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Click a topic from the left sidebar to view available resource documents. These documents answer commonly asked questions regarding the Off-Road Diesel Regulation:


Regulation Overview (English or Español): Explanation of the applicability of the rule and a summary of requirements.


Applicability Flow Chart (English or Español): Determine if your vehicle is covered under the Off-Road Diesel Vehicle Regulation.

General Applicability: Determine if your vehicles are exempt due to the personal use, snow removal, job corps, or other exemptions.

Agricultural Equipment: Equipment used in agricultural operations may have special exemptions in the regulation.

Electric Ground Support Equipment (GSE) at Airports: Electric GSE at airports may be reported for partial credit towards the emissions requirements.

Portable Equipment (English or Español): Self-propelled off-road diesel vehicles that may require registration as portable equipment.

Rail and Track Equipment: How to determine if your rail or track vehicle is covered by the regulation.

Two-Engine Vehicles: How to determine which regulation applies to both engines of two-engine vehicles, including those with an on-road engine.

Workover Rigs: How to determine if your rig is considered a workover rig in the off-road regulation.

Yard Trucks: How to determine which regulation applies to your yard truck.


Emission Factors: Explanation of emission factors, fleet averages, and sample calculations.

Fleet Portions: Explanation of fleet portions and how they report and comply.

Fleet Size - Private Fleets: How to determine fleet size for privately owned fleets.

Fleet Size - Public Fleets: How to determine fleet size for federal, state and local agencies.

Horsepower: Explanation of maximum horsepower and how it can be determined.

Model Year: Explanation of engine model year and how it can be determined.

Specialty Vehicles: Explanation of specialty vehicles and their requirements.


Adding Vehicles (English or Español): Requirements and restrictions on adding vehicles to a fleet.

Best Available Control Technology (BACT): An explanation of one method of satisfying the regulation’s compliance requirements.

Best Available Control Technology (BACT) Exemptions: A way of satisfying the regulation's compliance requirements.

Compliance Overview: Overview of off-road regulation requirements, including those in effect now and future requirements.

Compliance Snapshot: A compliance tool in DOORS that shows a fleet's compliance status.

Early Credit: Types of credit available to fleets before their first compliance year.

Emergency Use: Emergency use vehicles may be exempt from some aspects of the off-road regulation.

Fleet Average: An explanation of one method of complying with the regulation’s emission performance standards.

Low-Use Vehicles: Explanation of the low-use provisions, and how fleets may utilize these provisions to reduce compliance requirements.

New Fleets: Requirements for fleets newly formed in-state or a fleet that enters California.

Off-Road Engine Tier Life: Explanation of the length of time that an off-road engine tier may remain in a fleet.

Optional Compliance Schedule for Fleets with 500 Horsepower or Less (English or Español): Explanation of optional, simpler compliance option for the smallest fleets.

Order of Best Available Control Technology (BACT): An explanation of the order in which turnover must be taken in order to accrue BACT credit.

Potential Fines: Description of potential fines for noncompliance and where fine money goes.

Rental/Leased Vehicles: How to incorporate rental/leased vehicles into the Off-Road Regulation.

Rounding Provision: Explanation of the how the rounding provision works and when it applies.


Reporting Requirements: Explanation of the reporting requirements for all fleets.

Record Keeping: Explanation of the record keeping requirements.

ROAR and Annual Reporting (English or Español): Explanation of the Responsible Official Affirmations of Reporting (ROAR) form and annual reporting requirements for all fleets. 

Transfer of Ownership: Requirements for transferring ownership of a fleet or fleet portion.

Idling Policy Guidance: Information on what fleets should include in their written idling policies.

Labeling Vehicles (English or Español):Requirements for EIN labeling on vehicles, including label specifications.

Awaiting Sale Vehicles: Explanation of how awaiting sale vehicles are treated.

Disclosure: What information must be disclosed to the buyer when selling a vehicle.

Two-Engines Vehicles

Repowers Using On-road Engines: On-road engines may be used in off-road vehicles to lower emissions.

Enforcement Advisory 381: Enforcement of requirements to use on-road certified engines in on-road registered vehicles.


Conditionally Verified DECS: Use of conditionally verified Diesel Emission Control Strategies for compliance with the off-road regulation.

Credit for VDECS: Explanation of the credit available in the regulation for installing verified retrofits.

Excess PM VDECS Credit Provisions: How to install extra or early VDECS under either the off-road or truck and bus regulation to generate excess credits for the other regulation.

Using Unverified Exhaust Retrofits: What to do if you are using an unverified exhaust retrofit.

VDECS: Explanation of what a VDECS is and how they work.

VDECS Removal: What happens if a VDECS fails and/or is removed.

Funding and Other Topics

Incentive Funding: Explanation of how compliance credits are awarded for vehicles/engines/retrofits funded through incentive programs (Moyer, Showcase, SEP and other funds).

Water-Well Drilling: Description of requirements for both in-state and out-of-state two-engine water-well drilling rigs, including the exemptions for those operating exclusively within the Counties of Fresno, Tulare, for emergency purposes, such as a drought State of Emergency.

Captive Attainment Area Fleets: Explanation of compliance and reporting for fleets in the areas of the state with the cleanest air.

Vehicles Used for Parts: Vehicles used for parts may be exempt from some regulatory requirements.

Manufacturer Delays: What to do if equipment needed for compliance is delayed.


Agricultural Crop Preparation Services:
Explanation of requirements for equipment used in agricultural crop preparation services.

Airport Ground Support Equipment (GSE):
Explanation of the different types of airport GSE and requirements.

Equipment Identification Number Labeling:
Explanation of EIN specifications and labeling equipment.

Fleet Average Emission Level Standards:
Explanation of complying with the regulation's emission performance standards.

Limited Hours of Use Equipment:
Explanation of the limited hours of use provision, and how fleets may utilize these provisions to reduce compliance requirements.