Critical Mass At 20

How a bike ride in San Francisco started an international movement to reconsider car domination of our cities.

This page was published 11 years ago. Find the latest on Earthjustice’s work.

In the USA, transportation is the second largest emitter of carbon dioxide pollution causing climate change, just behind electricity generation. How we get around impacts our planet. If protecting our climate is your cause, reducing one’s transportation carbon footprint is a great place to start.

This week, a monthly bicycle ride in San Francisco known as Critical Mass celebrates its 20th Anniversary. The ride launched a new era of green transportation activism worldwide and is now celebrated in hundreds of cities. In Budapest, Critical Mass has drawn an amazing 80,000 riders.

This celebration of the bicycle no longer shocks, it can now be found in the travel books that international tourists carry through the streets of San Francisco each day.

But it wasn’t always so mainstream.

Back in 1992, a small cadre of environmentalists, artists and messengers commuted to their jobs in downtown San Francisco via bicycle. The commute was scary and the animosity from car drivers was palpable.

As activist Chris Carlsson remembers, “In those days, we cyclists liked to joke that we all knew each other because there weren’t very many of us. We were treated as idiots, second-class citizens or children. People would say, ‘grow up, get a car,’ as if that was somehow an act of adulthood.”

The decision was made that the group would gather at Justin Herman Plaza and ride home together. The original name of the ride was “The Commute Clot.” The goal was safety in numbers, and saving the planet, of course.

Early adopter Hugh D’Andrade recalls how he felt on his first Critical Mass ride. “Where before we darted about threatened, isolated, insecure, and risk for our lives—suddenly we felt safe. We had the space and the time to ride at a leisurely stroll, talk to people, feel the change of sunlight and shadow on our faces as we moved through the canyons of high rises. We began to see the city a whole new light, as a place to socialize, meet people, to explore and experience spatially.”

Riders committed to bringing their friends to the next ride and spreading the gospel through the internet of the time, copy-shop flyers posted on telephone poles.
Here is how one flyer explained Critical Mass.

Critical Mass isn’t BLOCKING traffic—We ARE Traffic!!!

At the end of every workday, thousands of people pour into the streets, in what has become a central ritual of life in the late twentieth century—the daily commute…

But one day a month, the ritual is transformed. Hundreds of us get together and ride through the streets on bicycles, providing motorists, as well as ourselves, with a vision of how things could be different. 

When word of this leaderless bicycle rebellion spread, Critical Mass bike rides began popping up around the world. Today, Critical Mass can be found in hundreds of cities including Chicago, Paris, Madrid, Rome, Guadalajara, Helsinki, Bilbao, Capetown, London and Dubai.

Critical Mass helped start a discussion about how our cities are organized and whether there are greener alternatives to the domination of the private automobile.

Julieta Cal reflects on the changes she has seen since the first Critical Mass in Buenos Aires:

The change has already started, because so far the ride has encouraged families, elders, handicapped, travelers, clerks and more to grab their bikes and try riding through the city of wretched traffic for themselves. Thus, many more brave hearts on two (non-motorized) wheels have appeared showing that self-propulsion is a beautiful thing.

To celebrate the 20th Anniversary, some of the original San Francisco riders will join with riders from around the world for the big ride on Friday, Sept. 28.

A week of celebration leads up to this ride, including lectures, art, music and the publication of an anthology of stories from around the world, “Shift Happens: Critical Mass at 20.”

For more information about the book, the history of this event, and the events taking place this week in San Francisco, visit

An Earthjustice staff member from 1999 until 2015, Brian used outreach and partnership skills to cover many issues, including advocacy campaign efforts to promote a healthy ocean.