Update of Data for Estimating ESALs (Equivalent Single Axle Load)


A revised procedure for estimating equivalent single axleloads (ESALs) was developed in 1985. This procedure used weight, classification, and traffic volume data collected by the Kentucky Transportation Cabinet’s (KYTC) Division of Planning.  The procedure was described and documented in ResearchReport UKTRP-85-30, “Estimation of Equivalent Axleloads.” There have been several changes made to the revised procedure since its adoption, including its documentation, which is described in Report KTC-95-7, “Equivalent Single Axleload Computer Program Enhancements.”

The results presented in Report KTC-95-7 addressed improvements in processing ESAL data. These improvements were made by aggregating functional classes to increase the accuracy of within-class estimates and converting computer programs used for processing data into versions usable on personal computers.

In addition, Report KTC-99-1,“Development of ESAL Forecasting Procedures for Superpave Pavement Design,” discussed analytical methods used to prepare ESAL estimates for Superpave projects. The methodologies integrated an interactive programthat let users access various databases in order to calculate ESAL Superpave estimates. Work undertaken in 2002 led to updates of this interactive program. Recent efforts have concentrated on the evaluation and calibration of WIM data collection equipment. Report KTC-04-12,” Assessment of Data Collection for ESAL Determinations for the Kentucky Transportation Cabinet, Division of Planning,” was completed in 2004 and included recommendations to more intensively monitor WIM equipment.

For the past 30 years the Kentucky Transportation Center (KTC) has provided KYTC with annual updates of data used to estimate ESALs. The last update came in 2008 with the publication of Report KTC 08-32/PL13-08-1F, titled “Annual Update of Data for Estimating ESALs.” This update entailed processing traffic characteristics data using a series of quality control and analytical programs to produce an estimateof the following parameters of interest.

  • Average daily traffic
  • Percent trucks
  • Percent trucksclassifiedasheavy/coal
  • Axles per truck
  • Axles per heavy/coal truck
  • ESALs per truck axle
  • ESALs per heavy/coal truck axle
  • Total ESALs

Computer programs were used to process classification data and process weight data. The combined output used to calculate ESALS are contained in the following report.

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