It’s difficult for the average human mind to fathom what an extremely vast volume like 6 billion gallons even looks like. But, believe it or not, that’s how much fuel vehicles consume annually — when they’re not even running. That figure comes directly from the U.S. Department of Energy’s Alternative Fuels Data Center (AFDC), which has included in its mission strategies for idle reduction.

Naturally, the first step it recommends for managers of medium-duty fleets, is the ever-popular “modify driver behavior.” For medium-duty vehicles that don’t require stationary power, AFDC advises turning off the truck when parked or stopped for more than 10 seconds, except while in traffic. Also, be mindful of no-idle zones, often at schools and other locations.

Beyond those basic behavioral shifts, AFDC recommends various idle reduction technologies. Separate, self-contained air heaters are one option, particularly when the driver is idling to stay warm in the cab. They blow warm air into the cab and use a fraction of the fuel that engine idling does.

To keep the engine warm, the agency suggests installing coolant heaters. The heaters are mounted on the engine compartment, drawing fuel from the tank to heat the truck’s coolant and then pumping it through the engine, radiator and heating box. The technology helps reduce the impact of cold starts.

Even when idling is necessary, there are methods to minimize harmful emissions. Empire Clean Cities, a non-profit that advocates for cleaner air in New York City and the Lower Hudson Valley of New York State, suggests installing an exhaust retrofit device on new or existing engines.

An example of such a device includes a diesel oxidation catalyst, an exhaust after-treatment technology that catalyzes a chemical reaction to break down pollutants by oxidizing hydrocarbons and carbon monoxide into carbon dioxide and water. Another is a passive diesel particulate filter, which is designed to filter out particulate matter from the exhaust of a diesel engine. Then there’s an active diesel particulate filter, designed for low exhaust temperatures or engines with very high emissions of particulate matter.

Meanwhile, there have been some recent developments among OEMs and their technology partners to help address idle-reduction-related issues. Earlier this year, Daimler Truck North America standardized Allison Transmission’s FuelSense 2.0 Neutral at Stop technology for Freightliner and Western Star trucks. The technology is designed to reduce fuel consumption and emissions by reducing or eliminating the load on the engine when the truck is stopped. Neutral at Stop ensures that fuel is used exclusively for movement and not idling.

Volvo Trucks has also been tackling idling issues with recent upgrades to its VNL series. Among those is the addition of a new parking cooler, an integrated climate-control feature that uses battery energy to power the cab’s HVAC unit while parked. It offers automatic restart so that the batteries remain properly charged.

On the flip side, the VNL series also has incorporated parking heaters. Its VNL 300 day cab now includes a short-stop parking heater that allows the driver to turn off the truck and provide heating for up to 30 minutes.

And it’s not just about climate and comfort. The VNL also features a five-minute idle shutdown component, which automatically turns off the engine after five minutes of idling.

The moment the truck stops, the five-minute timer starts.

For more detailed insights on idle reduction strategies, head to adfc.energy.gov and download the fact sheets “Work Truck Idling Reduction.” In addition, the site offers a downloadable worksheet from Argonne National Laboratory that helps fleets calculate idle reduction savings.