Gas-powered vehicles will supposedly still rule U.S. roads in 2040, according to a new study by the federal government.

Plug-in hybrid and electric vehicles won't catch up to gas-powered cars, and will account for just 1 percent of total sales in 2040, according to the Annual Energy Outlook 2014.

The approximate number of diesel vehicles on U.S. roads is expected to double from 2 percent in 2012 to 4 percent.

By 2040, 78 percent of all vehicles, including cars and trucks, will run on gasoline, compared to 82 percent last year, according to the report.

More fuel efficient vehicles will rise from 21.5 mpg in 2012 to 37.2 mpg in 2040, but it still won't be enough to catch gas-powered vehicles.

The report was published by the U.S. Energy Information Agency.

Advanced technology fuel efficiency subsystems and micro-hybrids will be found on just 42 percent of all vehicles by 2040.

The federal government feels that unleaded gasoline will cost drivers approximately $3.90 a gallon in 2040.

The cost of diesel fuel will rise to $4.73 a gallon by 2040, though numbers are adjusted for inflation, according to the study.

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