Traffic Supplement to Low Volume Road Best Practices Manual

Principal Investigator:

Gene Skok, Former University Researcher, Civil, Environmental and Geo-Engineering

Project Summary:

One of the most important factors needed for the design or rehabilitation of a roadway is the traffic loading over a given design period. The traffic loading is composed of a distribution of loads on single, Tandem and other axle load configurations. To estimate the load distribution it is necessary to know the total traffic (AADT), vehicle type distribution and truck factors which are an estimate of the number of ESAL's caused by one pass of that given vehicle type. Truck factors or other measures of load distribution are determined from Weigh-in Motion (WIM) data from around Minnesota. It is necessary to estimate vehicle type distributions to sum up the total load effect predicted for a given location. Automated vehicle classifiers are now available along with software to make estimates of vehicle type distributions. These classifiers have been used on 28 county roads from three counties in 1998 and 1999. It is possible that these vehicle type distribution-measuring devices could be used by counties and cities to determine distributions for roadways planned for construction or rehabilitation. The purpose of this project which will supplement the Low Volume Road Best Practices manual project is to review the 1998 and 1999 data from the road sections in Douglas, Olmsted and Kandiyohi counties to see if the measured distributions are significantly different than the statewide assumed values used for calculating ESAL's and evaluate this method using the classifiers to estimate ESAL's. If the determination of ESAL's can be shown to be more accurate using the automated classifiers the procedure currently used by MnDOT will be set up for the cities and counties and demonstrated for use in 2-3 agencies.

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