EPA-AA-IMS-81-23
Evaluation of I/M Effectiveness  Using Emission Factors Data:
    Phoenix vs.  Other Low-Altitude, Non-California Sites
                       October, 1981
                      James  Rutherford
              Inspection  and Maintenance"Staff
            Emission Control Technology Division
       Office of Mobile Source. Air Pollution Control
            Office of Air, Noise, and Radiation
            U.S.  Environmental Protection . ^ency
                    Ann Arbor,  Michigan

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1.0 INTRODUCTION

1.1 Purpose

The Emission Factors (EF) Testing Program is a  continuing project  in  which  the
Environmental  Protection  Agency  (EPA)  contracts  with  several   independent
laboratories  to perform  emission testing  of  samples  of  in-use  vehicles  in
several cities  in  the United  States.   Phoenix,  Arizona  has  been a site  for  EF
testing for several years both  before  and  after the advent of  its  Inspection/
Maintenance (I/M)  program.  Federal Test Procedure  (FTP) data  recorded  from  EF
testing  in Phoenix and  several  non-I/M  cities   provide  an  opportunity  to
evaluate  the  effectiveness  of  the  I/M  program  in reducing  emissions  from
in-use light duty vehicles.*

This  report  presents  an  analysis  of  EF  data  directed  toward estimating  the
effects of the Phoenix I/M program.

1.2 Summary

Preliminary evaluations  of  the means  of  the  raw  data indicate  a  definite
reduction  in  emissions  due to  I/M.   More sophisticated analyses  of the  data
using analyses  of  covariance  allow  for statistical testing and  quantification
of  the  differences due  to  I/M in Phoenix.   As a  result  of  the  analyses  of
covariance, the mean emissions  of FTP  HC  and  CO are found to  be  statistically
significantly   lower  after   I/M   in  Phoenix  than  in  the   other   non-I/M,
low-altitude,  non-California  EF testing sites  while there  was no  significant
difference  before  I/M began.   Within  about  two  years of  the start  of  the
Phoenix I/M program, reductions due  to I/M are about  twenty  percent for  both
HC and CO.  Analyses of  test  results  from vehicles  tested  in  more than  one  EF
program provide qualitative corroboration of the reductions  due to  I/M.
* EPA  has  taken advantage of  several  other opportunities previously;  reports
documenting this  previous  work are  listed  in  the bibliography at  the end  of
this report.

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2.0 ANALYSIS

2.1 Data Inclusion

Emission  Factors  testing  included  Phoenix, Arizona  in the  Fiscal Year  (FY)
1974, 1975, 1977 and  1979  programs.*   Other low-altitude,  non-California  sites
in  these  programs  were  Chicago,  Houston,  St.  Louis,  and  Washington,   D.C.
These four sites do not have I/M programs.   For this  analysis,  all as-received
FTP  tests  from the four non-I/M,  low-altitude, non-California sites  on  model
year  1972-1978  light  duty  passenger  cars  were  used.    For  Phoenix,  all,
as-received tests  for these model years  were  used from the  FY 1974  and  1975
programs.  For the FY  1977 and 1979  programs,  the  tests for  cars  of  these
model years in Phoenix were used if  there was  indication that the  vehicle  had
participated in the I/M program.  Some vehicles were too young when tested to
have participated yet;  others  may  have immigrated  to Phoenix too  recently to
have since participated.

The model years included in the analysis  provide  two  distinct emission control
technologies.   The  1972 through  1974  model years  are  pre-catalyst  vehicles
subject  to the  same  new  car emission standards  for  HC  and CO.   The   1975
through 1978 vehicles are  first  generation catalyst vehicles all  subject  to  a
more stringent set of new  car  standards for HC and CO.   In this  report,  these
two  groups of vehicles  are  referred  to  as  Technology  I and  Technology  II
vehicles  respectively.   Although  the  EF  programs  included  vehicles  of  model
years before  and  after the above mentioned groups,  they  are not  included in
this  analysis  since   they are  sufficiently  different  in  emission   control
technology and they are  not included in enough of  the  FY  programs  to provide
before  and  after  I/M  comparisons.   Model  years  before  1972  were subject  to
less stringent new car tailpipe emission  standards  defined on an  obsolete test
procedure.  Although 1979 model year vehicles were  subject to  the  same new  car
HC and  CO  standards as  the 1975-1978  model year vehicles,  the majority of  the
sample  for this model  year was General Motors vehicles  utilizing  sealed  idle
mixtures.  They have  emission  characteristics  sufficiently different  from  the
rest of  the sample  to cause variability problems  in  the analysis  if  included
with the 1975  through  1978  model  years.

