University of California Pavement Research Center

The work presented in this report is the culmination of a series of research projects, whose purpose is to support the Caltrans Quieter Pavement Research program. The goal of this program is to identify quieter, smoother, safer, and more durable pavement surfaces. The research has been carried out as Partnered Pavement Research Center Strategic Plan Element numbers 4.16, 4.19, 4.27, 4.29, and 4.39. This report presents six years of collected tire/pavement noise, ride quality, macrotexture, and other field data gathered on California pavements surfaced with four typical Caltrans asphalt mixes. The report also includes data from several pavement sections with experimental mixes and/or the results of side-by-side comparisons of different mixes. The experiment included pavements that ranged in age from newly paved (just after construction) to eight years old at the start of the study, resulting in data covering pavement surfaces with ages up to 15 years old. The six years of collected data were analyzed to evaluate how effective open-graded mixes are in reducing noise compared with other asphalt surface types, which included dense- and gap-graded mixes. The study also examined the ride quality performance of these mixes over time. Macrotexture, permeability, and other properties of the asphalt mixes were measured to help explain tire/pavement noise. Models for noise and ride quality that had been developed earlier, and improved with each year of additional data, appear in this report updated with data from the sixth year measurements. Conclusions about tire/pavement noise, smoothness, and durability are drawn by comparing the relative performance of dense-graded mixes against the performance of opengraded rubberized and non-rubberized mixes and rubberized gap-graded mixes. Lastly, the variables that affect tire/pavement noise are also examined. The results presented in this report are the final analysis and models from all six years of this program investigating noise and ride quality on Caltrans’ asphalt surfaces and indicate that the mix with the longest noise-reducing performance is rubberized open-graded asphalt. Tables are presented that show expected model-based life of noise and roughness reductions compared with dense-graded asphalt.