More than 1,000 costumed bicyclists took control of San Diego’s streets last Friday evening. Streaming out of Balboa Park with wheels rolling, bells ringing and lights flashing, this year’s Critical Mass Halloween bike ride rode into session.

As participants headed west toward downtown flying through red lights and flowing through gridlocked traffic, downtown partygoers cheered on the swarming spectacle. Many reached out for high fives and yelled out, “What is this?” Even a few passing drivers honked in camaraderie with the riders.

Given it’s size, it’s surprising that Critical Mass is not an organization but rather, a bunch of people from all different backgrounds who meet up on the last Friday of every month to take control of the streets.

According to San Francisco’s Critical Mass website, the phenomenon organizes itself. No one in particular is in charge, but whoever shows up to the ride makes spontaneous decisions about the route.

“Everyone is invited to Critical Mass and everyone is free to contribute their energy and ideas to the mix,” according to SFCriticalMass.org.

Critical Mass participants act like renegades, as traffic laws are usually ignored.

“It’s the one night where bikers take back the streets,” 27-year-old rider Daniel Botticelli said. “It’s not about breaking laws and being rebellious. It’s just about having fun; being a part of a community. I have

friends that I only see at (Critical) Mass.”

This massive bike ride originated in San Francisco to increase the visibility of bicyclists and like many U.S. towns, roads were built to only later considering bike safety. Since 1992, Critical Mass has evolved and spread to more than 300 cities around the world.

“It not only raises awareness for drivers, but people around your city and it encourages people to ride a bike, that it doesn’t matter how old you are.” Botticelli explains. “Riding a bike is something you can do ‘till you’re 90. This event also brings peEople together who would have never met or even talk to if it want for mass”

Critical mass leaves the Balboa Park Fountain at 7 p.m. every last Friday of the month.