This experimental project is being conducted as a part of WSDOT’s effort to produce pavements that reduce the noise generated at the tire/pavement interface. Experimental sections of open-graded friction courses were built using asphalt rubber and SBS (styrene butadiene styrene) modified binders. A section of conventional Class ½ inch hot mix asphalt (HMA) serves as the control section for the two experimental sections.
Sound intensity measurements were conducted using the On Board Sound Intensity (OBSI) method after construction. The most recent OBSI readings taken in December of 2009 indicated that the open-graded asphalt rubber and SBS modified sections were 3.5 to 2.0 decibels, respectively, quieter than the Class ½ inch HMA control section. This experimental evaluation will continue for the useful life of the pavement or a minimum of five years.