road shoulders

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Note added at 48 mins (2009-09-29 10:58:11 GMT)
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http://www.wsdot.wa.gov/Research/Reports/400/429.1.htm
Description:

This project examined the role that road shoulders play in the stormwater runoff process. The goal of the research was to determine the type of shoulder treatment that yields the least quantity of runoff of the highest quality. Three types of shoulder materials were tested: conventional asphalt, gravel, and porous asphalt. Porous asphalt allows water to penetrate and flow through the pavement to a sublayer, and it can be used in place of conventional asphalt on low-traffic roadways. Each of the three shoulder materials were tested in duplicate on a heavily traveled, two-lane road north of Redmond, Washington.