Idling Regulations

California has regulations that restricts the idling of heavy-duty vehicles.


Why Idling regulations? The California Air Resources Board (CARB) states: "Emissions from on-road heavy-duty vehicles are major contributors to poor air quality in California. In particular, diesel vehicles produce emissions in amounts highly disproportionate to the total population of these vehicles. The problem is complicated by the large number of heavy-duty vehicles, like line haul trucks, registered in other states that travel on California's highways and roads, while bringing goods and commerce into and out of our state. The Air Resources Board is working closely with the U.S. Environmental Protection Agency, engine and vehicle manufacturers, and other interested parties to address this issue and reduce heavy-duty vehicle emissions in California. Although this program targets both diesel-cycle and otto-cycle engines, more recent attention has been focused on diesel engines due to the identification of diesel PM1 as a known carcinogen."


In addition to the issue of air quality, there is CO2 emissions that contribute to climate change. In California, it is estimated that parked idling of all motor vehicles emit three million tons of CO2 annually2


California Air Resources Board (CARB) FACTSHEET:
Breathe easier, California! Turn off your engine.

California Idling Regulations


• Airborne Toxic Control Measure to Limit Diesel-Fueled Commercial Motor Vehicle Idling. This measure requires, among other things, that drivers of diesel-fueled commercial motor vehicles with gross vehicle weight ratings greater than 10,000 pounds, including buses and sleeper berth equipped trucks, not idle the vehicle’s primary diesel engine longer than five minutes at any location. Violation penalty: $300

CARB webpage on measure

Full language of measure


• School Bus Idling Airborne Toxic Control Measure. This measure limits school bus idling and idling at or near schools to only when necessary for safety or operational concerns. The program targets school buses, school pupil activity buses, youth buses, paratransit vehicles, transit buses, and heavy-duty commercial motor vehicles that operate at or near schools. Violation penalty: $300

Full language of measure as revised and enacted in Senate Bill No. 124, effective Jan. 1, 2010


CARB 2020 ANNUAL ENFORCEMENT REPORT including for Heavy-duty Diesel Program Field Inspections, Commercial Vehicle Idling Program. In 2020, CARB closed 90 heavy-duty vehicle idling citations for $30,100. "Staff inspected 7,010 idling trucks in 2020, approximately a 37% increase over 2019. 5,383 of these inspections (76%) occurred in disadvantaged communities, and others occurred at truck stops and similar locations. Results of our inspections are consistent with previous years, and show that approximately 3% percent of all idling trucks inspected by CARB are in violation of our idling regulations. Furthermore, these results do not appear to vary significantly across most communities. This means that when we identify idling trucks in communities, 97% of the time this idling is compliant with CARB regulations." NOTE THAT EACH OF THESE CARB COMPLIANT IDLING TRUCKS—NEARLY ONE MILLION—STILL EMIT ABOUT 22.38 POUNDS OF CO2 PER GALLON OF DIESEL FUEL CONSUMED.


• Idling limits for owners, operators, renters or lessees of in-use off-road diesel vehicles. The Off-road regulation is designed to reduce harmful emissions from diesel powered construction and mining vehicles operating in California. Fleet owners are subject to retrofit or accelerated replacement/repower requirements for which ARB must obtain authorization prior to enforcement from the United States Environmental Protection agency under the federal Clean Air Act. However, the Off-road regulation also imposes idling limitations on owners, operators, renters or lessees of off-road diesel vehicles, which the ARB is authorized to enforce. Violation penalty: up to $10,000 a day.

Full language of this measure.

Written idling policy requirements related to this measure.


California Laws/Regulations Related to Idling


Stopping, Standing, and Parking [motor on while unattended] 22515. ALL MOTOR VEHICLES.

(a) No person driving, or in control of, or in charge of, a motor vehicle shall permit it to stand on any highway unattended without first effectively setting the brakes thereon and stopping the motor thereof.

(b) No person in control of, or in charge of, any vehicle, other than a motor vehicle, shall permit it to stand on any highway without first effectively setting the brakes thereon, or blocking the wheels thereof, to effectively prevent the

 movement of the vehicle.

NOTE: this law only applies to vehicles on a highway, not while parked in a lot or elsewhere.


Some cities/municipalities may have more explicit ordinances for vehicles running while unattended, such as City of Sacramento code 10.36.090 Leaving ignition key in unattended vehicle prohibited: "It is unlawful and a misdemeanor for any person driving or in charge of a motor vehicle to permit it to stand unattended in any public place, or any used or new car lot, or private or public parking lot, without first stopping the engine, locking the ignition and removing the ignition key from the vehicle."


Heavy-duty diesel smoke emission testing, and heavy-duty vehicle emission control system inspections. Violation penalty: up to $1,800.

