Heavy-Duty Low NOx

This page last reviewed April 19, 2019

Background

Nonattainment Map A key measure in the Mobile Source Strategy is the establishment of low oxides of nitrogen (NOx) engine emission standards that result in a 90 percent reduction in NOx emissions compared to the emissions of today's diesel engines. This measure is critical for attaining federal health-based air quality standards for ozone in 2023 and 2031 in the South Coast and San Joaquin Valley air basins, and fine particulate matter (PM2.5) standards in the next decade. Under this measure, staff also plans to develop regulatory amendments to improve the certification requirements to better reflect emission control under low load urban driving operations, to improve engine and emission control system durability, and to expand and improve the in-use compliance testing program. These supplemental actions include:

  • Adopting a new low load certification test cycle;
  • Amending the warranty and useful life period;
  • Amending the certification durability demonstration procedures;
  • Amending the Not-to-Exceed (NTE) in-use compliance program; and
  • Warranty corrective action.

In 2013, California established optional low-NOx standards with the most aggressive being 0.02 g/bhp-hr, which is 90 percent below the current standard. The optional NOx standards were developed to pave the way for mandatory standards by encouraging manufacturers to develop and certify low NOx engines and incentivizing the purchase of certified low NOx engines. To-date, ten natural gas or liquefied petroleum gas engines have been certified to the optional NOx standards.

Need for federal action: As vehicles purchased outside the state account for a majority of the heavy-duty vehicle miles travel in the South Coast Air Basin on any given day, federal NOx engine emission standards are necessary in order to achieve emission reductions from vehicles operating in California that were purchased outside the state. Thus, the U.S. Environmental Protection Agency's (U.S. EPA) action to establish a new national low-NOx standard for heavy-duty trucks is critical. In response to petitions for a low NOx rulemaking from over 20 organizations including state and local air agencies from across the country, on November 13, 2018, U.S. EPA announced the "Cleaner Truck Initiative" to develop regulations to further reduce NOx emissions from on-road heavy-duty trucks and engines.

Research Activities: CARB is currently funding several research projects, hereinafter referred to as the Stages 1, 2, and 3 Heavy-Duty Low NOx programs, to assess the feasibility of lower NOx emissions. The Stage 1 project was a $1.6 million research contract with Southwest Research Institute (SwRI) to assess the feasibility of lower NOx emissions on a diesel and a natural gas heavy-duty engine through a combination of engine calibration, exhaust thermal management strategies, and advanced aftertreatment systems. The final report can be accessed at: https://www.arb.ca.gov/research/veh-emissions/low-nox/low-nox.htm.

The Stage 2 program is a $1.05 million follow-on project to the Stage 1 program with SwRI as the research contractor and the National Renewable Research Laboratory, or NREL, as a subcontractor. Stage 2's objectives are to develop a low-load certification cycle, optimize diesel engine calibrations for low load duty cycles and examine different "load" metrics for improvement of in-use testing. Stage 2 is expected to be finalized by March 2019.

The Stage 3 program is a follow-on to the Stages 1 and 2 programs. It is a $1.325 million research contract with SwRI to demonstrate low NOx emissions on an alternative engine platform on certification cycles and the low load cycles developed in the Stage 2 program. In addition to assessing different aftertreatment technologies, Stage 3 also includes investigation of different engine technologies that provide more thermal energy to the exhaust at low loads as well as reduce GHG emissions. Stage 3 is expected to be finalized by December 2019.

What's New


Posted April 18, 2019:

During recent meetings with CARB staff, many engine manufacturers stated to staff that they are in the process of settling on engine development plans to meet the 2024 model year (MY) Phase 2 greenhouse gas (GHG) requirements. They further stated that, in order to accommodate NOX reductions in their 2024 MY engine designs, they need to know as soon as possible what requirements CARB staff is considering to propose for 2024 MY engines. They described their need for sufficient product development time to incorporate NOX requirements together with the Phase 2 GHG requirements. Thus, in response, CARB staff has prepared this white paper that describes staff's current assessment of what it believes is achievable for 2022 through 2026 MY engines and an assessment of additional requirements for 2027 and subsequent MY engines Staff White Paper.

Posted December 24, 2018:

CARB staff invites you to participate in a public workshop to discuss regulatory concepts to reduce NOx emissions from new on-road heavy-duty engines. Staff will discuss various concepts including potential revisions to the heavy-duty emission standards and certification test procedures, certification and warranty requirements, and the Not-to-Exceed (NTE) heavy-duty in-use testing program (HDIUT). Staff will also provide an update regarding the low oxides of nitrogen (NOx) demonstration projects. Additional details can be found in this public notice.

