WASHINGTON Last month, when the Obama administration announced tougher requirements for automobile fuel efficiency, and a first-ever national greenhouse gas reduction standard for cars and light trucks, there was speculation similar rules could be proposed for over-the-road buses and trucks within the foreseeable future.

The Obama plan for cars and pickup trucks sold in the U.S. calls for a 30 percent reduction in carbon dioxide and other emissions and an overall auto fuel-efficiency standard equal to an estimated 35.5-miles-per-gallon rating by 2016.

One trucking industry environmental affairs specialist said the proposed auto rules may signal a tougher overall environmental policy by the Obama administration that could include heavy truck and bus standards as early as 2016.

However, before that policy could take effect, the Energy Independence and Security Act of 2007 requires that a heavy vehicle fuel efficiency study be completed by March 2010, and a National Highway Traffic Safety Administration fuel efficiency report be completed by fall 2010.

The National Highway Traffic Safety Administration could then begin a rulemaking process for fuel efficiency in heavy commercial vehicles.

However, there is a nascent move afoot to remove fuel efficiency standard setting from the NHTSA and park it in the U.S. Department of Environmental Protection where pollution standards are set. Such a move could accelerate the process and make it tougher on the commercial vehicle industry.

The new mileage and emissions regulations for cars and light trucks would be a joint, or so-called harmonized, effort of EPA and NHTSA, a departure from past practice.

Meanwhile, the American Clean Energy and Security Act of 2009, marked up by a House committee last month, calls for EPA to begin a greenhouse gas reduction rulemaking for new heavy vehicles by the end of 2010.

That bill, as currently configured, does not call for a joint rulemaking or harmonized approach to the differing tracks EPA and NHTSA have taken.