Estimation Of Winter Snow Operation Performance Measures With Traffic Flow Data Phase 2

Author : Helmut T. Zwahlen
Publisher :
ISBN 13 :
Total Pages : 190 pages
Book Rating : 4.3/5 (555 download)

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Download or read book Evaluation of ODOT Roadway/weather Sensor Systems for Snow & Ice Removal Operations written by Helmut T. Zwahlen and published by . This book was released on 2006 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: The major objective of the study was to develop a procedure to determine the level of service using the RWIS speed measurements. The procedure developed can be used by ODOT to evaluate winter maintenance activities and for winter maintenance decision making. Average traffic speeds for five minute intervals were measured using NuMetrics road sensors and they were related to the pavement and driving conditions. In addition speed data from two other studies was used. The pavement conditions were determined by conducting surveys at rest area buildings using a questionnaire form. It was found that the average traffic speeds were significantly lower during a major snow event even when periodic plowing and salting was done. The average speeds decreased almost linearly for the period of the snow storm reached the minimum and then climbed back slowly towards higher speeds. The speeds appear to be a fairly sensitive measure to judge the condition of the pavement. The motorist judgments about the pavement condition and their perception of the safety of driving decreases during a rather severe winter storm which is mirrored in the speed decrease. It appears from the survey that about two thirds of the motorists judge the deterioration of the road conditions and the inadequate level of road maintenance during a winter storm as bad or moderately bad. The responses obtained for the car and the truck drivers are fairly close to each other indicating that both groups can judge bad road condition equally well. The observed road conditions appear to influence the drivers in terms of how they subjectively feel about the level of safety and stress experienced during driving in the winter storm. A simple procedure was developed for winter maintenance management to determine the condition of the road (freeways) based on the average speeds observed by the RWIS sensors. If the average winter speed of the traffic is equal or greater than the historical established wet/salted pavement speed, the level of service is considered adequate. According to the Swiss study, the wet/salted surface winter speeds are about 85% of the dry surface speeds for freeways and 96 % for city streets. If the average winter speed is below the wet/salted surface speed, the level of service is considered inadequate. Any speed less than 50% of the wet/salted surface speed indicates fairly bad road conditions and an extremely inadequate level of service. It should be noted that the winter pavement conditions can be highly dynamic. Depending on the rate of accumulation of snow, frequency of the snow plowing, length of the snow plow route, the pavement condition can improve and deteriorate a number of times during a winter storm. The level of service can get worse even with maximum snow plowing and salting effort in a situation with a high rate of snow accumulation. The winter speeds observed as a percentage of the average dry surface speed can be correlated with the level of service. A relatively more fine graduation of the level of service as a function of the percentage of the average dry surface speed is proposed in the recommendations of the report.