Posted May 11, 2018:

On May 8, 2018, staff released the Public Hearing Notice and related material for the proposed amendments to the California emission control system warranty regulations and maintenance provisions for on-road heavy-duty diesel vehicles with gross vehicle weight ratings greater than 14,000 pounds and heavy-duty diesel engines in such vehicles. Follow the HD Warranty 2018 page to access these documents. Interested members of the public may present comments orally or in writing at the hearing and may provide comments before the hearing. The public comment period for this regulatory action begins on May 11, 2018. Written comments not physically submitted at the hearing must be received no later than 5:00 pm on June 25, 2018. Use the Submit Your Comments to the Board page to submit official comments before the Board Hearing. The Board Hearing is scheduled for 9:00 am on Thursday, June 28, 2018, at the Coastal Hearing Room, 1001 I Street, Sacramento, CA 95814.

Posted January 11, 2018:

The agenda, handouts, and presentations for the January 12, 2018 workshop have now been posted below in the meetings and workshops section of this page. The workshop will be available via webcast for those unable to attend in person. The broadcast can be accessed on the day of the workshop at http://www.aqmd.gov/home/news-events/webcast. Note that this webcast link is different than the link provided in the listserv notice sent on December 12, 2017.

Posted December 12, 2017:

CARB invites you to participate in a public workshop to learn more about a potential regulatory measure to reduce NOx emissions from new on-road heavy-duty vehicles by amending the emission control system warranty periods. Additional details can be found in this public notice.

Posted June 9, 2017:

CARB invites you to participate in a public workshop to learn more about potential regulatory measures to reduce NOx emissions from new on-road heavy-duty vehicles. Additional details can be found in this public notice.

Posted April 21, 2017:

The Heavy-Duty In-Use Compliance/Testing/Not-to-Exceed Workgroup and Heavy-Duty Low NOx Standard and Test Procedures Workgroup meetings were held on February 22, 2017 and March 6, 2017, respectively. At these workgroup meetings, CARB staff presented and solicited feedback regarding rulemaking timelines, status results of CARB-funded Heavy-Duty Low NOx research programs, analysis of in-use data to evaluate current NTE requirements and potential future revisions, and outside the box concepts and ideas. Staff presentations and summary of meeting notes have been posted on the "Meetings and Workshops" section of this page.

Posted November 1, 2016:

The agenda and presentations for the November 3, 2016 workshop, as well as the descriptions of workgroups have been posted on the workshops section of this page. The workshop is also available via webcast.

Posted October 5, 2016:

CARB invites you to participate in a public workshop to learn more about potential regulatory measures to reduce NOx emissions from new on-road heavy-duty vehicles.   Additional details can be found in this public notice.


Heavy-Duty Low NOx Program / Maintenance Provisions Meetings and Workshops

Date/Time Description Documents
January 23, 2019
9:00 am - 1:00 pm
Public workshop to discuss potential changes to the heavy-duty engine and vehicle emission standards, test procedures, warranty, and other related heavy-duty programs.
Workshop Notice
Agenda

Presentations:
Background
Credit Provisions
HD UL & Step 2 Warranty
Durability
Low NOx Demo Update
EWIR
HDIUT
LLC
January 12, 2018
9:00 am - 12:00 pm
Public workshop to discuss proposed amendments to the California emission control system warranty regulations and maintenance provisions for on road heavy duty vehicles with gross vehicle weight ratings greater than 14,000 lbs.
Workshop Notice
Webcast
Agenda
Presentation

Handouts:
Amendments To Sec 2035
Amendments To Sec 2036
Amendments To Sec 2040
Amendments to Sec 86.004-25
Revised Maintenance Intervals
July 12, 2017
10:00 am - 1:00 pm
Public Workshop to Discuss Proposed Amendments to the California Emission Warranty Regulations for On-Road Heavy-Duty Vehicles
Workshop Notice
Webcast
Agenda
Presentation
March 6, 2017
9:30 am - 11:30 am

Heavy-Duty Certification Standards and Test Procedures Workgroup Meeting:

Conference call meeting to discuss rulemaking timeline of the various Heavy-Duty Low NOx program elements, final results of the ARB-funded - SwRI Heavy-Duty Low NOx research program (Stage 1), and other outside the box concepts and ideas.
Agenda
Presentation
February 22, 2017
9:30 am - 11:30 am

Heavy-Duty In-Use Compliance/Testing/Not-to-Exceed Workgroup Meeting:

Conference call meeting to discuss rulemaking timeline of the various Heavy-Duty Low NOx program elements, CARB staff analysis of in-use data under NTE and moving average methods, and related research.
Agenda
Presentation
November 3, 2016
1:00 pm - 5:00 pm
Public Workshop to Discuss Potential Changes to the Heavy-Duty Engine and Vehicle Emission Standards, Test Procedures, Warranty, and Other Related Heavy-Duty Programs
Workshop Notice
Webcast
Agenda
Documents/Presentations

Email List

For more information on ARB’s heavy-duty low NOx efforts, please sign up for the Heavy-Duty Low NOx Email List

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