فن آوری های فضایی، دسترسی، و ساخت و ساز اجتماعی فضای شهری

Accessibility is both an important concept, and a powerful indicator, in the understanding of the impact of spatial technologies, i.e. transportation, communication, and information technologies. However, virtually all existing measures of intra-metropolitan accessibility incorporate only transportation without considering other means of spatial interaction. In this paper, the author argues that by carefully examining the relationship between transportation and communication, it is possible to develop measures that represent urban spatial structure more completely. Based on studies of teleworking in the United States, the author presents an accessibility measure that takes into account both travel and telecommuting. A case study of employment accessibility in the Boston Metropolitan Area indicates that advances in spatial technologies may generate the dual effect of locational equalization and socio-spatial polarization. In the urban space that is increasingly technologically delineated and socially constructed, low-income workers will very likely find themselves in a more and more disadvantaged position.

The term “spatial technologies”—adopted from Couclelis (1994)—is a collective name for the transportation, communication, and information technologies that modify spatial relations. Advanced telecommunication networks and digital information systems are dramatically redefining urban space. They are challenging many basic concepts and analytical frameworks of urban geography and planning, and raising numerous fundamental questions for scholars in these fields.1 This paper is aimed at addressing three such questions: Are traditional measures of accessibility useful in understanding conceptually the socio-spatial impacts of advanced spatial technologies? Can we modify some traditional accessibility measures to make them suitable for assessing such impacts? and How do advances in spatial technologies affect urban residents and neighborhoods with various socio-economic characteristics? Clearly, these questions are of critical importance to urban planners, whose primary function is to facilitate economic efficiency and social equity in spatial contexts. If we construct a proper analytical framework for measuring, interpreting, and simulating complex relationships between spatial technologies, urban physical environments, and social structures, we may become capable of better planning and managing our cities. In this paper, I shall first briefly review several existing accessibility measures which represent different views of the relationship between transportation technology and the city. I shall then discuss how we might extend some of the existing measures to include telecommunications as an important variable in the analysis of urban spatial structure. The discussion will be followed by the formulation of an employment accessibility measure which is useful for understanding the likely socio-spatial consequences of communication and information technologies. This extended measure will be applied to a comparative analysis of the urban spatial structure of the Boston Metropolitan Area under two different scenarios: (1) a negligible amount of teleworking; and (2) a substantial amount of teleworking. Finally, I will conclude the paper by drawing several implications from the research and defining some possible directions for future research.

A review of existing accessibility measures suggested that some are suitable for conceptualizing the impact of advanced spatial technologies in general. It also suggested that some of these measures provide a foundation for constructing new analytical tools. As an important element of this study, an existing accessibility measure was modified to build an extended framework that includes both transportation and telecommunication components. In that process, it became clear that the most critical step in building a composite measure is to define the nature of the relationship between transportation and telecommunication. Careful examination of this interrelation is essential for providing an empirical basis for specifying the impedance for telecommunication-based activities. The extended measure was useful for understanding the increasingly important role of technological—and more fundamentally social—factors in defining the meaning of urban space. The case study of employment accessibility in the Boston Metropolitan Area provided some important insights into the relationships between location, spatial technologies, and urban social fabrics. The results suggested that advances inspatial technologies may generate the dual effect of locational equalization and socio-spatial polarization. In the urban space that is increasingly technologically delineated and socially constructed, low-income workers in general—and those living in the inner city in particular—will very likely find themselves in a more and more disadvantaged position. This study is a preliminary effort to integrate transportation and telecommunication in the measurement of accessibility and in the exploration of urban spatial structure. It has some obvious limitations. First of all, it has so far developed only one accessibility measure to examine only home–work relationship, and applied the measure to only one metropolitan area. For future research, alternative measures should be explored, and other metropolitan areas should be studied so that some general conclusions can be made. Secondly, like most simulation studies, some simplistic estimates were used as input data in the simulation of the scenario for the year 2005. Subsequent sensitivity analyses indicated that results sometimes changed quantitatively—but not qualitatively—when alternative estimations of teleworkers, telecommunication-based jobs, and commuting frequency were made. To make this kind of study useful in real-world urban planning and policy making, it is essential to improve the definition and measurement of these basic variables. In the future, estimations should be refined when new empirical data become available. Thirdly, the study was based on the assumption that the spatial distribution of employment would remain the same in the year 2005. This study does not explore the likely consequences of alternative job distributions. Therefore, a useful extension of the research is to explore such alternatives and examine their socio-spatial consequences. Finally, the study has not taken any indirect effects into consideration. As some scholars have suggested, the reduction in distance friction caused by telecommunications may generate many secondary consequences. For example, it may encourage teleworkers to move to a more distant location, which would bring further decentralization (US DOT, 1993; Hall, 1996); it may cause future decline of public transportation (Batty, 1990). How to put all these pieces together so that we can see some reasonably complete pictures is perhaps the most challenging question for future research in modeling of urban spatial structure in the information age.