Edinburgh Peace and Justice Centre

Critical Mass is a monthly bicycle ride to celebrate cycling and to assert cyclists' right to the road. The idea started in San Francisco in September 1992 and quickly spread to cities all over the world.

Critical Mass has a different flavor from city to city -- there's a big variety in size, respect of traffic laws (or lack thereof), interaction with motorists, and intervention by police. So if you want to know more about Critical Mass, you'll really need to find out what your local ride is like.

Critical Mass has no leaders, and no central organization licenses rides. In every city that has a CM ride, some locals simply picked a date, time, and location for the ride and publicized it, and thus the ride was born.

CM is an idea and an event, not an organization

http://criticalmass.wikia.com/wiki/Edinburgh