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The use of road surfaces with low noise emission characteristics is one of the actions mostly applied all over the world to decrease the number of road traffic noise annoyed people. Since many Italian roads are going to be paved with such surfaces, the LEOPOLDO project (funded by the Tuscany Region and the Italian Ministry of Transportation) was planned to check the efficacy in time of this action. Among all solutions, rubberized road surface is one of the most applied in USA, Canada, Europe and Asia. This paper describes results obtained by monitoring four rubberized surfaces one year after the laying and by evaluating the time stability of LEOPOLDO one by means of the Close Proximity method (CPX). All surfaces here analyzed are laid in real scenarios, so the actual efficacy of this action is evaluated. The results on the LEOPOLDO surface show spatial homogeneity, a good time stability and a significant noise emission reduction. Instead, analysis of the four rubberized surfaces shows variability in the results, probably due to the pavement installation quality, as supported by the data. Thus, the rubberized road surface looks to be a very efficient mitigation technology, providing the installation have been carried out with care and proficiency. [ABSTRACT FROM AUTHOR]

Abstract: The Close Proximity Index (CPX) measurement method is proposed in the ISO/DIS 11819-2:2011 and it aims to evaluate different road pavements with respect to their influence on traffic noise, under conditions when tyre/road noise dominates. In this paper, a modified CPX-based methodology is presented, in order to improve the usefulness of tyre/road noise measurement in the evaluation of acoustical performances of a road surface, in terms of both temporal and spatial stability and in terms of effectiveness of a mitigation action. In particular, the proposed methodology uses a finer spatial resolution and improves the speed-levels relationship knowledge. Moreover, data variability and uncertainty related to tyre/road noise measurement results are here investigated. This paper is conceived within LEOPOLDO project, developed in Tuscany with the aim to study the acoustical characteristics of six new experimental road surfaces, and the proposed methodology has been applied to some of them. The evaluation of the local possible acoustical inhomogeneities of test pavements and a three years long monitoring of the time evolution of their acoustical performances were required by the project. Finally, a new criterion is proposed to make more reliable comparisons (differential criterion) between different road surface types and to better evaluate the temporal evolution. [Copyright &y& Elsevier]