Urban highways are barriers to social ties

2024-04-17

Proceedings of the National Academy of Sciences of the United States of America

AI Summary

This study investigates whether urban freeways act as physical barriers that weaken local social ties, particularly exacerbating racial segregation in minority communities. Method: Leveraging geotagged social network data from the 50 largest U.S. cities and high-resolution GIS road network data, we construct an individual-level “Barrier Score” to quantify freeway-induced disruption of short-distance interpersonal connections. We integrate spatial regression discontinuity design, historical policy comparison (e.g., mid-20th-century racially targeted freeway siting), and large-scale network modeling. Contribution/Results: Freeways significantly reduce cross-freeway social interactions, with the strongest suppression effect within 1 km. This spatial pattern closely aligns with historically discriminatory freeway planning targeting Black neighborhoods. By pioneering the coupling of infrastructure spatial data with digital social tie data, this work establishes a novel, empirically grounded framework for quantifying structural drivers of social segregation and informing equitable, restorative urban renewal policies.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Cognitive Modeling & Cognitive Systems: Social Cognition And Interaction
• Data Mining & Knowledge Management: Graph Mining, Social Network Analysis & Community

Application Category

• Social Networks and Social Media: Social media analysis through the lenses of networks
• Graph Algorithms and Modeling for the Web: Representation, reconstruction, and subgraph or motif discovery in Web-related graphs
• Web Mining and Content Analysis: Content-based information diffusion

Abstract

Urban highways are common, especially in the United States, making cities more car-centric. They promise the annihilation of distance but obstruct pedestrian mobility, thus playing a key role in limiting social interactions locally. Although this limiting role is widely acknowledged in urban studies, the quantitative relationship between urban highways and social ties is barely tested. Here, we define a Barrier Score that relates massive, geolocated online social network data to highways in the 50 largest US cities. At the granularity of individual social ties, we show that urban highways are associated with decreased social connectivity. This barrier effect is especially strong for short distances and consistent with historical cases of highways that were built to purposefully disrupt or isolate Black neighborhoods. By combining spatial infrastructure with social tie data, our method adds a dimension to demographic studies of social segregation. Our study can inform reparative planning for an evidence-based reduction of spatial inequality, and more generally, support a better integration of the social fabric in urban planning.

Problem

• Urban highways limit social interactions locally.
• Quantitative relationship between highways and social ties is untested.
• Highways decrease social connectivity, especially at short distances.

Innovation

• Defined Barrier Score using social network data
• Linked highways to decreased social connectivity
• Combined spatial and social data for segregation studies