  The city is a complex system that evolves through its inherent social and
economic interactions. Mediating the movements of people and resources, urban
street networks offer a spatial footprint of these activities; consequently
their structural characteristics have been of great interest in the literature.
In comparison, relatively limited attention has been devoted to the interplay
between street structure and its functional usage, i.e., the movement patterns
of people and resources. To address this, we study the shape of 472,040
spatiotemporally optimized travel routes in the 92 most populated cities in the
world. The routes are sampled in a geographically unbiased way such that their
properties can be mapped on to each city, with their summary statistics
capturing mesoscale connectivity patterns representing the complete space of
possible movement in cities. The collective morphology of routes exhibits a
directional bias that could be described as influenced by the attractive (or
repulsive) forces resulting from congestion, accessibility and travel demand
that relate to various socioeconomic factors. To capture this feature, we
propose a simple metric, inness, that maps this force field. An analysis of the
morphological patterns of individual cities reveals structural and
socioeconomic commonalities among cities with similar inness patterns, in
particular that they cluster into groups that are correlated with their size
and putative stage of urban development as measured by a series of
socioeconomic and infrastructural indicators. Our results lend weight to the
insight that levels of urban socioeconomic development are intrinsically tied
to increasing physical connectivity and diversity of road hierarchies.
