The levels and scales of urban networks

The urban networks discussed in this volume, and that appear in the literature more broadly, are characterized by significant diversity. This is perhaps not a surprise as the study of urban networks is necessarily interdisciplinary, drawing on theoretical foundations from geography, economics, psychology and sociology, and on methodological tools including ethnographic and qualitative methods from sociology, and quantitative methods from mathematics and physics. However, although the flexibility of network models to capture a wide range of urban phenomena is a key strength of the approach and a source of intellectual diversity, it can also be a source of confusion. Different fields and different research questions require studying different types of urban networks, often defined in very different ways, which obscures their commonalities. In this introductory chapter, we sketch a framework for integrating the diversity of urban networks by situating them along the dimensions of level and scale. These two dimensions define, respectively, the aggregation and spatial scope of the nodes, and therefore provide critical parameters for defining an urban network. In some instances, a network’s level and scale are defined implicitly by the research question, but we contend there is still value in being explicit about level and scale. Similarly, although a great deal of past research on urban networks has explored only specific intersections of level and scale (for example, networks of people at the local scale, or networks of cities at the global scale), we contend that exploring urban networks with different combinations of levels and scales offers opportunities for new insights that the reader will find in this volume. We begin by describing the level/scale framework in general, then discuss the case of economic urban networks as an extended example, and use the framework to explore commonalities among the diverse urban networks in this volume. We conclude by discussing ways that levels and scales can be made more explicit in urban networks, and the potential benefits for studying urban networks at multiple levels and scales.