EPA-AA-TEB-EF-8 4-1
Proposal for 1980 and Earlier Light-Duty
Gas Vehicle Emission Factors for MOBILE3
                   by


          Thomas L. Darlington
                May 1984
       Test and Evaluation Branch
  Emission Control Technology Division
        Office of Mobile Sources
  U.S. Environmental Protection Agency

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                            Table of Contents

                                                                   Page
1.0    SUMMARY                                                      3

2.0    BACKGROUND                                                   6
2.1    MOBILE2 Approach                                             6
2.2    MOBILES Approach                                             6
2.3    Other Items Pertaining to LDGV Emission Rates                6

3.0    BASIC EXHAUST EMISSION RATES                                 8
3.1    Identification of Tampered and Misfueled Vehicles            8
3.2    EGR Tampered Vehicles                                        8
3.3    Vehicles with High Lead Fuel Values                          9
3.4    Low Altitude Emission Rates                                 11
3.4.1  HC and CO Emission Rates                                    11
3.4.2  NOx Emission Rates                                          12
3.4.3  Summary of All Pre-1981 Low Altitude Rates                  13
3.5    High Altitude Emission Rates                                14
3.5.1  HC and CO Emission Rates                                    14
3.5.2  NOx Emission Rates                                          15
3.5.3  Summary of All Pre-1981 High Altitude Rates                 16

4.0    CORRECTION FACTORS                                          17
4.1    Normalized Bag Fractions                                    17

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1.0
SUMMARY
       New HC,  CO  and  NOX  emission  rates  were  developed  for  1975-1980
light-duty gasoline vehicles  (LDGV's)  at  low and  high  altitudes.   The
rates were not  updated for  the  California  region.  The  HC and  CO rates
were  developed  from  a  sample   of  vehicles  that  excluded  those  with
evidence  of  air  pump  tampering,  catalyst  removal  and misfueling.   The
NO  emission  rates  were developed  from a  sample  that excluded  the  same
vehicles  plus  those with evidence  of  EGR  tampering.   The new  rates  are
shown in  Table  1  below.  The HC  and CO rates for  1980  are substantially
lower than MOBILE2,  while  the HC, CO,  and NOX rates  for  1975-79  and  the
NOX  rates for  1980  are  little changed  from  MOBILE2.    The  effect  of
these new rates on  HC  and  CO emission  factors for light-duty  vehicles at
low  altitude  is  shown  in  Figures  1  and 2.  Only the  1975-80  emission
rates have been  changed for these figures;  all  other rates are  the  same
as  in MOBILE2.   It  should also  be  noted that the  1975-80 emission rates
used  did  not  reflect   misfueling,  whereas  the  1981  and  later  emission
rates did.   Including  MOB1LE2 misfueling  effects  in these new   1975-80
emission rates would have had  the  effect of narrowing  the gap between the
hOBIjJi2 and hObILE3 lines.

                                 Table  1

                     Emission Rates  of  1975-80 LDGV's
Region
Low Alt.
wYR Group
1975-76
1977-79
1980
                       	HC	
                        ZML*    DR**
                       1.07
                       1.07
                       0.36
                         0.27
                         0.27
                         0.10
                   	CO	
                   ZML      i)R

                   18.23    2.59
                   18.23    2.59
                    6.09    0.73
                             	NOx—
                             ZML

                             2.44
                             1.70
                             1.50
                            DR

                            0.03
                            0.09
                            0.07
High Ait.
   1975-76
      1977
   j.978-79
      1980
2.02
0.95
2.10
0.78
0.27
0.27
0.27
0.10
43.07
16.97
39.78
22.80
2.59
2.59
2.59
0.73
1.70
1.42
1.00
0.82
0.03
0.09
0.09
0.07
*   ZML = Zero mile level, gin/mi.
**  DR  = Deterioration rate, gm/mi/lOK miles.

