WASHINGTON, D.C. — Stricter fuel efficiency and greenhouse gas emissions rules for buses and trucks will go into effect for model year 2014, under an order from President Obama.

The presidential memorandum directs the administrators of the EPA and the National Highway Traffic Safety Administration (NHTSA) to immediately begin work on a joint rulemaking to establish fuel efficiency and greenhouse gas emissions standards for commercial medium- and heavy-duty vehicles beginning with model year 2014, with the aim of issuing a final rule by July 30, 2011.

“While the federal government and many states have now created a harmonized framework for addressing the fuel economy of and greenhouse gas emissions from cars and light-duty trucks,” Obama says in the memo, “medium- and heavy-duty trucks and buses continue to be a major source of fossil fuel consumption and greenhouse gas pollution.”

As part of the process, the EPA and NHTSA administrators are directed to propose and take comment on strategies to achieve substantial annual progress in reducing transportation sector emissions and fossil fuel consumption.

These strategies, the memo says, “should consider whether particular segments of the diverse heavy-duty vehicle sector present special opportunities to reduce greenhouse gas emissions and increase fuel economy.”

Obama noted that preliminary estimates indicate that large tractor-trailers, which reportedly represent half of all greenhouse gas emissions from the heavy-duty sector, can reduce their greenhouse gas emissions by as much as 20 percent and increase their fuel efficiency by as much as 25 percent with existing technologies.