U.S. Energy Secretary Spencer Abraham said that today 700 million cars navigate the industrialized world. He projected there will be 3.5 billion cars in 50 years.
Auto emissions are believed to be a major contributor to global warming, so for many it would be unacceptable to multiply today's emissions fivefold.
World oil use will grow to 120 million barrels a day by 2020, up from about 75 million barrels a day in 1999, Abraham said. However, experts say world oil production will peak between 2004 and 2008, which will force a change in transportation technology.
Abraham stressed that international cooperation is essential to come up with new energy technologies to power future transportation.
Abraham, with Michigan Gov. John Engler at his side, announced that the federal government will hold a major conference on new transportation technologies in Detroit in the fall.
At the G8 forum, held very close to General Motors' corporate headquarters, several automakers had advanced fuel-cell vehicles on display. Toyota's was powered by hydrogen. Daimler Chrysler's vehicle ran on a hydrogenated borax solution. The new autos are expected to become widely available within a decade.