Change in urban systems is a continuous process occurring simultaneously at different spatial levels. The traditional view on the local network of a city is that of daily urban systems (DUS) also called Functional Urban Regions (FUR's) or Standard Metropolitan Statistical Areas (SMSA's). Basic to these concepts are the two elements of an urban core and a suburban area surrounding it. The DUS came into being due to an increasing (auto)mobilization of labour supply which choose to live outside the city while labour demand stayed in the urban core. By this the DUS became a synonym for the local urban labour market. The hierarchical-nodal principle was the main mechanism of change. Important for the delineation of this urban labour market is that, although individual differences among demand and supply exists, aggregation of individual demand and suppliers is possible. In this, the concept fails back on the neoclassical labour market model, which starts from a homogeneous view on the labour market. Spatially the boundaries of local labour markets are based on the total labour supply directed at a location of labour-demand. There are numerous signs that this conceptual framework is no longer valid. The hierarchic structure is changing in a horizontal one. In consequence, at this local level, the nodal model becomes less attractive. Spatial processes are not any longer mainly controlled from a central core. Developments in the DUS are such that the traditional duality between centre and suburb disappears and a multi-centred urban area emerges with each part having a function of its own. The urban area gets a multi-centred appearance and suburbs are no longer sub (see Erickson, 1983; Van der Laan, 1987; Law, 1988; Ladd & Wheaton, 1991; Berry & Kim, 1993; Boamet, 1994; Palen, 1995). The consequence of this new form of urbanization is that the hierarchic functional organization becomes less important. A shift from a vertical hierarchic urban structure towards a more horizontal structure takes place. Changes at the local level occur within changes at the regional level. Summed up in a few words these changes may be described as a development towards a complex urban zone. It is characterised by a large scale multi-centred urban region - including various developing DUS - and a multifarious functional network in connection with spatial differentiation (Van der Knaap & Van der Laan, 1993; Knol & Manshanden, 1990). Urban centres increasingly function as nodes in a complex network. Two distinct evolutionary archetypes lead to this. On the one hand, there is the extension model, where such a network arises based on an outward oriented growth and intensification of a single large urban node and its suburbs. Examples of this are the developments of edge cities around older main cities. On the other hand, there is the model, where the network develops out of the integration of several older nodes located relatively close to each other. Examples of this are the German Ruhr-area and the Dutch Randstad. Although both models differ in their urban past, they have in common, that the central position of the urban centres is no longer determined by their position in relation to their immediate surroundings, but more and more by their position within a network of transactions. This network reflects both the local developments of the DUS and changes at the regional level. The effects of these developments are reflected in a multi-directed pattern of traffic flows. The combination of the regional urban changes and those of the local level urges for a analytical framework which gives room to both local developments and those occurring at higher levels. While this process has been studied quite extensive for the Anglo-American urban systems, studies of the changes in the continental-European system are less present. This paper analyses empirically the development of such an urban transactional system at the local and regional level in the Netherlands. For the analysis we use 26 daily urban systems as shown in figure I (see also Dieleman & Musterd, 1992; Frieling, 1994). The reader's special attention is asked for two groups of DUS in this figure to which we shall refer later on in the article. These are the North Wing and South Wing of the urban ring. The first is located in the northern part of the Randstad and its extension towards the east of the country. It includes the cities of Amsterdam, Utrecht and Arnhem. The South Wink encloses the Southern part of the Randstad and its easterly extension. This wing includes the cities of The Hague, Rotterdam and 's-Hertogenbosch. For the delineation of DUS and regional systems - as labour markets commuting is most important. Hereafter, firstly the general spatial pattern of commuting in the Netherlands is briefly sketched. Following this, changing networks at the local level of the DUS are described. In this we focus on the degree of nodality of the largest city within the local urban system. Are there signs of a decentralized pattern? After this, we turn to a higher spatial level and find out whether spatial integration of DUS at the regional level can be traced. After these sections we focus on the causal structure in the orientation of the commuting labour force of the daily urban systems. Which characteristics of the labour force causes their orientation towards the central city or to other locations? A concluding part summarizes the findings in a tentative multi-level model of urban system change. (A)
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