Percolation transitions in urban mobility networks in America's 50 largest cities

Urban mobility can be significantly disrupted by various extreme events. The disruptions threaten urban spatial connectivity and affect people's ability to access various essential services. Accurate characterization and timely alert of the critical transitions of urban mobility networks can help mitigate the above risks. However, there lacks an approach to characterize the critical transition state of urban mobility networks and warn their transitions during extreme events. The universality of the characteristics of disrupted mobility networks across different cities is another fundamental question that remains underexplored. By mining big geodata, we construct the mobility networks of the 50 most populous Metropolitan Statistical Areas (MSAs) in the U.S., and study their disruption patterns by conducting network percolation analysis. We find that all mobility networks experience abrupt transitions when reaching a universal critical threshold, at which the giant components of neighborhoods suddenly collapse and dissolve into small clusters. We also develop an indicator, by analyzing the neighborhood cluster distributions, that approximates how far a mobility network is to the critical threshold and provides an early warning of its critical transition. Our findings provide insights into mobility and neighborhood connectivity in cities, which can provide guidance for transportation management, epidemic control, and emergency evacuation.