American Society of Civil Engineers

Gray System Model for Estimating the Pavement International Roughness Index

by Yi Jiang, P.E., (Assistant Professor, Dept. of Building Construction Management, School of Technology, Purdue Univ., West Lafayette, IN 47907.) and Shuo Li, P.E., (Research Engineer, Research Division, Indiana Dept. of Transportation, West Lafayette, IN 47906.)

Journal of Performance of Constructed Facilities, Vol. 19, No. 1, February 2005, pp. 62-68, (doi:

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Document type: Journal Paper
Abstract: The international roughness index (IRI) is a measurement of pavement roughness that is widely accepted for evaluating pavement serviceability, especially its riding quality. Generally, as the age of pavement increases, its condition deteriorates and its IRI value increases. However, the IRI data collected from the Indiana highway system indicate that the IRI values vary considerably for similar pavements and traffic conditions at any given pavement age. This makes it difficult to establish the relationship between IRI and pavement age. In this study, the gray system theory was used to estimate the maximum, mean, and minimum IRI values at different pavement ages. It is believed that the three IRI values are essential for evaluating pavement serviceability. This paper presents the process of the gray system modeling for IRI estimation and discusses the effects of traffic volume on pavement roughness and the estimation accuracy of the gray system models.

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