  As cities expand, human mobility has become a central focus of urban planning
and policy making to make cities more inclusive and sustainable. Initiatives
such as the "15-minutes city" have been put in place to shift the attention
from monocentric city configurations to polycentric structures, increasing the
availability and diversity of local urban amenities. Ultimately they expect to
increase local walkability and increase mobility within residential areas.
While we know how urban amenities influence human mobility at the city level,
little is known about spatial variations in this relationship. Here, we use
mobile phone, census, and volunteered geographical data to measure geographic
variations in the relationship between origin-destination flows and local urban
accessibility in Barcelona. Using a Negative Binomial Geographically Weighted
Regression model, we show that, globally, people tend to visit neighborhoods
with better access to education and retail. Locally, these and other features
change in sign and magnitude through the different neighborhoods of the city in
ways that are not explained by administrative boundaries, and that provide
deeper insights regarding urban characteristics such as rental prices. In
conclusion, our work suggests that the qualities of a 15-minutes city can be
measured at scale, delivering actionable insights on the polycentric structure
of cities, and how people use and access this structure.
