Evaluating tire-pavement noise reduction of porous asphalt using close proximity tests: Comparative performance and long-term effectiveness

The objective of this study was to understand the long-term noise reduction effect of Porous Asphalt (PA) in an expressway environment. To this end, PA was compared with that of Stone Mastic Asphalt (SMA), tined concrete, and Next-Generation Concrete Surface (NGCS) at the time of construction. Then, the evolution of PA’s acoustic performance was characterized on 82 pavement sections over the period of 1 to 18 years. The Close Proximity (CPX) method was used to measure tire-pavement noise at three cruising speeds: 80, 100, and 120 km/h. Mean Profile Depth (MPD) and permeability time were considered as key functional measures of PA in the field. ANOVA tests revealed the relative impact of surface type, speed, and frequency on CPX noise. Upon construction, PA was able to reduce noise levels by up to 8.5 dB(A) relative to SMA and concrete surfaces. Over time, PA’s acoustic performance evolved at three stages: an initial growth phase (1-8 years), a stabilization phase (8–12 years), and a rapid deterioration phase (>12 years). Regression analyses and a Pearson correlation matrix confirmed a strong correlation between permeability time and CPX noise and revealed the potential of MPD as a good predictor for CPX noise in some later phases. Finally, noise prediction models for PA were developed based on permeability time and MPD, providing road agencies with a practical tool to assess the acoustic performance of PA.