Clean Air and Transportation

Alternatives to Idling
August 2003

ISSUE: Why should DOT be concerned about emissions from idling trucks, and what actions can be taken to address the issue?

BACKGROUND: The Administration issued its National Energy Policy (NEP) in May 2001. The NEP noted that the transportation sector accounts for nearly 30 percent of total U.S. energy consumption and that trucks and automobiles account for over three-fourths of the transportation sector's petroleum use, with the remainder attributable to rail, ship, air and pipeline systems.

One of the energy policy initiatives included in the plan was an idling reduction directive. The NEP recommended "that the President direct EPA and DOT 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. EPA and DOT will develop partnership agreements with trucking fleets, truck stops, and manufacturers of idle-reducing technologies (e.g., portable auxiliary packs, electrification) to install and use low-emission idling technologies."

DISCUSSION:
Continuous idling of heavy-duty diesel truck engines for cab space cooling and heating is costly to truck owners and operators, both in terms of fuel use and engine wear. Unnecessary idling is also wasteful of our Nation's energy supply and damaging to our environment. Idle-reduction measures can help meet multiple goals including energy conservation, energy security and environmental stewardship.

Truck drivers idle their engines during their rest periods to provide heat or air conditioning to the sleeper compartment, keep the engine and fuel warm during cold weather, and provide electrical power for their on-board appliances. They may also idle their engines based on safety concerns or habit; diesel engines traditionally would be idled to maintain brake air pressure. However, this long duration idling comes at a price.

• Trucks consume an estimated one gallon of diesel fuel for each hour at idle, using as much as 2,000 gallons (per truck) of fuel every year. This amounts to 1 billion gallons of diesel fuel consumed every year from idling costing approximately $1.8 billion.
• On average, each truck idling produces about 22 tons of carbon dioxide (CO2) and 0.38 tons of nitrogen oxides (NOx) totaling over 11 million tons and 150,000 tons respectively per year.
• Diesel exhaust also contains particulates, sulfur dioxide, carbon monoxide, hydrocarbons and various air toxics. Diesel exhaust particulate matter (PM) has been implicated in an increased risk of lung cancer and respiratory disease. EPA has concluded that diesel exhaust is likely to be carcinogenic to humans.
• Engine idling results in increased maintenance costs associated with substantial wear to the engine. Studies indicate that idling can cost approximately $2,000 (per truck) annually from maintenance costs alone.

There are several technologies available to reduce idling including direct-fired heaters, auxiliary power units (APUs), automatic engine idle systems, truck stop electrification (TSE), and advanced TSE. More detailed information for each technology is provided in the chart below.

Information provided by the U.S. EPA
¹ Technology can only operate to provide heat in cold weather
² Emission reductions are an average of hot and cold environments
³ This is an estimate - cost/per ton is difficult to quantify due to movement in and out of non-attainment area
⁴ PM emission reductions for TSE technologies are estimates