Kentucky's current procedure for estimating equivalent single axle loads (ESALs) was updated in 1990 to incorporate traffic data categorized by functional class rather than by statewide averages. This change resulted from the influx of data generated by automatic equipment used to classify and weigh vehicles in motion. A much wider range of geographic conditions and road conditions was sampled, and the expectation was that the data used in the estimation procedure would be more accurate as a result.

The 1990 revisions were quite extensive, and, although model calibrations using 1989 and 1990 data have proven useful, the Division of Planning has sought refinements which would improve the calibrations and make them more useful for specific needs. In addition, the continuing analysis of weight and classification data for coal trucks has identified potential improvements that could produce more representative data for these types of vehicles.

In response to these needs, a research study was proposed for FY 1992 with funds totaling $25,000 (Appendix A). Funding limitations delayed the study until FY 1993 and reduced the amount to $15,000. Although there was some decrease in scope, the study has been successful in 1) enhancing the accuracy of the calibration process; 2) improving the appearance, clarity, and utility of the output; and 3) potentially reducing year-to-year variations in the estimation of key quantities. In addition, a possible revision has been outlined which would eventually offer other benefits including a more definitive and accurate method for reflecting effects of coal movement.

The purpose of this report is to explain and document the progress that has been made toward improving the ESAL-estimation process and exploiting the wealth of data being generated by the new vehicle classification and weighing program.

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The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented hereiu. The contents do not necessarily reflect the official views or policies of the University of Kentucky or the Kentucky Transportation Cabinet. This report does not constitute a standard, specification, or regulation. The inclusion of manufacturer names and trade names is for identification purposes and is not to be considered an endorsement.