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Idle time: US drivers waste $21 billion per year while going nowhere
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Idle time: US drivers waste $21 billion per year while going nowhere

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Rick Sapienza lives and breathes automotive efficiency.

As director of the Clean Transportation Program at N.C. State University’s N.C. Clean Energy Center, one of Sapienza’s primary areas of focus is developing technology to improve emission-free vehicles, which will be crucial to slowing climate change.

Sapienza also leads sessions on how individual driving habits can improve fuel efficiency for cars and trucks, including those with traditional combustion engines.

But sometimes, even the experts have a thing or two to learn, he admits.

In Sapienza’s case, a late lesson involved the environmental and economic impact of fuel-powered automobiles whose engines are running while the wheels aren’t turning.

“An idling vehicle gets zero miles per gallon,” he says. “You can’t do any worse than that.”

In the U.S., passenger and commercial vehicles waste about 6 million gallons of fuel and $21 billion per year while going nowhere, according to the U.S. Department of Energy.

About half of that is attributable to idling personal vehicles, which annually generate about 30 million tons of carbon dioxide, a heat-trapping gas that is the leading human-created contributor to climate change. Eliminating that unnecessary idling would be the equivalent of taking 5 million vehicles off the road, the energy department estimates.

Like many statistics related to climate change contributors, those are the kinds of big numbers that can depersonalize the impact of an individual’s carbon footprint.

Sapienza suggests thinking of it another way: Two minutes of idling uses as much fuel as driving a mile.

“If you do it right, you’re saving money,” Sapienza adds. “It might seem like nickels and dimes, but it adds up to big dollars over the life of the vehicle.”

The first step toward changing drivers’ behavior is making them understand how much fuel a running car or truck is using, even when it’s not moving, he explains.

Sapienza’s realization led him to make some simple changes, including avoiding drive-thru windows and drive-up ATMs and shutting his vehicle down while it’s in an automated car wash.

“Once you start doing it, you get a little more enthusiastic about it,” he says of his anti-idling efforts.

Pandemic effect

As it has with many aspects of everyday life, the COVID-19 pandemic has had a dramatic impact on the way we shop, travel and interact in general.

“This is an issue I’ve been thinking more about over the last couple years as you see more folks sitting in drive-thru pickup lines when inside areas were closed,” says Sara Nichols, regional planner with the Regional Land and Sky Council, an Asheville-based nonprofit that partners with local governments on projects and programs aimed at improving communities.

Add mass drive-up COVID-19 immunization and testing clinics, as well as food distribution sites, and lines of exhaust-belching automobiles have become as commonplace as Amazon and FedEx delivery trucks.

“But the overlap of COVID issues has generally been good for mobile source pollutants,” Nichols adds. “We saw more folks working and conducting their life from home. It seems that some of those transitions are here to stay — with more work-from-home jobs, online educational opportunities and increased usage of telehealth — and a better balance … of where and why to travel may be a positive outcome.”

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Warm wishes

But old habits can die hard for those of us who still start the daily grind by climbing into a car or truck.

In North Carolina, a post-New Year’s cold snap created the backdrop for a familiar early-morning scene: empty vehicles, with their engines running, waiting for drivers and passengers to re-emerge from their homes and head to work, school or other destinations.

In most cases, comfort is the goal of such a.m. idle time — to make the trip toasty warm and/or to avoid manually scraping frost, snow or ice from the windshield and windows.

“Yeah, I get that,” Sapienza says.

For the most part, though, other traditional motivations for “warming up the engine” no longer apply.

With most modern vehicles, driving actually helps the engine reach its ideal operating temperature faster.

“Even on the coldest days, most manufacturers recommend avoiding idling and driving off gently after running the vehicle for about 30 seconds,” the energy department advises. “Not only will the engine warm up faster by being ‘at work,’ but the car’s interior will warm up more quickly as well.”

Turning engines off and on — even diesels — does no harm, and starters and batteries are much more durable now than they were in the past, the department adds.

Fleet feat

Emergency responders often leave vehicles running to power lights, instruments and equipment after responding to a call. But technology developed by Sapienza and other researchers has helped to drastically reduce idling time without impacting on-scene operations.

The Charlotte-Mecklenburg EMS Agency has installed idle-reduction devices on more than two-dozen of its 72 ambulances. After a preset period of time, the technology shuts off an idling engine and shifts power to a high-powered, rechargeable battery. Lights, heating and air conditioning systems, and refrigeration units for medications continue to operate normally with auxiliary power.

In 2021, the technology eliminated nearly 46,000 hours of idling time for the vehicles equipped with the devices, says agency spokeswoman Grace Nelson. That led to a savings of more than $69,000 in fuel costs and more than $7,600 that would have been spent on oil and filters, she adds.

The agency estimates the devices reduced its carbon dioxide emissions by 305 tons for the year.

Schools — with stop-and-go bus routes and parents’ vehicles stacked in student pickup lines — also experience extended periods of automobile idle time, Nichols, of the Regional Land and Sky Council, points out. Her organization has worked for years with districts and individual institutions to reduce the effect of running vehicles that are going nowhere.

In 2021, those efforts reduced greenhouse gas emissions by 886 tons for nearly 5,000 vehicles across 11 fleets. But, she admits, “It would be harder to convince folks to reduce idling in the winter when they are sitting in a cold car!”

It shouldn’t be, insists Sapienza.

“Think about it,” he says. “You start the car then go back inside and wait for five minutes when you could have been that far down the road. Your car would have warmed up faster, and you’d get to work faster.”

All while using less fuel and reducing emissions.

“A lot of it is common sense,” he says. “Sitting there isn’t the thing to do.”

John Deem covers climate change and the environment in the Triad and Northwest North Carolina. His work is funded by a grant from the 1Earth Fund and the Z. Smith Reynolds Foundation.



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