2.2 Analysis of Covariance

The  individual FY programs  of  the  EF testing provide convenient  discrete  test
points  for comparison  of  test  results  between  Phoenix  and the non-I/M cites.
One FY program was carried  out at approximately the same point in  time at  all
the  sites.  There was  a lapse  of time  between  FY programs.   The  FY74 testing
was  performed  before  the  advent of  the   Phoenix  I/M program.   Based on  the
January  1,  1977  start-up date for mandatory Phoenix I/M and test dates  from
the  FY75  EF testing  in  Phoenix,  it  is estimated  that  roughly  one-fourth  of
those tests were on vehicles which  had participated in the  I/M program. For
* See bibliography at the end of this report for EF testing  documentation.

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the FY77  and  FY79 programs,  information  was  available indicating whether  the
vehicles had experienced I/M  and only  data from vehicles in Phoenix which  had
experienced I/M were included in the analysis.

A  preliminary  indication of  I/M  effects  can  be gleaned  from examination  of
simple mean emissions  and  mileage  at the  test  points.  As  will be seen,  this
examination was performed.  However, variations  in accumulated  mileage  need  to
be  accounted  for  in  making  precise  comparisons.   This  was achieved  through
analysis  of  covariance.   The  effects  of  I/M  are  evaluated  by comparing  the
non-I/M cities with Phoenix at each test  point  after  accounting for mileage  as
a covariate.  The  initial analyses  of  covariance using raw data were  found  to
be  invalid due  to non-normality of residuals  as determined by the Lilliefors
adaptation  of  the Kolmogorov-Smirnov  test.   A  log  transformation  of  the
emissions  data  was performed.   The analyses  of covariance  performed on  the
transformed data were  found  to be  valid.   The  resultant analyses  performed  at
each test point within each  technology with groupings for Phoenix and  non-I/M
cites  and mileage  as  a  covariate provided  valid  statistical tests  of  the
effects of I/M.  The adjusted means for Phoenix and non-I/M  cites  also provide
good estimators of mean emissions at the  mean mileage  for total samples (i.e.,
mean mileage for Phoenix and non-I/M cites combined).

It  should  be  noted that  the validity of  log-transformed  data  in  the  analyses
of  covariance  and  the invalidity  of  raw data for  these   analyses  does  not
necessarily imply  non-linearity of  emissions  deterioration  with mileage.   The
usual linear estimation of  emissions deterioration on mileage  is  based on  the
useful life of vehicles.  This  is  a much  larger span of mileage than  was  used
in  each   of  these  analyses.   While  it  may   be more  appropriate  to assume
exponential deterioration of  emissions over the  relatively short mileage  spans
used  in  the  individual  analyses  of covariance  presented  in  this report,  it
could yet be more  appropriate  to assume  linear deterioration over the  life  of
a vehicle as is commonly done.

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3.0 RESULTS

3.1 Fiscal Year Results

As  explained  above,  the  individual  FY programs  provide convenient  discreet
points  for  estimating the  relative deterioration  in  emissions  that  occurred
over time in  the  EF data.  For  the FY74 program,  none  of the data come  from
vehicles exposed to I/M.  Approximately one-fourth  of  the Phoenix vehicles had
experienced I/M before  the  FY75 testing.  From  the  FY77 and FY79  programs  in
Phoenix, data was only used  from vehicles for which there was  indication  that
the vehicle had experienced I/M.

3.1.1 Raw Data Results

A  preliminary  examination  of the  I/M  effects  is  presented  in  Table  1  and
Figures  1  through  4.   The  general conclusion  from means of  the raw data  is
that the Phoenix mean emissions  are approximately  equal  to mean emissions  from
the other cites before I/M  (FY74 means).   After I/M, in  the later  EF  programs
(FY75,  FY77,  and  FY79),  the  mean  emissions  for Phoenix  are  lower than  mean
emissions for the other cites.

