EPA-AA-TEB-EF-90-01
Estimation of
Trip- and Emission-Weighted Temperatures
For MOBILE4
by
Celia Shih
January 1990
NOTICE
Technical Reports do not necessarily represent final EPA decisions
or positions. They are intended to present technical analysis of
issues using data which are currently available. The purpose in
the release of such reports is to facilitate the exchange of
technical information and to inform the public of technical
developments which may form the basis for a final EPA decision,
position or regulatory action.
Test and Evaluation Branch
Emission Control Technology Division
Office of Mobile Sources
U.S. Environmental Protection Agency
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1.0 BACKGROUND
In the MOBILE emission factor prediction model (e.g.,
MOBILES), the exhaust HC, CO, and NOx emissions were calculated
based on user specified ambient temperatures (in °F), which
were usually the average temperature of the days during either
high ozone or CO violation periods. The diurnal and hot soak
emissions were based on the default FTP temperatures (i.e., 60
to 84°F heat rise for the diurnal emissions, and approximately
82°F ambient temperature for the hot soak emissions). No
running loss emissions were assumed in MOBILES.
During 1986, a revised version of MOBILES (MOBILES
version 9, or M3V9) was created in support of a fuel volatility
control proposed rulemaking. In this revised version, in
addition to the temperature parameter used for calculating
exhaust emissions, users were required to specify another set
of temperatures (corresponding to the average daily minimum and
maximum ambient temperatures) for use in the diurnal emissions
calculation. These temperatures were, in general,
area-specific averages during the high ozone days. The model
required that the exhaust temperature be consistent with the
diurnal temperatures (i.e., the exhaust temperature must be
within the minimum and maximum diurnal temperatures). Due to
lack of information at the time, the temperature effect on hot
soak emissions was not directly modeled, but was indirectly
accounted for through adjustment of local fuel volatility
level. As in MOBILES, no running loss emissions were assumed
in M3V9.
In MOBILE4, as in M3V9, users are required to specify the
minimum and maximum ambient temperatures based on daily
averages during the high ozone days for the diurnal emissions
calculation. With the user-specified minimum and maximum
ambient temperatures, a set of both trip- and emission-weighted
temperatures is to be derived . The model will calculate the
temperatures used for adjusting the evaporative hot soak and
the new added running loss emission factors. Users must also
specify a temperature for use in calculating the temperature
correction to exhaust emissions. Or, as an option, the model
will calculate a trip- and emission-weighted temperature for
use of estimating the exhaust emissions on the basis of the
minimum and maximum temperatures.
Details of the methodology used to develop this
temperature simulation model are contained in the following
discussion, along with the results. It is assumed in this
paper that users have sufficient information and guidance on
how to choose the appropriate minimum and maximum ambient
temperatures for MOBILE4 to meet their modeling objectives.
-2-
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2.0 DISCUSSION
In order to complete this temperature simulation model,
the following three types of data were required:
1. Ambient Temperature Profile. One set of temperature
profile data used in the analysis was the 20-year average
hourly temperatures by month from Pittsburgh, PA. In addition,
average hourly temperatures from cities on either high ozone or
CO violation days during 1984 were also examined.
2. Trip Data. 1979 GM-National Purchase Diary (NPD)
survey data (described in more detail in Step 1, below).
3. Emissions vs. Ambient Temperature Data. The MOBILE4
temperature and fuel RVP correction factor models for the three
exhaust emissions, hot soak emissions, and running loss
emissions were used. In using these models the following
assumptions were made: no vehicle tampering, all vehicles
under FTP operating mode conditions (20.6% cold start, 52.1%
stabilized, and 27.3% hot start), at average speed of 19.6 mph,
with in-use fuel volatilities of 9.0, 10.4, and 11.7 RVP (in
psi), fuel tank fill level of 40 percent, and model years 1983,
1988, and 1992 carbureted vs. fuel-injected light-duty
gasoline-powered vehicle (LDGV) technology mix. Model year
1983 was chosen because all post-1983 LDGVs are equipped with
closed-loop catalyst technology. MOBILE4 has assumed the same
carbureted vs. fuel-injected technology mixes for 1992+ LDGVs.
