Diesel Enforcement Programs

This page last reviewed July 11, 2019

Statewide Truck and Bus Regulation

Link to the regulation: Statewide Truck and Bus Regulation

TruckStop website:
Truck Stop and truck and bus reporting
Or telephone: 1-866-6-DIESEL (1-866-634-3735).

Heavy-Duty Diesel Emission Control Label (ECL) Inspection Program

Commercial vehicles (trucks and buses) from Mexico and the U.S. have been subjected to travel limitations outside their own borders to a 20-mile commercial zone within the other country. The implementation of the transportation provisions of NAFTA will lift this moratorium and vehicles, including those from Canada, will be allowed to travel freely in either country. The ARB requires the engine of a Heavy-Duty vehicle to meet the federal and/or California emission standard applicable to the engine's model year at the time of manufacture. For more information, you may view relevant documents at the Heavy-Duty Diesel Emission Control Label (ECL) Inspection Program web site.

Idling Programs:

Commercial Vehicle Idling

A driver of a diesel-fueled motor vehicle with a gross vehicle weight rating (GVWR) greater than 10,000 pounds is prohibited from idling the vehicle's primary engine for more than 5 minutes at any location. For more information, please visit the Heavy-Duty Vehicle Idling Emission Reduction Program web page or contact Hortencia Mora at (626) 350-6590.

For an overview of California’s heavy-duty commercial diesel vehicle idling regulations and steps that cities can take to address unnecessary idling, please see "Options for Cities to Mitigate Heavy-duty Vehicle Idling".

School Bus Idling

Idling school buses and other heavy-duty equipment are now restricted in order to protect the health of children. Children riding in and playing near school buses and other commercial motor vehicles are exposed to a disproportionate level of pollutants from these sources. This measure requires the driver of a school bus, transit bus or other commercial heavy-duty vehicle to minimize idling at schools. Additional idling restrictions are imposed for such vehicles stopping within 100 feet of a school. For more information, please visit the School Bus Idling Airborne Toxic Control Measure web page, or contact Cynthia Ortiz at (626) 459-4322.

Periodic Smoke Inspection Program (PSIP)

The Periodic Smoke Inspection “Fleet” Program (PSIP) requires that diesel and bus fleet owners conduct annual smoke opacity inspections of their vehicles and repair vehicles with excessive smoke emissions. The ARB randomly audits the maintenance and inspection records of fleets and tests a representative sample of vehicles. All vehicles that do not pass the test must be repaired and retested. Fleet owners who neglect to perform the annual smoke opacity inspection on applicable vehicles are subject to penalties of $500.00 per vehicle, per year. For more information, please contact Tim Hartigan at at Tim.Hartigan@arb.ca.gov or at (916) 229-0504.

Announcement: New Opacity Standard Adopted in 2018 / New Training Required

In July 2018, the California Air Resources Board (CARB) approved amendments to the HDVIP and PSIP regulations, which require heavy-duty vehicles to meet a more stringent opacity limit of 5 percent opacity for most vehicles.  The new opacity limit goes into effect July 1, 2019.   


The new regulation requires persons who conduct PSIP opacity testing to obtain a CARB-approved smoke tester identification number.  To obtain this number, fleet owners or employees who conduct opacity tests on their own vehicles are required to take an online course, which will be offered at no cost through CARB’s website.  Non-fleet test operators who offer opacity test services to fleets are required to attend an in-person course (CCDET I or an equivalent course that has received CARB approval).  Current tester certificates will remain valid through the certificates expiration date.  All tests must adhere to the amended regulation requirements as of July 1, 2019.  In-person courses are currently available (http://ccdet.org/class-schedule/) and the online course will be available soon.  CARB will update this announcement when the online training becomes available.


For further information, please contact Tim Hartigan at Tim.Hartigan@arb.ca.gov or at (916) 229-0504.

Software Upgrade for Diesel Trucks (REFLASH)

Low NOx software upgrade is computer programming which reduces excess emissions of oxides of nitrogen (NOx) in 1993-1998 model year heavy-duty trucks, school buses, and motor homes with engines manufactured by Caterpillar, Cummins, Detroit Diesel Corporation, Mack/Renault, Volvo and International. The software is required to be installed during rebuilds of the engines listed above; however, ARB encourages voluntary efforts to have the software installed prior to engine rebuild. Engine manufacturers, working through their authorized dealers, distributors and repair facilities, will make available and install at no charge Low NOx Rebuild Kits in all covered Low NOx Rebuild Engines whenever requested or agreed to by any owner/operator of any reflashable vehicle in California. For more information, please view our Software Upgrade for Diesel Trucks web page.

Solid Waste Collection Vehicle Program

In an effort to reduce toxic particulate matter (PM) emissions, the Air Resources Board has implemented the Solid Waste Collection Vehicle (SWCV) Regulation. Owners of solid waste collection vehicles or diesel-fueled trucks with over 14,000 pounds gross vehicle weight, with model-year engines from 1960 to 2006, used to collect residential and commercial solid waste, are required to use Best Available Control Technology (BACT) for reducing diesel PM. For more information, please view our Solid Waste Collection Vehicle Rule web page, or contact Stephen Binning at (916) 229-0542.

Transport Refrigeration Units

ARB will require all transport refrigeration units (TRU) and TRU gensets that operate in California, regardless of where they are based, to meet in-use performance standards for particulate matter for model year 2001 and older units, beginning December 31, 2008. In-use performance standards for model year 2002 and subsequent engines must be met by December 31st of the 7th year after the date of manufacture. The level of the in-use performance standard for particulate matter depends on the model year. In addition, owners of California-based TRUs and TRU gensets must apply for an ARB Identification Number (IDN) by January 31, 2009; and All operators of California-based TRUs must submit an Operator Report no later than January 31, 2009. For more information, please visit the Transport Refrigeration Unit ATCM web page. You may also search ARB’s Equipment Registration (ARBER) system for the compliance status of TRUs and TRU generator sets by visiting the TRU Compliance Search Page.

Mobile Vehicle Diesel Programs