Report No. EPA 460/3-88-003
Analytical Support for
Emission Factors Development
and Air Quality Assessment
Work Assignment No. 0-01:
Analysis of California
I/M Review Committee Data
Task 1 Report
Supplemental Analysis of
Emissions Reductions and
Post-l/M Deterioration
prepared for:
U.S. Environmental Protection Agency
September 30, 1988
prepared by:
Sierra Research, Inc.
1521 I Street
Sacramento, California 95814
(916) 444-6666
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Report No. EPA 460/3-88-003
ANALYTICAL SUPPORT FOR
EMISSION FACTORS DEVELOPMENT
AND AIR QUALITY ASSESSMENT
EPA Contract No. 68-03-3474
Work Assignment No. 0-01:
Analysis of California
I/M Review Committee Data
Task 1 Report:
Supplemental Analysis of
Emissions Reductions and
Post-I/M Deterioration
prepared for:
U.S. Environmental Protection Agency
September 30, 1988
prepared by:
Thomas C. Austin
Thomas R. Carlson
Kathryn A. Gianolini
Sierra Research, Inc.
1521 I Street
Sacramento, CA 95814
(916) 444-6666
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1 . Summary
ANALYTICAL SUPPORT FOR
EMISSION FACTORS DEVELOPMENT
AND AIR QUALITY ASSESSMENT
Task 1 Report:
Supplemental Analysis of
Emissions Reductions and
Post-I/M Deterioration
Table of Contents
2. Introduction and Methodology 5
\
3. Results
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1. SUMMARY
During a recent evaluation of the California vehicle inspection and
maintenance program, laboratory tests using the Federal Test Procedure
were conducted before and after repairs at "Smog Check" stations. A
sample of the repaired vehicles was tested again after being
"recaptured" from customer service. In order to determine how the
emission reductions achieved under the current California program
might compare to that under alternative programs, EPA requested
further analysis of the California data to calculate the change in
emission reductions achieved on failed vehicles if certain vehicles
were removed from the sample. The vehicles removed from the sample
were those that were not fully repaired (i.e., vehicles receiving
waivers), those that failed only the underhood (visual or functional)
inspection, and those that failed only the 2500 rpm test.
The results of the analysis are summarized in Figure 1. As shown in
the figure, when vehicles receiving waivers or vehicles failing only
an underhood inspection are excluded from the sample, the average
emission reduction for the remaining repaired vehicles is higher for
HC and CO and lower for NOx. This is true both for the initial
emissions reduction and after some period of customer service.
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Figure 1
Emissions Reductions
and Post I/M Deterioration
All Repaired
Vehicles
Excluding
Waivers &
Underhood-Only
Failures
Excluding
Waivers,
U. H. -Only Fails.
& 2500-Only Fails
Legend
HC
Deteriorated
CO
Deteriorated
NOx
Deteriorated
HC
Initial
CO
Initial
NOx
Initial
-2-
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Table 1
Analysis of Emissions Reductions
and Post-I/M Deterioration
Emission Change
HC CO NOx
All Repaired Vehicles
initial -37.3% -26.9% -8.8%
deteriorated -28.4% -25.8% -5.5%
Excluding Waivers
& Underhood-Onlv Failures
Idle and/or 2500 Failures
initial -44.7% -35.3% -4.9%
deteriorated -30.1% -30.0% -1.1%
Idle Failures Only
initial -43.5% -34.6% -5.0%
deteriorated -29.2% -30.1% +1.1%
Table 1 presents the results of the analysis in tabular form. The
initial hydrocarbon emission reduction for repaired vehicles increases
from 37.3% to 44.7% when waivers and underhood-only failures are
excluded. After experiencing some deterioration in customer service,
the hydrocarbon emission reduction for repaired vehicles increases
from 28.4% to 30.1% when waivers and underhood-only failures are
excluded.
A similar trend is shown for carbon monoxide. The initial CO emission
reduction for repaired vehicles increases from 26.9% to 35.3% when
waivers and underhood-only failures are excluded. After experiencing
some deterioration in customer service, the CO emission reduction for
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repaired vehicles increases from 25.8% to 30.0% when waivers and
underhood-only failures are excluded.
NOx emission reduction percentages are affected in the opposite
manner. The initial NOx emission reduction for repaired vehicles
decreases from 8.8% to 4.9% when waivers and underhood-only failures
are excluded. After deterioration in customer service, the NOx
emission decrease for repaired vehicles changes from 5.5% to 1.1% due
to the exclusion of these vehicles.
Figure 1 and Table 1 also indicate that the exclusion of vehicles that
fail only the 2500 rpm test has no significant effect on the percent
emission reductions achieved from repaired vehicles. However, after
deterioration in customer service, the NOx emission effect for
repaired vehicles changes from a decrease of 5.5% to an increase of
1.1% due to the exclusion of these vehicles.
The prospect for higher reductions in HC and CO emissions with the
elimination of waivers is apparent from the analysis. The adverse
effect on NOx reductions is not unexpected as the exclusion of the
underhood inspection results in some of the NOx emissions defects
(e.g., disconnected EGR valves) being missed. Without loaded-mode
testing, tailpipe emission tests are only able to detect HC and CO
emission problems. In addition, since some repairs of HC and CO
defects tend to increase NOx emissions, there can be a net increase in
NOx associated with the elimination of the underhood inspection.