Model year 1988 was selected as an intermediate year between
1983 and 1992.
The following is a step-by-step discussion of the
methodology and results:
Step 1: Derive a trip weighting factor as a function of daily
minimum and maximum temperatures.
The 1979 GM-NPD survey data and the average hourly
temperature data from Pittsburgh (Table 1) were used to develop
this trip weighting factor. As the emphasis of this simulation
was on high ozone days, only temperatures from the months of
April through October were used. Figure l shows the July
temperature profile, in which the minimum temperature (Tmin) of
63°F occurs at both 6 and 7 AM, and the maximum temperature
(Tmax) of 80°F occurs from 3 to 5 PM.
The 1979 GM-NPD data base included survey results from a
total of 1964 households and 2870 household vehicles (both
passenger cars and light-duty trucks). Trips made by these
-3-
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household vehicles during the seven-day survey week (either May
14-20 or June 4-10, 1979) were recorded. A trip was defined as
"a one-way journey between two stops, visits, or locations."
Data recorded include days of the week, trip number, trip times
(both starting and ending), and trip distances (odometer
readings). Frequencies of trips by the starting hour were
calculated and percents of trips by each hour of the day
derived, as shown in Table 2.
It was assumed that the occurrence of trips by each hour
of the day remained constant daily. As can be noted from
Figure 2, the three peak starting times of trips are 5 PM, 12
noon, and 8 AM. With 5 PM being also the peak temperature of
the day, and 12 noon representing about 80% of the total
temperature rise of the day, it is anticipated that a large
portion of trips occur at the higher end of the range of daily
ambient temperatures.
Percents of trips by each hour of the day were matched
against the Pittsburgh temperature profile (April through
October), to obtain an estimate of trip percentage at each
ambient temperature of the day. For the hours that had the
same ambient temperature, percents of trips were combined. For
example, the Tmax of 80°F for July represented a total of 24.0
percent trips, which included 6.9 percent starting from 3-4 PM,
8.0 percent starting from 4-5 PM, and 9.1 percent starting from
5-6 PM.
Then, for each month between April and October, the
percent of trips was expressed as a function of temperature
rise (difference between Tmax and Tmin in °F, denoted as F°).
Since the absolute temperature rise varies from month to month
(for example, from 15F° in April and October to 17F° in May
through July in Pittsburgh), they were standardized as
fractions of 1:
R = (T - Tmin) / (Tmax - Tmin) (1)
where: R = Standardized temperature rise,
Tmin = Minimum ambient temperature, °F
Tmax = Maximum ambient temperature, °F, and
T = Any temperature between Tmin and Tmax.
Note that the R values in equation (1) are always within 0
(when T = Tmin) and 1 (when T = Tmax).
-4-
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A fourth degree polynomial equation was found to fit the
data best in describing the relationships between the percent
of trips and temperature rise:
WT = a + b*R + c*R**2 + d*R**3 + e*R**4 (2)
where: WT = Percent of trips,
R = Standardized temperature rise,
a = 6.4044
b = -75.533
C = 356.29
d = -571.55
e = 307.03
Between any given values of Tmin and Tmax, the percent of trips
at all temperatures could be estimated through equation (2).
The predicted percents of trips were then re-normalized, as
shown in Table 3. Figure 3 is a comparison between the actual
(shown as dots) and predicted (shown by the smooth curve)
percents of trips by ambient temperature at trip start, for the
month of July in Pittsburgh.
Step 2: Derive emission factors at all temperatures between
any given values of Tmin and Tmax.
The MOBILE4 temperature correction factor models for
exhaust HC, CO, and NOx emissions were used to calculate the
exhaust emissions temperature correction at each temperature.
For example, at temperatures equal to or above 75°F, the
combined temperature/fuel RVP correction equations were used
for each portion of the FTP operating mode (cold start,
stabilized, and hot start), for each fuel-metering system
(carbureted, ported and throttle body fuel-injected) of LDGVs.
At temperatures below 75°F, temperature correction factor
equations were used to account for temperature effect first.