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                        NOTE:
                    FIGURE 1
              Effect of Using MOBILE3
              1975-80 Emission  Rates
               on LDGV HC Emissions

              The MOBILES emission factor
              curve uses MOBILE2 emission
              rates for all years  except
              1975-80.
                                                                        Legend
                                                                       A  MOBILE2
                                                                       X  MOBILE3
1980
1985            1990
       CALENDAR YEAR
1995
2000

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 50-i
                          NOTE:
                    FIGURE 2
             Effect of Using MOBILES
             1975-80  Emission Rates
               on LDGV CO Emissions

             The MOBILE3 emission factor
             curve uses MOBILE2 emission
             rates for all years except
             1975-80.
                                                                            Legend
                                                                          A MOBILE2
                                                                          X HOBILE3
20
   1980
1985            1990
        CALENDAR YEAR
1995
2000

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2.0    BACKGROUND

2.1    MOBILE2 Approach

The 1979 and  earlier  LDGV  emission rates for MOBILE2 were  developed  from
an  analysis  of covariance  on all available  low altitude, high  altitude
and California  data in which mileage  was the  covariate  and the  regions
were  the  strata.   The  analysis   supported   the   assumption  of   equal
deterioration rates and separate zero-mile levels for the  regions.

For  the  1980 model year,  the deterioration  rate was assumed  to be  the
same as  for  1975-79 LDGV's.  The  zero-mile  level,  however, was  adjusted
to  reflect  the  fact  that  most  1980 LDGV's  would  be  equipped with  air
pumps, and to reflect the  fact  that the HC  and CO standards  were  lower
for 1980.

The  regressions obtained  from  the  analysis  of  covariance  were  used  as
emission  rates  in  MOBILE2  with  one   modification.   Emission rates  of
predominately  catalyst model  year  groups  (i.e.,  1975   and  later)  were
compensated  for misfueling effects, since it  was felt that  the  Emission
Factor  (EF)   test   sample  did  not  adequately  reflect  national  average
misfueling rates and  effects.   No  adjustments were made  for any  other
type of tampering such as catalyst removal or air pump disablement.

2.2    MOBILES Approach

The MOBILES  analysis  of pre-1981 LDGV  emission rates will focus primarily
on  1975-79 and  1980 emissions,  since no  new  data have been  collected  on
pre-1975 vehicles.  The  concept  for MOBILES is  to  develop  basic  emission
rates which  reflect a no  misfueling and  tampering  scenario, and  then add
the  tampering  and  misfueling  effects  on  separately.    As  a   result,
tampered vehicles must be  identified and  removed from the EF  sample prior
to  performing  analysis of  covariance.   This will be  discussed  further  in
Sections 3.1 through 3.3.

Analysis  of   covariance  has  been  used  to  develop  the   1975-79  emission
rates  for  MOBILES.   Also,  there  was  now enough data to  use this  same
technique on  1980 model  year  vehicles.   The California data were  used  to
develop  deterioration rates  where  technologies and  emission  standards
were  similar   to   the  non-California   low-altitude  case.    However,   a
specific analysis of California emission rates was not performed.

2.3    Other Items Pertaining to LDGV Emission Rates

Other items  pertaining to  the estimation of LDGV emission  rates  are  also
being updated  as a part of MOBILES.  These items  are  identified  in  the
list below, but will not be presented  in  this  document.   Documents  on the
humidity correction factor for NOX  and nonmethane  hydrocarbon emissions

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have already been  published,  and other  analyses  are under  way  either by
EPA  or under  a  support  contract.   It  should  be  noted   that  the  air
conditioning and  trailer  towing  correction factors  will  not be updated
for MOBILE3.

    1.    VMT vs. age distribution.
    2.    Kegistration vs. age distribution.
    3.    Diesel sales fractions.
   •4.    Speed correction  factors.
    5.    Temperature correction factors.
    6.    Evaporative emissions.
    7.    Idle emissions.

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3.0    BASIC EXHAUST EMISSION RATES

Sections  3.1  through  3.3 discuss  tampered  vehicles  identified  in  the
1975-80 emission  factor  sample and  their emissions.   However,  estimates
of  the  emission  impacts  of  tampering  for MOBILE3  were not  necessarily
developed  from  these  vehicles.   For more  information  on  the manner  in
which the  effects of  tampering  were included  in MOBILE3,  refer to  the
"Anti-Tampering and  Anti-Misfueling  Program  to  Reduce  In-Use  Emissions
From Motor Vehicles" report (December 31, 1983,  EPA-AA-TSS-83-10).

