Locomotive Fact Sheets

CARB is developing a regulation to reduce 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, staff are proposing an In-Use Locomotive Regulation. The Proposed 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

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

Pie chart showing the population breakdown of California locomotives by Tier. Over 90 percent are Tier 3 or older.

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

The Proposed In-Use Locomotive Regulation

1. Starting in 2024: Spending Account

Locomotive operators would 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 would be used to purchase the cleanest locomotives or upgrade existing locomotives to the cleanest tier.

2. Starting in 2030: In-Use Operational Requirements

Only locomotives less than 23 years old would 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 would be required to be ZE to operate in California.
Passenger locomotives with an original engine build date of 2030 and beyond would be required to be ZE to operate in California.
Class I line haul locomotives with an original engine build date of 2035 and beyond would be required to be ZE to operate in California.

3. Starting in 2024: Idling Limit

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

4. Starting in 2024: Registration and Reporting

Locomotives operating in the state would be required to register with CARB.
Locomotive activity, emission levels and idling data would be required to be reported annually.

5. Additional Options Under the Proposed Regulation

Alternative Compliance Plan: The Proposed Regulation offers an Alternative Compliance Plan, which would 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 Proposed Regulation.
Temporary Locomotive Operating Waiver: The Proposed Regulation allows operation of locomotives prohibited from operation in California under the In-Use Operational Requirement under specific circumstances, such as for maintenance
Small Business Hardship Extension: The Proposed 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 Requirement.
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 Requirement.

Emission Reductions from the Proposed Regulation

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

7,566 tons of PM
394,360 tons of NOx
21.7 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 would be achieved in each operating type by 2050.

Statewide PM2.5 Locomotive Emissions by Type

bar chart showing PM by locomotive type

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

Statewide NOx Locomotive Emissions by Type

bar chart showing NOx changes under the proposed regulation

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

Costs and Benefits from the Proposed Regulation

Costs: Staff estimate that the Proposed Regulation would 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 Proposed Regulation would 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 Proposed Regulation. CARB staff estimate $32.0 billion in monetized health benefits.

line graph showing costs and benefits of the proposed regulation from 2023 through 2050, the benefits are greater than the costs in every year of regulation implementation

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 would decrease by over 90%.

bar chart showing decreases in cancer risk due to exposure to locomotive emission under the regulation

Incentive Funding for New Technology

Based on development timelines for new technology, CARB staff estimate that ZE passenger and switch locomotives would be commercially available by 2030, and ZE line haul locomotives by 2035. CARB would release a Locomotive Technology Feasibility Assessment 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.

Next Steps

The Proposed In-Use Locomotive Regulation is anticipated to be presented to the Board in November 2022. For more information on the development of this Proposed Regulation, including opportunities to provide input, visit Locomotives and Railyards: Meetings & Workshops.