"When considering how cars and trucks generate such a large part of the world's greenhouse gas pollution, it's easy to overlook what lies beneath them. But under all that traffic, there are roads. And the paving material itself-the asphalt, concrete, and rock-and how it is placed, have an important impact on the atmosphere"  reports Marianne Lavelle of National Geographic News 

The article reports that John Harvey, principal investigator at the University of California's Pavement Research Center, says that "asphalt versus concrete" is the wrong way of looking at the environmental questions around pavement.  More than 90 percent of pavement is rock, no matter what kind of glue holds it together. One needs  to "keep remembering that rock is the primary ingredient, so there's tremendous energy that goes into the mining, crushing, and hauling of rock in the materials production phase" of a roadway. The UC center, housed at both Berkeley and Davis, is working on developing a framework and models to help government officials make better decisions about roadways, taking into account the entire lifecycle of these long-lived civil engineering projects.

The full article can be found at the National Geographic website here: http://news.nationalgeographic.com/news/energy/2011/10/111017-asphalt-concrete-road-building-energy/