Philadelphia is shutting down this September, and a lot of people there can’t wait.

Of course, it’s only for half a day on the weekend. It’s not the whole city, either. But it’s a pretty big chunk of it.

The city plans to close more than seven miles of major thoroughfares along the Schuylkill River and in City Center on Sept. 24 so that people can walk or bike or just hang out there.

The event, called Philly Free Streets, draws on a long-standing city tradition and a growing international movement to open streets to a wider variety of uses by temporarily closing them to vehicular traffic.

“The most important thing is, these are shared spaces,” Nate Hommel, who is one of the organizers, said in an interview last month.

Philly Free Streets represents the tactical urbanist’s approach to making big, livable effects on a city by starting small. In this case, it means transforming some downtown streets into boulevards for pedestrians and bicyclists, at least for short periods of time on a regular basis and — who knows? — maybe permanently someday. The bigger point is about using ordinary streets to broaden the ways people can navigate a metropolis and experience their environment.

The event was put together by Open Streets PHL, which is a nonprofit advocacy group, and the city’s Managing Director’s Office of Transportation and Infrastructure Systems. A news conference for the official announcement was held Friday.

The genesis of the event may also sound familiar to Washingtonians. As happened in the District, Philadelphia’s experience with open streets originated because of national security concerns that caused law enforcement to shut down some major streets. Howls arose — at first. Then people emerged from their two-ton shells of smoking steel and rubber and started walking around. Not so bad, they said. Not so bad turning major inner city streets into a concrete park for a while.

In the District, it’s happened on a small scale with a stretch of Pennsylvania Avenue — which, in all likelihood, will fully reopen only on the day when the lion lies down with the lamb. That is, never. In the City of Brotherly Love, the trigger was Pope Francis, whose visit last fall led security officials to shut off the flow of vehicular traffic in Center City.

“There was a big hullabaloo about closing down the grid, as people call it,” said Hommel, who is a spokesman for Open Streets PHL. “What happened was, basically the whole grid of historic City Center of Philadelphia was free of cars, and people just started walking in the street. And there were just these amazing things that happened.”

Hommel, who is also director of planning and design for the University City District, a special services district in the city, said Open Streets PHL formed soon after the pontiff’s visit to organize a larger open streets event that would occur regularly.

Their idea was to build on the success of the city’s seasonal, weekend closure of Martin Luther King Jr. Drive. They also followed the playbook of the Open Streets Project, an advocacy group that was formed in 2010 through an alliance of the Street Plans Collaborative and Alliance for Biking and Walking. Since then, Hommel said, the number of such open streets events has grown to more than 125.

The movement traces its origins to Seattle (where else?) in 1965 with “Bicycle Sundays,” according to the Open Streets Project’s guide. The idea soon spread to New York City (1966), San Francisco (1967) and Ottawa (1970). But the granddaddy of all is in Bogota, Colombia, where such events began in 1974. As many as 1 million people take part in “ciclovías,” as the events are known there, and they cover approximately 70 miles on Sundays and holidays, the guide says.

The events differ from street fairs in that the aim is to get people’s blood moving and celebrate alternatives to the automobile. When Hommel describes his vision, it sounds as if those newsreel shots of Brooklyn in the days when delivery trucks, pedestrians and hand carts all mixed on the street outside Ebbets Field, whose denizens borrowed their name from the sport of dodging trolley cars.

“Streets are public spaces — and a lot of people have forgotten that,” Hommel said.

On a much smaller scale, however, the District has also been living with an open streets event (or closed, depending on your point of view) on Pennsylvania Avenue near the White House. Except whenever the Secret Service is installing acres of cattle fencing or ordering people to move back — sometimes as far as Ohio — because of a fence jumper or some other event, the area has become one of the best parts of America’s Main Street. It often has the easy feel of a plaza where people are free to bike, stroll, pose for photographs or rant about a political cause.

In May, the District also held its inaugural D.C. Bike Ride, which was similar to other open streets events in that major thoroughfares were closed to vehicular traffic in the name of fun; but it differed in that the event was geared only to bicyclists.

In 1995, then-President Clinton ordered Pennsylvania Avenue’s closure after the Oklahoma City bombing — long enough almost for a generation to grow up thinking it’s always been closed. Maybe, with the help of the open streets movement and the D.C. Bike Ride, it’s time to build on that.

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