Critical Mass celebrated its 15th birthday/anniversary this past Friday. CM is an "unorganized" group bike ride that happens once a month here in the Bay Area and in other cities around the country and world. Over the years the participant numbers have grown and its escalated into a monthly parade/demonstration that may include hundreds (or occasionally thousands) of riders. The rides' message is part advocacy, part protest: somewhat amorphic, but generally "for" biking, "against" automobile traffic (and, as related, global warming, etc). The party line is that the rides have no official leaders or organizing body, though there is a website (www.criticalmass.info) which states "CM is an idea and an event, not an organization."

While the vibe of the Critical Mass rides I witnessed in Boulder, CO seemed good-spirited, hipster/hippie-ish, rag-tag and focused on having fun, the San Francisco rides are more politically charged. In the Bay Area there's an incident almost every month involving a Critical Mass participant vs. car and driver, ranging from arguments in the street to assault and broken windshields, with blame falling on either/both sides. The traffic in SF is pretty bad to begin with; a free-form bike parade snarling downtown traffic on a Friday afternoon, no matter what message its promoting, will more than likely face a tough crowd.

Read more from the San Francisco Chronicle below. Check the comments on each article for a sense of the community's response:

Critical Mass celebrating 15 years of free-form bicycle advocacy

Just another wild ride at 15th anniversary of Critical Mass in S.F.