Thirteen antiwar demonstrators who blocked part of Pennsylvania Avenue in downtown Washington for nearly an hour during yesterday's morning rush hour used a tactic that can infuriate commuters and stymie police.

The technique, increasingly popular at demonstrations across the country, employs lengths of plastic pipe to form a human chain that is impossible to move without separating the demonstrators from each other. It involves two protesters sticking one arm into each end of the pipe and chaining their wrists to hardware that has been installed inside the pipe.

"What they have to do is . . . bring out a circular saw and different cutting devices and cut each [length of pipe] open, very slowly. It takes a long time," said Andrew Willis, 20, an American University student who was part of the chain. He and the other demonstrators were arrested, charged with blocking the street and failing to obey police orders, and fined $150.

Police and activists say the technique first gained notoriety 31/2 years ago, at the anti-globalization demonstrations in Seattle during meetings of the World Trade Organization and has been taught by student activists on college campuses and via the Internet.

The chains, known as "sleeping dragons," "locking-downs," "lock boxes" and "bear's claws," also are formed when protesters lock themselves to cement-filled barrels or drive buses to the scene and attach themselves to the then-immobilized vehicles.

On Wednesday, 11 demonstrators handcuffed themselves together to close Fifth Avenue in New York City in protest of Israel's occupation of the West Bank and Gaza Strip. In San Francisco, human chains were used at many of the 40 intersections that were shut down by protests last week. Overwhelmed police officers dashed from corner to corner, with chainsaw-toting firefighters in their wake.

D.C. police said yesterday that they break up nearly two dozen human chains a year, though not all involve blocking streets. A 19-officer emergency services team, formed after the Seattle protests and before anti-globalization protests here three years ago, now has two trucks full of cutting and hydraulic lifting equipment and has yet to encounter a chain it cannot cut through, Lt. John Alter said.

"They're out there trying to make their voices heard. That's fine. We just want to make sure we remove them safely," said Alter, who commands the unit.

Yesterday, that meant cutting through lengths of PVC plastic piping to separate the protesters -- 11 AU students, one recent graduate of the university and a student from George Washington University, Willis said -- into groups of three. Police then dragged each threesome to the sidewalk.

Motorists who are blocked by the demonstrators are often angered by the delays. A couple of drivers yesterday seemed to want to accelerate right into the protesters, Willis said.

Lon Anderson, a spokesman for AAA Mid-Atlantic, said: "We have such a fragile transportation system that it essentially takes very little to destroy the commutes of tens of thousands of people. It puts our area motorists as hostages."

The protesters said they were aware of the problems and were even sorry. They were accompanied by fellow antiwar activists who handed out cards to commuters apologizing for the delays and explaining their opposition to the war.

But Willis said that blocking traffic generates media attention, which helps spread the antiwar message. And disrupting life in Washington, he said, seems a small inconvenience compared with the destruction wrought by U.S. military action.

"Our government is disrupting and destroying the lives of Iraqis and of American soldiers," he said. "We cannot go on with our lives as usual."

In a separate incident during the morning rush hour yesterday, three people were arrested by U.S. Park Police for trying to hang a banner, emblazoned with an antiwar slogan, between the statues that decorate the D.C. side of Memorial Bridge.

Staff writers Manny Fernandez and Evelyn Nieves contributed to this report.

Connected by plastic pipe, antiwar demonstrators block traffic at 14th Street and Pennsylvania Avenue NW.A protester, linked to others by pipe, lies in the street at 14th Street and Pennsylvania Avenue NW, awaiting arrest.Julia Skapik expresses herself at the antiwar demonstration during yesterday's morning rush hour. Thirteen protesters blocked traffic.