Long-term study of the effectiveness of rubberized asphalt in reducing tire-pavement noise

Under pressure from the public, the Arizona Department of Transportation undertook a large project to overlay most of the portland cement concrete pavement freeway system in the greater Phoenix area with a 25.4mm thick asphalt rubber friction course (AFRC) with the intent of reducing highway noise levels. As part of this project, wayside traffic noise and on-board sound intensity levels were measured before and after the overlay and then once or twice per year from 2004 to 2015. Initial noise reductions of up to 12 dB were reported at INTER-NOISE 2005 for both the tire-pavement source levels and the wayside measurements. After 121/2 years, reductions of up to 6 dB remained for the five wayside measurement sites and up to 5 dB for the 230 on-board sound intensity measurement locations. By 2019, the ARFC had physically deteriorated sufficiently that consideration for replacement is being made, however, spot sound intensity measurements indicated that reductions of up to 3 dB were still being achieved in some locations. In this paper, the results of these measurements are reported and the acoustical performance of the ARFC is compared to other quieter pavements regarding initial noise reduction and acoustic longevity.