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Mobile Source Regulations

Yorke Engineering has assisted well over 100 fleets with navigating the statewide and regional mobile source regulations that impact their operations. Our services include determining which mobile source regulations apply to the fleet, evaluating current compliance statuses with each applicable regulation, strategizing long-term compliance strategies, and assisting with reporting in the Diesel Off-Road Online Reporting System (DOORS); Truck Regulations, Upload, and Compliance Reporting System (TRUCRS); and the South Coast Air Quality Management District’s (SCAQMD’s) Program Online Portal (POP).

Advanced Clean Fleets (ACF)

The California Air Resources Board (CARB) has approved the next phase of regulations that will require the transition of fuel-based on-road vehicles to Zero Emission technologies, such as battery-electric and hydrogen fuel-cell vehicles, with initial requirements starting as early as January 1, 2024. CARB’s Advanced Clean Truck (ACT) regulation (established in 2021) requires manufacturers selling trucks in California to meet annual Zero Emission Vehicle (ZEV) or Near-Zero Emission Vehicle (NZEV) sales goals starting in 2024. Yorke has assisted dozens of “large entities” with operations in California to submit the required one-time report in 2021 on the Class 2b-8 vehicles of all fuel types that they own or direct in California. The following large entities will become subject to one of the fleet sections of the ACF regulations:

  • ACF Drayage trucks;
  • ACF State and Local Government (SLG) Agency fleets; and
  • ACF High Priority (private) and Federal (HPF) fleets.

Yorke has been tracking the development of the ACF regulation and it is slated to become law in 2023. To learn more about this suite of regulations, visit CARB’s website for the Advanced Clean Fleet program.

On-Road Heavy-Duty Vehicles and Fleets

Diesel vehicles with a gross vehicle weight rating (GVWR) greater than 14,000 pounds have distinct fleet requirements in California. Yorke has assisted fleets of varying sizes, including everything from small fleets with fewer than three vehicles to large fleets with over 1,000 vehicles. A few of the typical tasks we commonly perform are shown below as examples:

  • Compliance assessments and long-term compliance planning for companies subject to the Truck and Bus Regulation;
  • TRUCRS reporting assistance to demonstrate compliance with the flexibility options of the Truck and Bus Regulation, including low-use, emergency use, NOx-exempt area operations, heavy-crane, low-mileage work truck, phase-in, and agricultural provisions and exemptions;
  • Compliance support for the CARB Fleet Rule for Public Agencies and Utilities (PAU);
  • Compliance support for SCAQMD Public Fleet Rules (such as Rule 1186.1, 1191, and 1196);
  • Assisting with smoke test requirements, including the transition from the Periodic Smoke Inspection Program (PSIP) to the “Clean Truck Check” Program, also known as the Heavy-Duty Inspection and Maintenance (HD I&M) Program;
  • Assistance with overlapping on-road regulatory requirements, such as smoke test requirements, fleet compliance with historic regulations, and transitioning to the new ACF rules (see ACF section above);
  • Funding assistance, such as Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project) (HVIP) (see Funding section below);
  • Assisting with CARB fleet audits; and
  • Assisting with notices of non-compliance (such as DMV renewal holds).

Off-Road Diesel Fleets

In total, our clients have well over 250,000 horsepower (hp) in off-road diesel equipment. Some facilities have only a handful of equipment, and others have more than 50 pieces of equipment. No matter the fleet size, Yorke can help bridge the gap between CARB compliance requirements and a facility’s equipment maintenance management strategies. A few of the typical tasks we commonly perform are shown below as examples:

  • Fleet average and Best Available Control Technology (BACT) compliance calculations;
  • Long-term compliance planning, including beyond 2023;
  • DOORS reporting assistance;
  • Low-use tracking and strategies;
  • Flex engine reporting;
  • Agricultural provisions and exemptions;
  • Cargo handling equipment compliance assistance for operations at a Port or Intermodal Railyard;
  • Funding assistance, such as California Clean Off-Road Equipment (CORE) (see Funding section below); and
  • Preparing for the next phase of regulatory requirements due to the approved Amendments (November 2022), anticipated to become law in 2023, with the first set of amendment requirements to begin on January 1, 2024. The amendments include tier phase-outs and requirements for renewable diesel.

Large Spark-Ignition (LSI)

Yorke has assessed over 500 pieces of LSI equipment and found exemptions for about 15% of them. Yorke reported well over 350 LSI forklifts into DOORS for the initial reporting requirement that began on June 30, 2017. A few of the typical tasks we commonly perform are shown below as examples:

  • Fleet assessments and compliance strategizing;
  • Fleet average calculations;
  • Low-use tracking and strategies;
  • DOORS reporting assistance;
  • Agricultural provisions and exemptions; and
  • Preparing for the next phase of Zero Emission Forklift Fleet regulatory requirements (CARB intends to vote in 2023).


Since 2018 and the advent of AB 617, the push for funding for cleaner mobile sources has increased significantly. Yorke can help navigate funding programs to find potential opportunities that suit each facility’s operational needs, as well as assist with the application process. Some of the most common funding programs include:

  • HVIP;
  • CORE Voucher Incentive Program;
  • Carl Moyer Program Funding for Vehicle Replacement or Engine Repower (statewide funding with project types and timelines that vary by air district);
  • Carl Moyer Program Funding for Zero Emission Infrastructure;
  • EnergIIZE for ZE Infrastructure;
  • Funding Agricultural Replacement Measures for Emission Reductions (FARMER) program;
  • Surplus Off-Road Opt-In for NOx (SOON) Funding Assistance for very large fleets (over 5,000 hp) operating in the South Coast Air Basin;
  • Proposition 1B Goods Movement; and
  • Volkswagen (VW) Mitigation Funds, available statewide in a variety of categories, such as ZEV replacement, zero emission infrastructure, zero emission forklifts, etc.

Additional Mobile Source Regulations and Projects

Yorke has experience with a wide variety of fleets in both the public and private sectors. Below are examples of additional programs we also support.

  • SCAQMD Indirect Source Rules (ISRs) for Facility-Based Mobile Source Measures (FBMSMs), including Warehouse Rule 2305;
  • Transport Refrigerated Unit (TRU) regulation;
  • Cargo Handling Equipment (CHE) regulation;
  • Commercial Harbor Craft regulation;
  • Ocean Going Vessel (OGV) At Berth regulation;
  • Locomotive regulation;
  • Port-related studies and support;
  • EMFAC and OFFROAD modeling; and
  • Emission Inventory Reporting (EIR) emissions quantification and mitigation strategies.

Main Office:

31726 Rancho Viejo Rd. Suite 218
San Juan Capistrano, CA 92675

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