Lower pavement temperatures lead to longer lifetimes for the pavement. Examples of this are the effects of temperature on "rutting," "permanent shear strain," and the "aging of viscosity."

Rutting

Pavement failure due to rutting can be delayed if the pavement is kept cooler. Source: Dr. John Harvey, Institute of Transportation Studies, U.C. Berkeley.

The number of traverses of a single-axle load before a 1.3-cm rut is created is much larger when the pavement temperature is lowered from 50°C (122°F) to 40°C (104°F) (measured 5 cm below the surface). This suggests that failure due to rutting can be delayed if the pavement is kept cooler by a reflective coating. (The data is from Dr. John Harvey, Institute of Transportation Studies, U.C. Berkeley. Go to: The Institute of Transporation Studies.)

Permanent Shear Strain

Permanent deformation due to shear strain can be decreased if the pavement is kept cooler. Source: Dr. John Harvey, Institute of Transportation Studies, U.C. Berkeley.

An asphalt pavement that is subjected to repeated simple shear permanently deforms over time. This permanent deformation of pavement severely decreased as the temperature of the pavement is decreased from 60°C (140°F) to 40°C (104°F). The effect is similar to what may occur at bus stops, where vehicles apply shear when they brake and shove the pavement. (The data is from Dr. John Harvey, Institute of Transportation Studies, U.C. Berkeley. Go to: The Institute of Transporation Studies.)

Aging of Viscosity

Pavement deteoration increases rapidly with average annual temperature. The graph shows data for the cities Indio, Sacramento, Lake Tahoe, and Fort Bragg, California. Source: California Department of Transportation (Caltrans).

Even in the absence of traffic, asphalt binder deteriorates. The stiffening of asphalt is seen to increase by an order of magnitude when the asphalt is merely exposed in a sunny, hot climate, such as the desert area of Indio, California, compared to a climate as warm as Sacramento, California, where the average annual temperature is only 10°F (5.6°) less. This suggests that if sunlight were reflected and the samples were cooler, the asphalt would retain its quality. (The data is from the California Department of Transportation (Caltrans). Go to: California Department of Transportation (Caltrans) Home Page.