Consistently improving automotive technology and government policies may enable the U.S. to reduce its petroleum consumption and greenhouse gas emissions in cars and small trucks by as much as 80 percent in the next 37 years by using a combination of more efficient vehicles, the use of biofuels, electricity and hydrogen to power cars and government policies that will influence consumer choice, a report from the National Research Council found.

"To reach the 2050 goals for reducing petroleum use and greenhouse gases, vehicles must become dramatically more efficient, regardless of how they are powered," said Douglas M. Chapin, principal of MPR Associates, and chair of the committee that wrote the report. "In addition, alternative fuels to petroleum must be readily available, cost-effective and produced with low emissions of greenhouse gases."

Chapin said such a lofty transition will be costly and require several decades.

He also said the reporting committee's "model calculations, while exploratory and highly uncertain, indicate that the benefits of making the transition, i.e. energy cost savings, improved vehicle technologies, and reductions in petroleum use and greenhouse gas emissions, exceed the additional costs of the transition over and above what the market is willing to do voluntarily."

The report suggests a consumer shift away from traditional gasoline combustion engines and towards alternative power modes will be the driving force in reducing emissions by 2050, as improving motor efficiency alone will not be enough; the average vehicle on the road would have to exceed 180 miles per gallon, which is unlikely given current technology.

"Transportation is an engine of our economic strength, but it also represents a key challenge for the future of U.S. energy use," Austin Brown a senior analyst with the National Renewable Energy Laboratory said in a statement. "Transportation accounts for 71 percent of total U.S. petroleum consumption and 33 percent of our nation's total carbon emissions. It presents significant opportunities to cut oil dependence while taking a bite out of greenhouse gas emissions."

While there is no "silver bullet" for decreasing greenhouse gas emissions in petroleum-based transportation, factors such as raising fuel economy, reducing the overall use of individual transportation coupled with an increase of effective mass transporation and expanding the availability and affordability of low-carbon vehicles will help meet the 2050 goal.

"The finding that there are many options increases our confidence that a clean transportation solution is possible in the long term," Brown said.