TABLE 6-1 Fuel Use During Idling as Percentage of Total Fuel Use (million gallons per year)





Overnight Idling




Workday Idling (excluding vocational power take-off use)




Total Long-Duration Idling Fuel Use




Total Fuel Use for Commercial Trucks




Idling Percentage to Total Use by Fuel Type




SOURCE: Glen Keller, Linda Gaines, and Terry Levinson, U.S. Department of Energy, Center for Transportation Research, Idle Reduction Technologies,” Presentation to the committee, Washington D.C., February 8, 2007, Slide 3.

Environmental Protection Agency (EPA) to work together on reducing the time vehicles spend at idle.

Finding 6-1. Idle reduction is one of the most effective ways to reduce pollutant emissions (especially locally) and improve fuel economy. As a result of the Energy Policy Act of 2005, the authority for this effort now rests with EPA and DOT. Several important lines of research are carried on in the 21CTP. In addition, the EPA SmartWay Transport Partnership voluntary program is effective at promoting the use of electrified parking spaces. The 21CTP, in cooperation with several major shippers, has demonstrated a number of cost-effective technologies (such as fuel-fired cab heaters and coolers) that are being used by existing fleets. (One fleet is installing more than 6,000 heaters, and another is installing more than 7,000.) One trucking company reported that diesel-fired heaters provided 2.4 percent fuel savings and a payback in less than 2 years at $2.40 per gallon.

Recommendation 6-1. The 21CTP should continue to support R&D for the technologies that reduce idle time and address the remaining technical challenges (including California emission requirements, completely integrated APU/HVAC systems, and creep devices).


Goal 1.
Establish an Industry/Government Collaboration to Promote the Research, Development, and Deployment of Cost-Effective Technologies for Reducing Fuel Use and Emissions Due to Idling of Heavy-Duty Diesel Engines

DOE has for at least a decade carried out cooperative research and development to characterize and address the reduction of fuel use and emissions during idling of heavy-duty engines. In 2002 it began a study of diesel truck engine idle-reduction technologies, called the Advanced Vehicle Testing Activity (AVTA).2 The study identified several barriers to widespread use of existing idle-reduction technologies, including initial cost, driver education and receptiveness, reliability, and maintenance considerations. AVTA sponsored four idle reduction demonstration projects, each consisting of a team of a truck fleet, truck manufacturer, and idle-reduction technology manufacturer:

  • Engine-Off Cab Cooling and Heating. Schneider National Inc. led a project to demonstrate engine-off cab cooling and heating.

  • Engine-Off Accessory Power. Caterpillar Inc. is leading a project to demonstrate Caterpillar’s MorElectric technology, which applies electrically driven accessories for cab comfort during engine-off stops and for reducing fuel consumption during on-highway operation.

  • Combined Cab Heating and Cooling. Espar is leading a project to demonstrate combined cab heating and cooling systems. One system combines an air conditioner with a bunk heater. Another system combines an auxiliary power unit—which provides heating, cooling, and accessory power—with a bunk heater.

  • Factory-Installed Idle Reduction System for Sleeper Trucks. International Truck and Engine Corporation is leading a project to develop and integrate onboard idle-reduction technology into heavy-duty sleeper trucks as an original-manufacturer, factory-installed equipment option. The idle-reduction system consists of an auxiliary power unit, electric air conditioner, cab and engine preheater, and improved cab insulation. In 2006, five trucks equipped with the system began field evaluation in fleets. The evaluation will conclude in 2007. In addition, production orders for the factory-built system—in hot-climate and cold-climate versions—are already being delivered to customers.

DOE took a leadership role in conducting meetings with the industry and a significant report on time idling and its consequences was released in 2000, and continued to work closely with industry to identify and demonstrate potential idle-reduction technologies as discussed later in the report.

Other federal agencies involved with these programs are the EPA, Department of Transportation (DOT), and

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