Three approaches to study the reduction of pavement noise performances over time
Résumé
Low noise pavements are part of the techniques available for road traffic noise reduction. However, the unpredictable reduction of their acoustic performances over time is an obstacle to a wider development. Studying the ageing effect of pavement on noise reduction is difficult because of many parameters involved in the ageing process, linked to the mix design, to the traffic and the weather conditions. Furthermore, variations of noise levels over time can be small compared to the measurement accuracy. The paper presents a set of studies performed in France to better understand the reduction in noise performances of road surfaces, according to three different approaches. One is purely statistical and consists in analysing from the large national database of pavement noise performances, the average trend of noise level increase with age, for different types of pavements. The second one consists in measuring at a specific time, the noise performances on different sections of different ages of a same type of pavement. Both approaches lead to an observation and quantification of noise level increase, however, they generally do not help in understanding the phenomena involved, because detailed information is often missing in large databases or for existing pavements. In the third approach, a specific monitoring program is implemented regularly on a set of identified sections, starting when the section is newly laid and finishing some years later when the section is removed. Noise levels and texture profiles are measured every year. The paper presents some results of all the three approaches, concentrating on the most common type of low noise surface in France (i.e. semi porous thin layer called VTAC0/6). A synthesis of the results is finally made and respective advantages of the methodologies are discussed.