Publication Number: FHWA-HRT-05-027
Date: June 2005

Pilot Program Evaluates Quiet Pavements in Arizona

Demonstrating the effectiveness of quiet pavement technologies and evaluating their noise mitigation properties over time is the goal of the Federal Highway Administration's (FHWA) Quiet Pavement Pilot Program (QPPP). The first State to implement a QPPP in partnership with FHWA is Arizona, which is testing the noise reduction capabilities of asphalt rubber friction courses (ARFC) on 185 km (115 mi) of selected freeways in the Phoenix area. Also partnering with Arizona on the $34 million QPPP project is the Maricopa Association of Governments, the regional transportation planning body.

The Arizona Department of Transportation (ADOT) has used rubberized asphalt since 1988 to resurface roads across the State, at various elevations and in different climates. Rubberized asphalt consists of a mixture of aggregate combined with asphalt cement and crumb rubber from discarded tires. "The performance of rubberized asphalt overlays is comparable to other methods of resurfacing existing roads," says Mike Dennis of ADOT. As a result of this resurfacing application, more than 15 million tires have been recycled in Arizona since 1988. In addition to its value in rehabilitating existing pavements and recycling a waste product, the rubberized asphalt has demonstrated the added benefit of reducing traffic noise at the tire/pavement interface. Data collected for the QPPP has shown an average noise reduction of 5 decibels in residential neighborhoods. By participating in the QPPP, ADOT aims to confirm that the noise reduction is sustainable over the average 10-12 year life of an ARFC pavement overlay.

ADOT is measuring pavement noise on the test roads using three methods. The first measures noise at the tire/pavement interface of one tire on a trailer. "This tire is representative of what you would find on the average automobile," notes Dennis. Noise readings are collected at every milepost before and after application of the rubberized asphalt overlay. Measurements after application of the overlay are taken twice a year. For the second method, noise is measured at about 95 nearby residential sites both before and after application of the rubberized asphalt overlay. The third type of measurement is taken from the side of the roadway at five test road locations with no surrounding development. These measurements are taken before application of the overlay and twice a year after application.

ADOT expects to finish overlaying the 185 km (115 mi) of existing freeways with rubberized asphalt in December 2005. While the ARFC costs more than conventional asphalt concrete friction courses, the added expense has been offset by such benefits as the noise reduction properties and increased pavement smoothness.

Public reaction to the rubberized asphalt pavements has been favorable. "We already consider the project a partial success because of the positive feedback from the press and public," says Dennis. ADOT will now be compiling the QPPP research data to confirm the noise reduction benefit in neighborhoods and the sustainability of the noise reduction over the life of the rubberized asphalt overlay.

States interested in partnering with FHWA on a QPPP can find more information online at www.fhwa.dot.gov/environment/noise/qpppeml.htm. "We would like to see quiet pavements studied in different climates, using different pavement types and materials," says Chris Corbisier, a highway traffic noise specialist at FHWA. Requirements for participating in the QPPP initiative include documenting the smoothness, durability, cost, and safety of the test pavement, as well as public reaction to the project.

To learn more about Arizona's QPPP, visit www.quietroads.com, or contact Mike Dennis at ADOT, 602-712-7114 (email: mdennis@azdot.gov). For more information on the QPPP initiative, contact Chris Corbisier at FHWA, 202-366-1473 (email: chris.corbisier@fhwa.dot.gov).

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