Hordes of cyclists swarm San Francisco’s roads on the last Friday of every month for a day of two-wheeled protest, the Los Angeles Times reports. As many as 1,500 members of the cycling advocacy group “Critical Mass” spontaneously tour the streets as they trap stalled motorists “in their tin cans” and warn cross-walkers, “Get out of our way! We’re not burning fossil fuels!”
So-called “massers” once drew the ire of former Mayor Willie Brown, who declared war on the gang and accused them of “the ultimate arrogance" - but today's SF mayor is burying the hatchet. Still, some protests end in arrests and assorted hijinks against motorists. “Critical Mass” has spread to six continents and seen bike commuters double during their 15 years in San Francisco.