Reducing Heavy Vehicle Idling

Anyone who has driven on interstate highways knows that big rigs idle overnight while their drivers sleep. The trucks are kept running to

• Heat and cool the cab and sleeper,
• Mask noises,
• Keep the fuel warm in winter,
• Avoid cold starting, and
• Provide for personal safety.

Long-haul trucks typically idle 6 hours per day, or 1,830 hours per year, but actual practice varies, from idling 1-2 nights per week to hardly ever turning the engine off. In addition, all classes of trucks idle during the workday while waiting at depots, warehouses, border crossings, and work sites.

Buses idle for similar reasons. Even large freighters and cruise ships idle when in port.

Figure 1. Many technologies are available that can reduce idling time and its effects by as much as 90 percent.

Locomotive Engines

Locomotives are also idled overnight and part of the day as well. These much larger engines (1,500-6,000 horsepower) consume more fuel and produce larger emissions effects per engine. Even though the crew does not sleep in the cab, they must remain ready while cars are changed or while the train waits on sidings for other trains to pass — sometimes for as long as 8 hours.

In addition, heating is required to keep the engine warm overnight to make sure it starts and to keep the water in the toilet from freezing. Typically, switcher locomotives idle 75 percent of the time, accounting for 27 percent of their total fuel use.

Fuel Consumption and Emissions

Each year, about 20 million barrels of diesel fuel are consumed by idling long-haul trucks overnight. The total for all heavy vehicles is much larger.

Estimated truck emissions total about

• 10 million tons of CO₂,
• 50,000 tons of nitrogen oxides, and
• 2,000 tons of particulates.

Several technologies are available that can reduce these effects by as much as 90 percent. Technologies available for trucks include

• Direct-fired heaters,
• Auxiliary power units,
• Battery and thermal storage air conditioning, and
• Electrified parking spaces.

Most of these technologies could be applied to or adapted for use on locomotives, with even more dramatic results.

Reducing locomotive idling by only 8 hours per day reduces total fuel use by over 11 percent. Actual savings could be even higher because locomotives often run in "high idle" (Notch 3) in cold weather, where fuel flow is six times as high as it is at normal idle.

Argonne’s Research

Argonne has examined the energy use and emissions implications of heavy vehicle idling and compared economic benefits of alternative idling-reduction strategies. Figure 1 shows how total cost per hour varies as a function of fuel price, for a vehicle idling about 40 hours per week for 5 years.

In addition, Argonne prepares and distributes the National Idling Reduction Network News to keep a variety of stakeholders up-to-date on developments related to idling reduction, including regulations, funding opportunities, and industry news. 

Funding

This work is supported by the U.S. Department of Energy Office of Vehicle Technologies.

More

• Idling Publications

November 2009