3.1.2 Adjusted Mean Results

As  discussed  above,  the  next   step  in  this  investigation was  a  series  of
analyses  of  covariance   performed  at  each  test   point   (i.e.,  for  each  FY
program), for  each  technology,   for each  pollutant,  stratified by  presence  or
absence  of  I/M (Phoenix  or other sites) with mileage as a covariate.   These
analyses allow  valid  statistical testing of  I/M effects after accounting for
mileage effects and the estimation of mean emissions at the same mileage.

Table 2  and Figures  5  through   8  present  the results of these  analyses.   As
seen in  Table 2, there are  no significant differences between  Phoenix and the
other sites in the FY74 program  (before Phoenix  I/M).  Progressing  through the
EF  programs,  a significant  difference  develops  in both  HC and  CO for  both
technologies between Phoenix and the other sites.

The reader may notice a counterintuitive  result  in Table 2 and Figure 6.   The
adjusted mean  CO  emissions for  Technology  II vehicles  drop between the  FY74
and the FY75 programs for both  Phoenix and the other  sites.   An  investigation
of  this  phenomenon  indicated  that Technology II vehicles in the FY74 program
were primarily model year 1975 vehicles while in FY75  they were primarily  1976
vehicles.   The 1976  model  year  vehicles  in   addition  to  having  a  higher
percentage  of  catalysts  and air  pumps  may  also have  been more  reliable  than
the  1975 model year  vehicles  due to  one  year of  experience  with  the  new
emission control  technology.   Thus, the  drop in emissions  is  understandable.
It does not affect the comparison between Phoenix and other sites.

The I/M  program in Phoenix  became mandatory January 1, 1977.   All  testing for
the  FY74 EF  program  was  completed  before  that  date.    FY75  EF  testing  in
Phoenix  was performed in  the first  part of calendar  year 1977.   The Phoenix
testing  for the FY77  program was  carried out  in  the  last  three  months  of

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calendar year 1977.  The Phoenix  testing  for the FY79 program  occurred  in the
first part  of calendar year  1979.   From Table  2,  it  appears  that within the
first two  years  of the  implementation  of I/M  in  Phoenix,  there is  roughly  a
twenty  percent  reduction  in emissions  of  HC  and  CO  relative to  what  the
emissions would be without I/M.

3.2 Repeated Testing Results

Many  vehicles  in the  EF programs  experienced  repeated  tests,  that  is,  they
were  tested  in more  than  one  FY program.  Although  restricting analyses  to
only  the  vehicles  with  repeated   tests  reduces  sample  sizes  greatly  and
provides  less than  adequate  representation  of the  vehicle  fleet,  it  does
provide  a  qualitative corroboration  of  the conclusions  reached in  the  above
analyses.

Analyses analogous to  those  used in  the  results described above were  carried
out on  the  repeated  testing samples.  For  example,  for  all  vehicles included
in  both  the  FY74 and  FY75  programs,  an analysis  of  covariance was  performed
for each of  the  FY  programs,  for  each  pollutant, and  each technology.   The
adjusted means  are  then compared for these  repeated  testing  samples  between
Phoenix and the other sites for both FY programs.

The results of  these  analyses are presented in Table  3  and Figures  9  through
12.   The general  conclusion  reached from these  analyses  is that with  I/M the
vehicles tested in Phoenix show less  deterioration from one FY  program  to the
next  than the vehicles from  the other sites.   Thus, the  conclusion reached  in
the previous  section  are  supported by the  analyses  of  the repeated  testing
samples.

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BIBLIOGRAPHY

EPA I/M Evaluations

Becker,  J. ,   "Portland  Study:  First Preliminary  Analysis",  EPA-CAB-2/POR-1,
May, 1978.

Rutherford, J. ,  "Portland  Study Interim Analysis:  Observations  on Six  Months
of Vehicle Operation", EPA-IMS, January, 1979.

Rutherford, J.,  "Portland  Study Interim Analysis:  Update  With Nine Months  of
Vehicle Operation",'EPA-IMS-004/PS-2, May,  1979.

Becker,  J. ,   and   Rutherford,   J. ,  "Analysis  of  Oregon's  Inspection   and
Maintenance Program",  presented at  72nd  Annual APCA  Meeting and  Exhibition,
No. 79-7.3, June, 1979.

Rutherford,  J. ,  and  Waring,  R.,   "Update  on  EPA's  Study  of  the  Oregon
Inspection/Maintenance  Program",  presented  at 73rd  Annual  APCA  Meeting  and
Exhibition, No. 80-1.2,  June, 1980.

