The Volpe Center Acoustics Facility, in support of the California Department of Transportation, participated in a long-term study to assess several types of pavement for the purpose of noise abatement. On a 6.4-km (4-mi) stretch of a 2-lane highway in Southern California, several asphalt pavement overlays were examined. Acoustical, meteorological, and traffic data were collected in each pavement overlay section, where microphones were deployed at multiple distances and heights. Single vehicle pass-by events were recorded primarily for 3 vehicle types: automobiles, medium trucks, and heavy trucks. Data were analyzed to determine the noise benefit of each pavement as compared to the reference dense-graded asphalt pavement; this includes a modified Statistical Pass-By Index as well as average LAFmx values for each vehicle type. In addition, 1/3-octave band data were examined. Results from the study indicate that applying a quieter pavement overlay can reduce wayside-measured sound levels.