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Idling Reduction:
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About PDF Files
Why did EPA start an idling reduction program?In May 2001, the President's National Energy Policy directed EPA to "develop ways to reduce demand for petroleum transportation fuels by working with the trucking industry to establish a program to reduce emissions and fuel consumption from long-haul trucks at truck stops by implementing alternatives to idling, such as electrification and auxiliary power units at truck stops along interstate highways." A full copy of the National
Energy Policy (3.1M PDF, 170 pp.) is available from http://www.whitehouse.gov/energy/
Reducing engine idling is an important component of EPA's SmartWay
Transport Partnership, a collaborative voluntary program between
EPA and the freight industry that will increase the energy efficiency
and energy security of our country while significantly reducing
air pollution and greenhouse gases. The Partnership creates
strong market-based incentives that challenge companies shipping
products, and the truck and rail companies delivering these products,
to improve the environmental performance of their freight operations.
SmartWay Transport partners improve their energy efficiency, save
money, reduce greenhouse gas emissions, and improve air quality. Why do trucks and locomotives idle?Truck drivers idle primarily for cab comfort needs. As the driver rests in the truck sleeper compartment, he or she will often need to cool or heat the cab to rest comfortably. Even in moderate temperatures the cab will need air conditioning or heat because drivers usually do not sleep with their windows open for security reasons. Another popular reason for idling is to operate on-board appliances such as a television or microwave or off-board electrical equipment such as school bus flashers or cranes. In extremely cold weather, truck drivers will idle their engines to prevent the engine block from freezing. Another often overlooked reason for idling is habit: for many years, truck drivers have been taught to not turn off a diesel engine and, while there may be some need to do this with much older engines, it is not necessary for today's engines. Locomotives, on the other hand, must idle their engines when
the temperature reaches about 40° Fahrenheit. Since
most locomotive engines do not have anti-freeze, the engine risks
freezing at about this temperature. Heat is needed to maintain
the locomotive's engine coolant, fuel, oil, water and to maintain
battery charge. At temperatures above 40° F, locomotives
may idle to maintain a readily available engine, maintain comfortable
temperatures inside the operator cab, and, like trucks, out of
the habit of always keeping a diesel engine operating. How much fuel is consumed by long-duration truck and locomotive engine idling?Combined, truck and locomotive idling consumes over 1 billion gallons of diesel fuel annually. Long-duration truck idling consumes approximately 960 million gallons of diesel fuel annually and locomotive switcher idling consumes 60 million gallons of diesel fuel annually. Based on comprehensive EPA testing of idling heavy-duty diesel trucks, the average truck consumes 0.8 gallons of fuel an hour.
EPA's test program took into account wide ranges of idling behavior to better represent actual idling. For example, trucks were tested from low to high engine speeds (600-1200 rpm), with air conditioning or heat operating or no accessory load, in a controlled environmental chamber heated and cooled, and with different engine models and manufacture dates. Based on industry publications, locomotive switcher idling consumes
three to four gallons of fuel per hour. In extremely cold
weather (below 15° F), many railroad companies implement
a winter policy of idling at notch setting three, thereby consuming
eight to eleven gallons per hour at idle. What are the emissions at idle?Long-duration truck idling emits 11 million tons of carbon dioxide, 180,000 tons of nitrogen oxides, and 5,000 tons of particulate matter annually. For detailed information about idling nitrogen oxide emissions view EPA's Study on Long-Duration Truck Idling, above. Detailed information about idling particulate matter emissions are available in the study "Particulate Matter and Aldehyde Emissions From Idling Heavy-Duty Diesel Trucks." (683K PDF, 10 pp.) Annually, long-duration locomotive switcher idling emits 12,000 tons of nitrogen oxides and 500 tons of particulate matter.
"Guidance for Quantifying and Using Long-Duration Switch Yard
Locomotive Idling Emission Reductions in State Implementation
Plans." (343K PDF, 25 pp.) (EPA420-B-04-002, January
2004) contains detailed information about the nitrogen oxide and
particulate matter emission factors for locomotive engines. What are the truck maintenance and engine wear costs at idle? The trucking industry has analyzed the impact of idling on engines,
both in terms of maintenance and engine wear costs. Long-duration
idling causes more oil and oil filter deterioration and increases
the need for more oil and filter changes. Similarly, the
longer the idling time, the sooner the engine, itself, will need
to be rebuilt. The trucking industry estimates that long-duration
idling costs the truck owner $1.13 per day, based on the need
for more oil changes and sooner overhaul costs. What is the extent of idling? How long? How many?Determining the exact number of idling trucks is difficult. At best, estimates of the number of trucks traveling more than 500 miles on a given trip, thereby requiring a mandated rest period, may be an indicator of the number of idling trucks. The number of trucks with sleeper berths is another indicator of the potential number of idling trucks as is the number of available public and private truck parking spaces in the country. Conservatively, a range of 500,000 to 1,000,000 trucks may idle for extended periods. As for idling times per day, this number fluctuates as well. On average, truck driver surveys have revealed rest periods in the range of six to eight hours per day, over 300 days per year. When looking at an engine's electronic control module which calculates total idling times, data suggests idling times in the range of 30% to 40% of total engine operating time. For locomotives, the focus is mostly on freight locomotives, less on passenger engines. While passenger engines idle, freight locomotives idle more. There are two freight railroad engine types: line-haul and switcher. Line-haul engines travel throughout the country, while switcher locomotives remain in rail yards to push and pull other cars and engines around the yard. Of the two, switchers idle about 60% of total engine operating time and line-haul engines idle about 38% of total engine operating time. Typical annual idling times for switchers range from 2,500 to 3,000 hours per year. Of the three classes of railroads (Class I, II, and III), Class
I represents the largest number of locomotives in the country.
There are about 20,000 Class I locomotive engines and, of this
number, about 5,000 are switchers. The extent of switcher
idling is mostly a factor of weather temperatures, company policy,
and operator behavior. During cold temperatures, the locomotive
engine will idle when not in use to protect the engine from freezing.
At all other times, especially when the temperature exceeds 40°
F, idling is mostly a factor of company policy or habit. Should you turn off your engine while waiting in a line or in traffic? Obviously for safety and practical reasons it makes no sense
to shut an engine off in traffic that is moving. But any
time one anticipates the vehicle standing still for over five
minutes it makes sense, both in terms of fuel and emissions, to
shut down the engine. Are the "start-up" emissions after a long shut-down period more than the emissions if the engine just idled?Much depends on the age and maintenance of the engine, but it's safe to assume that the start-up emissions are negligible after either a short or long period of time. In other words, the start-up emissions are not as great as the idling emissions, so it's always better to shut down. Of course this ignores the main reason for idling which is to provide cab comfort. For example, we assume a truck consumes about 1 gallon per hour
at idle and emits 135 g/hr of NOx and 3.68 g/hr of PM. If
one were to argue that it is better to just idle overnight for
10 hours instead of shutting down, then one would have to claim
that the start-up emissions (i.e., the amount of emissions over
the time it took the engine to warm up) exceeds the idling emissions
for 10 hours. If the truck idled for 10 hours it would emit
1,350 g of NOx (135 g/hr x 10 hours). So the question is
would the start-up emissions exceed 1,350 g? While this
question has not been answered with test data, a fairly strong
argument can be made based on common sense that the start-up emissions
would not exceed this amount. |
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