Proof that a minority of streets handle the majority of traffic

In recent years, physicists have turned their penetrating gaze towards the structure of towns and cities. What they tend to do is measure the “connectedness” of a town by looking at how many roads each street is connected to. It turns out, that cities follow an 80/20 rule, that 80 percent of the streets have a below average connectedness while 20 per cent have an above average connectedness.

This is no surprise since the same kind of 80/20 pattern crops up with alarming regularity in all kinds of networks, particularly social ones. (The most famous is Pareto’s law which states that 80 per cent of the wealth is owned by 20 per cent of the people).

But so what? Pawing over maps and sweating over street names maybe a theoretical physicist’s idea of fun but nobody has actually proved that the 80/20 rule has any tangible effect on street use.

Now Bin Jiang at the Hong Kong Polytechnic University has come up with some actual data from a real town. He says that 80 percent of the traffic in a Swedish town called Gavle flows along 20 per cent of the streets. And 1 per cent of the most highly connected steets account for a phenomenal 20 per cent of the flow. What’s more, he says the flow is intimately linked to the topology of Gavle (a town of 70,00 people).

So there you have it. Although it seems only common sense to imagine that the most traffic flows along the best connected streets, we now have some evidence to prove it. Good, solid, unspectacular physics.
Ref: arxiv.org/abs/0802.1284: Street Hierarchies: A Minority of Streets Account for a Majority of Traffic Flow