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Home / News / Newsfeed / CARB Off-Road Diesel Amendments

CARB Off-Road Diesel Amendments

January 27, 2021
yellow dozer tractor on the right front-hand side of image with an orange dozer tractor in the back left of an image in a field of dirt with a dirt pile in the back left
On November 17, 2022, the California Air Resources Board (CARB) Off-Road Diesel amendments were approved. The amendments do not alter current requirements, but add additional obligations. The regulation applies to off-road diesel vehicles with engines rated at 25 horsepower (hp) or larger, with fleet sizes based on cumulative hp under common ownership in California. Fleets are required to clean up 10% of the fleet hp each year until meeting the final fleet average target (FAT), with excess cleanup points carrying over until 2023 for Medium or Large fleets and 2028 for Small fleets
(see Table 1).
Table 1: Fleet Sizes and Credit Expiry Dates

Size HP Carryover Expires
Small 25-2500 1/1/2028
Medium 2501-5000 1/1/2023
Large Over 5000 1/1/2023

Carryover Credits Restart

After the initial expiry dates in Table 1, carryover will restart and have no expiration.

Renewable Diesel

Starting January 1, 2024, fleets will need to demonstrate via annual fueling records (contracts/receipts) that the fleet and rental off-road vehicles solely use renewable diesel (RD) (R99 or R100). If RD is unavailable, the fleet must maintain quarterly records of attempts to obtain R99 or R100. Fleets will affirm compliance with the RD requirements during each annual report. Captive attainment fleets or fleets solely comprised of Tier 4-Final (T4F) (or cleaner) engines are exempt from RD requirements.

Tier Phase-Outs

Even if meeting its final FAT, every fleet must “phase out” Tiers 0-2 engines by the January 1st deadlines in Table 2, via conversion to permanent low use (200 hours per year) or engine removal from California operations. Only Tier 0 (T0) engines have a “backstop” that will ban all California operations starting in 2036.

Table 2: January 1st Phase-Out Deadlines

Fleet Size 2024 2026 2028 2030 2032 2036
Large T0 T1 T2 T0 Backstop
Medium T0 T1 T2 T0 Backstop
Small T0 T1 T2 T0 Backstop

Minimum Tier for Adding Vehicles

Starting January 1, 2024, there will be new minimum tier requirements for adding vehicles to a fleet, as shown in Table 3.

Table 3: Minimum Tier for Adding Vehicles

Minimum Tier for Adding Vehicles (Applicable January 1st of Each   Calendar Year)
Fleet 2023 2024 2025 2026 2027 2028
Med/Lrg Tier 3 Tier 4- Final (T4-F)
Small* Tier 3 Tier 4-Interim (T4-I) T4-F


Yorke Engineering specializes in air quality and environmental consulting for stationary and mobile sources, including dispersion modeling, health risk assessments, permitting, emission inventories, air quality compliance systems, etc. Yorke Engineering has assisted over 1,800 customers, including a wide variety of industrial facilities and government organizations throughout California. Learn more about how we can help you here: Air Quality | Yorke Engineering, LLC (yorkeengr.com).

Air Quality Tip

As California transitions to zero-emission technologies, companies may want to investigate incentive programs for on-road and off-road vehicle purchases, vehicle replacements, and infrastructure projects. Specific information about funding is available on the local air district websites. Also, plan ahead to source biodiesel.

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