Critical Mass is an event held typically on the last Friday of every month in cities around the world, where bicyclists and self-propelled people take to the streets en masse. Critical Mass has no leaders, and no goals other than to meet once every month and enjoy the security of riding, rolling and travelling through the city together.
I have been taking part in London Critical Mass since 2002 - for further information you might want to look at this website.
www.zenatode.org.uk Ian Gregory 2010