President Barack Obama signed a memorandum May 21, calling on two federal agencies to develop national standards for fuel economy and greenhouse gas emissions for medium and heavy-duty trucks.

The new rules, which will be written by the Environmental Protection Agency and the National Highway Traffic Safety Administration, would apply to commercial medium and heavy-duty vehicles beginning with model year 2014.

"This will bring down costs for transporting goods, serving businesses and consumers alike," Obama said. "We estimate that we can increase fuel economy by as much as 25 percent in tractor-trailers using technologies that already exist."

The President's announcement came one year after he announced plans for stricter fuel economy rules for passenger vehicles through model year 2016. In his speech, the President said the new fuel economy requirements would apply to vehicles starting with model year 2017.

NHTSA has been working on a fuel economy standard and is scheduled to publish a study on the subject in September. EPA is likely to issue a proposal in late summer or early fall, said Glen Kedzie, vice president and environmental counsel for American Trucking Association.