Raoul Salas

Transportation agencies need performance indicators to report the pavement condition. Many local transportation agencies use the Pavement Condition Index (PCI) to report the pavement condition. In 1986, the World Bank developed the International Roughness Index (IRI) to measure the irregularity of the road surface. IRI is an indicator of roughness for straight horizontal road segments simulating a quarter-car travelling at 50 mi/h. In the United States, the Federal Highway Administration (FHWA) has established criteria to report a pavement in good, fair, or poor condition. IRI, percentage of cracking, and rutting thresholds are established by the FHWA to assess the pavement condition. Local roads represent, in terms of mileage, the largest percentage of all roads in the U.S. IRI is not typically measured on local roads due to speed restrictions, short section lengths, traffic signals, traffic congestion, intersection treatments, and geometry characteristics. PCI and IRI represent different concepts and measure different aspects of pavement performance. Despite these differences, there is a need to report the pavement condition of local roads in a consistent manner. PCI and IRI datasets from a total of 25,229 asphalt surfaced pavement sections were analyzed using statistical descriptive analysis and expert knowledge to develop transfer equations. The product of this hybrid modeling approach is a best-fit sigmoidal equation presented in this paper to estimate the IRI value from the PCI value, and recommended threshold equivalent values to report the pavement condition

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