For example, an additive adjustment model was used for cold
start CO, and multiplicative adjustment models were used for
the other two FTP portions of CO and all three FTP portions of
HC and NOx emissions. Then, for temperatures between 41 and
74°F, a RVP effect was added. Figures 4 through 6 show the
calculated exhaust emission factors for the month of July in
Pittsburgh (from Tmin of 63 to Tmax of 80°F). Note that,
although the absolute values of the calculated three exhaust
pollutants are different, their trends of emissions vs. ambient
temperature are similar, i.e., emissions are higher at low
ambient temperatures, decrease as temperature gets closer to
75°F, and increase again when temperature is higher than 75°F.
-5-
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The MOBILE4 hot soak and running loss emissions models
were used to estimate hot soak and running loss emission
factors. Between any given values of Tmin and Tmax, when the
ambient temperature was above 40°F, hot soak and running loss
emissions were calculated (assuming no RVP reduction as a
result of fuel weathering). Figures 7 and 8 show the
calculated hot soak and running loss emissions at each
temperature for the month of July in Pittsburgh. Note that
both hot soak and running loss emissions increase with rising
ambient temperature.
Step 3: Calculate the trip-weighted emission factors for each
pollutant, and find out at what temperatures half of the
accumulated emissions occur. These are the approximate trip-
and emission-weighted temperatures.
Using the July temperatures from Pittsburgh as an example,
as shown in Table 4, emissions at each temperature (top
portion) were multiplied by the normalized trip weighting
factor from Table 3, and the cumulative trip-weighted emissions
were estimated (lower portion). The cumulative trip-weighted
emissions are also plotted in Figures 4 through 8. From these
cumulative emissions, the temperatures that correspond to half
of the accumulated emissions were about 76°F for the exhaust
HC, CO, and NOx emissions, and about 77°F for the evaporative
hot soak and running loss emissions. As expected, the trip-
and emission-weighted temperatures for the three exhaust
emissions were about the same because of their similar behavior
as a function of temperature, while the temperatures for hot
soak and running loss emissions were slightly higher.
Three different levels of fuel volatilities (9.0, 10.4,
and 11.7 RVP) were used in the simulation process. Results
showed that different fuel RVPs led to different levels of both
exhaust and evaporative emissions. In general, the higher the
fuel volatility, the higher the emission level. However, for
these given temperature ranges, the derived trip- and
emission-weighted temperatures were the same regardless of the
fuel volatilities. For this reason, only 11.7 psi RVP fuel was
used for simulations beyond Step 3.
Step 4: Generate sets of trip- and emission-weighted
temperatures by using various combinations of Tmin and Tmax.
The approach adopted here was to examine the average
hourly temperatures from cities on either high ozone or CO
violation days during the year of 1984, with the emphasis on
high ozone days. Two restrictions were placed on the data in
describing the temperature rise as a function of the daily
-6-
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minimum ambient: 1) Only data from the months of April
through October were used, since these were the most likely
potential high ozone occurrences during a year, and 2) Only
data with temperature rises greater than 5F° were used. (The
majority of days with 5F° and less temperature rises in this
1984 temperature data were from incomplete recordings. For
example, some weather stations were open and recording their
hourly temperatures only during the daytime.)
For hot soak and running loss emissions, an additional
restriction was placed: only days when the minimum ambient
temperatures were greater than 40 °F were used. This is
consistent with the MOBILE4 assumption that there are no
evaporative emissions (either hot soak or running loss) when
the ambient temperature is at or below 40°F.
Two regression equations were derived from this 1984
temperature data:
Rise = 21.901 - 0.11084 * (Tmin - 40.0) (3)
Rise = 22.478 - 0.13666 * (Tmin - 40.0) (4)
where equation (3) was used when Tmin was less or equal to
40°F, and equation (4) was used when Tmin was greater than 40°F.
