Evaluation of Weigh-in-Motion Data for Developing Axle Load Distribution Factors for Mechanistic-Empirical Pavement Design Guide

Axle load spectra are essential to structural pavement design using the new Mechanistic-Empirical Pavement Design Guide (MEPDG) developed under National Cooperative Highway Research Program (NCHRP) Project 1-37A. The axle load spectra can only be determined from traffic data collected at weigh-in-motion (WIM) stations. Studies have shown that traffic data collected at WIM sites, especially for those using temperature-dependent piezoelectric sensors, often have errors. Thus, quality control checks should be performed on the WIM data which are used for developing the design inputs. This paper presents the results of an extensive quality control evaluation of traffic data collected at 25 WIM sites selected for the development of statewide axle load spectra in Arkansas. The data were evaluated using the quality control procedure recommended by the Long Term Pavement Performance (LTPP) program. In addition, the influence of the WIM data accuracy on predicted pavement performance was also evaluated using the MEPDG software. Among the 25 sites, only ten stations provided WIM data suitable for the development of statewide axle load spectra in the MEPDG. Pavement performance predictions provided by the MEPDG software were found to be sensitive to underestimated and overestimated WIM data. The effect of misestimated WIM data can be minimized if the data meet the quality requirements specified by the LTPP.