Transportation expert Daniel Sperling estimates that the world's car population — which currently stands at one billion vehicles — is likely to double in the next 20 years.
Sperling is the co-author (with Deborah Gordon) of Two Billion Cars: Driving Toward Sustainability, a book that considers the environmental impact of so many automobiles and suggests ways that politicians, car companies and the general public can curb car-ownership and reduce climate change.
Sperling is a professor of civil engineering and environmental science and policy at the University of California, Davis and the founding director of University of California, Davis' Institute of Transportation Studies.
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