Belle Dumé in the NewScientist addressed recently the idea that city road networks grow like biological systems. The article is basically a description of the academic work of Marc Barthélemy and Alessandro Flammini who analysed street pattern data from roughly 300 cities, including Brasilia, Cairo, Los Angeles, London, New Delhi, and Venice. Using these cases, the researchers found interesting patterns showing that the road networks in cities evolve driven by a simple universal mechanism that follows a biological metaphor:
"The main influence on the simulated network as it grows is the need to efficiently connect new areas to the existing road network – a process they call "local optimisation". They say the road patterns in cities evolve thanks to similar local efforts, as people try to connect houses, businesses and other infrastructures to existing roads. (...) "Beyond the economic, demographic and geographic "forces" that shape a town, there are a myriad of small "accidents" that contribute" he says. "Although these are unpredictable, they can be understood in terms of statistics and simple modelling."
The team's model also reveals that roads often bend, even in the absence of geographical obstacles, and that road intersections are generally perpendicular."
And, as the authors described in their paper, "in the absence of a global design strategy, the evolution of many different transportation networks indeed follows a simple universal mechanism." Why do I blog this? I am not really into urban pattern modeling but I find interesting this notion of "local optimisation" and how it works for instance for roads and not for rail (because of its different nature and scales).
This is somewhat related to the elephant path (desire line) I often blog about here and there as pointed out by Space and Culture. A desire line can be turned into a design opportunity and thus into a new road.
Why is that interesting? certainly because it shows the contingencies of the urban infrastructure. I am wondering this hold true for other sort of infra, such as internet connections.