Assessment of data collection for ESAL determinations for the Kentucky Transportation Cabinet, Division of Planning.

The Kentucky Transportation Cabinet’s Division of Planning collects weight data, traffic volume data, and vehicle classification data. These data are used as inputs to determine equivalent single axle loads (ESALs). ESALs are used in the pavement design process to determine pavement thickness. There have been inconsistencies observed during the computation of the ESALs during the past three or four years. These inconsistencies have resulted in a significant inflation in the estimate of ESALs per year, which if used in the design process would result in significantly thicker pavements. For example, the ESALs per truck axle for rural principal arterials and rural minor arterials, between 1998 and 1999, more than doubled from, 0.275 to 0.555. Although there was only a small increase in this number after 1999, the value remained significantly higher than expected. The objective of this research study was to evaluate the weight data collection equipment, on-site calibration procedures, and sampling techniques used by the Division of Planning for the different Aggregate Classes of highways in an effort to standardize procedures used by the Division of Planning to collect weight data.