US Environmental Protection Agency (EPA)

National Clean Diesel Campaign

Building on the successes of EPA’s regulatory and voluntary efforts to reduce emissions from diesel engines, EPA created the National Clean Diesel Campaign (NCDC) to work aggressively to reduce the pollution emitted from diesel engines across the country through the implementation of varied control strategies and the aggressive involvement of national, state, and local partners.

EPA Sector Programs

EPA currently has programs focusing on Clean School Bus, Ports & Marine, Clean Construction, SmartWay Transport, and Clean Agriculture.

Smartway Transport

A voluntary program between EPA and the freight industry that will increase the energy efficiency while significantly reducing air pollution and greenhouse gases.

Truck and Bus Engine Emissions Standards

Guidance, regulations, and general information on emission standards for heavy-duty highway diesel engines and vehicles.

Nonroad Engine Emission Standards

General information, reports, and proposals for nonroad engine emission standards (e.g., marine diesel engines).

Tier 2/Gasoline Sulfur Home Page

Information on more protective tailpipe emissions standards for all passenger vehicles. Also information on standards for lower sulfur in gasoline.

Airborne Particulate Matter (PM) Research Centers - Original (1998) 

In May 1998, EPA's STAR Program issued a request for applications (RFA) for research grant proposals to establish five PM Centers following the recommendations from the National Research Council report, Research Priorities for Airborne Particulate Matter: 1) Immediate Priorities and Long-Range Research Portfolio, and direction from Congress in the Environmental Protection Agency's (EPA's) 1998 appropriation. The five centers established in June 1999, were selected from 22 applicants after a merit review by a panel of external scientific experts. These centers will advance the understanding of PM health effects, how they occur, and improve understanding of populations who are susceptible to health effects from exposure. 

The PM Research Centers are a central component of EPA's on-going integrated research program for PM which also includes ORD's intramural research program, interagency research and other STAR Program RFAs for individual research grants.

EPA Harvard Center for Ambient Particle Health Effects

EPA NYU PM Center: Health Risks of PM Components

Rochester PM Center

Southern California Particle Center and Supersite

Northwest Research Center for Particulate Air Pollution and Health

Airborne Particulate Matter (PM) Research Centers - New (2005)

While the U.S has made noticeable progress over the last four decades in reducing air pollution, substantial concern still remains about the health  effects of ambient particulate matter, a major component of the air pollution mix in many areas of the country.  In 2005, the EPA awarded $40 million to establish five cutting-edge research centers that will further improve our understanding of how particulate matter or PM affects human health and the types and sources of PM most responsible for these effects.

Johns Hopkins Particulate Matter Research Center

Harvard Particle Center

Southern California Particle Center

San Joaquin Valley Aerosol Health Effects Research Center (SAHERC)

Rochester PM Center

Biodiesel Emissions Program

Innovative State and Local Voluntary Emissions Reduction Programs

State Implementation Plan-Bundled Measures


US Department of Energy (DOE)

Clean Cities

A U.S. Department of Energy program that supports the idea of adopting practices that contribute to reduced petroleum consumption in the transportation sector.


National Idling Reduction Network News

The National Idling Reduction Network brings together trucking and transit companies, railroads, equipment manufacturers, local, state and federal government agencies (including regulators), and national research laboratories to identify consistent, workable solutions to heavy vehicle idling for the entire United States.

Vehicle Technologies Program

DOE’s Vehicle Technologies Program is developing more energy efficient and environmentally friendly highway transportation technologies that will enable America to use less petroleum. The long-term aim is to develop "leap frog" technologies that will provide Americans with greater freedom of mobility and energy security, while lowering costs and reducing impacts on the environment.

Alternative Fuels Data Center

The Alternative Fuels Data Center (AFDC) provides information, data, and tools to help fleets and other transportation decisions makers find ways to reduce petroleum consumption through the use of alternative and renewable fuels, advanced vehicles, and other fuel-saving measures.

Custom Alternative Fuels Comparison Chart (PDF)


US Department of Transportation (DOT)

Federal Highways Administration Air Quality Website

This web site provides information on FHWA's air quality programs, including transportation conformity, air toxics, and the Congestion Mitigation and Air Quality Improvement (CMAQ) program. 

U.S. Department of Transportation's Congestion Mitigation Air Quality CMAQ Program

These funds are available to improve air quality and reduce congestion.

Transportation & Toxic Air Pollutants

To address stakeholders concerns and requests for MSAT analysis during project development and alternative analysis, FHWA developed the Interim Guidance on Air Toxic Analysis in NEPA Documents. The guidance provides a tiered approach for analyzing MSAT in NEPA documents.