According to the Alternative Fuels and Advanced Vehicles Data Center, approximately 500,000 long-haul trucks cross U.S. highways each day. When truckers rest at the end of the day (about 10 hours per day), they idle their engines during rest periods to provide heat, air-conditioning, and electrical power, using approximately 838 million gallons of fuel per year on idling alone. When the idling of these vehicles is added to that of light- and medium- duty vehicles and school buses, annual fuel use due to idling approaches 3 billion gallons.

Idle reduction consists of strategies to help reduce this idling time for heavy-duty vehicles, but can also apply to light- and medium-duty vehicles, as well. They are many benefits to idle reduction, including money and fuel savings, reduced engine wear, and reduced emissions.

Idle Reduction: Heavy Duty Vehicles

Air Conditioners: Special air conditioners to cool just the sleeper cab are now available. These are often battery powered and help eliminate emissions caused by idling. Some systems use evaporative cooling, and researchers are working on other systems using thermal storage. Options are also available that cool the bed alone. Automatic Engine Stop-Start Controls: Automatic Engine Stop-Start Controls sense sleeper temperature and adjust accordingly by turning the engine on or off. During milder climate, this can be very effective to reduce idling. However, during more extreme temperatures, there is minimal fuel savings and emissions reduction resulting from the engine being on longer. In addition, the engine turning on and off may disturb sleep.

Auxiliary Power Units (APUs): APUs eliminate idling by providing power and climate control to heavy-duty vehicles without keeping the truck’s engine running. They are usually powered by small internal combustion diesel engines which then activate power generators and heat-recovery systems, though some APUs are now being designed to use hydrogen fuel cells instead of diesel. Simpler APUs are direct-fire heaters that only provide climate control. APUs reduce harmful emissions and noise pollution caused by long-term idling. They also help save on the cost of fuel and engine maintenance. APUs are proven idle-reducing technology and are widely available to the public. For a list of available APUs and their suppliers, please visit the the US EPA's Smartway page.

Cab and Block Heaters: Fuel-fired heaters provide heat to the cab and the engine block. They are separate technology from the vehicle’s primary engine, and thus only use a fraction of the fuel that would be used by idling. These heaters can also be paired with cooling technologies for a complete heating and cooling package.

Cylinder Deactivation: Cylinder deactivation limits combustion to part of the engine, allowing a small reduction of fuel use and emissions. It is most often used during light-load operation when the driver is only using a fraction of the engine’s maximum power. Unfortunately this equipment is not currently commercially available.

Truck Stop Electrification: Truck Stop Electrification (TSE) allows truckers to run necessary systems inside their vehicles without idling their engines, using electricity as a substitute power source. There are two types of TSE, single-system electrification and shore power (onboard) systems. In single-system TSE, heating, ventilation, and air conditioning (HVAC) systems are located above the designated parking area and are attached to the vehicle with a hose. To accommodate the HVAC hose, a special window adapter must be installed in the truck, but these are usually very inexpensive (starting at around $10 for IdleAire). Single-system stations are most often run by private companies and costs are usually by the hour. Shore power systems are essentially electric outlets that trucks can plug into. They require more equipment than single-system stations; trucks will need an inverter to convert 120-volt power, an electrical HVAC system, and the hardware to plug into an electrical outlet. The benefits of using TSE are abundant. Besides helping to keep our air clean, TSE significantly reduces fuel costs for trucker: the U.S. Environmental Protection Agency estimates that fuel savings could be as high as $3,240 per truck parking space. TSE also greatly diminishes noise pollution, which is a positive effect for neighboring communities, as well as the truckers, who sleep better as a result. To locate TSE stations across the US, please visit the Alternative Fuels Data Center's TSE locator.

Idle Reduction: School Buses

School buses idle to warm their engines and often idle while they are waiting to pick up children. Unfortunately, this idling creates serious health concerns for children who are sensitive to diesel exhaust, in addition to the environmental and financial problems caused by idling. The US Environmental Protection Agency has created the Clean School Bus USA program to assist bus drivers and schools in their mission to reduce idling, and make the air cleaner and healthier for children. This program explains how school bus diesel exhaust affects children, has information about retrofitting (or upgrading) school buses with clean technology, and much more on school bus idle reduction.

Idle Reduction: Light-Duty Vehicles

Light-duty vehicles can also reduce their idling, with simple strategies or improved technologies. Here are some easy tips from the US Department of Energy that any driver can do:

• Turn off your engine when you are parked or stopped (except in traffic) for more than a minute.

• Consider the purchase of a hybrid electric vehicle, which limits idling at traffic stops.

• Avoid using a remote vehicle starter, which encourages unnecessary idling.

• Avoid drive-thrus: walk inside instead.

• Encourage your local schools to enforce a no-idle zone for school buses and personal vehicles.

There are also several additions one can make to a light-duty vehicle to reduce idling. Coolant heaters, air heaters, and energy recovery systems are among the idle-reduction technology available. For more information on these technologies, please visit the Alternative Fuel Data Center.