Thousands of bikers took over the Loop Friday evening to mark the 10th anniversary of the Critical Mass bicycle ride.

The loosely organized rides are known for snarling traffic as participants gather at the Daley Center to ride colorfully decorated bikes through the city on the last Friday of each month.

"It's a huge mass of humanity and bikes," said Peter Condick, who has been riding for about four years. "It's about pleasure, exercise and social companionship," he said.

Some participants wore t-shirts with "all lanes bicycle only" road signs on them. But others seemed more interested in riding than making a statement.

"I just like to ride," said Jerry Boyle, of the National Lawyers Guild. Boyle also acts as legal observer in case of any confrontations with the police.

"It's cool to see all these people come together," said Kirsten Gray, a member of Rat Patrol. Rat Patrol is a nationwide organization whose members construct bikes out of old or discarded parts. Gray came from Tennessee with about a dozen other Rat Patrol members. "We like to drink, build and ride," she said.

Critical Mass is a worldwide phenomenon. Bikers from Berkely, CA to Budapest, Hungary gather on the last Friday of every month and take over city streets. Some rides report twenty participants, while others have thousands.

Information about the rides is mostly relayed through the organization's website, which is designed and updated entirely by volunteers, said Steven Long, 39, one of the website's updaters.

Long has been participating in Critical Mass Chicago for eight years. A few people just show up with maps of potential routes and circulate them, he explained. Whoever gets to the front of the path pretty much determines the route.

Because Critical Mass is neither and official organization nor an official event, no permits are needed from the city. "Happy Friday" is only official message.

In general Critical Mass enjoys a very good relationship with the Chicago police Department. The only restrictions bikers face are no riding on Lake Shore Drive or the Expressway, but these are for their own safety, said Commander Kevin Ryan.

"You'd be hood ornaments [on the Dan Ryan]," Ryan told a rider. "We just want nobody hurt, no fighting, and no drinking."