gasoline, is often cited as the inspiration for what was to come.  Citizens reacted to this steel/highway vision of their city. In 1955 the newspaper San Francisco Chronicle published a map of proposed routes of the freeways which helped to promote the opposition known as the “Highway revolts”, where 30,000 citizens mobilized to stop freeway building in San Francisco. This protests took place from 1950-1970 [5]. By 1991, there were established activists cycling groups that protested against the oil industry, indeed in this year, around 100,000 citizens participated in anti-Gulf War demonstrations, often on bicycle.  Within this context, where the car and oil industries helped to shape the city around the private vehicles, and with a growing protests from activists groups and a noticeable bicycle messenger community, one of the today best world-wide known cycling protests appeared: The “Critical Mass”. This anarchic type of protest/celebration today takes place in more than 300 cities around the world usually every last Friday of the month. This case describes the birth and evolution of this protest.

By 1992 in San Francisco a group of around 60 cyclists, which included bicycle messengers and activists among others, started to ride once a month, where they wanted to make their presence felt,  increasing their visibility and reclaiming the public space by making a “social use of the streets” [3]. It was initially called “the commute clot” [1], a spontaneous monthly gathering of bicyclists and activists, an “experiment in urban anarchy” [12]. Many interesting questions start to come up with these ridings “Why is there so little open space in our cities where people can relax and interact, free from the incessant buying and selling of ordinary life? Why are people compelled to organize their lives around having a car? What would an alternative future look like? ” [1]. Over time, the concept and movement started to take shape and the name of the movement evolved to Critical Mass[1]. With a double purpose: on one side “to celebrate de bicycle” and in the other to “dominate the streets for a change”. That is why many times it is referred as part celebration and part protest. It has also the purpose to allow people to experience; to experience what is “to be the majority”, to “experience what is like to be safe”[6]. Charles Higgins also describes the ride as a place to “express frustration about invisibility and, conversely, to celebrate human-scale community”  Xerography One of the remarks made in the San Francisco Critical Mass is that no one is in charge; no one is the owner, or the boss. One of the tools of the decentralized network of the critical mass is the “Xerography”, were participants can give different collectively meaning to the critical mass. The word “Xerography” comes from “Xerocracia”, a Greek word meaning the “government of the foreigners”; as many cyclists feel in the street roads, and the word “Xerox”, the classical printers[15]. With the “Xerocraphy” anyone is free to make copies of their ideas and passing them around “Ideas are spread, routes shared, and consensus sought through the ubiquitous copy machines” [10].  The mission of the ride is not set by a few ones, there is not a narrow attempt to have more bike lanes, people are there to promote “human powered transportation as a viable alternative, others seek the respect of motorists and city planners and some take part simply because they like riding bikes” [10].  This Critical Mass has received many titles; an “organized coincidence”, “a revolutionary act”, “just a bike ride” [2]. The several names that it receives reflects the fact that the critical mass is designed to be interpreted, shaped and redefined by the participants in each context [2] It has a decentralized structure.  How the protest/celebration is held:  Traffic tactics have evolved, in order to maintain the mass together through the city (the critical mass reached numbers of 5,000 people participating). Through Xerography (and nowadays with online social networks) the route and starting point is agreed, regularly the departure point is the same every Friday. One of the most important characteristics is that the mass should not split. That is the main idea, to be represented as a single vehicle, in order to be a mass. Therefore in the intersections some “corks” (random bicyclists that decide to stand in front of the motorized vehicles) stop the motorized traffic, until the last of the bicycle riders pass.

  [1] comes from the Ted White's documentary Return of the Scorcher, where in China had an understood method, were in the intersections without traffic lights each transport mode create an enough “critical mass” in order to pass [8]. In physics the name also makes reference to the smallest amount of fissile material needed for creating a nuclear chain reaction [7].

One of the obvious conflicts is with the car drivers, since they have to wait until the last rider to pass. But it is key to think of the car drivers not as enemies, but as possible future riders. As Chris Carlsson states “the people inside the cars cannot be categorized as bad” and having fun is one of the most subversive postures cyclists can take, instead of the anger…doing the unexpected [13].

Another conflict they face is the relationship with the police, who want to enforce the rules. In April 1, 1994 police “claim the sponsorship”. So the Critical Mass agreed that the police would stop the traffic for them, they will be the “corks”. They wanted to be the ones who stopped the traffic, in order for the Critical Mass to pass. But the experiment was a failure; they didn’t stop the traffic, and even arrested some cyclists trying to do so. Therefore, 75 people were left behind, creating dangerous situations [14]. The police intervention is no longer wanted, and it is avoided in many critical masses around the world.

Another type of conflict is that there are attempt to officialize it. Meaning that they will need a permit to do it, and the police would have the control of the routes, and the power to create “mini masses”. The overall aim is to reduce congestion, the car congestion.