Naked bicyclists stage rides in Portland at the World Naked Bike Ride

Portland, Oregon: Thousands of bicyclists, many of them stark naked, poured into the streets of Portland, Oregon on Saturday night for the 11th annual World Naked Bike Ride, a protest that promotes bike riding as an alternative to driving cars.

Nude cyclists with lights flashing in their tire spokes rang bells as they barreled down avenues lined with cheering spectators, while a naked, apparently pregnant woman rode in a bike trailer.

"This is a party, but it's also a protest," said Carl Larson, a ride spokesman. "It is about oil dependence, cycling vulnerability and body" image.

Cyclists showed up in Normandale Park an hour before the ride, shedding garments according to the ride theme "as bare as you dare".

The rides are held in more than 75 U.S. cities and in more than 20 other countries, but Portland's is believed to be the largest, with more than 8,000 participants last year.

But unlike events in other cities, the Portland ride works with local police, being considered as a protest. Officers direct traffic during what is generally a trouble-free event.

"We've had a few complaints from neighbors but overall not many issues of concern," said police spokesman Sgt. Peter Simpson before the ride, adding "for residents who don't want to see it, the best advice is to just not go outside."

Jennifer Young, 40, who was at the ride with her 16-year-old son and was painted blue head to toe with fairy wings on her back, saw the goal as showing cyclists' vulnerability, saying "I think it's a little more evident when we're naked."

Neighbors looked on as a marching band played and dancers kicked off the start. Later a naked punk band jammed from the sidelines as bikers rolled past.

Fred Tebo, 90, wasn't sure want to think of the hoards of naked people in the park across the street from the house he has lived in since 1971.

"It's entertaining and it's stupid at the same time," he said, sitting on his steps. But a few minutes later he let a young woman and man clad in their underwear use his bathroom.