3.1    Identification of Tampered and Misfueled Vehicles

The 1975 and later light-duty vehicle data  base was  searched for  vehicles
with  signs  of  air pump  tampering, missing  catalysts,  widened fuel  tank
filler  necks,   lead   values  in   gasoline  above  0.05  g/gal,   and   EGR
tampering.  Vehicles with  missing air pumps,  belts,  or disabled  air  pump
hoses were  considered  to have tampered  air pump  systems.   Vehicles  with
widened  filler  necks  or  lead fuel  values  exceeding  0.05  g/gal  or  both
were considered to be  misfueled vehicles.   Vehicles  with disconnected EGR
vacuum  hoses  or missing  EGR valves  were considered  to be  EGR  tampered
vehicles.  The number  of  tampered and misfueled vehicles found in the EF
sample is shown in Table 2.

                                 Table 2

           Number of Tampered or Misfueled Light-Duty Vehicles
                       1975-80 Vehicles,  All Regions

                                                    Number
    Tampering/Misfueling Type                       Tampered

    EGR                                               208
    Lead above 0.05 gms/gal                             66
    Filler Neck                                         39
    Air Pump                                            11
    Catalyst Removed                                     9

    Total Number of 1975-80
      Vehicles Searched                              4171

The  two  predominant   types  of tampering,  EGR tampering  and fuel  lead
values above 0.05 g/gal,  are discussed in the following paragraphs.

3.2    EGR Tampered Vehicles

The  number  of  vehicles  with   EGR  tampering  and  their  average   NOX
emissions as compared  to  the vehicles without  EGR tampering  are  shown in
Table 3.

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                                 Table 3

                         Number of EGR  Tampered
                        Vehicles and Average  NOX
                         Emissions, Low and High
                                Altitude

                              	Tampered	    	Untampered	
                                             Mean               Mean
Region            Group       N     %      NOx (gpm)   N_     NOx (gpm)

Low Altitude      1975-76     42    2.3      3.91      1825     2.49
(Non-Calif.)      1977-79     77    4.5      4.37      1632     1.98
                  1980        11    1.9      3.62       584     1.71

High Altitude     1975-76     10    3.8      2.49       251     1.79
                  1977-79      8    1.9      3.00       412     1.24
                  1980         4    3.2      0.92       120     0.89
The data  in Table 3  indicate that EGR  tampering rates in  the  EF sample
are  within   the   2-5%  range,  and   that   EGR  tampered   vehicles  have
significantly higher NOX emissions than those without EGR tampering.

3.3    Vehicles With High Lead Fuel Values

Not all  1975-80 EF vehicles had tests  for  lead content of  the  fuel.  In
fact,  very  few of the  i975-79 vehicles had  lead tests, while  many more
1980 vehicles had  lead tests.

The number  and percentage  of vehicles  with  high lead  values  (exceeding
0.05 grams/gal)  is shown in Table 4.   ihe  low and  high altitude regions
seem to have about the same rate (5-10%).

                                 Table 4

             Number and  Percentage* of  Catalyst  Vehicles  With
                High  Lead Values  (  greater  than  .05 g/gal)

                     —Low Alt.—             —High Alt.—
                     N    .   %                N       %
1^75-79             19      7.8               2       5.6
1980                36      7.7               8      10.5
*   The percentage  is  calculated as the number  of  catalyst vehicles with
    high  lead values  divided by  the  total  number of  catalyst vehicles
    with lead tests.

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                                                                        10
The average emissions of vehicles with  low and high lead  fuel  content  is
shown in Table  5.   For  1975-79 vehicles, HC  and  CO emissions  are  higher
in  the  high  lead  vehicles.   For  1980  vehicles,  the average  HC  and  CO
emissions of  vehicles with  high lead values  are  slightly lower  than the
low lead vehicles.
                                 Table 5

            Average Emissions of Cars with Low and High Fuel
                Lead Values: Low Altitude, Non-California
Pollutant
HC
CO
MYR Group

1975-79
1980

1975-79
1980

1975-79
1980
Low:  Less
than .05 g/gal

 2.10
 0.76

25.52
 9.43

 2.42
 1.75
High: Greater
than .05 g/gal

 2.80
 0.59

36.47
 8.22

 2.71
 1.54
The  1980  cars have  lower  emissions  in the  high  lead group  because that
group contains no  high  emitting  HC/CO  vehicles.   For example, the maximum
HC value  of  the  high lead cars  is  2.79 gm/mi.  In  contrast  to  this,  the
low  lead  group  contains seven vehicles over  4.1  gm/mi,  with  one  at 13.7
gm/mi.  A similar comparison could be made for CO.