Using the above steps, trip- and emission-weighted
temperatures were calculated for each of the combinations of
Tmin and Tmax, with Tmin ranging from 0.0 to 100.0°F, Tmax
ranging from Tmin+(Rise-10.0) to Tmin+(Rise+10.0), and Rise
calculated from either equation (3) or equation (4), depending
on the value of Tmin. Then, for each model year considered
(1983, 1988 and 1992), and for each pollutant (exhaust HC, CO,
and NOx, and evaporative hot soak), an equation was derived to
describe the relationships between the trip- and
emission-weighted temperatures and their corresponding given
set of Tmin and Rise. Note that for running loss emissions,
since the same emission rates were used for all 1981+ LDGVs,
only one temperature vs. Tmin and Rise equation is derived
(representing all three model years).
Regression coefficients are summarized in Table 5, and
predicted temperatures from a few selected combinations of Tmin
and Rise are listed in Table 6. As can be seen, for each
pollutant, the predicted temperature differences among the
three model years are very small, typically less than 1F°.
Within the same model year (e.g., 1988), the predicted
temperature differences among the three exhaust emissions are
-7-
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also small, typically around 1F°. The only exceptions are at
extreme low temperatures, where the predicted NOx temperatures
are about 3F° higher than the exhaust HC temperatures.
Considering the very small differences in the results of
the simulation for the three model years and three exhaust
pollutants, two simplifying assumptions were used in MOBILE4.
First, regression coefficients from model year 1988 were
selected to represent all model years. Second, coefficients
from exhaust HC emissions were also selected to represent the
other two exhaust emissions (CO and NOx).
3.0 RESULTS
A set of trip- and emission-weighted temperatures,
described as a function of the minimum and maximum ambient
temperatures has been derived for use in MOBILE4. The
equations are:
TEMPexhaust = 2.2857 + 0.97674 * Tmin + 0.56881 * Rise
+ 0.0024642 * Tmin * Rise
TEMPhot ,oate = -1.7474 + 1.029 * Tmin + 0.99202 * Rise
- 0.0025173 * Tmin * Rise
1'JKrtP running loss
= -1.1977 + 1.0205 * Tmin + 1.0181 * Rise
- 0.0023797 * Tmin * Rise
Using the above three equations, selected combinations of Tmin
and Rise are listed in Table 7.
-8-
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Table 1
Hourly Ambient Temperature Data
Pittsburgh, PA
Time
of
Day
• i •
0100
0200
0300
0400
0500
0600
0700
0800
0900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
Average Ambient Temperature (
Jan
25
24
24
24
24
23
23
23
23
23
25
26
28
29
30
30
30
29
28
27
27
26
25
25
Feb
26
26
25
25
25
24
24
24
24
25
27
29
31
32
33
33
34
33
32
30
30
29
28
27
Mar
36
36
35
35
34
34
33
33
34
36
39
41
42
44
45
45
46
45
43
42
40
39
38
37
Apr
46
45
44
44
43
42
42
43
46
48
51
53
55
56
57
57
57
57
55
53
52
50
49
47
May
55
54
53
52
51
51
51
53
57
60
62
64
66
67
68
68
68
67
66
64
62
60
58
57
Jun
63
62
61
60
59
59
60
62
65
68
71
73
74
76
76
76
76
75
74
72
70
68
66
64
Jul
67
66
65
65
64
63
63
66
69
72
75
77
78
79
80
80
80
79
78
76
73
71
70
68
Aug
66
65
64
63
63
62
62
63
66
69
72
75
76
78
78
78
78
77
76
74
71
69
68
67
oF)
Sep
60
59
58
58
57
57
56
56
59
62
66
68
70
71
72
72
72
71
69
66
64
63
61
60
Oct
48
47
47
46
46
45
45
45
46
50
53
55
57
59
59
60
59
58
55
54
52
51
50
49
Nov
40
40
39
39
38
38
38
38
38
39
42
44
45
46
47
47
47
45
44
43
42
41
41
40
Dec
31
31
31
30
30
30
30
30
30
30
32
33
35
35
36
36
36
35
34
