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Albedo: A Measure of Pavement Surface Reflectance

Paved surfaces (such as highways, roads, runways, parking areas, sidewalks, and driveways) typically constitute about 30 to 40% of developed urban areas. In the past few decades, the bane of urban cities has been the increased heating of the city by sunlight due to dark, heat-absorbing materials used in the construction of pavements and buildings. Urban areas are oftentimes up to 8°F warmer than the surrounding rural area, creating “urban heat islands.” If the urban surfaces were lighter in color, more of the incoming light would be reflected back into space, cooling the surfaces and ambient air. Cooler surfaces and air reduce the need for air conditioning, saving energy and reducing power plant emissions. Cooler air can also reduce air pollution by slowing the chemical reactions that produce smog. Solar radiation includes visible light (typically 43% of solar energy), near-infrared light (52%), and ultraviolet light (5%). Albedo, or solar reflectance, is the ratio of reflected solar radiation to the total amount that falls on that surface, known as incident solar radiation. Albedo values range from 0, for perfect absorbers, to 1, for perfect reflectors. In pavement structures, the topmost surface is the only layer which affects albedo. Therefore, pavement type selection should also include a consideration of albedo where heat generation is a concern.

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  • English

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Filing Info

  • Accession Number: 01159661
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 23 2010 2:29PM