Mobile Source Program

Over 70% of the total air pollution in San Diego County is generated from mobile sources. The purpose of the Mobile Source Program is to reduce public exposure to diesel particulate matter (PM) and smog-forming Nitrogen Oxide (NOx) emissions from diesel-powered trucks, buses, and other heavy duty equipment.

What Mobile Equipment Is Regulated and How?

Diesel-fueled trucks and buses greater than 26,000 lbs. must have a diesel particulate filter (DPF) installed or be approved for an exemption. Trucks and buses between 14,001 and 26,000 lbs. must upgrade to a 2010 or newer model year engine based on a compliance schedule.

Senate Bill 1, the Road Repair and Accountability Act of 2017 (SB 1), was signed into law on April 28, 2017.  This bill states that the California Department of Motor Vehicles (DMV) must check that vehicles are compliant with, or exempt from, CARB’s Truck and Bus Regulation. The new DMV compliance verification process will better enforce the regulation and level the playing field for businesses throughout California.

If a vehicle is not compliant with the rule, DMV can no longer register that vehicle. The deadlines are shown below:

January 1st, 2019

DMV automatic enforcement begins.

Light vehicles (14,001 - 26,000 lbs. GVWR) with engine model year 1999 need to be replaced or repowered to a 2010 or newer model year engine.  Please note CARB is already sending letters out to enforce the requirements applicable to these vehicles.

January 1st, 2020

DMV automatic enforcement begins.

Light vehicles (14,001 - 26,000 lbs. GVWR) with engine model year 2004 or older need to be replaced or repowered to a 2010 or newer model year engine.

Heavy vehicles (greater than 26,000 lbs. GVWR) with engine model year 2000 or older need to be replaced or repowered to a 2010 or newer model year engine.

Full Regulation

Regulation Overview

The Truck Stop: California Diesel Truck Info

Heavy-duty trucks and buses are prohibited from emitting smoke over a certain opacity. DPF and DPF monitoring systems must be properly functioning and an emission control label (ECL) verifying that the engine has met Californian emission standards must be affixed to the vehicle's engine.


Regulation Pamphlet

Diesel-fueled vehicles weighing more than 10,000 lbs. are prohibited from idling for greater than 5 minutes unless the engine meets a low-NOx idling emission standard and the truck is labeled with a "Certified Clean Idle" sticker. This sticker is invalid when the truck is idling within a restricted area. School buses and other heavy duty vehicles must turn off the engine immediately upon arriving at a school and depart within 30 seconds of starting the engine.

Full Regulation (Commercial Vehicles)

Commercial Vehicle Fact Sheet

School Bus Idling

School Bus Fact Sheet

Heavy-Duty Diesel Vehicle Idling Information


Diesel-fueled vehicles greater than 26,000 lbs. that transport cargo within ports and intermodal rail yards must meet engine emission standards. All drayage trucks must have a 2007 or newer model year engine.

Full Regulation

Regulation Fact Sheet

The In-Use Off-Road Diesel-Fueled Fleets Regulation (Off-Road Regulation) applies to all self-propelled off-road diesel vehicles 25 horsepower or greater used in California and most two-engine vehicles (except on-road two-engine sweepers). This includes vehicles that are rented or leased (rental or leased fleets). Equipment must be registered under the current owner with the California Air Resources Board(CARB) Diesel Off-Road Online Reporting System (DOORS ).Each vehicle is assigned anEquipment Identification Number (EIN) which must be labeled on both sides of the vehicle. Fleets must meet emission targets.

The California Air Resources Board (CARB) approved amendments to the In-Use Off-Road Diesel-Fueled Fleets Regulation (Off-Road Regulation) on November 17, 2022, aimed at further reducing emissions from the off-road sector.

2022 Amendments Regulatory Language

2022 Amendments Fact Sheet

Off-Road Regulation Knowledge Center

DOORS Resources

DOORS User Guide

ROAR Reporting

Two-engine Vehicles FAQ

  • CARB Online Training

MS504 Online - How to Comply with the Off-Road Regulation - Overview (

Workshops and Meetings | California Air Resources Board

The purpose of the Commercial Harbor Craft regulation is to reduce emissions of oxides of nitrogen (NOx), a key precursor to ozone formation, and diesel particulate matter (PM) from harbor craft engines. San Diego County is not in attainment with a federal and state health-based ground-level ozone standard. Ground-level ozone (or smog) is a respiratory irritant that negatively impacts at-risk people, including children, the elderly, and people with respiratory ailments. Reducing exposure to diesel PM can lower cancer risks and reducing exposure to ground level ozone will help to improve the health of all San Diego County residents and visitors.

