Published online 4 June 2008 | Nature | doi:10.1038/news.2008.874


Mobile phones demystify commuter rat race

Tracking study proves that humans are creatures of habit.

rush hourResearchers monitored the everyday movements of 100,000 people by tracking their phones.Evlin M. During

Researchers have come up with a new use for the ubiquitous mobile phone: tracking human movements. By monitoring the signals from 100,000 mobile-phone users sending and receiving calls and text messages, a team from Northeastern University in Boston, Massachusetts, has worked out some apparently universal laws of human motion.

The results could help epidemiologists to predict how viruses will spread through populations, and help urban planners and traffic forecasters to allocate resources.

Albert-László Barabási and his colleagues show that most people, perhaps unsurprisingly, are creatures of habit. They make regular trips to the same few destinations such as work and home, and pepper these with occasional longer forays such as vacations.

The distances people covered varied widely between individuals, but follow a similar pattern — most people move on average a short distance on a daily basis, whereas a few hardy souls move long distances in a short time. The results are reported in Nature1.

On track

These patterns might sound obvious, but as data on individual human movements are difficult to come by, researchers haven't been able to study them precisely. “We don’t really know how humans move around,” says Barabási. “When you look at the population as a whole, there is no way of describing the patterns. The problem with answering this question is that people normally are not tracked — but today we are tracked thanks to the phones we carry with us.”

So Barabási and his colleagues teamed up with a mobile-phone company (unidentified to protect customers' privacy), who provided them with anonymized data on which transmitter towers had handled the calls and texts for 100,000 individuals over the course of 6 months.

The results fit with a 2006 attempt to track human movements using banknotes as a proxy measure, also published in Nature2. Researchers led by Dirk Brockmann, now at Northwestern University in Illinois, analysed the movements of more than half a million US one-dollar bills as they were passed around over five years. The team found similar patterns of lots of short movements and occasional longer ones.

Mobile money

But because banknotes are passed from person to person and rarely stay in the same pocket for long, that study could only derive an average picture of movement. Barabási's study “answers questions about individual variability that we were unable to address with the dollar bills”, Brockmann says.

Strict data-protection laws prevented Brockmann from carrying out his own version of the mobile-phone study in Germany, where he was based until recently. Mobile-phone data have the potential to reveal information about where individuals live and work. “I’ve been trying to get my hands on mobile-phone data but it isn't possible,” he says.


Because of privacy considerations, Barabási’s report does not divulge where in the world the data are from – location could conceivably affect the patterns a great deal in light of people's differing daily habits in different countries.

“It’s weird to see such mathematical regularities in such complex behaviours,” says Brockmann. The challenge now is to find out why something as complex as human movement follows such consistent patterns, he says. “Neither study can answer that question.” 

  • References

    1. González, M. C., Hidalgo, C. A. & Barabási, A.-L. Nature 453, 779–782 (2008).
    2. Brockmann, D. D., Hufnagel, L. & Geisel, T. Nature 439, 462–465 (2006).
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