Michael,  B.,   "Evaluation  of  California  Change-of-Ownership  I/M  Program",
EPA-IMS Memo,  January, 1981.

Tiao, G.C., Leaolter, J. ,  and Hudak, G. ,  "Statistical Analysis  of the  Effect
of  Inspection and  Maintenance on  Carbon  Monoxide  Air Quality  in  Portland,
Oregon", EPA-460/3-81-016,  May, 1981.

Michael, B.,  "Emission  Reductions   from  Inspection and Maintenance:  Vancouver
Versus Portland Snapshot",  EPA-AA-IMS-81-18, August, 1981.


Emission Factors Testing Documentation

Bereus, A., and Hill, M.,  "Automobile Exhaust  Emission Surveillance -  Analysis
of the FY 1974 Program", EPA-460/3-76-019,  September, 1976.

Rutherford, J. , "Automobile Exhaust Emission  Surveillance  -  Analysis of  the  FY
1975 Program", EPA-460/3-77-022, December,  1977.

"A  Study  of  Emissions  from Passenger Cars  in Six  Cities",  EPA-460/3-78-011-
a-b, January,  1979.

"FY79  Study  of  Emissions  from Passenger  Cars in  Six Cities",  EPA-460/3-80-
020A-B, October, 1980.

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                             8

                          Table 1

Mean FTP Emissions and Mileages for Phoenix and Other Sites
              by EF Program and Technologies
EF
Program
N
Other Sites
Mileage HC
Technology
FY74
FY75
FY77
FY79
470
518
889
600
8454
14058
26141
31947
1.33
1.49
1.97
2.15
Technology
FY74
FY75
FY77
415
398
432
29646
39875
56701
3.79
3.86
4.88
CO
N
II (1975-78 Model
22.73 117
22.16 200
25.94 179
28.21 135
I (1972-74
46.33
50.32
55.64
Model
82
145
112
Phoenix
Mileage
Years)
10249
15983
20349
28805
Years)
32821
44579
53023

1
1
1
1

3
3
3
HC

.30
.34
.56
.51

.53
.67
.48
CO

23
17
18
19

45
51
43

.65
.56
.68
.63

.71
.52
.02

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                                         Table  2

          Adjusted Mean FTP Emissions and Mileages for Phoenix and Other Sites
                             by EF Program and Technologies
  EF            Other
Program Mileage Sites
                               HC
                   Phoenix
                           Difference
Sig.
                                                                 CO
Other Phoenix
Sites
                        Difference
Sig.
                           Technology  II  (1975-78 Model Years)
FY74
FY75
FY77
FY79
8812
14595
25170
31370
1.07
1.19
1.53
1.62
1.05
1.06
1.23
1.32
                                   2
                                  11
                                  20
                                  19
                                       ns
                                        *
                                       **
                                       **
          15.24  16.02      5        ns
          13.47  11.08     18         *
          17.26  13.82     20        **
          19.03  15.95     16         *
                           Technology I (1972-74 Model Years)
FY74    30170   3.31    3.15       5       ns
FY75    41131   3.37    3.21       5       ns
FY77    55944   3.80    3.05      20       **
                                                  37.16   37.98      2        ns
                                                  41.75   43.32      4        ns
                                                  45.93   35.39     23        **
  Sig. =      Statistical  Significance of  the  difference
              emissions between Phoenix and other sites.
         Significant at .01 level;
         Significant at .05 level;
    ns:  Not significant at .05 level.
**
*
                                                         in  adjusted mean

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                                      10  .

                                    Table  3

     Adjusted Mean FTP Emissions and Mileages for Phoenix and Other Sites
          from Repeated Testing Samples by EF Program and Technology
            Sample Size
HC
CO
Sample*
74/75
75/77
77/79

74/75
75/77
Other
Sites Phoenix Mileage
Technology II
86 29 7743
21416
106 90 13386
28461
69 36 19735
35264
Technology I
127 42 26854
37443
87 84 38868
50577
Other
Sites
(1975-78 Model
1.09
1.28
1.16
1.59
1.25
1.74
(1972-74 Model
3.32
3.29
3.50
3.63
Phoenix
Years)
1.16
1.41
1.10
1.32
.98
1.27
Years)
3.12
3.12
3.17
3.22
Other
Sites

16.43
16.87
13.47
17.80
13.84
19.93

36.97
36.84
40.79
45.49
Phoenix

15.83
16.39
11.16
13.90
12.05
15.21

42.10
41.85
43.84
40.17
*   The samples are  restricted  to vehicles tested  in  both FY  programs,  e.g.,
    the 74/75 sample  includes  only vehicles tested in  both  the FY74 and  FY75
    EF programs.

