LTTP Data Analysis: Factors Affecting Pavement Smoothness

TRB’s National Cooperative Highway Research Program (NCHRP) Research Results Digest 264: LTTP Data Analysis: Factors Affecting Pavement Smoothness highlights the factors affecting pavement smoothness, identified in National Cooperative Highway Research Program (NCHRP) Project 20-50(08/13), on the basis of the data available from the Long-Term Pavement Performance (LTPP) studies. The research, completed in August 2001, provided preliminary conclusions regarding the factors affecting pavement smoothness of different types of new and rehabilitated pavement structures. Data related to pavement structure and features, rehabilitation techniques, climatic conditions, traffic levels, layer materials and properties, pavement distress variables, and other factors that may contribute to changes in pavement were extracted from the LTPP data tables and compiled in a project-specific database to facilitate the analysis. The International Roughness Index (IRI) was adopted as the measure of pavement smoothness. This digest provides a summary of the work performed in this research.