Next time you are lost in an unfamiliar city, console yourself with the knowledge that the layout of its roads are probably much the same as in any other.

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. The resulting patterns are much like the veins of a leaf.

'Not just planning'

The researchers developed a simple mathematical model that can recreate the characteristic leaf-like patterns that develop, growing a road network from scratch as it would in reality.

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.