A  better  comparison of  the  emission  effects of misfueling  for  1980  EF
vehicles would be  to focus on the emissions  of high lead  versus low lead
cars  in  the sample of  vehicles  that  omits all   low   lead  cars  with
emissions above  the highest  emission value  of the  high  lead cars.   This
technique  removes  those  low lead  cars  that  have  high emissions  for
factors other than misfueling.  The comparison is shown in Table 6.

                                 Table 6

                      Average  Emissions  of 1980 Cars
                    with Low and  High Lead Fuel Values
                   without High-Emitting  Low  Lead Cars
                 Pollutant

                    HC
                    CO
                   —Emissions (gm/mi)—
                   Low Lead        High Lead
                     0.56
                     7.30
                  0.59
                  8.22

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                                                                        11
The data  in Table 6  indicate that  the  emissions of  high-lead  cars  are
higher than  low  lead  1980 cars, but  only slightly.    One  explanation  for
the small difference  in emissions  of high and  low lead cars  is  that  the
owners  with  the high  lead  cars   that   have   agreed  to  participate  in
emission  factor  programs  may  only  infrequently misfuel with • leaded fuel.
This type of  infrequent misfueling does  not  damage  the catalyst  as  much
as persistent misfueling with leaded fuel.

3.4    Low Altitude Emission Rates

3.4.1  HC and CO

The low  altitude HC and  CO  1975-79 and  1980  emission rates  for vehicle
samples  with  and  without   the   tampered   and  misfueled  vehicles   are
presented in  Table  7.  Model year groups are  the same as those  used  in
MOBILE2.  The  "all"  code under Tamp/Mfuel  status means that  no vehicles
are excluded.  The "no  tamp"  status means that vehicles with  evidence  of
air pump  tampering> filler neck tampering,  lead values above 0.05 gms/gal
or with catalysts removed are excluded.   Vehicles with EGR tampering were
included  for  the HC  and CO emission  rates,  since EGR  tampering  has  been
demonstrated  to  not  influence HC  and CO emission rates  significantly.*
The  emission  rates   in  Table  7  are  somewhat  lower than   the  MOBILE2
emission rates,  which are presented in Table 8.
                                 Table 7

     Low  Altitude  Emission Rates  of  1975-80  LDV's  —  Current  Analysis

          Tamp/Mfuel                	HC	        	CO	
          Status          N_        ZML       DR        ZML     DR

1975-79   All             3576       1.09      0.26      18.33   2.16
          No Tamp         3512       1.07      0.27      18.23   2.59

1980      All             595       0.36      0.10       6.10   0.74
          No Tamp         556       0.36      0.10       6.09   0.73
Removal of tampered and misfueled  vehicles  seems  to have little impact on
the emission  rates.   This was expected, since  the  frequency of tampering
in the EF sample was found to be low  (each  item with the exception of EGR
tampering is  less than 3.5%).
    This  was a  conclusion  in  "Light  Duty Driveability  Investigation",
    EPA/460-3-78-012, Dec.,  1978.   When fourteen 1978  cars  underwent EGR
    disconnections, average HC decreased  1.4%,  average  CO  increased 0.9%,
    and average NOX increased 210%.

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                                                                        12
                                 Table 8

                MOBILE2 HC  and  CO  Exhaust  Emission  Rates
                    for 1975-80  LDGV's at Low  Altitude

                      	HC	             	C0;	
MYR Group             ZML        DR              ZML       DR

1975-79               1.29       0.29            20.16     2.86
1980                  0.29       0.29             6.14     2.86
The most  notable differences between  MOBILE2 and  MOBILE3  are  in  the HC
and CO deterioration rates  for  1980 vehicles:  the new estimates are about
one-third of the MOBILE2  estimates.  The 1980 EF sample includes the  1980
GM  vehicles  which have  sealed  carburetors.*   Recent regressions  of 290
1980 GM  vehicles have  estimated the HC  and CO DR's  to  be  0.06 gm/mi/lOK
and  0.42  gm/mi/lOK,  respectively.    These   are  lower  than  the   DR's
developed ror the 1980 EF sample which includes all manufacturers.