2022 CHC Regulation Amendments Approved by Office of Administrative Law, Effective January 1, 2023.

On December 30, 2022, the Office of Administrative Law (OAL) approved amendments to the Commercial Harbor Craft (CHC) Regulation, section 2299.5, title 13, division 3, chapter 5.1 and section 93118.5, title 17, chapter 1, subchapter 7.5 of the California Code of Regulations (CCR). The amended CHC Regulation is effective January 1, 2023.


New Amended Regulation Text

Final Regulation Order (


The amended CHC Regulation will reduce emissions from harbor craft operated near California’s coast and improve public health in nearby communities, many of which are disadvantaged. By 2035, the amended CHC Regulation is expected to result in an 89 percent reduction of diesel particulate matter and a 52 percent reduction in nitrogen oxides. The amended regulation will also reduce the cancer risk to over 22 million residents who live near the coast and up to 50 miles inland.

To assist regulated parties with implementation, CARB staff is preparing several “fact sheet” documents to explain the core requirements of the amended regulation and posting the fact sheets on the CHC Program Factsheet Page as they become available.


Fact Sheets

Commercial Harbor Craft Factsheets | California Air Resources Board


Implementation Dates for the 2022 Amendments to the CHC Regulation

CHC Factsheet: Implementation Timeline | California Air Resources Board

Transport Refrigeration Units (TRU) are refrigeration systems powered by diesel internal combustion engines designed to refrigerate or heat perishable products that are transported in various containers, including truck vans, semi-truck trailers, shipping containers, and railcars.  Although TRU engines are relatively small, ranging from 9 to 36 horsepower, significant numbers of these engines congregate at distribution centers, truck stops, and other facilities, resulting in the potential for health risks to those that live and work nearby.  Since diesel particulate matter (PM) pollutant emissions have been identified as a toxic air contaminant, CARB adopted (on February 26, 2004 with amendments in 2010, 2011, and 2022) an Airborne Toxic Control Measure (ATCM) for TRUs, TRU generator sets, and facilities where TRUs and TRU generator sets operate.

Fact Sheet for 2022 Amendments to the Airborne Toxic Control Measure for In-Use Diesel-Fueled Transport Refrigeration Units (TRU) and TRU Generator Sets, and Facilities Where TRUs Operate (

Hoja informativa de TRU (Español) (

Other General TRU Information

How Do We Ensure Compliance?

The California Health and Safety Code grants District staff the right of entry to conduct inspections and enforce air pollution regulations. District inspectors enforce mobile source requirements through unannounced inspections of on-road and off-road equipment. Inspections of mobile sources may also occur concurrently with inspections of permitted stationary equipment. A Memorandum of Understanding (MOU) was signed with CARB in 2014 designating which regulations the District will enforce. 

A new MOU was signed in 2021 authorizing the District to inspect commercial harbor craft vessels including, but not limited to, ferries, excursion vessels, tugboats (including ocean-going tugs), towboats, push boats, crew and supply vessels, barge and dredge vessels, work boats, pilot vessels, and commercial passenger fishing vessels in San Diego County. A Compliance Advisory was issued on April 14, 2022 to notify vessel operators of these inspections.


How Can I Learn More?

CARB hosts informational trainings about these regulations at various locations throughout the year. To browse the training calendar navigate to the CARB training page, select Log In, then select "Prefer to browse first" under the New Students section.

You can also subscribe to receive CARB Training Updates via email or via text messages.


How Should I Respond to an SDAPCD Citation?

For more information about District violations please see our Violation Information page.


Off-Road Vehicle Violations

Violation Recommended Action
Failure to Report Vehicle in DOORS Register the vehicle to your company in DOORS. If the vehicle has already been assigned an EIN you must move that EIN into your fleet. Vehicles should be registered within two weeks of the citation issuance.
Failure to Display EIN The EIN should be properly displayed on both sides of the vehicle. Send pictures of both sides of the vehicle with the labels in place to the Air Quality Inspector within two weeks of the citation issuance.


TRU Violations

Violation Recommended Action
Failure to Report TRU in ARBER TRUs based in California should register with CARB's Equipment Registration System (ARBER) within 14 days of the citation issuance.
Failure to Display IDN The Identification Number (IDN) of the TRU should be labeled on both sides of the unit. Send pictures of both sides of the TRU with the IDN properly labeled to the Air Quality Inspector within two weeks.
TRU Not Compliant with In-Use Standards Remove from service by following the steps outlined in this CARB Advisory or comply with in-use standard requirements within 30 days of the citation issuance. Send proof of compliance to the Air Quality Inspector.


What Incentives are Offered for Mobile Source Compliance?

For eligible mobile source operators, the District administers a number of grant programs for partially funding the replacement of older engines or vehicles with new, less polluting models. Learn more

Compliance Division Contact

If you have any questions, please contact the SDAPCD Mobile Source Coordinator at or phone at (858) 586-2650.