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
              -9-

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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
                          -11-

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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
                             -12-

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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.
                              -13-

-------
                              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

-------