Date:  Tuesday, May 26, 2009

Contact: Travis Phelps, WSDOT Communications, 206-440-4472 (Seattle)
Tom Baker, WSDOT Materials Lab, 360-709-5401 (Olympia)

SEATTLE – After several years of testing two types of modern quieter pavement on southbound I-5 through Lynnwood and on SR 520 between Medina and Bellevue, data collected by WSDOT engineers shows the new pavements are not quieter after all.

“So far, our quieter pavement test sections are not performing well,” said Tom Baker, WSDOT State Materials Engineer. “Any audible noise reduction was lost within the first six months after paving. Today both quieter pavement test sections are just as loud to the human ear as sections paved at the same time with our standard asphalt.”

Additionally, severe winter storms in late 2008 significantly affected the durability and noise reduction capabilities of both quieter pavement test sections.

“The freeze thaw cycle, use of snow chains and studded tires, sanding and frequent plowing caused the pavement on both I-5 and SR 520 to start breaking apart,” said Baker. “Drivers may have noticed the rutting in the roadway. At this rate, both half-mile-long test sections will need to be replaced with new asphalt within three years.”

Third and final quieter pavement test section coming to I-405 in Bellevue in August

But, the experiment is not over yet. This August, WSDOT contractor crews will install the third and final quieter pavement test section on northbound I-405 through Bellevue.

Engineers believe several factors make the test on I-405 in Bellevue unique:

• Temperature: Quieter pavements have proven successful in states with warm climates such as Arizona, California, Texas, Georgia, Alabama and Florida. Engineers believe that the surface and air temperature during paving may affect the long-term durability and noise reduction abilities of the quieter pavement. To test this theory, WSDOT crews will install the quieter pavement test section in Bellevue during the day in August when temperatures in the Puget Sound are the warmest.
• Paving over concrete: The final quieter pavement test section will be installed over existing concrete. WSDOT engineers want to know if installing quieter pavement over a ridged concrete base will affect the pavement’s durability and noise reduction capability.

“These pavements have been successful in states like Arizona that have hot climates,” Baker added. “We want to make sure we have the answers on whether quieter pavement will work or not work on our northwest highways. Allowing our testing lab to continue the trial by putting down the final test section on I-405 later this summer will give us a more complete picture about the future of quieter pavement in our state.”

Noise is a common complaint near highways across the state. Residents and the Washington State Legislature have told WSDOT they want solutions to reduce traffic noise. WSDOT began testing quieter pavement in summer 2006 to find out if modern quieter pavements used in warmer states like Arizona stand up to the Northwest’s unique driving and climate conditions: heavy rain, snow, studded tire use, etc. Engineers also want to know how great the initial noise reduction might be, and how the pavement’s durability will affect its noise reduction capabilities. WSDOT engineers will study each test section for a period of at least five years or until the pavement reaches the end of its useful life.

More information on quieter pavements and frequently updated noise test results are available on the Web at: www.wsdot.wa.gov/Projects/QuieterPavement

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