The development of GIS and its adoption for transportation applications closely mirrors the evolution of computer technology itself. The history of computer-based GIS dates back to the 1960s, with some of the earliest work conducted at the Harvard Graduate School of Design’s Laboratory for Computer Graphics and Spatial Analysis. These early GIS applications focused on area-based analyses, overlaying multiple layers of attributes associated with areas (e.g., population density, land use, etc.) in order to create composite thematic maps. Computer technology during this period was slow and expensive to run by today’s standards, and was limited in the amount of data that it could store and process. Consequently, early GIS data structures were designed to minimize unnecessary information in order to maximize processing efficiency; only those attributes essential to the specific application were included. Also, since each application was unique and the geospatial data were generally developed from scratch, data sharing was not an important consideration.
Throughout the 1970s, GIS technology was mostly limited to research institutions and large government agencies that had access to large mainframe computers. Beginning in the early 1980s, the next generation of computer technology – minicomputers and workstations – packaged much of the processing power of a mainframe computer into a smaller, more affordable hardware platform. At the same time, some of the early GIS researchers developed commercial versions of their GIS software and designed them to operate on specific minicomputers and workstations. This combination of minicomputer technology and commercialization of GIS software enabled many more organizations to begin experimenting with GIS, along with other computer-intensive applications such as computer-aided drafting and design (CADD), and database management systems (DBMS).
State DOTs began developing and maintaining computerized databases on highway and bridge characteristics, traffic volumes, etc. during the 1970s. Information contained in these databases was typically linked to a location on the physical facility using linear referencing methods. State DOTs also were responsible for preparing state and county highway functional classification maps, as required by FHWA regulations (23 CFR 470.105). Through the 1970s and 1980s, most highway maps were prepared using manual methods or computer-aided mapping programs that operated more like CADD systems than GIS. Access to commercial GIS software allowed some State DOTs (e.g., New York, Wisconsin) to begin applying GIS technology to help manage road inventory databases and create thematic maps for statewide planning. Information on some of the most common commercially available GIS software may be accessed on the GIS Software page on FHWA’s GIS in Transportation website.
In 1987, AASHTO held the first GIS for Transportation (GIS-T) Symposium. Its purpose was to bring together transportation professionals to identify and discuss potential applications and unresolved issues in using GIS technology in transportation. A second symposium was convened in 1989, and the event has been held annually since then. Since its inception, this conference has helped measure the rate of adoption of GIS in State DOTs, and has provided a showcase for innovative applications, technologies, and research.
Perhaps the most significant catalyst for adopting GIS technology by the transportation community was the creation and widespread dissemination of the Census Topologically Integrated Geographic Encoding and Referencing (TIGER) database in conjunction with the 1990 decennial Census. TIGER was the first nationwide database of combined geospatial features including roads, railroads, rivers and other water bodies, and political boundaries. Furthermore, the Census Bureau took a proactive role in marketing TIGER to potential user groups, including planners, demographers, and business marketing groups. TIGER/Line files were released using standardized, well documented formats, on CD-ROM media, and at very low cost. The Census Bureau also worked with GIS software vendors to develop programs for translating TIGER/Line files into the vendors’ proprietary formats.
By providing a nationwide database of key geospatial features, TIGER significantly reduced the labor intensive and costly task of building geospatial databases from scratch. This made it much easier for smaller transportation agencies like MPOs to begin using GIS to display and analyze recently collected Census demographic data for input into transportation planning models, and for many more State DOTs to investigate use of GIS for planning applications.
Another key factor was the “coming of age” of microcomputers, with increased processing power and a de facto standard operating system (i.e., Windows), which enabled software developers to produce application programs that would run on different hardware platforms. Although most major GIS software developers were initially wary about migrating their commercial GIS software from workstations to microcomputers, by the early 2000s nearly all commercial GIS developers had produced a fully functional microcomputer version of their GIS software.
Access to GIS functionality using a microcomputer significantly increased the adoption of GIS technology both within and across transportation agencies. Smaller State DOTs and MPOs no longer had to purchase dedicated GIS workstations, and could therefore make GIS available to a larger number of agency staff working in different application areas, rather than limiting access to a few GIS specialists. According to information collected through the AASHTO GIS Symposium, the number of State DOTs that had established an officially recognized GIS unit within their organizational structure increased from less than 20 percent in 1990 to 100 percent by 2007. Significant increases in GIS use also occurred at MPOs, and to a lesser extent in the planning divisions of transit agencies, although these increases are less well documented.
The U.S. Department of Transportation (USDOT) also played a significant role in promoting the use of GIS for transportation applications. In the early 1990s, FHWA used GIS to develop the National Highway Planning Network (NHPN), a network database of the nation's major highway systems, which is used to display and maintain information about the National Highway System (NHS) and the Strategic Highway Network (STRAHNET). Around the same time, legacy FHWA databases, such as the Highway Performance Monitoring System (HPMS) and the National Bridge Inventory (NBI), were modified so that they could be linked to the NHPN. These enhancements enabled what were previously just tabular summaries to be mapped, providing a more informative picture of the geographic distribution of national transportation facilities, and improving the quality of the data.
In 1995, an Office of Geographic Information Services was established within the USDOT’s Bureau of Transportation Statistics (BTS). Major goals of this office were to promote the use of GIS technology within the transportation community, encourage and facilitate data sharing partnerships for transportation geospatial data, and serve as a focal point for dissemination of national transportation geospatial information. This office created and continues to disseminate the National Transportation Atlas Database (NTAD), a compilation of national level geospatial databases of transportation networks, facilities and related areas, which is updated annually. It also functions as the federal lead agency for the coordination of transportation data standards within the Federal Geographic Data Committee (FGDC). FGDC is an interagency committee that promotes the coordinated development, use, sharing, and dissemination of geospatial data through the National Spatial Data Infrastructure (NSDI).
As adoption of GIS technology has grown among state DOTs, particularly over the past decade, GIS activities are typically divided between basic core functions and applications. Two essential components of a state DOT’s core GIS program are (1) a geospatial database of the state’s road network, and (2) one or more linear referencing systems to link the agency’s legacy databases to the road network.
Most state DOTs have devoted considerable effort to developing, maintaining, and updating these two components. Approximately one third of the state DOTs also have begun developing an enterprise data warehouse to consolidate all of the agency’s geospatial data using GIS as the integrating platform. Additionally, about two thirds of the state DOTs are actively engaged in developing web-based GIS applications to facilitate access to agency data and plans, both internally among agency staff and externally to the general public.
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