Performance Trends on Interstate Highway Sections of the Long-Term Pavement Performance Program

The Moving Ahead for Progress in the 21st Century Act required FHWA to identify pertinent performance measures and to establish minimum acceptable levels for infrastructure condition. Because of differences in data collection and analysis between state highway agencies (SHAs), a comparison of the performance data from states is not viable. The Long-Term Pavement Performance (LTPP) sections are spread across various states but have been monitored following the same standards. With the use of LTPP data, analyses were conducted to gain insight into actual deterioration rates and the impact of maintenance and rehabilitation activities on the performance of Interstate highway pavements. An evaluation of the decline in longitudinal and transverse profiles showed that about 90% of pavement sections had experienced nominal changes from year to year. The reason for these changes could be that SHAs had been actively applying preservation strategies. The average annual rate of roughness progression increases when the surface ages. The highest annual rate of increase in the international roughness index (IRI) occurs when the surface is between 8 and 12 years old for flexible pavements and between 16 and 20 years old for rigid pavements. The percentages of significant annual changes (more than 20%) were approximately the same between increasing and decreasing IRI rates. These figures could mean that SHAs had been addressing roughness with proper treatments at the same rate as roughness had been progressing. In agreement with previous research findings, the current work found that milling before overlay increased the average IRI reduction but did not improve the effectiveness of overlays in reducing rutting.