“People have to be motivated and give up some of these comforts,” said Janel Sterbentz, a 32-year-old demonstrator from San Jose who said she had never owned a car.

The gulf spill, and the attention it has focused on the United States’ oil dependency, is seen by some as an opportunity to push the environmental movement further  beyond merely green, mass transit first, or pro-cycling.

For some, the mission now is anti-car.

This notion may be anathema to most Californians, those who worship car culture, but that does not intimidate Joshua Hart, an organizer of the Arco protests, which have attracted as many as 100 demonstrators. “We need to use less fossil fuels,” he said. “We need to have simpler lives.”

Mr. Hart, 34, of Menlo Park, said he was anti-car, not anti-driver.

“We need to treat people who are addicted to their cars like people with an illness, people who are sick, rather than people who are intentionally destroying the planet,” he said.

Image Joshua Hart was flanked by San Francisco police officers on July 2 after blocking the Fell Street entrance to an Arco station. Credit... Adithya Sambamurthy/The Bay Citizen

Mr. Hart said he had been arrested three times for protesting environmental issues. He has not owned a car since 1999 and stopped flying in 2006 when he took trains and a cargo ship to travel to graduate school in England. He said many environmental groups had not taken a strong enough stand against automobiles. “They’re terrified of offending people,” he said.