Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
TR N EW S 28 8 SE PT EM BE Râ O CT O BE R 20 13 40 The author is Senior Scientist, Illingworth & Rodkin, Inc., Petaluma, California. As its name implies, quieter pavement is a rel-ative term. Tire noise produced by pave-ments has a large range; the noise from some pavements is perceived as much louder than that from others. At highway speeds, the noise from tireâpavement interaction often determines the intensity of the traffic noise; therefore reducing this component can have a dramatic effect. Highway agencies and the public in general have been interested in quieter pavement for more than a decade. Quieter pavement controls noise at the sourceâthe most preferred approachâand can have lower initial costs than traditional noise barriers; more- over, quieter pavements can offer a solution when bar- riers may not be viable because of physical or performance limitations or a lack of cost-effective- ness. Nevertheless, the quietness of a pavement remains relative, and if the original or proposed pavement is not considered loud, the noise reduction may be limited. The noise performance of pavements tends to degrade over time, and the quieter pavements typically degrade more quickly. Because the âacoustic longevityâ is uncertain, federal policy does not consider quieter pavements as options for noise abatement. In response to these issues, several state agencies have been conducting research and demonstration projects on the initial effectiveness, the acoustic longevity, and other properties of quieter pavements, including safety, durability, and response to climate and weathering and to other special conditions, such as exposure to studded snow tires. Applying the research results, several agencies have adopted policies on when to consider quieter pavement and on what design specifications to follow. California and Arizona have the longest-running research programs on quieter pavements. California has documented the initial performance and acoustic longevity of both asphalt and concrete pavement sur- face textures for more than 10 years. Grinding concrete surfaces to reduce tireâpavement noise has become a common practice in the state. In Arizona, a pilot pro- gram with the Federal Highway Administration has monitored the performance of a rubber asphalt pave- ment overlay applied extensively for noise reduction in the greater Phoenix area since 2003. This quieter pave- ment offers the additional benefit of recycling tire rub- ber as an ingredient. Although quieter pavements are gaining application in some states, more knowledge is needed. Pavements age, and their noise performance deteriorates, but the mechanisms of the effects on tire noise are not under- stood, nor are the means to improve a pavementâs acoustic longevity. Recent projects under the National Cooperative Highway Research Program have devel- oped a method for evaluating the life-cycle cost of qui- eter pavement and noise barriers1 and for maintaining performance; the adoption and integration of these methods into practice is yet to come. Similarly, noise performance is only starting to be considered in pave- ment performance specifications and in pavement per- formance monitoring systems. 1www.trb.org/main/blurbs/169200.aspx. Quieter Pavements for Roads P A U L D O N A V A N Environmental Sustainability in Transportation P H O TO : T R EV O R W R A Y TO N, V IR G IN IA D O T P H O TO : B R U C E R Y M ER, C A LTR A N S A quiet pavement project on Route 199 near Williamsburg, Virginia. Pavement noise measuring equipment in use by Caltrans, which also participates in the Transportation Pooled Fund TireâPavement Noise Research Consortium.