General approach to payment adjustments for flexible pavements

The quest for developing a payment adjustment plan for contractors considering several distress indicators simultaneously is hindered by three issues: (1) different measurement units for the distress indicators; (2) possible correlation among those indicators; and (3) variation in each of the indicators. In this study, three procedures are compiled together to cope with the preceding issues. First, normalization of each distress indicator is employed to create a dimensionless indicator. Second, principal components analysis, a multivariate statistical technique, is applied to eliminate the possible correlation among the distress indicators. Finally, through a proposed reliability analysis procedure, the pay factor is determined by the ratio of the reliability of the uncorrelated principal components of the as-built pavement over that of the as-designed pavement. Reliability refers to the level of confidence that exists in the distress indicators, not to exceed a certain limit. The results showed that pay factors based on multiple distress indicators are usually lower than those based on one single indicator when the variation in influencing factors such as asphalt concrete thickness is large.