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Idling Vehicle Emissions:
US road data. 2000 |
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| Reducing idling time is not only good environmental policy, but it is also good business policy as well.
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).
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 MOBILE5b highway vehicle emission factor model (VOC, CO, NOx) and the PART5 model (PM10 for heavy-duty diesel vehicles only). These emission 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.
Acronyms:
CO: Carbon monoxide
GVW: Gross vehicle weight
NOx: Oxides of Nitrogen (mostly NO and NO2)
PM10: Particulate matter, diameter ¾ 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 lb Gross Vehicle Weight (GVW) (gasoline fueled passenger cars)
LDGT: Light-duty gasoline-fueled trucks, up to 8500 lb GVW (includes pick-up trucks, minivans, passenger vans, sport-utility vehicles, etc.)
HDGV: Heavy-duty gasoline-fueled vehicles, 8501+ lb GVW (gas heavy-duty trucks)
LDDV: Light-duty diesel vehicles, up to 6000 lb GVW (passenger cars with diesel engines)
LDDT: Light-duty diesel trucks, up to 8500 lb GVW (light trucks with diesel engines)
HDDV: Heavy-duty diesel vehicles, 8501+ lb GVW (diesel heavy-duty trucks)
MC: Motorcycles (only those certified for highway use; all gasoline-fueled)
Winter Conditions (30°F, 13.0 psi RVP gasoline)
| Pollutant |
Units |
LDGV |
LDGT |
HDGV |
LDDV |
LDDT |
HDDV |
MC |
| VOC |
g/hr |
21.1 |
30.7 |
44.6 |
3.63 |
4.79 |
12.6 |
20.1 |
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g/min |
0.352 |
0.512 |
0.734 |
0.061 |
0.080 |
0.211 |
0.335 |
| CO |
g/hr |
371 |
487 |
682 |
10.1 |
11.5 |
94.6 |
388 |
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g/min |
6.19 |
8.12 |
11.4 |
0.168 |
0.191 |
1.58 |
6.47 |
| NOx |
g/hr |
6.16 |
7.47 |
11.8 |
6.66 |
6.89 |
56.7 |
2.51 |
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g/min |
0.103 |
0.125 |
0.196 |
0.111 |
0.115 |
0.945 |
0.042 |
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Summer Conditions (75°F, 9.0 psi RVP Gasoline)
| Pollutant |
Units |
LDGV |
LDGT |
HDGV |
LDDV |
LDDT |
HDDV |
MC |
| VOC |
g/hr |
16.1 |
24.1 |
35.8 |
3.53 |
4.63 |
12.5 |
19.4 |
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g/min |
0.269 |
0.401 |
0.597 |
0.059 |
0.077 |
0.208 |
0.324 |
| CO |
g/hr |
229 |
339 |
738 |
9.97 |
11.2 |
94.0 |
435 |
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g/min |
3.82 |
5.65 |
12.3 |
0.166 |
0.187 |
1.57 |
7.26 |
| NOx |
g/hr |
4.72 |
5.71 |
10.2 |
6.50 |
6.67 |
55.0 |
1.69 |
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g/min |
0.079 |
0.095 |
0.170 |
0.108 |
0.111 |
0.917 |
0.028 |
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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 PM10 are the same.
| Engine Size |
Emissions |
| Light/Medium HDDVs (8501-33,000 lb GVW) |
2.62 g/hr (0.044 g/min) |
| Heavy HDDVs (33,001+ lb GVW) |
2.57 g/hr (0.043 g/min) |
| HDD buses (all buses, urban and inter-city travel) |
2.52 g/hr (0.042 g/min) |
| Average of all heavy-duty diesel engines |
2.59 g/hr (0.043 g/min) |
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