United States Air and Radiation EPA420-F-98-014
Environmental Protection April 1998
Agency
Office of Mobile Sources
&EPA Emission
Facts
Idling Vehicle Emissions
There are situations in which estimates of emissions from idling
vehicles are needed. As with driving emissions, idle emissions are
affected by a number of parameters. For analyses not requiring detailed
specific emission estimates tailored to local conditions, this summary of
idle emission factors can be used to obtain first-order approximations of
emissions under idle conditions (e.g., drive-thru lanes).
Introduction
The following tables present idle emission factors, in grams per hour (g/
hr) and grams per minute (g/min) of idle time, for volatile organic
compounds (VOC), carbon monoxide (CO), and oxides of nitrogen
(NOx). Idle emissions of particulate matter (PM10) are provided for
heavy-duty diesel vehicles only; PM10 emissions from gasoline-fueled
vehicles are negligible, especially when the elimination of lead in
gasoline and reductions of sulfur content are accounted for. Emission
factors are provided for both summer and winter conditions for VOC,
CO, and NOx. These idle emission factors are from the MOBILESb
highway vehicle emission factor model (VOC, CO, NOx) and the
PARTS model (PM10 for heavy-duty diesel vehicles only). These emis-
sion factors are national averages for all vehicles in the in-use fleet as of
January 1, 1998 (winter) or July 1, 1998 (summer). PM10 idle emission
factors for heavy-duty diesels are as of January 1, 1998.
> Printed on Recycled Paper
-------
Acronyms:
CO: Carbon monoxide
GVW: Gross vehicle weight
NOx: Oxides of Nitrogen (mostly NO and NO2)
PM10: Particulate matter, diameter < 10 microns
psi: Pounds per square inch
RVP: Reid vapor pressure, a common method of expressing the
volatility (tendency to evaporate) of gasoline; RVP is vapor
pressure measured at 100°F (38°C).
VOC: Volatile organic compounds (for vehicles, this refers to exhaust
emissions from incomplete combustion of gasoline, which is
composed of a blend of hydrocarbon compounds)
Definitions of Vehicle Types:
LDGV: Light-duty gasoline-fueled vehicles, up to 6000 Ib Gross
Vehicle Weight (GVW) (gasoline-fueled passenger cars)
LDGT: Light-duty gasoline-fueled trucks, up to 8500 Ib GVW (in-
cludes pick-up trucks, minivans, passenger vans, sport-utility
vehicles, etc.)
HDGV Heavy-duty gasoline-fueled vehicles, 8501+ Ib GVW (gas
heavy-duty trucks)
LDDV: Light-duty diesel vehicles, up to 6000 Ib GVW (passenger cars
with diesel engines)
LDDT: Light-duty diesel trucks, up to 8500 Ib GVW (light trucks with
diesel engines)
HDDV Heavy-duty diesel vehicles, 8501+ Ib GVW (diesel heavy-duty
trucks)
MC: Motorcycles (only those certified for highway use; all gaso-
line-fueled)
-------
Winter Conditions (30°F, 13.0 psi RVP gasoline)
Pollutant
VOC
CO
NOx
Units
g/hr
g/min
g/hr
g/min
g/hr
g/min
LDGV
21.1
0.352
371
6.19
6.16
0.103
LDGT
30.7
0.512
487
8.12
7.47
0.125
HDGV
44.6
0.734
682
11.4
11.8
0.196
LDDV
3.63
0.061
10.1
0.168
6.66
0.111
LDDT
4.79
0.080
11.5
0.191
6.89
0.115
HDDV
12.6
0.211
94.6
1.58
56.7
0.945
MC
20.1
0.335
388
6.47
2.51
0.042
Summer Conditions (75°F, 9.0 psi RVP Gasoline)
Pollutant
VOC
CO
NOx
Units
g/hr
g/min
g/hr
g/min
g/hr
g/min
LDGV
16.1
0.269
229
3.82
4.72
0.079
LDGT
24.1
0.401
339
5.65
5.71
0.095
HDGV
35.8
0.597
738
12.3
10.2
0.170
LDDV
3.53
0.059
9.97
0.166
6.50
0.108
LDDT
4.63
0.077
11.2
0.187
6.67
0.111
HDDV
12.5
0.208
94.0
1.57
55.0
0.917
MC
19.4
0.324
435
7.26
1.69
0.028
Particulate Matter Emissions
The only vehicle category for which EPA has idle PM10 emission factors
is heavy-duty diesels. Particulate emissions are also observed to be
relatively insensitive to temperature, and so "winter" and "summer"
emission factors for idle PM,n are the same.
10
Engine Size
Light/Medium HDDVs (8501-33,000 Ib GVW)
Heavy HDDVs (33,001+ Ib GVW)
HDD buses (all buses, urban and inter-city
travel)
Average of all heavy-duty diesel engines
Emissions
2.62 g/hr (0.044 g/min)
2.57 g/hr (0.043 g/min)
2.52 g/hr (0.042 g/min)
2.59 g/hr (0.043 g/min)
-------
For More Information
Additional documents on emissions from mobile sources are available
electronically from the EPA Internet server at:
http ://www. epa.gov/OMSWWW
Document information is also available by writing to:
U.S. Environmental Protection Agency
Office of Mobile Sources
2565 Plymouth Road
Ann Arbor, MI 48105
------- |