3.4.2    NOX Emission Rates

The  low  altitude NOX  emission  rates  for  1975-80  vehicles  are  shown in
Table  9.   These were estimated  after  the  same tampered  and misfueled
vehicles  were  removed  as were  removed  for the HC/CO  analysis,  with the
addition  that  EGR tampered  vehicles were  also removed.  Removal  of the
EGR  tampered  vehicles had  a small  impact on  the emission  rates.   Also
shown are the MOBILE2 NOX emission  rates.

                                 Table 9

                              Low  Altitude
                  NOX Emission Rates for  19/5-80  LDGV's

                                    Current
                                 —Analysis—       —MOBILE2—
MYR Group           N            ZML        DR       ZML       DR

1975-76            1815          2.44       0.03     2.43      0.04
1977-79            1582          1.70       0.09     1.69      0.10
1980                544          1.50       0.07     1.56      0.10

The emission rates from  the current analysis  in  Table  9 are changed  very
little from the  MOBILE2 emission rates.
    Although  GM  used  sealed  carburetors  on  most   1979  models,  their
    proportion   of   the  1975-79  sample  is  much   smaller   than  their
    proportion of the 1980 sample.

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                                                                        13
3.4.3  Summary of all Low Altitude Pre-1981 Rates

The  proposal  is  to  use  the  new  estimates  as  presented   in  Tables  7
(without  tampering)  and  9 for  1975-79  and  1980 emission  rates  at  low
altitude  for MOBILE3.   The pre-1975 emission  rates  would be  the  same as
in MOBILE2.   This ignores  the  effect of  tampering on  pre-1975 emission
rates.   However,  the  current  analysis  has demonstrated  a  rather small
impact on the  emission  rates  from  the  low  level of tampering  in  the EF
sample*  Also, pre-1975  vehicles  had  few emission controls to be tampered
(catalysts,  for  example),  so  tampering  was  likely  a smaller  problem on
these vehicles.   Therefore,  ignoring  pre-1975 tampering  very likely does
not  pose a  problem  of  accuracy with  respect  to  the  pre-1975 emission
rates.

The  new  rates  for  all  pre-1981 years  are presented  in Table  10.   The
MOBILE2 50K emission levels are presented for comparison.

                                 Table  10

                 MOBILE3 Exhaust Emission Rates  for  1980
                    and  Earlier Low Altitude 49-State
                  Light-Duty Gasoline  Powered  Vehicles

             Model                        50K Mile         MOBILE2  50K
Pollutant    Years       ZML      PR       Emission Level   Emission
HC           Pre-1968    7.25    0.18      8.15             8.15
             1968-69     4.43    0.25      5.68             5.68
             1970-71     3.00    0.37      4.85             4.85
             1972-74     3.36    0.17      4.21             4.21
             1975-79     1.07    0.27      2.42             2.74
             1980        0.36    0.10      0.86             1.74

CO           Pre-1968   78.27    2.25     89.52            89.52
             1968-69    56.34    2.55     69.09            69.09
             1970-71    42.17    3.13     57.82            57.82
             1972-74    40.78    2.44     52.98            52.98
             1975-79    18.23    2.59     31.18            34.46
             1980        6.09    0.73      9.74            20.44

NOX          Pre-1968    3.44    0.0       3.44             3.44
             1968-72     4.35    0.0       4.35             4.35
             1973-74     2.87    0.04      3.07             3.07
             1975-76     2.44    0.03      2.59             2.63
             1977-79     1.70    0.09      2.15             2.19
             1980        1.50    0.07      1.85             2.06

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                                                                        14
3.5    High Altitude Emission Rates

3.5.1  HC and CO Emission Rates

Analysis of  covariance  yielded  the high  altitude  zero  mile  levels  and
deterioration rates in a manner similar to low altitude.

In the MOBILE2 analysis, a test of  equal DR's  for all three pollutants at
low and  high  altitudes was rejected only  once (1970-71  CO emissions) at
the 5% level  of  significance.   Therefore,  the low and  high altitude DR's
were assumed  to  be the  same.  Since then,  more data have  been collected
at low and high altitude.  The new  data  is  showing that the assumption of
equal  low  and high  altitude  Dk's  is  being rejected also  for .HC  and CO
emissions  of  1978-79  vehicles.    The  significance  levels  are shown in
Table  II.  By the  MOBILE2 criteria a  significance  level  greater than  .05
indicates  that  the hypothesis that  the  DR's are  equivalent  is accepted.
Significance  levels   less  than  .05  indicate  that   the  hypothesis  is
rejected.

