United States Air and Radiation EPA420-F-03-002
Environmental Protection February 2003
Agency
Office of Transportation and Air Quality
vvEPA
Facts
Impacts of Truck Idling on Air
Emissions and Fuel Consumption
In the United States, heavy-duty diesel truck idling contributes
significantly to both energy consumption and air emissions. EPA
estimates that idling trucks consume, annually, over 950 million gallons
of diesel fuel, and emit over 10 million tons of carbon dioxide (CO2) and
approximately 200,000 tons of oxides of nitrogen (NOx). This fact sheet
summarizes the results ofEPA's comprehensive truck idling test
program. The full report is available at the following web address:
www. v/otag/retrofit/idling, htm.
idling Test Program
EPA's truck idling test program was conducted over a two year period at
the U.S. Army's Aberdeen Test Center in Aberdeen, Maryland. EPA
developed an idling test program that was reviewed by the American
Trucking Association and the 21st Century Truck Partnership (govern-
ment-industry group consisting of major U.S. truck and engine manufac-
turers).
To test actual long duration idling conditions, we
selected representative truck idling scenarios that
included the following categories:
• truck selection
• temperature ranges
• engine speed (rpm) ranges
• accessory loads
Average Truck Idling
Emissions & Fuel Use
•140g/hrofNOx
»8200g/hrofCO2
• 0.80 gul/hr of diesel fuel
> Printed on Recycled Paper
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Truck Nine heavy-duty diesel trucks were selected for testing, from model years
Selection 1985-2001; thus representing the trucks traveling the roads today. The
trucks/engines were manufactured by leading U.S. companies, including
Caterpillar, Cummins, Detroit Diesel, Ford, Freightliner, International,
Ken worth, and Volvo.
Temperature
Ranges
Engine
Speed
The trucks were tested in a climate controlled chamber, at 0° F, 65° F, and
90° F. This temperature range accounts for idling not only in weather
extremes, but in moderate conditions as well.
Since truck drivers can adjust the engine speed (rpms) to provide more
power at idle, the test program included engine tests from 600-1200 rpm.
Use of the air conditioning or heat would normally require higher engine
rpms, usually above 1000 rpm. Since not all idling takes place during air
conditioner/heat needs, we also tested at the lower 600 rpm.
Accessory Since truck drivers idle for different reasons, the test program tested
Loads trucks under the following loads: air conditioning operating, heat operat-
ing, and no accessories operating. The first truck was tested for six hours
to determine the emissions steady state, that is, the point upon which the
emissions remained the same. We determined that this point was three
hours. Therefore, all subsequent tests were for three hours per truck.
Results
After 42 unique test scenarios that represent actual long-duration truck
idling conditions, the test program concluded that, on average, a typical
1980s-2001 model year idling truck emits 140 grams per hour (g/hr) of
NOx and 8200 g/hr of C02 and consumes about 0.80 gallons per hour of
diesel fuel.
For information
You can access the full report, "Study of Exhaust Emissions from Idling
Heavy-Duty Diesel Trucks and Commercially Available Idle-Reducing
Devices" (EPA420-R-02-025, October 2002), at:
www.epa.gov/otaq/retrofit/idling.htm
You can also contact the OTAQ library for document information at:
U.S. Environmental Protection Agency
2000 Traverwood Dr.
Ann Arbor, MI 48105
(734)214-4311
E-mail: Group AALibrary@epa.gov
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