Urban highways are barriers to social connections
Researchers from IT University of Copenhagen have proved that urban highways limit social connections in the 50 largest cities in the US. It is the first ever quantitative evaluation of the barrier effect of urban highways in reducing social connections across neighborhoods.
Anastassia VybornovaLuca Maria AielloMichael SzellResearch
Written 5 March, 2025 10:06 by Mette Strange Mortensen
Have you ever asked yourself whether highways connect or rather disconnect people? For many years, it has been suspected that urban highways have a negative impact on social connections amongst citizens. Now, for the first time ever, a research team led from IT University of Copenhagen has shown this to be true. By using geolocated online social network data from the 50 largest US cities, the researchers mapped out peoples’ connections across urban highways.
“Imagine a map of the city charting all the streets, highways, rivers, and all other natural and human-made elements that together make up the urban environment. Onto this map, we overlay a social network extracted from Twitter, where nodes are the estimated home locations of people, and links connecting them are all their Twitter friendships within the city”, says Associate Professor at ITU Luca Aiello. “With this complete view of a georeferenced social network we can use statistical models to determine whether the likelihood of forming a social connection between any two areas decreases when these areas are separated by a highway.”
The researchers calculated a Barrier Score – a way to measure the association between highways and social ties crossing them. They found that the presence of urban highways did have a strong impact on social connectivity, even after discounting the effect of sociodemographic factors and of other physical barriers such as rivers and railroads.
“A dominant narrative of the past 60 years depicts the private car as a way for people to move around freely and facilitate their access to services and opportunities,” says Luca Aiello. “However, as our study shows, car-centric urban design comes not only at the cost of polluting the environment and losing precious urban space to transportation infrastructure, but also at the cost of tearing the social fabric of communities”.
The researchers found out that the barrier effect of highways is especially strong at distances below 5 km, and consistent with historical cases of highways that were built to purposefully disrupt or isolate Black neighborhoods.
Controversial highways
According to the researchers, in the US, there has been a long history of building large highways through dense neighborhoods, causing segregation and deterioration of local opportunities. By quantifying the correlation between highways and social connectivity, the researchers hope to provide relevant information to policymakers to reconnect urban communities.
“Until recently, the U.S. Department of Transportation had funded the Reconnecting Communities Pilot Program, to partly undo the damage that highways have created in urban centers. Unfortunately, this program has been dismantled by the new US government and is unlikely to be reinstated in the near future. Our study proves that there is a desperate need for these reconnection plans to improve the quality of life of people living in cities”, says Luca Aiello. “We hope our research will be used to inform lawmakers and local administrations also in Europe, to avoid repeating errors of the past”.
The paper has been published in the Proceedings of the National Academy of Science (PNAS). It is a collaboration between Associate Professor Luca Aiello, Associate Professor Michael Szell and Postdoc Anastassia Vybornova from the IT University of Copenhagen, and researchers from the Corvinus University of Budapest, and the University of Amsterdam. The research has been supported by EU Horizon Project JUST STREETS.
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