                                 Table  11

                        Significance Levels of the
                         Assumption  of  Equal  DR's
                      Between Low and High  Altitude:
                             1978-79 Vehicles

Pollutant      Region            N[             DR           Significance

   HC          Low        '        1027          0.23            .004
               High               290          0.44

   CO          Low                1027          1.92            .0002
               High               290          5.87
An  examination  of  the  scatter  plots  of  emissions  versus  mileage  of
1978-79  vehicle at  low and high  altitudes reveals  that  there  are many
more  high mileage  vehicles (i.e.,  60-100K) in  the  low  altitude  sample
than  in the  high  altitude sample.   This  Leaves  the  imprv-ssion  that  if
more high mileage  high altitude vehicles had been  tested,  the DR's would
have been  similar.   However,  an examination of  the CO  data  in the high
altitude  mileage   range  (0-68K  miles)   for   both  altitudes   revealed
significantly  more gross  emitters  in the  high  altitude  sample  than the
low altitude  sample.   At high  altitude,  4.5% of  the vehicles were between
100  and  150  gin/mi  CO.   At  low altitudes, the  percentage  of   vehicles
between 100 and  150 gm/mi  CO was 0.7%.

The  data on  balance  indicates that  separate   DR's   should  be  used  for
1978-79 vehicles at  low and high  altitude.   However, since only one group
is  involved  it  was  decided  to  preserve  the  consistency  of  the  model
(i.e.,  DR's of  all  model year  groups at  low and  high altitude are  equal)
rather  than  to make an  exception for  one model year  group.   Also,  using

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                                                                        15
different DR's  for this  group  would not  have much  impact  on the  fleet
emission rates.   For example, on January 1,  1988,  the  1978  and 1979  model
year groups  accumulate less  than  8% of  the  fleet  VMT.   Therefore,  the
data at  all  altitudes  and  all  regions will  be  used  to establish  DR's
(where  technologies and  standards  are similar   between  Ca-1 Eornia  and
non-California vehicles),  while the  non-California altitude-specific  data
will be used to establish the low and high  altitude zero mile levels.

For MOBILE2,  the  emission rates of  1977 vehicles at high  altitudes  were
separated from  the 1975-79  group  creating  three groups:  1975-76,  1977,
and 1978-79.  The reason  for  this  was to adequately reflect  the situation
in  1977  in  which manufacturers were  required  to meet  the  new  vehicle
emission standards at low and high altitudes.   Manufacturers  responded by
selling  very few  models  at  high  altitudes,  and the  requirement  for
meeting standards at high altitude was relaxed for the  1978  model  year.
Consequently, the MOUILE2  emission rates  for  high  altitude  are  lower for
the 1977 model year than for the surrounding model year groups.

The new HC  and  CO emission  rates  for LDGV's at high altitudes are  shown
in Table  12.  Vehicles  that were  misfueled  or had  evidence  of  tampering
(except for EGR tampering) were removed.   Also shown are  the MOBILE2 high
altitude emission rates.

                                Table 12

               High Altitude LDGV HC and CO Emission Rates

                   	HC	      	CO	
                    Current       MOBILE2        Current       MOBILE2
            N      ZML    DR     ZML    DR      ZML    DR     ZML    DR
1975-76
1977
1978-79
1930
255
124
290
114
2.02
0.95
2.10
0.78
0.27
0.27
0.27
0.10
2.41
1.07
2.10
0.46
0.29
0.29
0.29
0.29
43.07
16.97
39.78
22.80
2.59
2.59
2.59
0.73
50.46
19.55
39.39
18.22
2.86
2.86
2.86
2.86
3.5.2  NOX Emission Kates

The  new  NOX  emission rates  for LDGV's  at  high  altitude  are shown  in
Table 13.  The data set  that was used  in  the  preceding  HC/CO analysis was
used, except that EGR-tampered vehicles were also reuoved.

