High Quality Content by WIKIPEDIA articles! Critical Mass is a cycling event typically held on the last Friday of every month in over 300 cities around the world. The ride was originally founded in 1992 in San Francisco. The purpose of Critical Mass is not usually formalized beyond the direct action of meeting at a set location and time and traveling as a group through city or town streets on bikes. Some bigger scale events as in Budapest, Hungary, have an activist group formed around it, organizing the rides and communicating the desires and problems of the cyclists to the city council.