United States Department of Transportation
i
Guidelines for preliminary selection of the optimum interchange type for a specific location
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1999-01-01
[PDF-4.80 MB]
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Edition:Final report
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Abstract:In Virginia, when new construction or major reconstruction is planned, the current practice is for a location and design engineer to select the interchange type (diamond interchange, single-point urban interchange, trumpet interchange, full cloverleaf interchange, partial cloverleaf interchange, or directional interchange) for a given location. The engineer relies upon projected traffic data, right-of-way needs, environmental concerns, safety, and project costs to help determine which interchange configuration will most efficiently serve the needs of a certain area. The purpose of this study was to develop guidelines to aid designers in the selection of the optimum interchange type at a location. This study will give the engineers a starting point to begin their analyses, which, it is hoped, will result in reduced costs, improved levels of service, and increased uniformity. A number of sources were used to develop the guidelines. A literature and a nationwide survey of state engineers helped to determine current methods for interchange selection. These surveys also helped determine the relative advantages and disadvantages of the various interchange types. Also, 10 interchanges throughout Virginia were studied in order to find their operational and safety characteristics. Extensive computer simulation of the interchange types was performed in order to determine traffic characteristics that affected operations at the interchanges. Based on all of these sources, some general guidelines for preliminary interchange type selection were created.
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