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  2.50
  2.00
CD
  1.50
CJ
X

£1.00
u_



 0,50




 0.0
                                          11

                                        Figure 1

                Mean EC Emissions and Mileages  for  Phoenix and Other Sites
                          by EF Program:  Technology II Vehicles*
                                               .-•X
                                         .*"'
                         .-X
OTHER  SITES

PHOENIX
            0      10000      20000       30000
              5000      15000      25000       35000
                           MILEflGE
    * X's indicate  FY74, FY75, FY77,  and FY79 means, respectively, from left to
    right on each line.  "Other Sites"  includes no I/M vehicles.  "Phoenix"
    includes no I/M for FY74, about one-fourth I/M for FY75,  and all I/M for
    FY77 and FY79.

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                                     12
                                  Figure 2

          Mean CO Emissions and Mileages for Phoenix and Other Sites
                    by EF Program:  Technology II Vehicles
 30



 25



 20
a:
e_

o!5

c_

^10
                                          ..x
                                   .*••'
OTHER SITES

PHOENIX
     0       10000      20000       30000
        5000       15000       25000       35000
                     MILEflGE
*   X's  indicate FY74, FY75, FY77, and FY79 means, respectively,  from  left  to
right on  each  line.   "Other  Sites"  includes  no  I/M  vehicles.   "Phoenix"
includes  no  I/M  for  FY74, about one-fourth  I/M for FY75,  and  all  I/M  for  FY77
and FY79.

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 5.0
 H.O
:3.0
:2.0
 1.0
 0.0  I	L
                                          13
                                      Figure  3

              Mean HC  Emissions and Mileages for Phoenix and Other  Sites
                        by EF Program:  Technology I Vehicles*
f.
   X	   OTHER  SITES

   *	   PHOENIX
     20000      30000     40000     50000     SOOOO
                         MILERGE
       *   X's  indicate FY74,  FY75,  and  FY77 means, respectively,  from  left  to  right
       on each  line.   "Other Sites"  includes no  I/M vehicles.  "Phoenix"  includes no
       I/M for  FY74, about one-fourth I/M for FY75, and all I/M  for FY77.

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                                        14
                                    Figure 4

            Mean CO Emissions  and Mileages for Phoenix and Other Sites
                       by  EF Program: Technology I Vehicles *
  SO
  50
Q_
O
o30
o
 '20
  10
                 *"
                                       _L
                                  j_
                                       X	  OTHER  SITES

                                       X	  PHOENIX
     20000
30000
 40000
MILERGE
50000
60000
   *  X's indicate FY74,  FY75,  and FY77 means, respectively, from left to
   right on each line.  "Other Sites" includes no I/M vehicles.  "Phoenix"
   includes no I/M for FY74, about one-fourth I/M for FY75, and all I/M
   for FY77.

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                                        Figure 5
                                                                              15
           Adjusted Mean HC Emissions and Mileages for Phoenix and  Other  Sites
                          by EF  Program: Technology II Vehicles*
  2.0
  1.5
c.
err
a.
^~
u.
   . 0
  0.5
  0.0
                                                        X	   OTHER  SITES

                                                        X	   PHOENIX
           0       10000       20000       30000
             5000       15000      25000       35000
                           MILERGE
        *  X's  indicate  FY74,  FY75,  FY77,  and  FY79  means,  respectively,  from  left  to
        right  on  each  line.   "Other  Sites"   includes  no I/M  vehicles.   "Phoenix"
        includes no I/M for FY74,  about  one-fourth I/M for FY75,  and all  I/M for FY77
        and  FY79.   The means  have  been  adjusted  relative  to  Figure  1 .to  provide.
        estimates at identical mean mileages.   (See page 5 of text.)