Full language of this measure.

California Idling Regulations

1Particulate matter: the black soot that emanates from a diesel vehicle's exhaust (note that due to EPA mandated emission controls, properly maintained diesels manufactured from 2010 emit much less PM).


2U.S. Dept. of Energy: "Researchers estimate that idling from heavy-duty and light-duty vehicles combined [in the U.S.] wastes about 6 billion gallons of fuel annually." Studies conclude that about half of all idling occurs when parked (not in traffic). For California, then, it is estimated that idling when parked emits three million tons of carbon dioxide, in the process consuming 300 million gallons of fuel.

Complaint Forms: Vehicle Idling, Smoking Vehicles

Report commercial vehicle idling, or school buses or commercial vehicles at or near school (vehicle must be greater than 10,000 lbs.): Idling commercial vehicles are detrimental to California's air quality. You can help reduce the harmful air pollutants caused by idling vehicles by completing a complaint form. The ARB will be in contact with the vehicle owner to address the issue. To reach the ARB's Vehicle Complaint Hotline, please call 1-800-363-7664 or 1-800-END-SMOG.



Report smoking vehicle (ANY motorized vehicle): Smoking vehicles are detrimental to California's air quality. Here's how you can help reduce harmful air pollutants caused by smoking vehicles:

• Keep up the maintenance on your own car, truck, or other vehicle. A well-maintained vehicle is a cleaner-running vehicle.

• Report smoking vehicles (ANY MOTOR VEHICLE: CAR, SUV, PICKUP, HEAVY-DUTY TRUCK OR BUS) on the roadway.

Call the Air Resources Board or local Air Pollution Control District:

Air Resources Board (throughout California) 1-800-END-SMOG

Bay Area AQMD 1-800-EXHAUST

San Diego County APCD 1-800-28-SMOKE

San Joaquin Valley Unified APCD 1-800-559-9AIR

Shasta County AQMD 1-888-249-SMOG

South Coast AQMD 1-800-CUT-SMOG

Ventura County APCD 1-800-559-SMOG

ONLINE SMOKING VEHICLE COMPLAINT (includes link to complaint form)

Call CARB Vehicle Complaint Hotline:

1-800-END-SMOG (1-800-363-7664)

Please have the following information ready to report:

Vehicle type

• License plate number

• Date, time, and location of the incident

• Make and model of the vehicle




• American Transportation Research Institute (ATRI) Compendium of Idling Regulations (October 2021)

• U.S. Dept. of Energy Clean Cities IdleBase (scroll down to Idle Reduction Policies subhead to download IdleBase Excel document) contains information about known laws for all classes of on-road vehicles.


• States (7) with regulations or laws for all motor vehicles: Connecticut, Hawaii, Massachusetts, Maryland, New Hampshire, New Jersey, Vermont. NOTE THAT THE STATE OF CALIFORNIA DOES NOT HAVE AN ALL MOTOR VEHICLE IDLING REGULATION

Washington D.C. all motor vehicles

New York City all motor vehicles

• States (11) with regulations/laws for commercial diesel or all diesel vehicles: California, Delaware, Maine, Nevada, New York, Oregon, Pennsylvania, Rhode Island, South Carolina, Virginia, West Virginia

• 12 additional states have jurisdictional regulations

Idling Regulations and Laws: Other States



The following California municipalities are known to have non-binding vehicle idling ordinances and policies that extend beyond the State of California idling regulations by incorporating light-duty vehicles:

COMMERCE: initiative

CUPERTINO: Climate Action Plan (extracted pages pertaining to anti-idling policy)

PALO ALTO: Palo Alto Municipal Code to Regulate Unnecessary Idling of Vehicles

SAN JOSE: Green Fleets Policy (includes idle reduction)

SANTA BARBARA: Sustainability Action Plan (extracted pages pertaining to vehicle anti-idling policy)

SANTA BARBARA: Municipal Code: Title 10: Transportation and Parking 10.48.095 Idling of Parked Vehicles

SANTA CRUZ: Anti-idling ordinance

In addition, an unknown number of municipalities have ordinances banning drive-thrus to reduce vehicle idling.



California Assembly Concurrent Resolution to protect children from vehicular idling

In 2016, the California legislature took an important step on behalf of school student health by adopting ACR 160. Sponsored by assemblymember David Hadley, this resolution addresses the issue of vehicular air pollution, specifically motor vehicle idling and children. This measure encourages motorists to not idle their motor vehicles near places where children congregate.

California Idling Ordinances, Policies, Resolutions


Why it is time for the State of California to extend the diesel commercial vehicle idling regulation to include light-duty vehicles.


Visit the Expanding Idling Regulation page for details!