The project summarized the most recent information on the subject of pavement smoothness and identified the primary issues pertaining to pavement smoothness that require concerted efforts for advancement.

Pavement smoothness has been recognized as one of the measures of pavement performance. Several Long Term Pavement Performance (LTPP) studies addressed certain aspects of pavement smoothness, including roughness development, measurement methods, and modeling. Other projects determined, based on data available from LTPP studies, the factors that cause changes in pavement smoothness and quantified the contributions of these factors to pavement smoothness. Recognizing these advancements in the state of practice and knowledge of pavement smoothness, there was a need to provide state highway agencies, researchers, industry, and others concerned with pavement performance with the most recent information on this subject, particularly with the findings derived from the LTPP studies.

The project included convening a national workshop on pavement smoothness to review the findings of related research and identify the primary issues pertaining to pavement smoothness that require concerted efforts for advancement; a report that summarizes the findings of the workshop was also prepared. The report includes an appendix, titled "Pavement Smoothness Measurement and Analysis: State of the Knowledge," that covers several related topics. Among these topics are user perception of ride quality, benefits of smooth pavements, equipment for smoothness measurement, profile indices, operational characteristics of profilographs, factors affecting measurements, specifications, application of smoothness data, and findings from related studies. The final report is available as NCHRP Web Document 42.