How idling your vehicle - even for just a few seconds - contributes to climate change

While many of us are accustomed to idling our cars while we wait as a train passes by, in line at the end of a school day or in the morning to warm up our vehicles, the habit creates more smog and greenhouse gases than we might think.

Limiting the practice, scientists say, could have a measurable impact on the health of the environment.

Idling for more than just 10 seconds produces more emissions - and uses more fuel - than stopping and restarting your engine does, according to the U.S. Department of Energy.

Personal vehicles create around 30 million tons of carbon dioxide annually just by idling.

"While the impact of idling may be small on a per-car basis, the impact of the 250 million personal vehicles in the U.S. adds up," the Department states. "For saving fuel and reducing emissions, eliminating the unnecessary idling of personal vehicles would be the same as taking 5 million vehicles off the roads."

In terms of fuel, researchers estimate idling from heavy-duty and light-duty vehicles combined wastes about 6 billion gallons of fuel annually, about half of which can be attributed to personal vehicles, according to the department.

The tailpipe emissions gas-powered cars emit while idling also contribute to ground-level ozone air pollution - more commonly known as smog.

"We're concerned about vehicles for burning gasoline in part because the carbon dioxide they produce affects climate, but also because they produce nitrogen oxides and hydrocarbons and particles, all of which can be harmful to human health directly as pollutants," said Donald Wuebbles, a climate scientist at the University of Illinois at Urbana-Champaign.

This is a potent concern in the Chicago area, one of the worst regions in the country for air pollution. In July, the American Lung Association ranked the Chicago metro area ​​16th out of 226 areas in average days per year with high ozone.

Wuebbles, who co-led a 2021 statewide climate change assessment, added that stronger winds in the Chicago region help alleviate the smog issue for the area, but higher temperatures make air quality worse.

"The warming climate is going to make air quality worse because those reactions that form ozone are temperature-dependent," he said. "If the emissions would remain constant, with the number of vehicles going up and the amount per vehicles remaining constant, then the ozone issue and the particle issue would both get worse because of the changes in climate."

While many newer vehicles already automatically stop and restart at traffic lights, people can take further steps to reduce idling by manually turning off their vehicle when having to wait for an extended period of time.

To ease our reliance on cars generally, there's a range of actions the state, municipalities, public transportation organizations and individuals can take, said Jim Merrell, the advocacy director at Active Transportation Alliance.

While a lot of our dependence on cars stems from structural problems, or is affected by ability, income level or where we live, we do have options or choices, Merrell said.

People can start by asking themselves what trips they usually make, such as to and from school, work and the grocery store, and looking into alternatives, whether it's walking, riding a bike or using public transportation.

"Even just replacing one of those trips and finding an alternative mode can really help people build up their alternative transportation muscles," Merrell said.

At the community level, Merrell added that schools and municipalities can take steps to form travel plans that both include and prioritize walking and biking.

"It doesn't all have to start with building a new train or transforming every street. It could be simpler things. Related to idling, a lot of schools will have what they call a school travel plan," he said. "The plan starts a conversation at your school about how kids and staff and parents are arriving to and from the school, and then explores alternatives to just the car-oriented options."

Creative group solutions include a walking or biking "school bus," where a group of people walk or bike to school together and, just like a regular bus, pick people up along the way.

With municipalities, Merrell said one solution lies in having the right plans in place, such as one that identifies and prioritizes projects to improve walking and biking for your community.

"Often, a lot of municipal governments are really short-staffed and don't have the people power to be able to develop all those plans. That's another kind of structural barrier: How can we support particularly the higher-needs communities in developing these walking and biking plans and accessing the money that's out there?" he said.

Another consideration is having land use policies that works in tandem with pedestrian- and biker-friendly initiatives, because they're less effective if municipalities approve housing developments in locations without access to walkable and bikeable infrastructure.

"In suburban communities where the land use is often so car-oriented, that's part of a trap that we fall into, the way we decide where to put things," Merrell said. "Oftentimes, building more dense housing or dense amenities is prohibited by antiquated zoning laws, but those two things go hand in hand - transportation infrastructure and having development that supports walkable, livable communities."

• Jenny Whidden is a Report For America corps member covering climate change and the environment for the Daily Herald. To help support her work with a tax-deductible donation, see

  Cars idle last week in Chicago. Experts say idling vehicles contribute both to increased pollution and to long-term climate change issues. Brian Hill/
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