California Air Resources Board

The In-Use Locomotive Regulation was approved by the Board on April 27, 2023.  

The In-Use Locomotive Regulation (Regulation) will achieve emission reductions from diesel-powered locomotives and increase the use of zero-emission (ZE) technology. The Regulation will help meet California’s public health, air quality and climate goals by reducing criteria pollutants, toxic air contaminants, and greenhouse gas emissions for locomotives in-use.    

• Locomotives are self-propelled off-road equipment used to push or pull rail-mounted cars carrying freight or passengers. 
• Diesel-powered locomotives emit multiple air pollutants, including diesel particulate matter, fine particulate matter (PM2.5), oxides of nitrogen (NOx) and greenhouse gases (GHG).
• Locomotives travel throughout the state to seaports, railyards and other locations that are near where people work and live.
• Exposure to toxic and harmful diesel emissions is known to lead to cancer and increases in asthma, cardiopulmonary illness, hospitalizations, and premature mortality.
• Communities near rail operations bear a disproportionate health burden due to their proximity to harmful emissions.

To help meet California’s public health, air quality and climate goals, CARB has approved In-Use Locomotive Regulation. The Regulation would achieve emission reductions from diesel-powered locomotives and increase the use of zero-emission (ZE) technology.

There are several types of locomotive operators in California. Select a locomotive type to view the fact sheet.

Locomotive Emissions

• As of 2022, locomotives are projected to produce:
  • Over 640 tons per year of PM2.5
  • Over 29,800 tons per year of NOx

• Locomotive emission standards, called Tiers, are described in the graphs below. The standards are divided between two locomotive power levels, referred to as line haul (locomotives greater than 2,300 horsepower) and switch (locomotives 1,006 - 2,300 horsepower)

Line Haul Locomotive Emission Standards

Historic locomotives are not included in this PM2.5 graphic due to insufficient population data.

Switch Locomotive Emission Standards

Historic locomotives are not included in this PM2.5 graphic due to insufficient population data.

2020 California Locomotive Population by Tier

Historic locomotives are not included in this population graphic due to insufficient population data.

The In-Use Locomotive Regulation

1.  Spending Account

• Locomotive operators will be required to fund their own trust account based on the emissions created by their locomotive operations in California. The dirtier the locomotive, the more funds must be set aside.
• Spending Account funds will be used in the following manner:
  • Until 2030, to purchase, lease, or rent Tier 4 or cleaner locomotives, or for the remanufacture or repower to Tier 4 or cleaner locomotive(s).
  • At any time, to purchase, lease, or rent ZE locomotive(s), ZE capable locomotive(s), ZE rail equipment, or to repower to ZE locomotive(s) or ZE capable locomotive(s).
  • At any time, for ZE infrastructure associated with ZE locomotive(s), ZE capable locomotive(s), ZE rail equipment.
  • At any time, to pilot or demonstrate ZE locomotives or ZE rail equipment technologies.

2.  Starting in 2030: In-Use Operational Requirements

• Only locomotives less than 23 years old will be able to be used in California.
• Switchers operated by Class I, Class III, industrial and passenger locomotive operators with an original engine build date of 2030 and beyond will be required to operate in a ZE configuration to operate in California.
• Passenger locomotives with an original engine build date of 2030 and beyond will be required to operate in a ZE configuration to operate in California.
• Class I line haul locomotives with an original engine build date of 2035 and beyond will be required to operate in a ZE configuration to operate in California.

3.  Idling Limit

• All locomotives with automatic shutoff devices will not be permitted to idle longer than 30 minutes, unless for an exempt reason. Exemptions align with those described by U.S. EPA and will be granted for reasons like maintaining air brake pressure or keeping the driver cabin heated or air conditioned.

4.  Registration and Reporting

• Locomotives operating in the state will be required to register with CARB.
• Reporting includes an annual administrative payment.
• Locomotive activity, emission levels and idling data will be required to be reported annually.

5.  Additional Options Under the Regulation

• Alternative Compliance Plan: As an alternative to the Spending Account, the In-Use Operational Requirements, or both, the Regulation offers an Alternative Compliance Plan, which will allow locomotive operators to reduce emissions through other strategies, provided those strategies are not already required.  Alternative Compliance Plans must achieve emission reductions equivalent to or greater than those under the Regulation.
• Alternative Fleet Milestone Option: As an alternative to the Spending Account and the In-Use Operational Requirements, the Regulation will allow locomotive operators to reduce emissions by committing to four operational milestones, and to offset the use of older locomotives that will have been banned under the main regulatory pathway:
  1. Beginning January 1, 2030, 50 percent of annual fleet usage in California must be from Tier 4 or cleaner locomotives.
  2. Beginning January 1, 2035, 100 percent of annual fleet usage in California must be from Tier 4 or cleaner locomotives.
  3. Beginning January 1, 2042, 50 percent of annual fleet usage in California must be from ZE locomotives, ZE capable locomotives, or ZE rail equipment.
  4. Beginning January 1, 2047, 100 percent of annual fleet usage in California must be from ZE locomotives, ZE capable locomotives, or ZE rail equipment.
• Compliance Extensions:
  1. Temporary Operating Extension: The Regulation allows operation of locomotives prohibited from operation in California under the In-Use Operational Requirements under specific circumstances, such as for removal or for maintenance.
  2. Compliance Extension for delays due to compliant equipment (including infrastructure) manufacture or installation delays, or unavailability.
• Small Business Hardship Extension: The Regulation offers a process for small businesses to apply for a temporary extension of their obligations under the Spending Account and/or the In-Use Operational Requirements.
• Historic Railroad Low-Use Exemption: Historic locomotive operators that meet specific requirements may receive permission to be exempt from obligations under the Spending Account and/or the In-Use Operational Requirements.

Emission Reductions from the Regulation

Total Emission Reductions (2023-2050): The Regulation is expected to reduce statewide locomotive emissions by approximately:

• 7,400 tons of PM
• 386,300 tons of NOx
• 21.6 million metric tons of GHG, roughly equivalent to removing all heavy-duty diesel trucks from California’s roads for all of 2030.

The graphs below show percent reductions (in tons per day) of PM2.5 and NOx that will be achieved in each operating type by 2050.

Statewide PM2.5 Locomotive Emissions by Type

Historic locomotives are not included in this PM2.5 graphic due to insufficient population data.

Statewide NOx Locomotive Emissions by Type

Historic locomotives are not included in this NOx graphic due to insufficient population data.

Costs and Benefits from the Regulation

Costs: Staff estimate that the Regulation will cost $13.8 billion in costs for new equipment and labor, with the costs to households averaging an estimated $42/year.

Benefits: It is estimated that the Regulation will eliminate approximately 3,200 premature deaths, 1,100 hospital admissions and 1,500 emergency room visits. Health benefits are monetized to quantify savings from the Regulation. CARB staff estimate $32.0 billion in monetized health benefits.

Decrease in Cancer Risk from the Transition to Tier 4 Locomotives

Cancer Risk: Using a conservative approach, CARB staff modelled cancer risk assuming all locomotive use in California is at an average of Tier 4 emission levels. In the two railyards modelled, it is estimated cancer risk will decrease by over 90%.

Incentive Funding for New Technology

Based on development timelines for new technology, CARB staff estimate that ZE passenger and switch locomotives will be commercially available by 2030, and ZE line haul locomotives by 2035. CARB released the Technical Support Document: Zero Emission Locomotive Conversion along with the regulatory package prior to the Board hearing.

CARB offers grant funding to upgrade or replace locomotives to Tier 4 or ZE. Visit CARB Incentives for Locomotives for more information.