The project is aimed at investigating the increase in roughness of flexible pavements due only to environmental factors. In the Long-Term Pavement Performance (LTPP) program, starting with the use of the inertial profiler in 1996, profile data have been collected along the two wheelpaths as well as along the center of the lane. The data collected along the center of the lane are not available in the LTPP database. However, the data are available in AIMS (Ancillary Information Management System). When evaluating the changes in roughness that occurs along a wheelpath, effects of the environment cannot be separated from traffic effects. The profile data collected along the center of the lane can be used to evaluate the change in roughness that is only due to environmental effects. Environmental effects can cause changes in the moisture content of the subgrade from the as-constructed value, which can cause the subgrade to shrink or swell. Freezing temperatures can cause frost heave. All of these factors can cause a change in the profile of a pavement, thereby increasing the roughness. The analysis will be performed on the test sections contained in SPS-1 (Specific Pavement Study) projects. This project will provide information on how environmental conditions interact with subgrade conditions and influence increase in roughness for the different pavement structures that are present on a SPS-1 project. The different pavement structures in a SPS-1 project have different material being used for base layers, including a drainage layer (i.e., permeable asphalt-treated base) in some sections.
The project will investigate and report the findings of the increase in roughness of flexible pavements due to environmental factors.