IMS-004/PS-2
Portland Study Interim Analysis:
Update with Nine Months of Vehicle Operation
May 1979
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 Agency
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Introduction
This is the third in a series of interim reports on EPA's Portland
Study, a large scale passenger car testing program designed to study the
Oregon Motor Vehicle Inspection Program. The study, which is currently
in progress, has as its primary goal the evaluation of the costs and
effectiveness of an ongoing inspection and maintenance (I/M) program.
The first report, issued in May 1978, was a brief report, highlighting
I/M's immediate effectiveness following maintenance and the costs of
repairs. The second report, issued in January 1979, covered the study
design and background more extensively than did the first report, and
also included much more data analysis. Two of the key questions regarding
I/M are 1) the effectiveness of a short test in identifying vehicles
which are polluting excessively; i.e., are in need of remedial maintenance,
and 2) the amount and duration of emission reduction obtained immediately
after maintenance is performed on failed vehicles. These two questions
were addressed in the second interim report using data from the first
six months of the program. More extensive data are now available.
The present report will be a brief follow-up of the analysis contained
in the second report, focusing primarily on the above two questions.
The second interim report, which is available from the inspection
maintenance staff, should be referenced for background and study design
information, as well as for information on questions which are not
covered in the present report. The final report on the Portland Study
is expected to be completed in about six months. In the meantime,
requests for further information should be addressed to Janet Becker
(313-668-4351).
Summary
Based on data for 1975-77 model year cars in the Portland Study, substantial
reductions in emissions due to I/M are observed through three quarters
of a year. Specific conclusions are as follows:
(1) At a failure rate of 35%, the Oregon DEQ state inspection test
successfully identified the worst emitters of FTP HC and CO. The
average FTP CO level of the failed vehicles was three times that of
passed cars. The average FTP HC level of the failed cars was more
than twice that of the passed cars.
(2) The state inspection test identified as needing maintenance 56% of
all excessive FTP HC and CO emitters. These failed vehicles accounted
for 80% of the FTP HC and CO emissions which were in excess of the
Federal standards.
(3) For the I/M fleet (Portland vehicles), mean FTP HC had deteriorated
to the pre-maintenance level by the third quarterly retest; however,
it is still below that of the non-I/M fleet (Eugene vehicles).
Mean FTP CO is still below the pre-maintenance level at the third
quarterly retest.
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Discussion
This analysis is being prepared based upon data available from the
Portland Study as of April 11, 1979. The effort to address short test
effectiveness in identifying excessive polluters was complete. A total
of 2,207 1975-77 model year cars have been tested. Approximately 500 of
these vehicles had been tested over nine months' time to determine the
duration of I/M effectiveness. The goal of the study is 600. The
distribution of the 500 cars by model year and pass/fail status is given
in Table 1. Since the analysis is incomplete, estimates and tentative
conclusions are subject to revision.
This report presents data on vehicles through the first three quarters.
At completion, data will be presented for cars through four quarters.
(Once analysis is completed on the fourth quarterly results another
interim report will be issued.) Also, results for the 1972-74 model
year vehicles are not presented here due to the lack of appropriate
estimates to weight the results to make them representative of the
Portland area vehicle population. An attempt is being made to develop
these weights; in the meantime, the six month interim report should be
referenced.
Short Test Effectiveness
An indication of the Oregon Department of Environmental Quality's (DEQ)
short test effectiveness in identifying high FTP emitters is given in
Figures 1 through 3. The DEQ short test consists primarily of an idle
test, but also includes a brief physical inspection. Based on the 2,207
vehicles in 1975-77 model year sample, vehicles experienced a 35%
failure rate at the state inspection lane. This failure rate agrees
closely with that observed by the Oregon DEQ for all 1975 and later
model year cars in the Portland area. As is seen in the figures, mean
FTP HC and CO emissions are much higher for failed than for passed cars
(three times as high for CO and more than twice as high for HC). This
indicates that the DEQ test is successful in classifying cars as high or
low emitters of FTP HC and CO. The Oregon inspection test is not designed
to identify high emitters of FTP NOx and, as is seen in Figure 3, there
is practically no difference in mean NOx emissions between the passed
and failed cars. From an air quality standpoint, only 56% of the FTP
failures are caught, however, 80% of the FTP HC and CO emissions in
excess of the Federal standards are identified. This means that in
general the I/M test catches the worst emitters while letting the more
marginal emitters get by.
Emission Deterioration over Nine Months
Since the last interim report on the Portland Study, sufficient data
have been obtained and sufficient analysis has been performed to make
estimates of emission deterioration through three quarterly retests
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(approximately nine months following the initial inspection). These
results are presented in Table 2 and Figures 4 through 7.* Over nine
months, FTP CO deterioration for the I/M fleet remains fairly linear and
only slightly steeper than for the non-I/M fleet; however, FTP HC
deterioration is substantially steeper than the non-I/M fleet's deter-
ioration, especially during the second and third quarters. Idle emission
deterioration between the second and third quarters does not follow the
same pattern as the corresponding FTP deterioration, as illustrated in
Figures 4 and 5. It is seen that in nine months, mean FTP HC emissions
for the Portland fleet have deteriorated to the pre-maintenance level,
however, are still below the non-I/M fleet level. As seen in Table 2,
the failed cars which received maintenance have not returned to their
pre-maintenance levels. Mean FTP CO emissions for the Portland fleet
remain below pre-maintenance levels at the third quarterly retest.
