3
Figure 1 Typical Tractor-Trailer
Section 1
Introduction
Intercity tractor-trailers (like the one shown in Figure 1) and other vehicles with diesel
engines idle a significant portion of the time. A typical intercity tractor-trailer idles an estimated
1,830 h/yr when parked overnight at truck stops. Nationally, a significant amount of fuel is
consumed this way -- trucks that travel more than 500 mi/d consume about 838 million gal of
diesel fuel annually during idling. Drivers have many reasons for keeping the diesel engine
running in a tractor-trailer: (1) to keep the cab and/or sleeper heated or cooled, (2) to keep the
fuel warm in winter, (3) to keep the engine warm in the winter to permit easier startup, and
(4) because all the other drivers do it (LaBelle 1986). Other trucks and vehicles with diesel
engines are also idled for long periods: school bus drivers idle their buses in the morning to
defrost the windshield and heat the bus, and transit bus drivers idle their buses to heat or cool the
bus while waiting to pick up passengers at terminals (Jessiman 1996). Off-highway vehicles and
locomotives are idled to keep the engine and fuel warm in cold weather.
1,830 h/yr when parked overnight at truck stops. Nationally, a significant amount of fuel is
consumed this way -- trucks that travel more than 500 mi/d consume about 838 million gal of
diesel fuel annually during idling. Drivers have many reasons for keeping the diesel engine
running in a tractor-trailer: (1) to keep the cab and/or sleeper heated or cooled, (2) to keep the
fuel warm in winter, (3) to keep the engine warm in the winter to permit easier startup, and
(4) because all the other drivers do it (LaBelle 1986). Other trucks and vehicles with diesel
engines are also idled for long periods: school bus drivers idle their buses in the morning to
defrost the windshield and heat the bus, and transit bus drivers idle their buses to heat or cool the
bus while waiting to pick up passengers at terminals (Jessiman 1996). Off-highway vehicles and
locomotives are idled to keep the engine and fuel warm in cold weather.
Idling also produces airborne emissions and noise; a number of cities and municipalities
have banned or restricted idling to reduce pollution and noise. For example, Philadelphia bans
idling of heavy-duty diesel-powered motor vehicles (City of Philadelphia 1986). Exceptions are
made during cold weather. Idling is limited to up to 5 consecutive minutes when the ambient
temperature is less than 32
idling of heavy-duty diesel-powered motor vehicles (City of Philadelphia 1986). Exceptions are
made during cold weather. Idling is limited to up to 5 consecutive minutes when the ambient
temperature is less than 32
°
F and up to 20 minutes when the ambient temperature is less than
20
°
F. Buses may be idled up to 20 consecutive minutes if they are equipped with air-
conditioning and the ambient temperature is 75
°
F or greater.
Various off-the-shelf technologies are available to heat and cool the sleeper and cab of a
truck and to keep the engine and fuel warm in the winter without idling the engine. However,
many of these technologies have draw-
backs that limit market acceptance.
Other technologies are less mature but
promise to eliminate the drawbacks of
the current technologies. This report
presents a brief overview of (1) the
extent of truck diesel engine idling,
(2) technology options to reduce truck
diesel engine idling, (3) estimated
energy and emissions impacts of each
technology option, and (4) the estimated
cost of each technology option. A more
detailed analysis of technology options,
costs, and benefits is recommended,
given the potentially significant energy
savings and emissions benefits from
reducing truck diesel engine idling.
many of these technologies have draw-
backs that limit market acceptance.
Other technologies are less mature but
promise to eliminate the drawbacks of
the current technologies. This report
presents a brief overview of (1) the
extent of truck diesel engine idling,
(2) technology options to reduce truck
diesel engine idling, (3) estimated
energy and emissions impacts of each
technology option, and (4) the estimated
cost of each technology option. A more
detailed analysis of technology options,
costs, and benefits is recommended,
given the potentially significant energy
savings and emissions benefits from
reducing truck diesel engine idling.