The Scales of Human Mobility

TL;DR

This paper resolves the paradox between scale-free human mobility patterns and the meaningful scales in geography by showing that daily movements are confined within spatial containers of typical sizes, which can be inferred from trajectories.

Contribution

The authors introduce a model that infers meaningful geographical scales from individual trajectories, reconciling empirical scale-free patterns with geographic scale concepts.

Findings

Human mobility contains meaningful spatial scales.

The model accurately infers neighborhood and city sizes from trajectories.

Trajectories of over 700,000 individuals reveal typical container sizes.

Abstract

There is a contradiction at the heart of our current understanding of individual and collective mobility patterns. On one hand, a highly influential stream of literature on human mobility driven by analyses of massive empirical datasets finds that human movements show no evidence of characteristic spatial scales. There, human mobility is described as scale-free. On the other hand, in geography, the concept of scale, referring to meaningful levels of description from individual buildings through neighborhoods, cities, regions, and countries, is central for the description of various aspects of human behavior such as socio-economic interactions, or political and cultural dynamics. Here, we resolve this apparent paradox by showing that day-to-day human mobility does indeed contain meaningful scales, corresponding to spatial containers restricting mobility behavior. The scale-free results arise from aggregating displacements across containers. We present a simple model, which given a person's trajectory, infers their neighborhoods, cities, and so on, as well as the sizes of these geographical containers. We find that the containers characterizing the trajectories of more than 700,000 individuals do indeed have typical sizes. We show that our model generates highly realistic trajectories without overfitting and provides a new lens through which to understand the differences in mobility behaviour across countries, gender groups, and urban-rural areas.