Best Practices for Road Weather Management Version 2.0
Fuzzy Variable Speed Limit Device Modification and Testing: Phase II
In a previous project, Northern Arizona University (NAU) and the Arizona DOT designed and implemented the prototype of a variable speed limit (VSL) system for rural highways. The VSL system implements a real-time fuzzy control algorithm that utilizes information provided by Road Weather Information Stations (RWIS). This system continuously displays highway speeds appropriate to the atmospheric and road surface conditions at locations of interest along the I-40 corridor in rural northern Arizona. At the time of this initial project, none of the RWIS sites along I-40 were providing the complete data set needed for full utilization of the fuzzy control algorithm. A main objective of the current project described in this document was to fully upgrade an RWIS site on I-40 so that it could be used as a test site to monitor the complete data set of atmospheric and road surface conditions needed by the fuzzy control algorithm. A second objective was to enhance this upgraded site so that it would supply traffic flow data. The remaining objectives of the project were to collect atmospheric, road surface, and traffic data over a wide variety of weather conditions and to use this data to assess the reliability and appropriateness of the speed limits produced by the VSL system. The first two objectives of implementing a full RWIS site upgrade and enhancement were achieved and are discussed in detail in this report. However, reconfiguring software and hardware for the project, installing power and telephone lines, and installing and calibrating sensor and traffic detection systems consumed most of the time allotted to the project. Collection of project data did not begin until July of 2001, just as this report was being written. Nonetheless, an interactive web site has been developed which employs software tools that will be used to analyze and compare the RWIS data and the traffic flow data when it is collected. The web site and its software tools are discussed in this report.
Northern Arizona University, Prepared for the Arizona DOT
Road Weather Information System (RWIS)
Environmental Sensor Station (ESS)
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