In fact, the study by the Pew Center on Global Climate Change found that the US transport sector alone produces nearly one-third of the country's entire CO2 emissions.

"The US is the owner of the world's largest transportation system, and reducing emissions from this system is critical to an effective GHG (greenhouse gas) reduction strategy," Pew Center president Eileen Claussen said in a statement.

"The US transportation system emits more CO2 than any other nation's total economy, except that of China, and presently accounts for seven of 10 barrels of oil this nation consumes," Claussen said.

But, if the United States were to put to use existing technology and investments, carbon emissions could be cut by some 20 percent by 2015 compared with 'business as usual'.

The study, "Reducing Greenhouse Gas Emissions from US Transportation", found that such action could lead to 50 percent cuts by 2030. And it identifies policies and technology that would achieve big enough GHG reductions to make a difference.

"Many of the actions that would reduce emissions from transportation would also address other national priorities, including US dependence on foreign oil," Claussen added.

The study, written by David Green of Oak Ridge National Laboratory and Andreas Schafer of the Massachusetts Institute of Technology, found that:

- Fuel economy for new cars and light trucks could be boosted 25-33 percent in the next 10-15 years just by using available technology

- Mandatory policies to put more technological improvements in the market place are needed on top of voluntary efforts and current levels of research and development

- And while fuel cell and hydrogen technology offer a "tantalizing" promise of eliminating GHG emissions from the sector, government must give clear policy direction to drive private investment in that direction.

SPACE.WIRE