Investigation of Increase in Roughness Due to Environmental Factors in Flexible Pavements Using Profile Data from Long-Term Pavement Performance Specific Pavement Studies 1 Experiment

From the start of the Long-Term Pavement Performance (LTPP) Program, the longitudinal profiles along the two wheelpaths at test sections have been collected using an inertial profiler. In December 1996, starting with the K.J. Law T-6600 inertial profiler, all profilers used in the LTPP Program have collected profile data along the center of the lane in addition to collecting data along the two wheelpaths. The change in the profile along the center of the lane in flexible pavements was expected to be affected mainly by environmental effects. The goal of this project was to evaluate the changes in the International Roughness Index (IRI) along the center of the lane at Specific Pavement Studies 1 test sections over time and identify environmental and subgrade parameters that contribute to an increase in IRI along the center of the lane. The following activities were performed for this project: (1) analyze the center of the lane IRI (CLIRI) and mean IRI (MIRI) (i.e., average IRI of the left and the right wheelpaths) at test sections to evaluate changes over time, (2) compare the change in IRI for the center of the lane with the change in MIRI at the test sections, (3) identify subgrade and environmental parameters that contribute to an increase in IRI along the center of the lane, (4) perform a detailed evaluation to identify how the CLIRI changes for a select group of test sections, and (5) develop models to predict the change in CLIRI at the test sections.\n