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04/26/2008
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(Date Posted:04/29/2008 09:27 AM)
This article for FYI. The Superpave™ pavement was researched at UT and installed in San Antonio. Since it appears that it basically seems to cut the noise of vehicles on pavement by 50%, Superpave might be a better alternative to soundwalls. The UT link is at http://www.utexas.edu/research/superpave/index.html. I don't know if this is the kind of road surface FM 2181 will be made of, but it seems like it would certainly make this area suffer less from traffic noise.
I'd appreciate any input from civil engineers, traffic specialists so that we can know how valid this article is.
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http://www.acppubs.com/article/CA449409.html
PFC: Safe, Strong And Durable
Permeable friction course makes a positive impression as a wear surface in San Antonio.
By Jim Hedderichs -- Texas Contractor, 1/19/2004
After many years and over $50 million spent in research, the Strategic Highway Research Program has developed the Superpave system to provide asphalt roads that will be more durable, safer and longer lasting. Thus far the new mixes that have evolved from this research have proven themselves to meet these requirements while also being a cost-effective pavement choice.
Along with addressing pavement designs and mix selections, another concern is to construct pavement with as smooth a ride as possible. The public is appreciative of a smoother ride but builders know that if it is built smoother, it will last longer as well. The accelerated loading of traffic over a rough road is minimized, resulting in less damage.
Beyond providing a stronger, smoother pavement, the asphalt mix designs also have provided a side benefit that only enhances it as the No. 1 surface pavement in Texas. It is simply that the open-graded mixes such as stone matrix asphalt (SMA) and permeable friction courses (PFC) have also helped alleviate traffic noise.
As part of The National Environmental Policy Act of 1969, documents are developed for all federal-aid highway projects, to address impacts to the human and natural environment. Typical traffic noise analysis will include such elements as:
1. Determine existing noise level
2. Predict future noise
3. Compare predicted noise levels with the noise abatement criteria and existing noise levels
4. Analysis of noise abatement measures (i.e. noise barriers, vegetation, traffic management, or buffer zone)
There is no mention of pavement selection in this analysis as there are many things that influence noise such as exhausts, engines, number of trucks, etc. In addition, pavement condition and/or pavement type will change throughout the life of the highway. The Federal Highway Administration is not yet at a point where they can reduce project costs by eliminating a noise wall in lieu of choosing a quieter pavement, but it should be a consideration. Sound barriers can cost as high as $1.2 million per mile. In urban areas this cost can more than double.
The use of open-graded friction courses, such as the TxDOT permeable friction course is mandated throughout England as the specified wear surface because not only does it reduce water spray and increase the skid resistance of the surface, it also provides a quieter environment.
Arizona recently announced a three-year program to deal with noise pollution and is overlaying 115 miles of highway using this new mix, providing "a way to enhance the quality of life in neighborhoods," while restoring the service of the pavement surface.
On a project recently completed in the TxDOT San Antonio district, Dean Word Company overlaid a section of I-35 with a permeable friction course to improve the safety of the deteriorated concrete road and improve the ride quality. The single overlay with an average thickness of 1.5 inches improved the skid resistance by 200 percent and improved the smoothness by more than 60 percent. The additional benefit was that noise was also reduced by over 12dBA.
How much more quiet is it? One customer along the route commented that, "she no longer had to go out and turn off her car alarm during the work day." While 12dBA may not sound like much, we must keep in mind that decibels are logarithmic units. This amount of reduction will be perceived by an observer as a reduction of noise by one half.
Where PFC has been applied in other districts, TxDOT employees report receiving phones calls asking where the district had put the traffic, because it had become so quiet.
The mix designs, originating from the need to construct smoother, safer, longer-lasting roads with improved visibility through reduction of splash and spray, and these mixes have provided the desired benefits. The additional benefit of noise reduction may mean that some day the road surface, along with other noise abatement measures, will be a method to eliminate those costly eyesores we call noise barriers.
(Message edited by Dryad On
04/29/2008 17:09 PM)
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