33
33
32
32
31
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Table 2
Trip Distributions by Starting Time
1979 GM-NPD Survey Data
Time of Day
0100
0200
0300
0400
0500
0600
0700
0800
0900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
Frequency
0
38
110
65
203
969
3432
6244
5272
5675
5734
7017
6170
5608
6585
7623
8663
7086
5535
4268
3473
2483
1583
1029
Percent
0.0
0.0
0.1
0. 1
0.2
1.0
3.6
6.6
5.6
6.0
6.0
7.4
6.5
5.9
6.9
8.0
9.1
7.5
5.8
4.5
3.7
2.6
1.7
1.1
Total 94865
100.0
-10-
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Table 3
Percent of Trips vs. Ambient Temperature
Month of July, Pittsburgh, PA
Ambient
Temperature
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Percent of Trips
Total:
Actual
4.6
0.2
0.2
6.6
0.0
1.1
5.6
1.7
2.6
6.0
3.7
—
6.0
4.5
7.4
12.3
13.4
24.0
Predicted
6.40
3.08
1.58
1.33
1.85
2.77
3.76
4.64
5.26
5.59
5.68
5.68
5.82
6.40
7.84
10.62
15.33
22.64
Normalized
5.51
2.65
1.36
1. 14
1.59
2.38
3.24
3.99
4.52
4.81
4.89
4.89
5.00
5.50
6.74
9.13
13.19
19.47
99.9
116.25
100.00
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Table 4
Trip-Weighted Emission Factors
Month of July, Pittsburgh, PA
Temperature
Exhaust Emissions (q/mi)
(°F)
HC
CO
NOx
Emission Factors
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Cumulative
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
Half
0.651
0.642
0.634
0.625
0.617
0.609
0.601
0.594
0.586
0.579
0.572
0.565
0.558
0.562
0.566
0.570
0.574
0.578
Trip-Weighted
0.036
0.053
0.062
0.069
0.078
0.093
0.112
0.136
0.163
0.190
0.218
0.246
0.274
0.305
0.343
0.395
0.471
0.583
0.292
8.866
8.694
8.520
8.343
8.165
7.984
7.801
7.616
7.429
7.240
7.049
6.856
6.662
6.821
6.986
7.157
7.334
7.517
Emissions
0.488
0.719
0.834
0.930
1.060
1.250
1.502
1.806
2.142
2.490
2.834
3.169
3.503
3.878
4.349
5.003
5.970
7.434
3.717
0.751
0.747
0.743
0.739
0.735
0.731
0.727
0.723
0.720
0.716
0.712
0.708
0.705
0.706
0.707
0.708
0.709
0.710
0.041
0.061
0.071
0.080
0.091
0.109
0.132
0.161
0.194
0.228
0.263
0.297
0.333
0.372
0.419
0.484
0.577
0.716
0.358
Hot Running
Soak(q) Loss (q/mi)
1.612
1.633
1.655
1.676
1.698
1.720
1.741
1.763
1.853
1.945
2.037
2.131
2.225
2.321
2.417
2.514
2.613
2.712
0.089
0.132
0.155
0.174
0.201
0.242
0.298
0.368
0.452
0.546
0.645
0.750
0.861
0.989
1.151
1.381
1.726
2.254
0.667
0.696
0.725
0.754
0.783
0.812
0.841
0.870
0.899
0.928
0.957
0.986
1.015
1.044
1.073
1.102
1.131
1.160
0.037
0.055
0.065
0.074
0.086
0.105
0.133
0.167
0.208
0.252
0.299
0.347
0.398
0.456
0.528
0.629
0.778
1.004
1.127
0.502
Corresponding Temperature (° F) at Half
75.58 . 75.57 75.64
76.85 76.64
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Table 5
Regression Coefficients*
Pollutant
Exh. HC
Exh. CO
Exh. NOx
Hot Soak
Model
Year
1983
1988
1992
1983
1988
1992
1983
1988
1992
1983
1988
1992
Coefficient
A
2.7519
2.2857
1.9567
1.3244
1.3425
1.2407
1.1217
1.0298
0.90704
-1.8253
-1.7474
-1.7245
B
0.97105
0.97674
0.98127
0.99437
0.99013
0.99023
0.99526
0.99587
0.99729
1.0265
1.0290
1.0328
C
0.51087
0.56881
0.59618
0.61650
0.62733
0.63723
0.68549
0.69668
0.70475
0.97658
0.99202
1.00120
D
0.0031863
0.0024642
0.0020810
0.0016654
0.0018822
0.0018631
0.00064995
0.00055230
0.00046836
-0.0018361
-0.0025173
-0.0030849
Running
Loss
All
-1.1977
1.0205
1.0181
-0.0023797
*The trip- and emission-weighted temperature equation has the form:
Temp = A + B * Tmin + C * Rise + D * Tmin * Rise
where: Temp = trip- and emission-weighted temperature in °F,
Tmin = ambient minimum temperature in °F,
Rise = difference (in °F) between ambient maximum and
minimum temperatures.
