A recent Federal Highway Administration survey indicated that 48 states and Puerto Rico use smoothness specifications for hot-mix asphalt (HMA) pavement construction. As this is a relatively new concept, many states have adapted the Portland cement concrete pavement specifications of Profile Index using the standard 5-mm blanking band (PI5.0) for use on HMA pavements. However, PI5.0 may not provide a reproducible or portable smoothness measure for HMA pavements because of the technical limitations of the equipment and procedures.
The International Roughness Index (IRI) or the Profile Index using a 0.0-mm blanking and (PI0.0) seem to provide a more repeatable and portable smoothness standard. However, one barrier to more widespread implementation of these new smoothness standards is the lack of objective, verifiable correlation methods for use in establishing specification limits using the IRI or PI0.0. Assistance in selecting appropriate IRI and PI0.0 specification limits is needed to provide a basis for modifying current specifications to these more reproducible and portable smoothness indices.
This research effort has developed a relationship between IRI and PI that can assist in transitioning to a reproducible and portable initial IRI or PI0.0 smoothness specification for HMA pavement.