Physically, it is quite simple to re-paint a street for a horde of bicycles. One small, determined adult could do this useful task in two or three nights. If they asked no permission from anyone. If they demanded no money for doing it. If they carried out that act with cool subterfuge and with crisp graphic precision, so that it looked ‘official’. If they calmly risked any possible arrest and punishment for this illicit act. And if they told no one, ever, about the work they did, or why, or how.

White Fungus by Bruce Sterling on, well, guerilla urbanism.