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What Is Idle Reduction?

No-idle zone sign

Idle reduction is typically used to describe technologies and practices that reduce the amount of time that vehicles idle their engines. These vehicles can be broken down into three categories:

  • Light-duty vehicles, such as passenger cars and light trucks,
  • Medium-duty vehicles, such as delivery trucks and utility vehicles
  • Heavy-duty vehicles, such as over-the-road tractor-trailer trucks, buses, locomotives, and marine vehicles.

All of these vehicle types can benefit from idle reduction strategies. Reducing idle time saves fuel, engine wear, and money, while reducing emissions and noise. Consider the following:

  • Although it is difficult to quantify idling by passenger cars, if you drive by any school at the start or end of the school day, you will see that it is a potentially huge problem, especially when added to passenger car idling at railroad crossings, stop lights, and shopping centers.

  • Medium-duty trucks use about 2.5 billion gallons of fuel to idle each year, or 6.7% of the total fuel they consume (source: Transportation Research Board).

  • More than 650,000 long-haul heavy-duty trucks idle overnight for required rest stops at least some fraction of the time. As the trucks idle their engines during rest periods to provide heating, cooling, and electrical power, and to keep the engine warm and the battery charged, they use more than 685 million gallons of fuel per year (source: Transportation Research Board).

Idle reduction strategies for heavy-duty can be as simple as turning the vehicle off, or as complex as adding onboard equipment that can perform the functions the idling engine performs now. A variety of technologies are available in a range of prices, depending on the vehicle type and power needs. Onboard equipment such as automatic engine stop-start controls, secondary batteries, and auxiliary power units can be used wherever the vehicle might be. Where available, electrified parking spaces enable trucks to hook up to stations that provide power and other amenities during rest stops for an hourly fee.

Additional strategies are available for light- and medium-duty vehicles and school buses. When the idling of these vehicles is added to that of the heavy-duty trucks discussed above, estimates of annual fuel use due to idling approach 6 billion gallons.