major limitation in the use of transportation models is the difficulty of obtaining adequate data for them. Geographical information systems are a means of addressing this need. A geographical information system (GIS) is a “computerized database management system for the capture, storage, retrieval, analysis, and display of spatial (i.e., vocationally defined) data.’ ” GIS-T is the adoption and adaptation of GIS for transportation purposes. The adaptation of GISs—particularly in areas of the development of methods for data storage and the provision of appropriate analytical abilities—will lead to the adoption of GIS-T by transportation agencies. GISS are principally a product of the 1980s, although they have been around in some form since the 1950s. Many municipalities have installed either complete systems or limited, prototype systems; others are currently investigating the use of such systems. The use of GISS is growing rapidly. Municipalities are seeking to use these systems to increase productivity, effectiveness, responsiveness, and quality of operations, as well as to reduce costs. The inclusion of transportation analysis features within a GIS may have important long-term ramifications for planning as a whole. The analysis of land use and transportation has long suffered from being completed within separate institutions, each with its own sets of data and tools. Harris has said: It is thus a great misfortune for American city planning that the functions of land-use and transportation planning have been institutionally divorced, and rarely cohabit. It is vitally significant that the GIS packages currently in use provide very little opportunity to study transport and other forms of interaction, and to judge the outcome of even current events on the basis of their consequences in these respects.”z The ability of transportation analysts to readily access urban data through GIS provides a major opportunity to overcome this schism. The general virtues of GIS are often extolled. The downside is not as well publicized. The average city planner and urban analyst may find a GIS to be difficult to set up, maintain, use, and master. There are more than 1,000 commands in each of the two packages commonly used in the GIS courses taught at the Computer Resource Lab a
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