FUNCTIONAL REGIONS WITHIN THE CITY CENTRE: A STUDY BY FACTOR ANALYSIS OF TAXI FLOWS IN CENTRAL LONDON

This paper examines the problem of measuring the relationship between movement patterns and the location of activities within the city centre. Emphasis is placed on the problem of defining and analysing complex linkage systems. Data on taxi flows are presented as a single indicator of multi-faceted functional linkages within Central London. Cartographic analysis reveals a complex pattern of flows; correlation and factor analysis are therefore applied to the data to determine the underlying structure of the taxi-flow system. Traffic zones are compared in terms of the zones from which they receive trips; high factor loadings reveal groups of zones receiving trips from common origins; the related factor scores specify these origins. Linking groups of origins and destinations on a map reveals five functional regions. Hierarchical grouping of zones produces an objective classification of zones in terms of similarities in linkage characteristics. Comparison of the pattern of functional regions with familiar structural regions suggests a basic isomorphism between such regionalizations. More important, the analysis reveals the usefulness of the methods for investigating the structure of complex flow systems so as to specify the principal groups of observations and the linkages they have in common. THE CLOSE connection between movement and the distribution of activities in spatial systems is a well-established geographical axiom. At the national level B. J. L. Berry has used multivariate statistical procedures to measure the relationships between the state of a system, expressed in terms of the distribution of productive activities, and the behaviour of that system, expressed in the form of commodity flows between various places.1 He has structured these relationships within the framework of a general field theory of spatial behaviour, in which the pattern of flows, summarized as a set of functional regions, is held to be both a resultant and a determinant of the spatial distribution of activities, summarized as a set of uniform regions.2 Berry's formulation is in some ways a more general statement of A. K. Philbrick's principle of'areal functional organization'.3 Similarly, O. Wameryd, in his conceptual model of the urban system, has stressed the importance of functional interdependencies in explaining changes in the state of the system.4 It would be reasonable to assume that the interdependence of flows and spatial structure also holds within urban areas, in particular within large metropolitan centres. However, at this level the measurement of the relationships involved creates numerous conceptual, empirical and technical problems, many of which are insuperable at the present time. While several studies of city centre structure have emphasized the role of 'linkages' between highly specialized activities as a determinant of location, little progress has been made in measuring these linkages. 5 Most rrevious research has focused on the distribution of activities; linkages have then been inferred from locational associations among these activities.6 For instance, within the financial core of the City of London, multivariate analysis of detailed employment data has highlighted the existence of distinctive spatial clusters of offices whose composition closely reflects the wellknown functional organization of the City.7 Within the broader compass of the London Central Area, floorspace data have suggested a number of sub-areas with distinctive land-use combinations.8 I6I This content downloaded from 157.55.39.35 on Wed, 31 Aug 2016 04:35:39 UTC All use subject to http://about.jstor.org/terms According to Berry's general field theory formulation, such pronounced spatial differentiation within city centres should simultaneously be determined by, and call forth, a correspondingly structured pattern of movement. Yet very few studies have been made of physical linkage patterns in the city centre, in relation to the activities that generate and attract these movements. In part this is because of data difficulties. While detailed information can be collected on the distribution of activities, a corresponding breakdown of movement patterns associated with each of these activities would require extensive surveys. More important, linkages frequently involve information flows that are extremely difficult to differentiate, that use a variety of communication channels and which often do not involve obvious physical movements.9 Some of these difficulties can be by-passed by considering only physical movements of a given type, as a single indicator of multi-faceted functional linkages. But even then, observed movement patterns are extremely complex. It is therefore the object of this paper to suggest a method for analysing the complex linkage structures that are represented by movement patterns in the city centre. As the first stage in the scientific description of any complex pattern involves the development of a classificatory framework, numerical taxonomic procedures are applied to observed patterns of flows. This yields a more readily appreciated series of functional regions that can be compared with uniform regions derived from a similar analysis of activity distributions. The Data and Study Area For the purposes of this paper, the movements of taxis within Central London have been taken as the best available single indicator of functional linkages. Of the principal travel modes, the use of taxis is most characteristic of the Central Area; in fact, 55 per cent of all taxi trips in Greater London both begin and end in the centre. 10 However, taxis still represent only one type of communication and the subsequent analysis is therefore forced to ignore linkages maintained on foot, by private vehicles, public transport, telephone and post. The Registrar General's definition of the Central Area for the I96I census is taken as the limit for the study area, which for practical purposes has to be regarded as a closed system (Fig. i). This area was subjectively extracted from the existing administrative framework by aggregating enumeration districts to provide an additional unit for collecting future census and planning data. Defined in this way, the Central Area includes an area of 28 km2, which is much larger than the Central Business District defined using R. E. Murphy and J. A. Vance's criteria.11 In fact, the Central Area includes both C.B.D. 'core' and 'frame' using E. M. Horwood and R. R. Boyce's terminology, thus containing the main-line rail termini, which are major generators of taxi traffic. 12 The data were collected in I962 as part of the London Traffic Survey. They are based on journey logs kept by an effective 10 per cent sample of all cabs registered in the Survey Area for one week in July.13 As the logs were completed by taxi drivers, the data failed to differentiate trips according to passenger's journey purpose. An additional shortcoming of the data from the linkage standpoint is that non-fare paying trips (that is, trips made between setting down one passenger and picking up another) are not excluded. Because drivers tend to cruise back into the areas where most trips are generated, the major nodes in the system could be over-emphasized. Both of these limitations are overcome in a second survey of taxi usage conducted in July I969 as part of a Home Office investigation into the London taxicab trade. Trip origins and destinations determined from the logs have been assigned to seventy I62 J. B. GODDARD This content downloaded from 157.55.39.35 on Wed, 31 Aug 2016 04:35:39 UTC All use subject to http://about.jstor.org/terms FUNCTIONAL REGIONS IN CENTRAL LONDON FIGURE I-London Central Area FIGURE 2-Traffic zones traffic zones in the Central Area and averaged to give 24-hour weekday flows. All but eight of the zones consist of aggregations of enumeration districts delineated with due consideration of land-use characteristics. The remaining eight zones comprise sections of major shopping streets, for example, Oxford Street (three zones) and Piccadilly (two zones) (Fig. 2). i63 This content downloaded from 157.55.39.35 on Wed, 31 Aug 2016 04:35:39 UTC All use subject to http://about.jstor.org/terms