Urban highways are barriers to social ties (2404.11596v3)

Abstract: Urban highways are common, especially in the US, 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 unprecedented 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 new 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.

• The paper introduces a novel Barrier Score that quantifies the reduction in social ties due to urban highways using geolocated Twitter data.
• It employs a systematic comparison of 2.7M Twitter interactions across 50 metropolitan areas against a reshuffled null model to uncover significant connectivity disruptions.
• Findings indicate that longer highways and lower urban density intensify social segregation, offering insights for mitigating these effects in urban planning.

Quantitative Analysis of Urban Highways as Barriers to Social Connectivity in U.S. Metropolitan Areas

Introduction

Urban highways, particularly in the United States, have been associated with several socioeconomic issues including segregation and reduced social connectivity. Despite the widespread acknowledgment of highways as physical barriers, there has been a dearth of empirical research quantifying their impact on the social fabric of cities. The paper in question addresses this gap by introducing a novel methodological framework to systematically quantify the barrier effect of highways on social ties across the largest metropolitan areas in the U.S. Utilizing geolocated Twitter data, this paper represents a significant stride in understanding how infrastructure influences social interactions within urban settings.

Methodology

The paper hinges on a "Barrier Score" which encapsulates the reduction in social ties crossing highways. This metric is derived by comparing the observed social connections in empirical data with a null model—where ties are reshuffled without consideration of highway locations. The null model retains overall topological features of the social network but removes any geospatial biases related to highways, providing a baseline for normal interaction levels. The Barrier Score is then computed for each highway segment and aggregated for each city to reveal generalized impacts.

Through a robust data assembly, the research captures roughly 1M Twitter users across the top 50 U.S. metropolitan areas, linked by over 2.7M mutual connections, with users' interactions anchored to a highly detailed urban highway network extracted from OpenStreetMap.

Findings

The paper unveils several notable patterns:

• The presence of highways consistently correlates with a decrease in the number of social ties across all examined cities, confirming the hypothesis that highways serve as significant barriers to social connectivity.
• The effect of highways on limiting social ties is more pronounced among neighborhoods closer to each other, generally peaking at distances below 5 km and diminishing after 20 km.
• Metropolitan areas with extensive highway networks, lower fragmentation of neighborhoods by highways, and lower population density exhibit higher Barrier Scores. This suggests that longer highways increase social disconnect, while denser and more connected urban fabrics mitigate the barrier effects of highways.

Contextual Analysis

Using regression analysis, the paper further explored factors influencing variance in Barrier Scores across cities. Results indicate that cities with a more complex network of highways (longer highways and extensive infrastructure) have systematically higher Barrier Scores, which suggests a direct relationship between urban planning decisions and social segregations.

Theoretical and Practical Implications

The findings of this paper underscore theoretical understandings of spatial segregation's mechanisms, emphasizing how urban infrastructure shapes social interactions. Practically, this research offers quantifiable evidence that can inform urban planning and policy-making—suggesting reconsideration of highway designs to foster greater urban cohesion and proposing interventions to convert highways into less divisive structures.

Conclusion and Future Research

The paper concludes that while highways connect disparate parts of cities, they concurrently fragment densely populated urban quarters, curtailing local interactions. Future research could explore the caustic impacts of highways beyond social interaction—such as economic disparities and access to amenities—and explore longitudinal impacts of urban planning interventions aimed at mitigating highway barrier effects.

Overall, this robust analysis provides a critical framework for understanding and addressing the consequences of urban highway infrastructure on societal cohesion, contributing to more equitable urban development strategies.