The Federal Government's Role in Reducing Heavy Duty Diesel Emissions 2004-01-2708

Over the past 30 years significant progress has been made in reducing air pollution from heavy-duty diesel engines. In the coming decades additional reductions will occur. These important emission reductions have occurred because of a series of increasingly stringent emission standards. These requirements began in 1970 with standards for opacity smoke emissions from highway heavy-duty engines. During the 1980's and 1990's, additional pollutants, primarily particulate matter and oxides of nitrogen, were controlled through changes in emission standards and test procedures (hydrocarbon and carbon monoxide standards were also included, but were targeted primarily at gasoline fueled rather than diesel fueled heavy-duty engines). In the mid-1990's, emission standards for nonroad diesel engines were implemented for the first time. During the next few years we will see the widespread introduction of aftertreatment systems such as particulate filters to comply with the highway 2007-2010 standards. In the next decade, a similar transformation of the nonroad diesel engine market will begin with the implementation of the land-based nonroad diesel Tier 4 emission standards.

This paper discusses why these reductions are necessary, and how the Government, and in particular the Environmental Protection Agency, has establishes and implements emission standards for highway and nonroad heavy-duty diesel engines, vehicles, and equipment.

The paper includes:

• A history of Federal mobile source emission standards in the U.S., with a focus on heavy-duty diesel engines.
• A brief summary explaining why pollution from heavy-duty diesel engines is a concern for public health and welfare, as well as a discussion of the progress that has been made in the last 20 years.
• An overview of the organizational structure within EPA and specifically the Office responsible for mobile source emission standards.
• A discussion of the Clean Air Act with emphasis on the provisions for heavy-duty highway engines and vehicles.
• A detailed discussion of the public rulemaking process under which EPA has established heavy-duty diesel engine standards.
• A discussion of the programs and requirements for the implementation of heavy-duty standards.
• A brief discussion of efforts for worldwide harmonization of heavy-duty emission standards.
• An overview of voluntary EPA programs that impact heavy-duty diesel engines and vehicles.
• A look at future heavy-duty and nonroad regulatory programs.

This paper is the first of a series of three in the Buckendale series that will focus on the commercial vehicle industry and emission standards. This paper will be followed by a 2005 paper focusing on how heavy-duty diesel highway and nonroad engine manufacturers have responded to EPA emission standards. The final paper in 2006 will discuss how EPA emission standards have impacted highway heavy-duty vehicle manufacturers and nonroad diesel equipment manufacturers.