Pavement Albedo

"Albedo" or reflectivity is the ratio of the amount of light reflected from a material to the amount of light shone on the material. In the case of pavements, a lower albedo suggests that more sunlight in absorbed by the pavement. This sunlight is converted into thermal energy and the pavement gets hotter. Pavements with higher albedos albedo less energy and are thus cooler. Link to: Cool Pavements Lower Temperatures This reduction in temperature would reduce the heat island effect, save energy by reducing the demand for air conditioning, and improve air quality. Link to: The Cost of Hotter Pavements. This reduction in temperature would also improve the durability of pavements and extend their lifetimes. Link to: Pavement Durability.

We measured the albedos of various asphalt concrete pavements. The most recently paved surfaces have an albedo of about 0.04, because the asphalt (bitumin) coats the aggregate. (A typical asphalt concrete pavement is about 85% by volume of mineral aggregate and 15% asphalt.) Within 5 years the albedos increase to a mean value of 0.12 because the asphalt wears away, revealing some of the aggregate.

Over time, the albedo of asphalt concrete approaches 0.12.

The data of the graph above is plotted as a histogram. The average albedo is about 0.12. The maximum does not exceed 0.16. Note that a specific pavement's albedo would depend on the kind of aggregate used and the history (e.g. sunlight, soiling, traffic) of the pavement.

Over time, the average albedo of asphalt concrete is about 0.12.

There may also be a collateral effect of pavements with higher albedos: Nighttime visibility is improved on higher albedo pavements. Link to: Pavement Albedo at Night

For an overview of some benefits of low-albedo (cooler) pavements, link to: "Benefits of Cooler Pavements"

Back to: Cool Pavements | Heat Island Group Home Page

This web page last modified by Brian Pon on June 30, 1999Questions? E-mail: