Skip to main content

American Idling: The Ecological Cost of Keeping the Engine Running

The quick, simple act of turning your car off instead of idling whenever possible could play an enormous role in slowing the rate of climate change.
  • Author:
  • Updated:

When academics and policymakers consider ways to curtail greenhouse gas emissions, they tend to think in big-picture terms. But quick, simple fixes could play an enormous role in slowing the rate of climate change, and one of the most promising involves an unnecessary, habitual activity most drivers indulge in every day.

According to “Costly Myths,” a paper just published in the journal Energy Policy, Americans idle the engines of their personal car, truck or SUV an average of 16 minutes per day — only half of which involves being stuck in traffic. The remainder is split roughly evenly between “warming up” the engine and waiting to pick up a passenger.

“The CO2 emissions associated with idling accounts for roughly 1.6 percent of the total U.S. (greenhouse gas) emissions,” conclude the researchers, led by psychologist Amanda Carrico of Vanderbilt University. According to their calculations, sitting in place while the engine is running cumulatively wastes more than 10 billion gallons of gasoline each year.

Granted, some of that idling is inevitable (sitting at stoplights), and reducing time spent sitting in traffic is an issue more for urban planners and highway designers than for individual drivers, but subtracting those factors still leaves nearly eight minutes per day spent with the car in park and the engine running. And that environmentally unfriendly behavior can be traced to a combination of bad habits and misinformation.

The researchers conducted an online survey of 1,300 U.S. residents in the fall of 2007 to determine their idling habits. (The average age of the respondents was 43.) The survey yielded not only the statistics cited above, but also a sense of how mistaken people are in their beliefs about idling.

Nearly half of the respondents reported that 30 seconds or more generally elapse between the time they start their vehicles and the time they put them in motion. That means they typically exceed the maximum warm-up time recommended by the Environmental Protection Agency.

As a team led by Vanderbilt law professor Michael Vandenbergh reported in another paper last year, this behavior stems from “a common set of false beliefs that cars need to warm up for a significant time before being driven.

Also on, research suggests being aware of one's environmental footprint could cause an ecological backlash.

“Another is that shutting off the engine briefly and then restarting it consumes more fuel and produces more pollution than allowing the engine to idle. Although this may once have been the case, modern fuel-injected engines need almost no warm-up time, and restarting a warm engine consumes less fuel and emits less pollution than idling for five to 10 seconds.”

This will be news to the driving public. As Carrico and her colleagues note: “The average respondent believed it is better to idle for over three and a half minutes than to turn a vehicle off and restart it when it is time to move. Beliefs regarding idling to reduce vehicle wear and tear were particularly exaggerated, perhaps reflecting outdated information that turning a vehicle off and on again is harder on the engine than allowing it to idle.”

So the bad news is we still believe the myths our fathers taught us when we were learning to drive (which may have been true when he was cruising the boulevard in his ’52 Packard). The good news is that an educational campaign could change people’s behavior — especially if combined with laws restricting the amount of time idling is allowed. True, these statutes would be largely unenforceable, but they could still have an impact: Nothing heightens awareness of traffic laws like the threat of getting a ticket.

“A campaign targeting idling in school parking lots in one Canadian suburb resulted in a 34 percent decline in the number of vehicles observed idling while waiting,” the researchers note. A similar campaign in another Canadian city “reduced the mean duration of idling among residents from 8 to 3.5 minutes.

“A nationwide campaign in the U.S. that achieved similar results would prevent between 7 and 26 million tons of CO2 from entering the atmosphere each year and reduce fuel consumption by 660 million to 2.3 billion gallons a year,” Carrico and company add.

A change in wasteful behavior that will save drivers money while reducing fossil fuel consumption and greenhouse gas emissions would seem to be a win-win-win. But it would be foolish to underestimate the difficulty of getting people to alter their well-established routines, especially when they are based on “wisdom” passed down generationally.

Still, this would clearly be a campaign worth waging. An idle mind may be the devil’s playground, but an idling motor will help make the planet hotter than hell.

Sign up for our free e-newsletter.

Are you on Facebook? Become our fan.

Follow us on Twitter.

Add our news to your site.