Positive or earlier called critical Mass has existed as at least to my understanding as an "unorganized coincidence" since the early nineties, when a group of cyclists in America decided to cycle home from work en masse on the last Friday of every month. The initial numbers involved were small but it has not only gained attraction in small parts but has grown into a world-wide phenomenon, with rides across the globe attracting thousands of cyclists and Critical Mass itself becoming a symbol of successful, kind of peaceful protest.
Positive Mass biking and the omnipresent motorbike and in last years the growing numbers of automobiles has certainly more than a symbolic value in the streets of Hanoi.
So cycling is an anarchistic but friendly activity, one, which requires a different idea of city space than you would think driving a motorbike or even a car. The ideal perception of public space and responsibility towards environment is a positive approach.
So hopefully the positive mass will prosper and change the hectic traffic in Hanoi in a way or another.