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                                                                        16
                                 Table  13

                     High  Altitude  NOX  Emission  Rates

                                 	Current.-—         	MOBILE2	
MYR Group           N            ZML        DR         ZML        DR

1975-76            247           1.70       0.03       1.70       0.04
1977               121           1.42       0.09       1.42       0.10
1978-79            285           1.00       0.09       1.02       0.10
1980               110           0.82       0.07       1.02       0.10


3.5.3  Summary of Pre-1981 High  Altitude Emission Rates for MOB1LE3

Using  the data  from  the current  analysis,  the  high  altitude emission
rates  for pre-1981  LDGV's  for  MOBILE3  are presented  in Table  14.   The
MOBILE2 50K emission levels have also  been  presented for comparison.

                                 Table  14

                 Exhaust Emission Rates for High Altitude
              49-State  Light-Duty Gasoline  Powered Vehicles

             Model                         50K Mile         MOBILE2  50K
Pollutant    Years      ZML      DR       Emission Level   Emission Level

HC           Pre-1968     9.35   0.18       10.25            10.25
             1968-69      5.60   0.25       6.85              6.85
             1970-71      4.58   0.37       6.43              6.43
             1972-74      4.58   0.17       5.43              5.43
             1973-76      2.02   0.27       3.37              3.86
             1977         0.95   0.27       2.30              2.52
             j.978-79      2.10   0.27       3.45              3.55
             1980         0.78   0.10       1.28              1.91

CO           Pre-1968   -117.70   2.25      128.95           128.95
                                                            98.29
                                                            95.29
                                                            87.83
                                                            64.76
                                                            33.85
                                                            53.69
                                                            32.52

NOX          Pre-1968     1.96   0.0        1.96              1.96
             1968-72      2.91   0.0        2.91              2.91
             1973-74      1.91   0.04       2.11              2.11
             1975-76      1.70   0.03       1.85              1.90
             1977         1.42   0.09       1.87              1.92
             1978-79      1.00   0.09       1.45              1.52
             1980         0.82   0.07       1.17              1.52
Pre-1968
1968-69
1970-71
1972-74
1975-76
1977
1978-79
1980
-117.70
85.54
79.64
75.63
43.07
16.97
39.78
22.80
2.25
2.55
3.13
2.44
2.59
2.59
2.59
0.73
128.95
98.29
95.29
87.83
56.02
29.92
52.73
26.45

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                                                                        17
4.0
 CORRECTION FACTORS
The  speed  and temperature  correction factors are  being updated under  a
support contract  from  EPA data generated  in  FY83.   The NOX  vs.  humidity
correction  factor  relationship was  presented  in another analysis*.   The
trailer towing  and air  conditioning correction  factors  used in  MOBILES
will be the same as those used in MOBILE2.

4.1    Normalized Bag Fractions

Normalized  bag  fractions  are ratios  of  a  bag's  emissions  to  the  FTP
composite zero mile levels.   They  are used to predict  the  emissions  if  a
user  selects operating   mode characteristics   that  are  different  from
standard  conditions   (20.7%   cold   start,  52.1%  stabilized,   27.3   hot
start).  New normalized bag fractions were computed from the new data for
1975-80 model years.  The same  values  are  used  at  both  low and  high
altitudes.  The new bag fractions are presented in Table 15.

                                Table 15

                       Normalized Bag Fractions for
                                 LDGV's
Pol

HC


CO
Model Year

1975-79
1980

1975-79
1980
—Seg. 1	
 Bl     Dl

1.856  0.345
2.200  0.714

1.792  0.177
2.403  0.278
—Seg. 2	
 Bl     D2

0.765  0.233
0.571  0.171

0.882  0.157
0.649  0.061
—Seg. 3	
 B3     D3

0.802  0.196
0.914  0.143

0.628  0.109
0.612  0.076
-Total Test-
 Bo     Do
1.000
1.000

1.000
1.000
0.246
0.274

0.148
0.110
NOx   1975-76     1.297  0.012   0.781  0.004   1.194  0.016
      1977-79     1.371  0.040   0.766  0.046   1.166  0.063
      1980        1.313  0.047   0.810  0.034   1.125  0.054
                                                         1.000  0.009
                                                         1.000  0.049
                                                         1.000  0.042
      Memo from  C.  Shih to  R.  Stahman,  September  1,  1983,  "New Humidity
      Correction Factors for MOBILE3."

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