Road or vein?

According to research by French and US physicists road networks don't just look like the veins of a leaf: mathematical models show that they grow in a similar way. In fact road networks in all cities are driven by the same simple mechanism in spite of cultural and historical factors.

'Cities are not just the result of rational planning - in the same way that living organisms are not simply what is in their genetic code,' comments co-author Marc Bethelemy of the French Atomic Energy Commission.

Jukka-Pekka Onnela  of Oxford's Department of Physics, tells New Scientist that these results, from a simple mathematical model, agree well with data from real city road networks. He says that using the local efficiency of connections to drive road network growth looks to be a truer fit with reality than using the total cost of travelling across the network: 'Especially given that the time scale of city growth (possibly thousands of years) and the time scale of urban planning (perhaps tens of years) are so clearly different.'

Dr Jukka-Pekka Onnela is a Junior Research Fellow in Complex Systems and Networks Research at Wolfson College