"French and US physicists have shown that the road networks in cities evolve driven by a simple universal mechanism despite significant cultural and historical differences. Marc Barthélemy of the French Atomic Energy Commission in Bruyères-le-Châtel and Alessandro Flammini of Indiana University, US, analysed street pattern data from roughly 300 cities, including Brasilia, Cairo, Los Angeles, London, New Delhi, and Venice."Old world, new world, grid city or not, the researchers found that all of these cities have road networks that are mathematically similar. According to the article's abstract,
"We propose a simple model based on a local optimization process combined with ideas previously proposed in studies of leaf pattern formation. The statistical properties of this model are in good agreement with the observed empirical patterns."
The mathematical model assumed that road networks based on immediate needs to connect destinations - a downtown area to a new factory, for example, or a neighborhood to a train station. As more houses and businesses get built, they connect to existing roads. Which is exactly how capillary networks grow as new cells develop in living organisms.
This organic development of roads holds true even in cities, like Los Angeles, that ostensibly follow a north-south, east-west grid layout. LA's grid streets are only a small part of a larger, more chaotic network of big freeways (like major arteries) and tiny cul-de-sacs (like capillaries):
And so, just as two genetic clones will develop different patterns of veins, capillaries, and arteries depending on chaotic environmental factors during cell growth, so a city's infrastructure develops randomly regardless of its social or governmental DNA. Whether it's a built-from-scratch city like Brasilia or an ancient city like Paris or a master-planned, for-profit city like Texas's The Woodlands, the city grows organically.