The Big 3 U.S. automakers unveil a green fleet for the future with some designed hybrids getting up to 80 miles per gallon. They also promise that even sport utility vehicles will run cleaner. Some analysts say it’s the start of a race to build a supercar for the new millennium. Laura Knoy spoke with Amory Lovins about these development. Mr. Lovins is the director of research at the Rocky Mountain Institute in Snowmass, Colorado, and a leader in the field of fuel-efficient vehicles.