Heavy Trucks, Buses, and Engines

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This page presents emission-related information about heavy-duty highway engines, such as those used in trucks and buses. Much of this content is focused on diesel engines, but requirements also apply for gasoline-fueled and other spark-ignition engines. The requirements apply to engines installed in all vehicles with Gross Vehicle Weight Rating above 14,000 pounds, and to some engines installed in vehicles with Gross Vehicle Weight Rating between 8,500 and 14,000 pounds. This page describes the emission standards and related requirements for criteria pollutants -- NOx, HC, CO, and PM. See Greenhouse Gas Standards for requirements that apply for CO2, N2O, and CH4.

General Information
Regulations and Related Documents
Certification Guidance
Additional Provisions
Related Links

General Information

National Clean Diesel Campaign Publications
Health Assessment Document for Diesel Engine Exhaust
How to Maintain or Rebuild Engines Certified to EPA Standards (PDF) (4 pp, 142K, EPA-420-F-12-052, August 2012)

Regulations and Related Documents

Summary of CI exhaust emission standards, SI exhaust emission standards, and evaporative emission standards
Nonconformance Penalties for On-Highway Heavy-Duty Diesel Engines (signed August 30, 2012)
Emergency Vehicle and SCR Maintenance Rule (published June 8, 2012)
EPA’s direct final rule for emergency vehicles went into effect August 7, 2012, allowing manufacturers of engines for fire trucks and ambulances to request modifications to emission control systems so they do not interfere with emergency missions. In a parallel action, EPA also proposed revisions to establish minimum maintenance intervals for urea refills with SCR systems. EPA also proposed short-term relief for general purpose nonroad equipment during emergencies. A public hearing was held June 27, and the comment period ended July 27. Public comments and the hearing transcript are available in the rulemaking docket.
- Fact Sheet: EPA Grants Relief for Fire Trucks and Ambulances; Proposes SCR Maintenance and Short-Term Relief for Nonroad Equipment (PDF) (4 pp, 560K, EPA420-F-12-025, May 2012)
- Direct Final Rule (PDF) (19 pp, 603K, published June 8, 2012)
- Notice of Proposed Rulemaking (PDF) (30 pp, 602K, published June 8, 2012)
- See Nonroad Diesel Engines for more information about similar rulemaking changes for nonroad engines
2010 Technical Amendments -- In-Use Testing Revisions (published November 8, 2010)
- Direct Final Rule (PDF) (20 pp, 366k)
- See In-use Testing for more information.

Greenhouse Gas Reporting Rule (published October 30, 2009)
- Final Rule (PDF) (260 pp, 1.40MB)
- See Greenhouse Gas Reporting for more information.
2008 Technical Amendments -- Nonroad SI Rule (published October 8, 2008)
- Final Rule (PDF) (343 pp, 3.7MB)
- See Nonroad SI Rule for more information
2008 Technical Amendments -- Locomotive-Marine Rule (published June 30, 2008)
- Final Rule (PDF) (255 pp, 2.10MB)
- See Locomotive-Marine Rule for more information
2006 Technical Amendments (published August 30, 2006)
- Fact Sheet: Highway Heavy-Duty Diesel Engine Regulatory Amendments (PDF) (9 pp, 215K, EPA-420-F-06-059, August 2006)
- Direct Final Rule (PDF) (9 pp, 219K)