The Botany of Roads

Lewis Mumford wrote admiringly of the medieval city, formed through thousands of small decisions over long periods of time. He marveled at how this organic kind of growth would actually yield very sensible results. The gently curving cow path, adapted into a road, often fit the human practice of walking better and provided more visual stimulus than the strict grids later imposed though a centralized plan.

Now some French and American physicists are attempting to draw mathematical parallels between the cellular structures of certain organisms and the roads from various cities around the world. When the system grows gradually rather than being planned according to the larger scale, they have found that the efficiency is localized. As new nodes are developed, which need a means of transporting nutrients or waste, they connect into the system at the closest point and form gentle curves. Their thesis is that this pattern is, in fact, universal across cultures and economies.

From New Scientist,

"Previous models of urban development assumed that efficient transport across the entire network motivated the system's growth – as if planned from the top down. Focusing instead on the structure of local connections seems truer to real life."