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On Friday, the National Research Council (NRC) released a report that offers insight into ways that NHTSA and EPA can improve upon the current fuel economy and greenhouse gas (GHG) regulations for medium and heavy duty vehicles. The report, Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two: First Report, was published by the National Academy of Sciences. The report devotes a great deal of attention to the potential benefits of NGVs, and includes specific recommendations on the ways future regulations can better accommodate NGVs.

One recommendation is that the agencies should establish a separate standard for NGVs along the lines of the current ones for gasoline and diesel vehicles. Regulations in place today provide different levels of emissions control and sometimes different phase-in periods for gasoline and diesel fueled engines and vehicles. Under the EPA and NHTSA

regulations, NGVs can fall under the gasoline regulations or the diesel regulations depending on whether the natural gas engine was derived from a base gasoline or diesel engine. The latest regulations also provide some flexibility, allowing manufacturers of heavy duty natural gas engines to choose which designation to use but, once a category is established, the natural gas engine must meet all of the requirements set out for the particular engine-type, including meeting criteria pollutant emissions (e.g., NOx, PM) for that engine category. Requirements that are specific to gasoline or diesel engines may not in some cases be appropriate for natural gas. If NGVs were to be regulated separately, EPA and NHTSA could fashion rules based on what is technologically and economically feasible for natural gas.

A second recommendations specific to natural gas include modifying the Greenhouse Emissions Model (GEM) to specifically include examples of natural gas engine types. GEM is used by manufacturers to demonstrate compliance with the standards, but to date it does not include any inputs for natural gas. A third recommendation (this one made with respect to other fuels – not just natural gas) is to include an assessment of upstream emissions in order to ensure that any benefits provided by tailpipe emissions or fuel economy performance are not otherwise negated by upstream emissions.

The report recommends that the government and private entities should support technical improvements to natural gas engine efficiency as well as cost reductions to storage systems and emissions controls in order to better take advantage of the greenhouse gas and petroleum reduction potential of natural gas. There also is a recommendation that EPA and NHTSA evaluate the need for and potential benefits and costs of setting an in-use fuel specification for natural gas. The chapter on natural gas devotes much attention to discussing the economic benefits of natural gas, its lower greenhouse gas emissions potential, and the challenges facing the use of natural gas as a transportation fuel.

The report otherwise spends a lot of time talking about the shortcomings of the Greenhouse Emissions Model and the need for real-world data to help regulators establish baseline fuel economy and emissions in order to guide an assessment of progress that is being made.

The full report is available here.