* It is noted that the six month data presented in this report do not
exactly match the six month results presented in the second interim
report. This is to be expected. Different groups of vehicles had
completed three quarterly retest sequences than had completed two
quarterly retest sequences as of the last report. Also, the weights
used to make the sample estimates more representative of the Portland
population have been improved by the addition of more data.
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Table 1
Number of Test Sequences Completed by I/M Study Vehicles
(as of 11 April 1979)
Retest After First Second Third Fourth.
Initial Maintenance Quarterly Quarterly Quarterly Quarterly*
113
123
106 95
134 117
113
126
108
121
94
114
98
113
106
107
91
105
93
95
103
101
84
88
88
78
97
94
77
83
80
75
Portland, Model Years
72-74, passed
Portland, Model Years
75-77, passed
Portland, Model Years
72-74, failed
Portland, Model Years
75-77, failed
Eugene, Model Years
72-74
Eugene, Model Years
75-77
*Fourth quarterly results have not been included in this report.
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Table 2
Odometer (Miles)
Idle HC** (ppm)
Idle CO** (%)
FTP HC (gpm)
FTP CO (gpm)
FTP NOx (gpm)
Ongoing Effects of I/M*
1975-77 Model Year Cars
Portland Pass
Portland Fail
Initial
23257
70
.24
1.20
11.93
2.60
First
Quarterly
26629
91
.33
1.21
12.07
2.77
Second
Quarterly
29468
116
.48
1.28
13.54
2.64
Third
Quarterly
32051
104
.53
1.55
14.56
2.60
Initial
24660
311
3.03
2.87
40.63
2.29
After
Maintenance
25506
84
.16
1.64
20.51
2.36
First
Quarterly
28218
138
.66
1.85
24.30
2.27
Second
Quarterly
31079
196
1.06
2.28
24, 96
2.35
Third
Quarterly
33807
176
1.11
2.32
27.79
2.40
* All numbers have been weighted to give best estimates for the Portland tri-county vehicle population. Eugene
vehicles do not undergo I/M but are matched to the Portland sample and weighted to represent the Portland
population in the absence of I/M.
** Based on measurements taken at the contractor's lab. The lower of the two curb idle measurements was used
as the idle level for each car.
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Table 2 (continued)
Portland Composite
Eugene
Initial
23763
157
1.25
1.80
22.28
2.49
After
Maintenance
24068
75
.21 .
1.36
15.03
2.51
First
Quarterly
27202
108
.45
1.44
16.48
2.59
Second
Quarterly
30049
145
.69
1.64
17.66
2.54
Third
Quarterly
32684
130
.75
1.83
19.33
2.53
Initial
22668
163
1.37
1.98
25.79
2.71
First
Quarterly
26248
188
1.66
2.00
26.83
2.63
Second
Quarterly
29641
187
1.59
2.02
27.84
2.45
Third
Quarterly
33828
193
1.38
2.09
27.76
2.69
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Figure 1
Mean FTP CO Emissions for
1975-77 Model Year Vehicles
Passing and Failing the DEQ Inspection
30
o
a
o
20
10
FfllL
35X
OEQ INSPECTION
PflSS
65X
(N-2207)
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Figure 2
Mean FTP HC Emissions for
1975-77 Model Year Vehicles
Passing and Failing the DEQ Inspection
3.0
2.5
2.0
Q_
O
1.5
O
z:
o_
ti.o
0.5
0.0
FfllL
35%
DEQ INSPECTION
PflSS
65X
CN-2207)
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Figure 3
Mean FTP NOx Emissions for
1975-77 Model Year Vehicles
Passing and Failing the DEQ Inspection
3.0
2.5
2.0
C9
X
o
1.5
0.5
0.0
FfllL PflSS
35X 65X
DEQ INSPECTION (N-2207)
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Figure 4
Ongoing Effects: • 1975-77 Model Year
Portland Population Estimated Means
VEHICLES HITM THREE QUARTERLIES
200
175
150
•125
»
»
t
100
75
50
25
0
o
UJ
PORTLAND
EUGENE
22000 2*iOOO 28000
26000
MILEAGE
30000 32000
34000
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Figure 5
Ongoing Eff.ects: 1975-77 Model Year
Portland Population Estimated Means
2.0
VEHICLES WITH THREE QUARTERLIES
1.5
o
UJ
1.0
0.5
0.0
PORTLflNO
EUGENE
22000 24000 26000 28000 30000 32000 34000
MILEAGE
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Figure 6
Ongoing Effects:' 1975-77 Model Year
Portland Population Estimated Means
VEHICLES KITH THREE OURRTERLIES
2.50
2.00
£1.50
o
1.00
0.50
0.0
PORTLflNO
EUGENE
22000 24000 26000 28000 30000 32000 34000
MILEflOE
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Figure 7
Ongoing Effects:' 1975-77 Model Year
Portland Population Estimated Means
30
25
VEHICLES WITH THREE OURRTERLIES
15
LIO
PORTLAND
EUGENE
22000
24000
26000
28000
HILERGE
30000
32000
3*000
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