Date:  April 3, 2014




Regulation of Natural Gas Vehicles and Trailer Modifications Among Recommended Strategies to Reduce Fuel Consumption in Medium- and Heavy-Duty Vehicles


WASHINGTON -- Expanding the use of natural gas as a transportation fuel and greater use of aerodynamic devices on trailers are among the strategies recommended by a new National Research Council report on the fuel consumption by tractor-trailers, transit buses, commercial vehicles, trucks, and other medium- and heavy-duty vehicles.


The report follows a 2010 Research Council report whose findings and recommendations informed the “Phase I Rule” on fuel consumption and greenhouse gas emissions of medium- and heavy-duty vehicles issued jointly by the National Highway Traffic Safety Administration and U.S. Environmental Protection Agency.  The new report offers guidance for the “Phase II Rule” under development, which is directed at technologies and programs in the post-2018 time frame.


Among the new engine and vehicle technologies introduced since the Phase I Rule, the emergence of natural gas as a transportation fuel is significant, the report says.  Due to low carbon content, the greenhouse gas emissions of natural gas are lower than for gasoline or diesel fuel, but this benefit is partially negated by the lower efficiency in currently available engines and may be offset by the increased greenhouse gas effects of methane.  In addition, the natural gas fueling infrastructure is underdeveloped and will require large investments to provide enough stations to prevent disruption in routes and travel times for longer-haul trucks.


In light of these trade-offs, the report recommends that NHTSA and EPA develop a separate standard for natural gas vehicles as is presently the case for diesel- and gasoline-fueled vehicles.  It adds that the agencies should begin to consider the “well-to-tank” energy consumption and greenhouse gas emissions associated with natural gas vehicles as well as for other vehicle and energy technologies that include biofuels, dimethyl ether, and hydrogen fuel cells.


The committee that wrote the report found that the majority of both new and in-use van trailers currently do not use fuel-saving aerodynamic devices.  Use of these devices, in particular side skirts, provides a full return on investment through fuel savings in about one year, on average. However, when a trailer is not owned by the tractor owner/operator (who pays for fuel), there is no incentive for the trailer owner to purchase fuel-saving devices.  The report recommends that the agencies adopt a regulation requiring that all new 53 foot or longer dry van and refrigerated van trailers meet performance standards that will reduce fuel consumption and CO2 emissions. 


The 2010 Research Council report recommended that NHTSA conduct a pilot program to collect baseline data for evaluating the effectiveness of regulations on fuel consumption in various industrial sectors and parts of the country.  While the agency was unable to undertake the pilot program due to its mandate to issue its rule quickly, the committee recommends that NHTSA establish a repeatable, reliable data collection process as soon as possible.


A number of strategies that do not involve changes to the engine or vehicle are also available for reducing fuel consumption, the report says.  These include changes to fleet operations and logistics, innovations in infrastructure, traffic management, and driver training and other behavioral initiatives.  Market or regulatory factors may also directly or indirectly affect fuel consumption.  NHTSA should carefully consider and attempt to quantify the impacts of these nonvehicle approaches on the costs and feasibility of future fuel consumption improvements, and work with EPA, Federal Highway Administration, U.S. Department of Energy, and the private sector to create incentives that capture the benefits of approaches other than regulating the vehicle.


This report was intended to inform the development of the Phase II Rule.  The committee will expand upon this work and issue a final report in 2016 that will cover a broader range of technologies and approaches that address the 2025-2030 time frame.


The report was sponsored by the U.S. Department of Transportation.  The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies.  They are private, independent nonprofit institutions that provide science, technology, and health policy advice under a congressional charter granted to NAS in 1863.  The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering.  For more information, visit  A committee roster follows.



Lauren Rugani, Media Relations Officer

Monica White, Media Relations Assistant

Office of News and Public Information

202-334-2138; e-mail

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Pre-publication copies of Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two: First Report are available from the National Academies Press on the Internet at or by calling 202-334-3313 or 1-800-624-6242.  Reporters may obtain a copy from the Office of News and Public Information (contacts listed above).



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Division of Engineering and Physical Sciences

Transportation Research Board


Committee on Assessment of Technologies and Approaches for Reducing the Fuel Consumption

of Medium- and Heavy-Duty Vehicles, Phase Two


Andrew Brown Jr. 1,3  (chair)

Vice President and Chief Technologist

Innovation and Technology Office

Delphi Corp.

Troy, Mich.


Ines Azevedo

Assistant Professor

Department of Engineering and Public Policy

Carnegie Mellon University



Rodica A. Baranescu


Department of Mechanical Engineering

University of Illinois



Thomas Cackette

Retired Chief Deputy Executive Officer

California Air Resources Board



Nigel N. Clark3

Professor and Director, Center for Alternative Fuels, Engines, and Emissions

Department of Mechanical and Aerospace Engineering

West Virginia University



Ron L. Graves3

Director of the Sustainable Transportation Program

Oak Ridge National Laboratory

Knoxville, Tenn.


Daniel M. Hancock1

Retired Vice President, Global Strategic Product Alliances

General Motors Corp.



Michael Hanemann2

Wrigley Chair in Sustainability

Department of Economics

Arizona State University



Winston Harrington

Senior Fellow

Resources for the Future

Washington, D.C.


Gary Marchant

Professor of Law, Executive Director, and Faculty Fellow

Center for the Study of Law, Science, and Technology

College of Law

Arizona State University



Paul Menig



Sherwood, Ore.


David F. Merrion3


Merrion Expert Consulting LLC

Brighton, Mich.


Amelia Regan


Department of Computer Science

University of California



Michael Roeth

Executive Director

North American Council for Freight Efficiency

Fort Wayne, Ind.


Gary W. Rogers

President and Chief Executive Officer

FEV Engine Technology Inc.

Auburn Hills, Mich.


Charles K. Salter3

Independent Consultant

Chambersburg, Pa.


Christine Vujovich

Retired Vice President, Marketing and Environmental Policy

Cummins Inc.

Columbus, Ind.


John Woodrooffe3


Transportation Safety Analysis Division

Transportation Institute

University of Michigan

Ann Arbor


Martin Zimmerman3

Ford Motor Company Clinical Professor of Business Administration

Ross School of Business

University of Michigan

Ann Arbor



Martin C. Offutt

Study Director



1 Member, National Academy of Engineering

2 Member, National Academy of Sciences

3 Member, 2010 Committee