Abstract
In April 2003, the Arizona Department of Transportation (ADOT) initiated a Quiet Pavement Pilot Program in cooperation with the Federal Highway Administration (FHWA). Under this program, many freeway segments in the Phoenix metropolitan area with Portland Cement Concrete pavement surfaces received 25.4-mm thick asphalt rubber friction course overlays to reduce highway-related traffic noise. This pilot program represented the first time that pavement type was allowed as a noise mitigation strategy on federally funded projects. As part of this program, ADOT developed a 10-year research program with FHWA to evaluate the long-term acoustic performance of this noise mitigation approach. The final measurements were completed in 2015. The program was done with three types of measurements: Type 1 examined tire/pavement noise at the source at 115 milepost locations; Type 2 examined noise in residential neighborhoods near the freeways; and Type 3 evaluated noise using direct measures of traffic noise adjacent to the freeways. Sound absorption measurements were also made at specific sites at various times throughout the project. Type 1 measurements documented an average initial reduction of 8.7 dBA and an average increase of 0.5 dB/year. The Type 2 measurements revealed an average initial reduction of 5.2 dBA, whereas the Type 3 measurements showed an average initial reduction of 9.1 dBA and an average increase of 0.5 dB/year. The measured reductions were also compared with ADOT and FHWA noise abatement criteria.
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