Quantifying long-term evolution of intra-urban spatial interactions

TL;DR

This study uses three years of mobility data to analyze how a new metro line in Singapore affected urban spatial interactions, revealing dynamic changes in community structures despite stable traditional mobility indicators.

Contribution

It introduces a novel approach to assess long-term urban infrastructure impacts by analyzing temporal community structures rather than static mobility measures.

Findings

Community structures became more consistent after the metro extension.

Traditional mobility indicators showed minimal change.

Spatial reorganization of areas was significant over time.

Abstract

Understanding the long-term impact that changes in a city's transportation infrastructure have on its spatial interactions remains a challenge. The difficulty arises from the fact that the real impact may not be revealed in static or aggregated mobility measures, as these are remarkably robust to perturbations. More generally, the lack of longitudinal, cross-sectional data demonstrating the evolution of spatial interactions at a meaningful urban scale also hinders us from evaluating the sensitivity of movement indicators, limiting our capacity to understand the evolution of urban mobility in depth. Using very large mobility records distributed over three years we quantify the impact of the completion of a metro line extension: the circle line (CCL) in Singapore. We find that the commonly used movement indicators are almost identical before and after the project was completed. However, in comparing the temporal community structure across years, we do observe significant differences in the spatial reorganization of the affected geographical areas. The completion of CCL enables travelers to re-identify their desired destinations collectively with lower transport cost, making the community structure more consistent. These changes in locality are dynamic, and characterized over short time-scales, offering us a different approach to identify and analyze the long-term impact of new infrastructures on cities and their evolution dynamics.