Expanding Idling Regulation

The State of California currently has an idling regulation for commercial heavy-duty diesel vehicles and school buses. While passenger vehicles — cars, SUVs, vans, pickup trucks — comprise more than 85% of the vehicles on California's roads, there is no restriction for idling of these vehicles when parked. This has a significant negative impact on air quality, carbon emissions that contribute to climate change, and the wasting of energy. California has stood out as a leader in legislation and regulations to reduce greenhouse gas emissions. But when it comes to idling, California trails seven U.S. states that already have all motor vehicle idling regulations/laws.


Reducing these emissions is more imperative than ever. First are the somber findings in the recent Fourth National Climate Assessment. Second is the Air Resources Board's 2018 Progress Report: California’s Sustainable Communities and Climate Protection Act statement (page four): “California is not on track to meet the greenhouse gas reductions expected under SB 375 for 2020, with emissions from statewide passenger vehicle travel per capita increasing and going in the wrong direction…”. In seeking additional solutions to reduce transportation emissions, the low-hanging fruit opportunity to include passenger vehicles in California's idling regulation can no longer be overlooked.







Idle-Free California strongly advocates for such a regulation statewide. However, if an incremental approach will allow for a quicker result, Idle-Free California advocates for a regulation to address the particularly important issue of idling on school property. Prolonged idling at California's 10,000+ schools during afternoon dismissal has a negative impact on health, particularly for children.






(This would enable an enforceable version of the California legislature's non-binding resolution — ACR 160 — that encourages motorists not to idle where children congregate.)



1. Passenger vehicles, aka light-duty vehicles (LDVs), despite being 98-99% cleaner than in the 1960s, still emit harmful exhaust chemicals that negatively impact air quality and health in the following circumstances:

A. idling engines do not operate at peak temperature causing them to emit more pollution than when traveling

B. in the common practice of excessive stationary warm-ups, the catalytic converter is not functional in converting

    exhaust gas to less toxic pollutants until the vehicle is driven

C. idling caravans, such as in drive-thrus and school dismissals, which cause idling “hot spots”, increase toxicity

    around the vehicles

D. idling exhaust chemicals are exacerbated during weather extremes

E. an out-of-tune vehicle pollutes more

F. and no matter how clean internal combustion engine vehicles are, they still emit about 20 lbs. of CO2 per gallon of

    fuel consumed


2. Commercial heavy-duty diesel powered vehicles emit four timesLos Angeles ozone pollution in 2015 more pollutants than LDVs. But LDVs comprise more than 85% of the vehicles in California


3. The onset of mobile devices has led to greatly increased idling while parked; this has become known as "Smartphone Idling"


4. LDV IDLING AT SCHOOLS negatively impacts the health of students. To help address this issue, California ACR 160 -- Relative to vehicular air pollution -- encourages motorists to not idle their motor vehicles near places where children congregate; an LDV idling regulation on school property would make this non-binding resolution more effective


Further, the EPA states, "Idling vehicles contribute to air pollution and emit air toxins, which are pollutants known or suspected to cause cancer or other serious health effects. Monitoring at schools has shown elevated levels of benzene, formaldehyde, acetaldehyde and other air toxics during the afternoon hour coinciding with parents picking up their children. Children’s lungs are still developing, and when they are exposed to elevated levels of these pollutants, children have an increased risk of developing asthma, respiratory problems and other adverse health effects. Limiting a vehicle’s idling time can dramatically reduce these pollutants and children’s exposure to them."


5. An all motor vehicle regulation would provide recourse for those affected by prolonged idling of LDVs in neighborhoods, schools, etc.