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                                      Figure 6
                                                                             16
         Adjusted Mean CO Emissions  and  Mileages  for Phoenix and Other Sites
                        by EF Program: Technology II Vehicles *
  20
  15
a:
a.
olO
c_>
a.
t—
u.
                                                       X	  OTHER SITES

                                                       X	  PHOENIX
          0       10000       20000       30000
            5000       15000      25000       35000
                          MILERGE
    * X's  indicate  FY74,  FY75,  FY77,  and FY79 means,  respectively,  from left  to
    right  on each  line.    ".Other  Sites"  includes  no  I/M  vehicles.   "Phoenix"
    includes no I/M for FY74,  about  one-fourth I/M for FY75, and all  I/M  for  FY77
    and  FY79.   The means  have  been  adjusted  relative   to  Figure  2  to provide
    estimates at identical mean mileages.  The drop in mean emissions  from FY74  to
    FY75 appear to be  due to  increase in proportion of model year  1976  vehicles.
    (See page 5  of text.)

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                                     Figure  7

        Adjusted  Mean HC Emissions and Mileages for Phoenix and  Other  Sites
                       by EF Program:  Technology  I Vehicles *
                   17
  4.0


  3.5


  3.0
o.
o
z
a.
  i . o
  0.5
  0.0
X	  OTHER  SITES

X	  PHOENIX
      20000     30000     40000     50000     60000
                           M1LERGE
     * X's indicate FY74, FY75, FY77 means,  respectively, from  left  to  right on
     each  line.  "Other Sites" includes  no  I/M vehicles.  "Phoenix"  includes no I/M
     for FY74, about one-fourth  I/M  for FY75, and all I/M for  FY77.  The means have
     been  adjusted  relative  to Figure  3  to provide  estimates  at  identical  mean
    .mileages.  (See page 5 of text.)

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                                      Figure  8

         Adjusted  Mean CO Emissions and Mileages for Phoenix and  Other Sites
                        by EF Program:  Technology  I Vehicles*
                                                            18
  50
= 30
u
o
u

-20
u_
  10
                                        j_
                                                       X	  OTHER 'SITES

                                                       X	  PHOENIX
     20000
3000.0
 40000
H1LERGE
50000
60000
     * X's indicate FY74, FY75,  FY77  means,  respectively,  from  left  to right  on
     each  line.   "Other Sites" includes no  I/M vehicles.  "Phoenix" includes  no- I/M
     for FY74, about one-fourth.I/M  for FY75,  and all I/M for FY77.  The  means  have
     been  adjusted relative   to  Figure  4 to  provide  estimates  at  identical  mean
     mileages.  (See page 5 of text.)

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                                     19
                                   Figure 9


         Adjusted Mean HC Emissions and Mileages for Phoenix and Other Sites

         from Repeated Testing Samples by EF Program: Technology II Vehicles
2.0
  1.5




z
Q_


ol .0
3:

o.
i—
u.



  0.5
0.0
        0     10000     20000     30000     40000

          5000     15000     25000     35000

                       MILEflGE
                                                      •-  OTHER  74/75


                                                      ••••••••  OTHER  75/77


                                                      —  OTHER  77/79


                                                      —  PHOENIX  714/75


                                                          PHOENIX  75/77


                                                          PHOENIX  77/79

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                                    20
                               Figure 10


    Adjusted Mean CO Emissions and Mileages for Phoenix and Other Sites

    from Repeated Testing Samples by EF Program: Technology II Vehicles
20
  15




Z
0.
o

olO


0.
                                                  	  OTHER 74/75


                                                  ::::::::::::  OTHER 75/77


                                                  	  OTHER 77/79


                                                  	  PHOENIX 74/75


                                                         PHOENIX 75/77


                                                         PHOENIX 77/79
       0     10000     20000     30000     40000
         5000     15000     25000      35000
                      MILERGE

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                                      21
                                   Figure  11


        Adjusted Mean HC Emissions and Mileages for Phoenix and Other Sites

         from Repeated  Testing Samples by EF Program: Technology I Vehicles
a.
C3

u2
                   _L
                                         OTHER 7U/75


                                         OTHER 75/77


                                         PHOENIX 71/75


                                         PHOENIX 75/77
   25000
35000         45000
      MILERGE
55000

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                                     22
                                     Figure 12

          Adjusted Mean CO Emissions and Mileages  for Phoenix and Other Sites
           from Repeated Testing Samples by EF Program: Technology I Vehicles
  50
  40
= 30
o
a
o
  20
  10
                                         OTHER 74/75

                                         OTHER 75/77

                                         PHOENIX 74/75

                                         PHOENIX 75/77
    25000
35000         45000
      MILEflGE
55000

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                           ORIGINAL
                          DO NOT TAKE
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