On any given morning, bicyclists and automobiles uneasily share city streets. Cyclists grumble that the cars don't give them room. Drivers complain that the cyclists are too slow.

But not this weekend.

For more than six hours on Sunday morning, miles of streets in the heart of Philadelphia will be closed to cars for TD Bank Bike Philly. The event, a fund-raiser for the nonprofit Bicycle Coalition of Greater Philadelphia, offers something for riders both young and old, professional and amateur.

"It's a chance to experience the city in a way folks aren't used to," said the coalition's executive director, Alex Doty. "We'll take you from skyscrapers to hidden corners of Fairmount Park."

The ride starts at the Museum of Art steps and winds its way through a 10-mile route that takes cyclists under the Ben Franklin Bridge, into Queen Village, through Center City, and back to the museum. Interested riders can follow another 10-mile stretch through the park, and a few can follow an even longer ride on shared roads that touches the suburbs.

Tired riders can visit rest stops along the route or seek to be revived by the bands and choirs performing along the way and - it's hoped - cheering throngs.

TD Bank helps the Bicycle Coalition start the riding season in June with a competitive race that casual riders can watch. This leisurely ride is a perfect way to end the season, Doty said.

"It's a relaxed, laid-back ride," Doty said.

Philly is striving to be more bike-friendly. In October, Mayor Nutter fulfilled a campaign promise by naming a city pedestrian and bicycle coordinator. There has been talk of starting a bike-share program similar to the one in Washington, D.C.

The city is experimenting with designated bike lanes on Pine Street in Center City. (Philly already has more than 215 miles of bike lanes, but only about four miles weave through Center City, the most cycled neighborhood, Doty said.) A recent City Council ordinance requires developers building multifamily units to include bicycle parking.

The number of cyclists on city streets doubled between 2005 and 2008, according to surveys done by the coalition. The organization says more than 300,000 Philadelphians bike at least once a month, and 36,000 commute by bike.

Similarly, the number of participants in the coalition's ride has increased since the inaugural event in 2007 - from 2,400 riders that year to 3,200 in 2008. This year, more than 4,000 riders are expected. Doty hopes that one day the ride is comparable to New York's Five Borough Bike Tour, which attracts more than 30,000 people.

Another endorsement comes from Philadelphia's first lady, Lisa Nutter, the ride's honorary chairwoman. She stressed that Sunday's event is a ride, not a race.

"I'm not going to the Tour de France," she said. "No one gets dropped. It's billed as, and will be, a fun ride."

The entire Nutter clan rode in 2007, the first time the coalition offered the car-free tour.

"I thought it was a great family ride," she said. "It was interesting how they could galvanize all these families and people who shared an interest in riding."

Only later, she said, did she learn more about the coalition and its long-term goals of introducing people to cycling, exposing them to different parts of the city, and promoting fitness and environmental friendliness.

Nutter's not sure whether her husband or their teenage daughter will make this year's ride. But she promised she'd be there, leading the charge.

"This is a very different way of viewing the city," she said. "This gets people out of their cars and exploring things."