Gyratory traffic schemes, extended one - way systems etc

A bunch of motorcyclists regularly protested against (I think) parking charges in Westminster by doing laps around the roundabout just South of Trafalgar Square. It completely fucked traffic in the area with only twenty or so of them.

Yeah they had engines, and probably looked scary.

If a bunch of hipsters tried that, it would be a massacre. Haha

No seriously we could try something like that, but wouldn't that just be like Critical Mass?