Heterogeneous Development of Metropolitan Spatial Structure: Evidence from Commuting Patterns
3.6 Concluding Remarks and Limitations
The geography and planning literature has often assumed that all modern metropolitan systems are becoming polycentric. At the same time, the heterogeneity in the development of city-regions has not been the main object of various studies. Our analysis of commuting and employment data shows that, although many city-regions are becoming more polycentric, the spatial structure is differing considerably across city-regions. A related question is which kind of spatial structure prevails in specific regions. During the period 1981 – 2001 decentralisation in the spatial structure occurred across city-regions. These
84
results are in line with the findings of De Goei et al. (2010) for the Greater South East UK, which also observed decentralisation at the intra-urban scale, exemplified by a relative increase in exchange and criss-cross commuting. Similar trends towards decentralisation of employment and population at the intra-urban scale are observed in Denmark (Nielsen and Hovgesen, 2005), France (Aguilera and Mignot, 2004), and Germany (Guth et al., 2009).
Nevertheless, the extent of change in the overall spatial pattern is modest. In addition, the results show a large spatial differentiation. It was found that not all city-regions are moving in the same direction. Whereas the majority of city-regions in South England and the Midlands are becoming more polycentric, the spatial structure of many city-regions in North England is hardly changing or even becoming more monocentric. Having observed these different trends, the question remains why some city-regions become polycentric in form and other city-regions do not. Further empirical research should address this question in detail by quantitatively linking the spatial heterogeneity in the dynamics of metropolitan spatial structure with the heterogeneity in the initial shape, economic and socio-cultural developments and local and regional land use policies across city-regions.
Further research can use different approaches (De Goei et al., 2010). First, more detail on the relationship between changing metropolitan spatial structure and the increasing flexibility and mobility of firms is needed. In particular, the link between advancements in transport, ICT, a developing service economy, and changes in metropolitan spatial structure deserves further attention. A starting point here would be the research of Ioannides et al. (2008), which has shown that ICT weakens agglomeration forces and provides incentives to relocate economic activities to smaller centres. Particular attention should be paid to how changes in the balance between agglomeration economies and diseconomies (e.g., pollution, crime) trigger changes in the spatial organisation of metropolitan areas and how a group of functionally linked centres share agglomeration economies (Meijers and Burger, 2010).
Secondly, the relationship between the changing metropolitan spatial structure and increasing flexibility and mobility of households can be further examined. Advances in transport and ICT make households not only more mobile, but can also change residential preferences. Advances in transport and ICT allow for the potential of changes in the demography of developed economies and the life styles of people and can thus affect metropolitan spatial structure (Champion, 2001). Such demographic developments include the rise of two-earner and single person households, the increasing number of working
85
women, higher life expectancy, and a lower fertility (Hall and White, 1995). These demographic developments have changed the residential preferences of large groups of people, causing changes in the spatial organisation of urban systems (Van Ham, 2002).
Thirdly, the effect of local and regional policies on metropolitan spatial structure is a matter that can be analysed further. This includes policies that have the explicit intention to change metropolitan spatial structure and policies which unintentionally result in a change in metropolitan spatial structure. Likely, here are multiple drivers behind the changing spatial organisation of city-regions. However, these drivers may differ across various locations. In addition, the original shape of city-regions also influences changes in their spatial organisation are. Accordingly, it will be important to distinguish between city-regions and different determinants of metropolitan spatial structure.
Although commuting constitutes one of the most important economic interactions within a city-region, an important limitation of this study is that it only examined commuting and employment data. Several authors have pointed out that journey-to-work travel is not a perfect indicator for all economic interaction within a territory and should be used alongside other forms of economic interaction to gain a realistic insight into the interdependence of places and structure in urban systems (Lambregts et al., 2005; Hewings and Parr, 2007). Accordingly, policymakers should be careful drawing inferences solely based on this study. Places are not only functionally connected through labour market relations, but also through trade, capital movements, leisure trips, and shopping trips (Lambooy, 1998; Parr, 2005). Admittedly, commuting trips are often the only type of data available and may provide a surrogate representation of other types of spatial interaction (Parr, 2005).Yet the degree to which commuting relations are a good proxy for other types of spatial interaction is far from clear and should be addressed in future research on metropolitan spatial structure. In particular, it is interesting to examine whether polycentric city-regions can still be regarded as functional polycentric when other types of economic interaction are taken into consideration. A similar point can be made with regards to morphological polycentricity and the internal characteristics of centres taken into consideration.
The evaluation of spatial structure is quintessentially scale-dependent and contingent on both the choice of analytical framework (European, national, regional, local) and the measurement of functional spaces dependent on the type of economic interaction (Hall and
86
Pain, 2006; Parr, 2008).16 In our analysis, we evaluated the spatial structure of city-regions delimited on the basis of commuting and employment data. However, some urban functions, such as centres of corporate control and the supply of specialised goods and services, have a larger geographical scope and are concentrated in only a few major cities (Parr, 2008). In this light, the city-regions of Brighton, London, Northampton, Reading, Southampton, and Portsmouth studied in this chapter can be considered secondary city-regions within some primary city-region at a higher geographical scale with London as principal centre.
Lambregts et al. (2005: 32) then also rightly remark that ‘polycentricity is up to certain extent in the eye of the beholder’. Preferably, indicators suggesting a territory is polycentric should be weighed against indicators suggesting otherwise, taking into account the spatial scale at which polycentricity is studied. Only in this fashion, it will be possible to completely grasp how territories are spatially organised and how this spatial organisation changes over time. Such thorough understanding of these processes is necessary in order to explain the dynamics of spatial structure and to inform policy.
16 Of course, the delimitation is to some extent also dependent on the delimitation algorithm and procedure that is used (Cörvers et al., 2009).
87