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Table 6
Predicted Trip- and Emission-
Weighted Temperatures
Temperature (°F)
Tmin
( °F)
Model
3.0
24.0
34.0
45.0
60.0
66.0
77.0
88.0
100.0
Model
3.0
24.0
34.0
45.0
60.0
66.0
77.0
88.0
100.0
Model
3.0
24.0
34.0
45.0
60.0
66.0
77.0
88.0
100.0
Rise
(F°
Year
26.
23.
22.
21.
24.
18.
17.
15.
14.
Year
26.
23.
22.
21.
24.
18.
17.
15.
14.
Year
26.
23.
22.
21.
24.
18.
17.
15.
14.
)
1983
0
0
0
0
0
0
0
0
0
1988
0
0
0
0
0
0
0
0
0
1992
0
0
0
0
0
0
0
0
0
Tmax
( °F)
29.0
47.0
56.0
66.0
84.0
84.0
94.0
103.0
114.0
29.0
47.0
56.0
66.0
84.0
84.0
94.0
103.0
114.0
29.0
47.0
56.0
66.0
84.0
84.0
94.0
103.0
114.0
Exhaust
HC
19
39
49
60
77
79
90
100
111
20
40
49
60
78
79
90
100
111
20
40
50
60
78
79
90
100
111
.2
.6
.4
.2
.9
.8
.4
.1
.5
.2
.2
.9
.5
.1
.9
.4
.0
.4
.6
.4
.0
.6
.1
.9
.4
.0
.3
CO
20
40
49
60
78
80
90
100
111
20
40
50
60
78
80
90
100
111
20
40
50
60
78
80
90
100
111
.5
.3
.9
.6
.2
.0
.6
.3
.7
.8
.6
.2
.9
.5
.2
.7
.4
.8
.9
.7
.3
.9
.6
.3
.8
.4
.8
NOx
22.0
41.1
50.5
60.9
78.2
79.9
90.3
99.8
111.2
22.2
41.3
50.6
61.0
78.3
80.0
90.3
99.8
111.1
22.3
41.3
50.7
61.0
78.3
80.0
90.3
99.9
111.2
Hot
Soak
44
53
63
80
81
91
100
111
44
53
63
80
81
91
100
111
44
53
62
79
80
90
100
111
*
.3
.2
. 1
.6
.3
.4
.7
.9
*
.4
.2
.0
.2
.0
.1
.4
.5
*
.4
.1
.9
.8
.8
.8
.1
.3
Running
Loss
*
45.4
54.1
63.9
81.0
81.7
91.6
100.7
111.8
*
45.4
54.1
63.9
81.0
81.7
91.6
100.7
111.8
*
45.4
54.1
63.9
81.0
81.7
91.6
100.7
111.8
MOBILE4 does not calculate hot soak or running loss emission
factors at these temperatures.
