  Networks often possess mesoscale structures, and studying them can yield
insights into both structure and function. It is most common to study community
structure, but numerous other types of mesoscale structures also exist. In this
paper, we examine core-periphery structures based on both density and
transport. In such structures, core network components are well-connected both
among themselves and to peripheral components, which are not well-connected to
anything. We examine core-periphery structures in a wide range of examples of
transportation, social, and financial networks---including road networks in
large urban areas, a rabbit warren, a dolphin social network, a European
interbank network, and a migration network between counties in the United
States. We illustrate that a recently developed transport-based notion of node
coreness is very useful for characterizing transportation networks. We also
generalize this notion to examine core versus peripheral edges, and we show
that the resulting diagnostic is also useful for transportation networks. To
examine the properties of transportation networks further, we develop a family
of generative models of roadlike networks. We illustrate the effect of the
dimensionality of the embedding space on transportation networks, and we
demonstrate that the correlations between different measures of coreness can be
very different for different types of networks.
