California Air Resources Board

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.  

• Class II locomotive operators pull freight over short and medium distances, generally between a small number of states.
• Class III locomotive operators pull freight over short distances, generally between a port and railyard or between a railyard and an industrial client.
• Typically, industrial locomotive operators use locomotives to move freight out to a main track so that it can be connected to a larger train.
• Class III and industrial locomotive operators generally use switch locomotives or “switchers” – locomotives 2,300 horsepower or less.
• As of 2022, the Class III and industrial locomotive populations consist of predominantly Pre-Tier 0 locomotives, which is the oldest and highest-polluting type.
• Class II, Class III, and industrial switchers often idle for long periods, bringing continuous emissions into surrounding communities.

2022 Class II and III Locomotive Population Breakdown by Tier*

*Currently there is a single Tier II locomotive operator working in California, CARB staff have not found sufficient data to characterize this population, therefore it is not included here.

2022 Industrial Locomotive Population Breakdown by Tier

Class II, Class III, and Industrial Operators and 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 must 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 will be able to be used in California.
• Beginning in 2030, all switch and industrial locomotives with an original engine build date of 2030 or newer will be required to operate in a ZE configuration—i.e., qualify as either a ZE locomotive or ZE capable locomotive 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.
• Locomotive activity, emission levels and idling data must be required to be reported annually.

Flexibility in the In-Use Locomotive Regulation for Class III and Industrial Locomotive Operators

• From collaborative discussions with Class III and industrial locomotive operators, CARB staff has developed the Alternative Compliance Plan and the Small Business Hardship Extension.

Alternative Compliance Plan

• Alternative Compliance Plans will be able to be used in lieu of regular compliance pathways for the either Spending Account, the In-Use Operational Requirements, or for both.

Small Business Hardship Extension

• The Small Business Hardship Extension will allow qualifying applicants to be granted a reduced Spending Account payment, a limited extension of eligibility to operate under the In-Use Operational Requirements, or a combination of these relief options. 

Visit the California Locomotives Fact Sheet to learn how the Regulation will apply to all locomotive operators, including industrial operators.

Class III and Industrial Locomotive Emission Reductions Under the In-Use Locomotive Regulation

Class II, III, and industrial diesel-powered locomotives create emissions of particulate matter (PM2.5) and oxides of nitrogen (NOx) which have been shown to be harmful to human health, causing illness and premature death.

Under the Regulation PM emissions from Class III and industrial locomotives are projected to be reduced by approximately 96 percent and 98 percent respectively, and NOx emissions by over 95 percent compared with the baseline scenario.

The significance of bringing just a single switch locomotive to ZE is shown in the graphic below.

PM2.5 Reduction from Bringing One Tier 0+ Switch Locomotive to Zero-Emissions

Class II, Class III, and Industrial Operations and Locomotive Technology

• Because they operate within a smaller area where they will remain close to charging infrastructure, Class III and industrial operations are ideal for battery‑electric locomotive operation. Class III and industrial locomotive operators could provide critical pilot and demonstration opportunities for ZE technology.
• Based on development timelines, CARB staff estimates that ZE switchers used by Class III and industrial operators will be commercially available in limited quantities beginning in 2025, and in greater quantities by 2030; beginning January 1, 2030, Class III and industrial locomotives operating in California with an original engine build date of 2030 or newer will be required to be a ZE locomotive or ZE capable locomotive.

Incentive Funding

CARB offers funding to operators seeking assistance to upgrade or replace locomotives to Tier 4 or ZE. Visit the incentives webpage for more information: CARB Incentives for Locomotives: California Air Resources Board