PAVEMENT SMOOTHNESS INDICES RESEARCH BRIEF

The primary source of information for this report was National Cooperative Highway Research Program (NCHRP) Project 1-31, "Smoothness Specifications for Pavements," published in March 1997. The indices from NCHRP 1-31 are listed and described, followed by a discussion of selection criteria. The following road smoothness measuring devices are described: profilograph; response-type devices; inertial devices; and inclinometer devices. In accordance with NCHRP Project 1-31 recommendations, because of the lack of proven replacement, the profile index (PI), notwithstanding its limitations, is the recommended index for portland cement concrete and asphalt concrete pavements initial smoothness measurements. However, it is recommended that the blanking band be eliminated and PI statistics be computed from surface profiles measured using inertial-based systems. The inertial-based equipment will provide a faster, more versatile, and accurate system to measure profiles.