  The polycentric city model has gained popularity in spatial planning policy,
since it is believed to overcome some of the problems often present in
monocentric metropolises, ranging from congestion to difficult accessibility to
jobs and services. However, the concept 'polycentric city' has a fuzzy
definition and as a result, the extent to which a city is polycentric cannot be
easily determined. Here, we leverage the fine spatio-temporal resolution of
smart travel card data to infer urban polycentricity by examining how a city
departs from a well-defined monocentric model. In particular, we analyse the
human movements that arise as a result of sophisticated forms of urban
structure by introducing a novel probabilistic approach which captures the
complexity of these human movements. We focus on London (UK) and Seoul (South
Korea) as our two case studies, and we specifically find evidence that London
displays a higher degree of monocentricity than Seoul, suggesting that Seoul is
likely to be more polycentric than London.
