Covering U.S. highways with solar panels would provide enough electricity to power the entire nation, says an Idaho engineer charged by the government to develop self-sustaining roads. There are 25,000 square miles of roadways in the lower forty-eight states, says Scott Brusaw, engineer and winner of a U.S. Department of Transportation grant to build a road that "pays for itself". As the price of asphalt, a petroleum based product, has skyrocketed over recent years, goals of building a self-sustainable interstate system have quickly taken on much larger proportions. Brusaw, who believes we will see the death of asphalt in fifty years due to price increases, says solar panels running at fifteen percent efficiency would produce nearly enough electricity annually to power the entire world.