6. An all motor vehicle regulation will make all motorists responsible - more equitable than targeting commercial vehicles alone


7. Financial impacts of idling:

A. Idling actually gets negative MPG. The average LDV consumes .375 gallons of fuel an hour. With gasoline at $3.25 a gallon, needlessly idling while parked for 15 minutes a day can consume $75 to more than $200 a year

B. Idling puts "ghost miles" on an engine causing needless wear including carbon soot buildup on engine components, shortening the life of motor oil, spark plugs, and exhaust system


8. Many vehicle owners' manuals advise limiting idling


9. Idling LDVs are here to stay: despite California being a leader in sales of non-idling hybrid and electric vehicles, more than 90% of California vehicles sold in 2015 and 2016 are powered by conventional internal combustion engines


10. Reducing idling of LDVs will help California meet requirements in AB 32 to reduce its GHG emissions to 1990 levels by 2020


11. Seven U.S. states have all motor vehicle regulations/laws: Connecticut, Hawaii, Maryland, Massachusetts, New Hampshire, New Jersey (gasoline), New Jersey (diesel), Vermont


12. In California it can be estimated that idling of all vehicles when parked emit 2.7 million tons of carbon dioxide annually, in the process consuming 270 million gallons of fuel; conservatively, about one half of this is attributable to LDVs.*



• The U.S. Dept. of Transportation - Office of Highway Policy Information - Motor Fuel Use - 2018: U.S. fuel consumption 180,737,076,000 gallons

• The U.S. Dept. of Energy originally stated in 2012 and maintains today: "Each year, U.S. passenger cars, light-duty trucks, medium-duty trucks, and heavy-duty vehicles consume more than 6 billion gallons of diesel fuel and gasoline—without even moving. Roughly half of that fuel is wasted by passenger vehicles."



•The U.S. Dept. of Transportation - Office of Highway Policy Information - Motor Fuel Use - 2018 - California fuel consumption 18,010,964,000 gallons

• Factor that decreases idling in California since 2012 U.S. DOE statement: as of the 3rd quarter of 2019, 7.9% of all vehicles in California are plug-in hybrid and electric. Additionally, hybrid sales are higher in CA than the rest of the country; this represents an approximately 10% idling decease in CA than nationally

• Factors that increase idling in California (and elsewhere) since 2012 U.S. DOE statement: nearly 5% increase in vehicle fuel use statewide; in-vehicle behaviors such as use of devices like smartphones; door-to-door delivery and ride-hailing services

• Putting this all together (in lieu of no far ranging studies on vehicle idling in California), based on U.S. overall transportation fuel consumption vs U.S. vehicle idling fuel consumption, it is estimated that all vehicles in California consume approximately 600 million gallons of fuel when idling annually. This results in six million tons of CO2 emitted by all idling vehicles in the state. This equates to idling in California being approximately 10% of idling nationally.


Studies show that about one-half of all idling occurs when parked (not in traffic).1, 2. Therefore, it is estimated all vehicles idling when parked in California consume 300 million gallons of fuel, resulting in three million tons of CO2 emissions. MOST OF THIS IDLING IS CONSIDERED UNNECESSARY.


IDLING PERCENTAGE: all vehicle idling (in traffic and when parked) is estimated to be 3.4% of all vehicle fuel consumption/emissions; vehicles idling when parked is estimated to be 1.7%.


1Vanderbilt University study: Costly myths: An analysis of idling beliefs and behavior in personal motor vehicles (p.4). "...the average American idles for roughly 16 min a day. Over 51%...can be accounted for by individuals idling while in traffic...the remaining 49%...results from idling to warm and while waiting, both of which are avoidable and, in many cases, unnecessary."

2University of Vermont study: Passenger vehicle idling in Vermont (p.25): "Discretionary idling is a large enough percent of all idling in Vermont (approximately half) to suggest policies to pursue behavior change over purely vehicle technologies which eliminate all idling emissions by turning off during travel and at stops."

The State of California's idling regulation for commercial heavy-duty diesel vehicles and school buses limits idling to five minutes. For a passenger vehicle statewide idling regulation, Idle-Free California recommends a three-minute idling limit; for a school property only passenger vehicle idling regulation, a 30-second idling limit (with exceptions). For a school property only passenger vehicle idling regulation, Idle-Free California proposes a mandate for the installation of NO IDLING signage at all schools.


To be effective, an all vehicle idling regulation will require more than just enforcement. It will require a low-cost but far reaching educational campaign by a State of California agency. This will also need to include education from various sectors, including air districts, health and environmental organizations, and schools.