A city street becomes an entirely different landscape when you take the cars away. It creates opportunities for people to come out and exercise, meet their neighbors, and learn to appreciate their city in a whole new way."