it means that the city needs the critical mass. >> bill of times of new york has spent three decades as an environmental activist trying to increase awareness and push the benefits of bikes. >> you're in a car and you're very isolated. so you don't realize, hey, that person is on a bicycle or on the street. you almost has this huge weapon. and then you have the bike culture which is completely different. you smell the trees. you feel the bumps, you know. >> but not everyone is on board with the critical mass philosophy. critics accuse of group of trying to obstruct traffic. and in new york city, riders have had high profile confrontations with the nypd. two of which were caught on camera. the first was captured by a critical mass rider in 2007. the second in 2008. filmed by a tourist in times square and given to a critical mass representative shows rookie officer patrick hogan shoving