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Big data boffins crunch GPS traces, find altruistic route planning is good for everyone

Except, darn it, the nice guys still probably finish last

GPS and navigation systems make it a lot easier to find the most direct way to get where you're going, but with a downside: they funnel everybody onto the same congested route.

People who know a city well already know the best response to this: take an alternate route. Navigation systems know about alternate routes as well, but they don't look at the issue from a whole-of-system point of view.

That's the contention made by US and UK researchers in this paper in Nature Communications. “Although approaches to modify demand and capacity exist, the possible limits of congestion alleviation by only modifying route choices have not been systematically studied,” they write.

The number-crunch was carried out by MIT's Serdar Çolak and Marta González and the University of Birmingham's Antonio Lima.

Their study took GPS traces from mobile phones – billions of them, supplied by carriers – to look at “peak hour” traffic models in Boston and the San Francisco Bay Area in the United States, Rio de Janeiro in Brazil, and Lisbon and Porto in Portugal.

Their finding is that if even a handful of motorists let their routes be guided by a “socially aware” routing model – taking a slightly less convenient route instead of just adding themselves to the congested routes (selfish routing) – overall congestion could be cut by as much as 30 per cent.

Routes in San Francisco

Altruistic routes take longer but help everyone

(Image: MIT, OpenStreetMap, MapBox)

In the San Francisco Bay Area, for example, the image shows the choices a navigation system could take – the selfish route (purple) and two optional routes including the slowest socially optimal route.

A relatively small number of drivers giving up a little convenience would yield travel time benefits of as much as ten minutes for “tens of thousands of vehicles,” the paper states.

The challenge, however, is that the socially optimal routing offers at best an indirect benefit to most individuals:

“The observed time benefits the average individual receives are marginal, ranging from 1 to 3 min. Furthermore, these times are below the travel time variability based on events, weather conditions or traffic lights.”

The best idea, if governments can't be persuaded to try approaches like offering better public transport, is to try and work out some kind of incentive scheme for drivers willing to let their navigation systems send them down the road less travelled. ®

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