Polycentricity and the Multiplexity of Urban Networks

Abstract

Empirical studies on polycentric urban regions (PURs) tend to analyse their spatial organization by examining only one type of functional linkage between cities. However, it has generally been accepted that urban networks are multiplex phenomena and that spatial interactions between cities can take many different forms, for example, commuting, shopping trips, and inter-firm trade. The spatial organization of each of these functional linkages is not necessarily identical, and, therefore, a region can appear to be polycentric and spatially integrated based on the analysis of one type of functional linkage but monocentric and loosely connected based on the analysis of another type of functional linkage. The aim of this paper is to stimulate further discussion on the multiplexity of urban networks with regard to the relational complexity of urban regions. Focusing on one PUR (Randstad Holland), we compare the geographical scope and spatial structure of different functional networks within it. Our results indicate that the spatial organization of the urban network depends on the lens through which it is assessed.

Acknowledgements

We would like to thank two anonymous reviewers for their comments on an earlier draft of this paper. All errors remain those of the authors.

Notes

1. At the same time, evidence that a polycentric region was functionally integrated would also support planning on larger geographical scales than that of the city or region in question to manage those spatial interdependencies (Turok & Bailey, 2004).

2. This has been demonstrated empirically by, for example, Lambregts et al. (2006), whose analyses of commuting and intra-company office networks give very different pictures of the spatial organisation of the Randstad region in Holland. Similar conclusions can be drawn with regard to other regions based on the work of Limtanakool et al. (2009) and Lühti et al. (2010).

3. As Davoudi (2008) points out, this has also resulted in the dominance of an economics-based conceptualization of functional regions.

4. Similarly, an urban system may have a predominantly polycentric structure at the regional level and a predominantly monocentric structure at the local level or vice versa. For example, commuting, trade and shopping could be multidirectional at the level of the PUR but unidirectional at the level of the individual metropolitan areas (see also De Goei et al., 2010).

5. Lüthi et al. (2010, p. 114) observe a similar pattern in the Munich region, which they classify as “a hierarchically organized polycentric mega-city region and high-grade localized system of value chains”.

6. The weighting factors were included in the data as analysed.

7. A random, stratified sample, taking size and region into account, was extracted from the LISA database, which is an employment register including all Dutch establishments (see Van Oort, 2007). The survey focused on companies' 10 most important selling and purchasing relationships with other establishments within or outside of their own municipality. The limitation of the data to 10 relationships may lead to a potential bias in the analysis of the network structure towards large establishments, but large establishments are not over-represented in cities in the Randstad (Van Oort et al., 2010). We were not able to analyse the different sectors separately.

8. Because of the limitations of the data, we are not able to distinguish between incoming and outgoing connections in this case.

9. We used the specification of Gabaix and Ibragimov (2011) to estimate the coefficients.

10. It should be noted that these distinctions depend on our definition of the Randstad. A large number of trips that we analyse as having originated outside the Randstad in fact originated in urban centres that are in close proximity to the Randstad but are not part of the Randstad according to our delimitation. Because we are mainly interested in comparing different types of functional linkage and are focusing on the polycentricity and integration of the four largest urban centres in the region, this delimitation is appropriate. However, this caveat underlines that the definition of the boundaries of functional regions is heavily dependent on the functional relationship under consideration (see also, Brown & Holmes, 1971).

11. However, it is often difficult to obtain such detailed, broken-down data for functions of interest. For example, it is well known from the central-place literature that most inter-regional shopping trips are for purchases of luxury goods rather than daily shopping goods (Dijst & Vidakovic, 2000). Although these trips represent different types of functional linkage, it is most often not possible to make such distinction in the analysis of data on shopping trips.