Off-Road Compression-Ignition (Diesel) Engines and Equipment

This page last reviewed September 8, 2008

All documents are provided in chronological order in Adobe Acrobat (PDF), unless otherwise indicated.

View the meeting presentations.

View the formal regulatory documents.




At the December 9, 2004 hearing, the Board directed staff to work with industry to refine modifications proposed by staff to the off-road diesel Tier 4 regulations. Staff is complying with the Board's directive and will soon be making available for public comment an official notice of modified text along with the associated revised regulatory language and test procedures. In the interim, staff is providing a draft of its proposed modified regulatory language for public review in advance of its official release. A comment period of 45-days will be provided beginning once the official notice is made available.

April 20, 2005

On December 9, 2004, the Board adopted a fourth phase of emission standards (Tier 4) that are nearly identical to those finalized by the U.S. EPA on May 11, 2004, in its Clean Air Nonroad Diesel Rule. A copy of the Resolution presented to the Board at the hearing, including staff's suggested changes to the original proposal, is now available.

  • Resolution 04-43 (PDF - 69KB)

  • Attachment B-1: Staff's suggested changes to the original proposal. (PDF - 85KB)

January 19, 2005

View the Staff Report and proposed Regulations and Test Procedures for the Tier 4 Off-Road Diesel Engine Rulemaking will be available after 5p.m. PST, Friday, October 22, 2004.

October 20, 2004

The Draft Proposed Regulations for the upcoming Tier 4 Off-Road Diesel Engine Rulemaking are now available. The submittal of comments regarding this draft is not necessary. ARB intends to release the official proposal for a 45-day public comment period on October 22, 2004.

October 1, 2004

ARB is in the process of preparing the regulatory package to support its proposed amendments for more stringent exhaust emission standards, compliance provisions and test procedures for off-road diesel engines.

August 23, 2004

Letter to Manufacturers (PDF - 87K) Request for information on the development of emission control technologies capable of meeting Tier 2 and Tier 3 off-road compression-ignition emissions standards and beyond. (Mailout #MSC 01-17) (NOTE: Comment period has been extended to January 21, 2002.)


ARB adopted new standards of diesel engines in 2000. These documents include, but are not limited to, the staff report, regulations, test procedures, and 15-day notice(s).


Mailout MSC 01-09: Public Hearing Notice regarding Proposed Regulations for 2003 and Later Spark-Ignition Sterndrive and Inboard Marine Engines

June 11, 2001