  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.
