Universal law to predict human mobility

Human mobility impacts many aspects of a city, from its spatial structure to its response to an epidemic. It is key to social interactions, innovation, and productivity, but at the same time gives rise to traffic congestion and pollution, and fuels the spread of contagious diseases.

Despite the importance of human flows, our understanding of the flows of individuals to locations has remained incomplete – the question of how their travel patterns affect the number of visitors to a location has remained largely unanswered.

Places attract individuals for reasons as diverse as work, shopping or recreation at different frequencies. It is this heterogeneity of trips that dictates the rate at which individuals from different neighbourhoods, regions or parts of the world share the same space and may interact with each other.

A study led by FCL Global principal investigator Asst Prof. (Adj.) Markus Schläpfer, together with FCL alumnus Hadrien Salat and collaborators, reveals a surprisingly simple but powerful travel law. The development of the theory begun while Schläpfer was a post-doctoral fellow at the Santa Fe Institute working with physicist and co-author Geoffrey West, and further collaborating with Carlo Ratti and team at MIT’s Senseable City Lab. The paper external page "The universal visitation law of human mobility" published in Nature opens up new possibilities to accurately predict recurrent population flows of varying frequencies and provides insights into how people interact with each other in a city.

Imagine you are standing on a busy city plaza and you see people coming and going. This may look pretty random and chaotic, but the discovered travel law shows that these movements are surprisingly structured and predictable. It basically tells you how many of these people are coming from 1, 2 or 10 kilometres away and how many are visiting once, twice or 10 times a month. The visitation law states that if we double the number of visits or if we double the travel distance, the visitor count decreases by a factor of about four.

Big data analyses demonstrate that population flows obey this theoretical prediction in virtually all tested areas across the globe, ranging from Singapore in Asia to Boston in the US, Lisbon in Europe or Dakar in Africa.

By accounting for both travel distance and the frequency of visits, the visitation law allows us to consider both the spatial and temporal aspects of human mobility patterns, and thus offers practical applications for the mitigation of epidemic spread, urban planning, infrastructure design and other applications.

Asst Prof. (Adj) Markus Schläpfer is currently principal investigator in the Powering the City research module at Future Cities Lab Global.