The mapping of large-scale human movements is important for urban planning, traffic forecasting and epidemic prevention. Work in animals suggested that their movements might be explained in terms of a random walk, a mathematical rendition of a series of random steps, or a Lévy flight, a random walk puncuated by an occasional larger step. The role of Lévy statistics in animal behaviour is controversial, but the idea of extending it to human behaviour was boosted in 2006 by a report of Lévy flight-like patterns in human movement tracked via dollar bills. Our study, based on tracking the trajectory of 100,000 cell-phone users for six months, reveals behaviour close to a Lévy pattern, but deviating from it as individual trajectories show a high degree of temporal and spatial regularity: work and other commitments mean we are not as free to roam as a foraging animal. But by correcting the data to accommodate individual variation, simple and predictable patterns in human travel begin to emerge.
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