-14-
-------
Table 7
Trip- and Emission-Weighted Temperatures
Temperature (°F)
Tmin
( °F)
3.0
8.0
14.0
18.0
24.0
29.0
34.0
39.0
44.0
49.0
53.0
55.0
60.0
60.0
66.0
67.0
71.0
77.0
82.0
88.0
93.0
99.0
100.0
Rise
(F° )
26.0
25.0
24.0
24.0
23.0
23.0
22.0
22.0
21.0
21.0
20.0
20.0
20.0
24.0
18.0
18.0
18.0
17.0
16.0
15.0
15.0
14.0
14.0
Tmax
( °F)
29.0
33.0
38.0
42.0
47.0
52.0
56.0
61.0
65.0
70.0
73.0
75.0
80.0
84.0
84.0
85.0
89.0
94.0
98.0
103.0
108.0
113.0
114.0
Exhaust
20.2
24.8
30.4
34.6
40.2
45.3
49.9
55.0
59.5
64.6
68.5
70.1
75.2
78.1
79.9
80.9
85.0
90.4
94.7
100.0
105.1
110.4
111.4
Hot Soak
*
*
*
39.5
44.4
49.2
53.2
58.0
62.0
66.9
70.0
71.9
76.8
80.2
81.0
82.0
86.0
91.1
95.2
100.4
105.3
110.5
111.5
Running
Loss
*
*
*
40.6
45.4
50.2
54. 1
59.0
62.9
67.7
70.7
72.7
77.5
81.0
81.7
82.6
86.5
91.6
95.7
100.7
105.7
110.8
111.8
* MOBILE4 does not calculates hot soak or running loss emission
factors at these temperatures.
-15-
-------
Figure 1 : Ambient Temperature vs. Time of Day
Month of July, Pittsburgh, PA
85
80 ^
0)
JH
I
0)
75 H
•
0)
.i-H
,0
70 H
65 H
60
0
6 9 12 15
Time of Day
18
24
85
0)
^
-75
-------
Figure 2 : Percent of Trips vs. Time of Day
1979 GM-NPD Survey Data
w
£
S-l
O
-------
Figure 3 : Percent of Trips vs. Ambient Temperature
Month of July, Pittsburgh, PA
OH
-------
Figure 4 : Exhaust HC Emissions vs. Ambient Temperature
Month of July, Pittsburgh, PA
0.70
0.65-
W
g 0.60-
o
0.55-
0.50
HC Emissions
Trip Weighted
Half Line
63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
Ambient Temperature (F)
0.6
0.5^5
W
fl
o
••H
w
^0.4 .2
-0.3
-0.2
0)
-0.1
a
3
0.0
-------
Figure 5 : Exhaust CO Emissions vs. Ambient Temperature
Month of July, Pittsburgh, PA
9
8.5-
ft
ft
ft
8-
8 7-5
ft
3
05
7-
6.5
CO Emissions
Trip Weighted
Half Line
63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
Ambient Temperature (F)
8
-7
dfi
ft
-eg
ft
ft
-5
W
-------
Figure 6 : Exhaust NOx Emissions vs. Ambient Temperature
Month of July, Pittsburgh, PA
0.76
0.75-
O
«rH
W
0.74-
0.73 -I
w
X 0.71-
0.70
NOx Emissions
Trip Weighted
i i
0.8
ho.7
w •
-0.6 §
L0.5
-0,4
W
I
-0.3 '
-0.2
-0.1
0.0
63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
Ambient Temperature (F)
-------
Figure 7 : Hot Soak Emissions vs. Ambient Temperature
Month of July, Pittsburgh, PA
w
CO
w
2.5-
O
CO
-»->
O
a
2-
1.5
Hot Soak Emissions
ip Weighted
Half Line
63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
Ambient Temperature (F)
2.4
-2.2
CtO
-—'
CO
O
hl-8 *w
CO
-1.6 3
-1.4
-1.2 ^
^
-0.8
-0.6 ^
r"^*H
-0.4 g
-0.2
0
-------
Figure 8 : Running Loss Emissions vs. Ambient Temperature
Month of July, Pittsburgh, PA
1.2
1.1-
w 1-
o
• i-H
CO
0.9-
0.8-
£ 0.7-
CO
O
0.5
Running Loss Emissions
--'""Trip Weighted
Half Line
63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
Ambient Temperature (F)
1.1
-0.9
co
-0.8 .2
CO
w
-0.7
-0.6
-0.5
-0.4
(1)
-0.3 >
-0.2
-0.1
cti
3
0
------- |