Increase in Roughness due to Environmental Factors in Flexible Pavements

This study concentrates on the increase in pavement roughness due to environmental factors. The objective of the study is to demonstrate a way to help predict pavement performance over time with respect to environmental factors. The International Roughness Index (IRI) is utilized to quantify the roughness of pavement. Changes in the IRI rating of different pavement sections were compared with respect to the climate, pavement structure, subsurface layers and drainage provisions. The data analysis is limited to flexible pavements in Texas. Data was collected for 7 different asphalt pavement sections in Texas from the Federal Highway Administration's (FHWA) Long-Term Pavement Performance (LTPP) program. The IRI values were obtained for the left and right wheel paths, as well as the center lane. They were then evaluated over time to determine the rate of change of the IRI. These rates were then related to the different subgrades, drainage provisions and climate present at each pavement section. The findings demonstrate a high effect of drainage on IRI, with better drainage provisions leading to a lower change in IRI over time. It can be inferred that a climate with less precipitation may also demonstrate less change in IRI due to that factor. The effect of different subgrade properties also had a large impact on the change in IRI, with the fine-grained soils leading to a higher roughness increase. Other factors were also related, though the differences that could be correlated resulted in negligible IRI changes. After comparing the various trends with respect to change in IRI, different math models were evaluated for their corresponding predictions. The efficacy of each prediction model was explored and potential improvements for the models were documented.