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Creating an intelligent variable speed limit system for rural highways
Published June 14, 1999 by ISATA - Dusseldorf Trade Fair in United Kingdom
Event: ISATA 1999
Northern Arizona University and the Arizona Department of Transportation (ADOT) are working together to design a variable speed limit (VSL) system for rural highways that utilizes information provided by Road Weather Information Stations (RWIS). A VSL system that relies on fuzzy logic is now running at the ADOT district office in Flagstaff, Arizona. This system continuously reads data about atmospheric and road surface conditions provided by different RWIS sites and then displays maximum speed limits that are appropriate to the conditions detected at those sites. This paper discusses the important components of the development of this VSL system. First the basics of the computational engine utilized by the VSL system is explained. This computational system is based on Bart Kosco's Standard Additive Model which defines a model of fuzzy systems that is powerful yet conceptually and computationally simple. In the next section, an examination of the essential steps in the design of the fuzzy algorithm for the VSL system is provided. Selection of the input and output dimensions, partitioning of these dimensions, and development of the fuzzy rule set through the use of metarules and logic diagrams are all discussed. Finally, future research being planned for testing and further development of the VSL system is considered.