The Virginia Department of Transportation (VDOT) with guidance from a Quiet
Pavement Task Force initiated a highway pavement study to evaluate lower-noise
pavement technologies, which are now called Quiet Pavement (QP) technologies. The
overall objective of this initiative is to develop specifications for QP technologies and
other sound mitigation alternatives that can be used in future highway pavement
construction projects where sound mitigation is a consideration. The study initiated in
2011 includes QP technologies for reducing noise from both existing asphalt pavements
and existing Portland cement concrete pavements.
The existing highway pavements used in the asphalt pavement portion of this study had
to meet the following criteria: (1) four lanes having posted speed limits at least 55 mph;
(2) good pavement structure and cross-section; (3) good overall corridor geometrics;
(4) limited at-grade intersections; (5) a 1-mile length for each QP technology being
evaluated; (6) no curb and gutter, and (7) minimal existing sound mitigation measures.
These criteria were used to make sure that tire-pavement noise would be a significant,
measurable source of overall traffic noise. Having good pavement structures, crosssections, and geometrics were important for attaining (1) uniformity among the QP technologies being compared; (2) good pavement performance and (3) safety during
the study.
The QP technologies applied to the asphalt pavements consisted of three porous
friction courses (PFC) having the potential of reducing tire/pavement noise. The three
quiet mixtures used in these overlays consist of the following: (1) a PFC stone gradation
combined with a rubberized asphalt binder, (2) a comparable PFC stone gradation
combined with a polymer-modified asphalt binder, and (3) a third PFC stone gradation
having a larger stone size and combined with a polymer-modified asphalt binder. The
fourth mixture included in this study is a stone matrix asphalt (SMA) mixture which
serves as the control mixture. The third quiet mixture is being used to evaluate the
effect of maximum stone size on noise and other pavement properties. It has a
maximum stone size of 12.5 mm compared to 9.5 mm for the other three mixtures.
To obtain a measure of variability, the four mixtures were placed at three highway
pavement test sites in Virginia in 2011: (1) State Route 7 Bypass at Leesburg in
Northern Virginia, (2) State Route 199 west of Williamsburg and (3) State Route 288
near Chester, which is south of Richmond. For these three test sites, approximately
7,550 tons of rubberized asphalt mixture was produced.
The following properties are being measured: (1) tire/pavement noise, (2) community
wayside noise, (3) ride quality, (4) pavement surface texture and resistance to skidding,
and (5) performance during winter. While the key property is the amount of noise
produced the pavements, the other properties are being measured to make sure that
ride quality and safety are not sacrificed when using QP technologies.
An interim report on this project was published in June 2012, which was after one winter
and spring of service. The three QP technologies were measurably less noisy than the
control SMA on average, and noticeably more quiet in several specific cases, which is
defined as a reduction in noise of 3 decibels or greater. In regards to the quiet mixture
with the rubberized asphalt binder, it has been noticeably more quiet than the control
SMA at two locations while performing the same as the control SMA at the third
location. Ride quality and safety have not been sacrificed by the QP technologies, and
in some cases, have been improved. The interim report is titled, “Virginia Quiet
Pavement Implementation Program,” Interim Report, HB2001 (2011), VDOT, Richmond,
VA, June 2012.
A final report on this two-year study will be published by the end of June 2013. In
addition to the rubberized asphalt used in the current study, VDOT and the asphalt
industry are planning to install a 2-inch thick rubberized asphalt mixture in the Northern
Virginia district and a rubberized asphalt SMA’s in both the Culpeper and Northern
Virginia districts.