  Millions commute to work every day in cities and interact with colleagues,
customers, providers, friends, and strangers. Commuting facilitates the mixing
of people from distant and diverse neighborhoods, but whether this has an
imprint on social inclusion or instead, connections remain assortative is less
explored. In this paper, we aim to better understand income sorting in social
networks inside cities and investigate how commuting distance conditions the
online social ties of Twitter users in the 50 largest metropolitan areas of the
United States. Home and work locations are identified from geolocated tweets
that enable us to infer the socio-economic status of individuals. Our results
show that an above-median commuting distance in cities is associated with more
diverse individual networks in terms of connected peers and their income. The
degree that distant commutes link neighborhoods of different socio-economic
backgrounds greatly varies by city size and structure. However, we find that
above-median commutes are associated with a nearly uniform, moderate reduction
of social tie assortativity across the top 50 US cities suggesting a universal
role of commuting in integrating disparate social networks in cities. Our
results inform policy that facilitating access across distant neighborhoods can
advance the social inclusion of low-income groups.
