What Is Idling?

When a vehicle’s engine is on but the vehicle is not in motion, it is idling. Sitting at traffic lights, waiting in a running car to pick someone up, trucks idling while their drivers make deliveries or sleep during rest stops - these are all examples of idling.

Why Care About Idling?

Although many individual idling episodes are small, the cumulative impacts of idling are large! Consider that idling in the United States uses more than 6 billion gallons of fuel at a cost of more than $20 billion to consumers and businesses EACH year. Other reasons to reduce idling include the fact that many states and municipalities are adopting stringent anti-idling laws and imposing large fines for those who violate the laws, and that the federal and some state governments offer incentives for those who adopt idling reduction measures.

How Can Idling Time be Reduced?

That depends on the type of vehicle and why it is idling. The good news is that reducing idling time need not compromise driver or passenger comfort.

For light-duty vehicles such as passenger cars, the answer is pretty simple; turn off the engine whenever running it is not truly necessary, such as while waiting to pick up children after school, waiting at long freight train crossings, or waiting for someone at the grocery store. For light-duty vehicles that require more extensive heating and power support, retrofits such as air heaters and auxiliary power systems can fill the gap.

For medium- and heavy-duty vehicles such as tractor-trailer trucks and locomotives, the answer depends a little more on why the vehicle is idling; there is no one-size-fits-all solution to idling. With support from the U.S. Department of Energy, Argonne National Laboratory has pioneered research into the science and economics of reducing idling, resulting in several landmark studies and tools to help drivers and organizations determine the best and most cost-effective ways to reduce the time they idle their vehicles.