A new book by a UC Davis researcher offers a solution for the environmental consequences of the booming world car population. There are now about 10 cars for every 100 persons on the planet, compared to 2 cars per 100 in 1950. "We are on the cusp of a technological and regulatory revolution," says Dan Sperling, director of the UC Davis Institute of Transportation Studies and author of "Future Drive: Electric Vehicles and Sustainable Transportation" (Island Press, 1994). The book will be available Dec. 16. "We have an extraordinary opportunity to create a sustainable transportation and energy system," he says. "The key to sustainability is electric-drive vehicles and more flexible and incentive-based government intervention." In "Future Drive," Sperling outlines strategies for creating an environmentally benign transportation system. Better technology holds more promise than changing people's travel behavior (such as through mass transit or less driving), he says.