-H-H-H-
tl It it
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2. INTRODUCTION AND METHODOLOGY
Under a contract with the U.S. Environmental Protection Agency (EPA)
for "Analytical Support for Emission Factors Development and Air
Quality Assessment," Sierra Research, Inc. (Sierra) performs a variety
of Work Assignments for the Emission Control Technology Division
(ECTD) of EPA's Motor Vehicle Emissions Laboratory in Ann Arbor,
Michigan. Work Assignment 0-01 directed Sierra to perform analysis of
California I/M data for the ECTD Technical Support Staff (TSS). Task
number 1 of that Work Assignment required an evaluation of how
alternative I/M test procedures would affect the emission reductions
achieved from failing vehicles and the post-I/M deterioration of those
vehicles.
The general direction provided by TSS was as follows:
The Technical Appendix (to Sierra's previous report on the
California I/M Evaluation Program) shows mean data for 290
cars that failed their California smog check, were repaired,
and then retested after a period of deterioration. The sample
includes vehicles which may not have been fully repaired, cars
that failed only for tampering, and vehicles which had
inconsistent emissions test results between ARB and the smog
check station(s). The contractor shall repeat the analysis,
and any relevant more detailed analysis, for the subset of
vehicles which were as-received emissions failures at the
first smog check station (with and without consideration of
2500 rpm status) and which were emission passes after
commercial repair.
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The 290 vehicles referred to above were "undercover" vehicles used in
an ARB-sponsored study to evaluate the emissions effects of the
California Smog Check program. As described in Sierra's previous
report to ARB ("Evaluation of the California Smog Check Program -
Technical Appendix," April 1987), these 290 vehicles were "repaired"
vehicles that had been "recaptured". Each vehicle in the sample
received repairs at a Smog Check station and subsequently passed the
test. In most cases the repair was sufficient to get the vehicle to
pass the I/M standards. In other cases, the vehicle was not repaired
to the point where tailpipe emission levels met the I/M test standards
and the vehicle received a "certificate of compliance" by virtue of
getting a "waiver". Sierra's previous analysis showed how the
immediate emission changes associated with repair of these 290
vehicles compared to the emissions after the vehicles were recaptured
from customer service some months later.
Table 2 presents the results of Sierra's earlier analysis with the
addition of a column entitled "Weighted Composite". This new column
presents the average emission results for all model year groups after
they have been weighted to reflect the population and estimated annual
VMT of each model year group. (The original analysis was for the 290
vehicle sample with no weighting factors applied to reflect annual VMT
differences.) The weighting factors were developed from the VMT
estimates contained in Table 8-15 (pg. 118) of Sierra's earlier report
and the frequency of "initial" tests for various model year groups
computed from a random sample of Test Analyzer System data. The
vehicle population was estimated to be 20% pre-1975, 30% 1975-1979,
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Table 2
Changes in Emissions by Model Year Group
For All Vehicles
(Immediate and Deteriorated)
HC Emissions (g/mi)
before I/M
after repair
deteriorated
% Emission Changes
initial
deteriorated
CO Emissions (g/mi)
before I/M
after repair
deteriorated
% Emission Changes
initial
deteriorated
NOx Emissions (g/mi)
before I/M
after repair
deteriorated
% Emission Changes
initial
deteriorated
Mean Mileages
baseline
deteriorated
A Mileage
Pre-1975
10.29
5.97
7.66
-42.0%
-25.6%
72.01
63.04
65.83
-12.5%
- 8.6%
3.33
3.07
2.83
- 7.8%
-15.0%
103,359
108,427
5,068
75-79
4.61
3.03
3.59
-34.3%
-22.1%
48.29
39.18
40.36
-18.9%
-16.4%
2.77
2.39
2.50
-13.7%
- 9.8%
86,228
92,996
6,768
Post-1979
2.08
1.37
1.34
-34.1%
-35.6%
34.41
21.83
21.59
-36.6%
-37.3%
1.22
1.15
1.26
- 5.7%
+ 3.3%
50,875
59,147
8,272
1
' All i
5.15
3.19
3.82
-38.1%
-25.8%
49.38
39.08
40.17
-20.9%
-18.7%
2.36
2.12
2.15
10.2%
- 8.9%
78,106
84,975
6,869
Weighted
Composite
3.73
2.34
2.67
-37.3%
-28.4%
42.43
31.03
31.50
-26.9%
-25.8%
1.82
1.66
1.72
- 8.8%
- 5.5%
Sample Size
73
115
102
290
-7-
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and 50% post-1979 models. Combining the vehicle population fractions
with the annual VMT estimates for each model year group, the
relationship between model year group and travel fraction was computed
to be as follows:
Model Year Range Travel Fraction
pre-1975 14.1%
1975-1979 19.5%
post-1979 66.4%
all 100.0%
To conduct the requested analysis, it was necessary to eliminate
the following vehicles from the full sample of 290 vehicles that
received repairs at Smog Check stations:
O Vehicles which failed only because of a visual or functional
inspection, and
O Vehicles that were not fully-repaired (i.e., vehicles that
received "waivers").
After recomputation of the emissions with these vehicles removed, it
was necessary to repeat the analysis after removing vehicles that only
failed the 2500 rpm test.
The results of the analysis are contained in the following section of
the report.
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3. RESULTS
As explained in the previous section, to conduct the supplemental
analysis of emission reductions and I/M deterioration, it was
necessary to eliminate certain vehicles from the full sample of 290
vehicles that received repairs at Smog Check stations. For the first
recomputation of the results:
sixty-two vehicles were eliminated because they experienced
underhood failures only, and
sixty-four vehicles were eliminated because they received
waivers.
In addition, twenty-five vehicles were eliminated from the sample
because the the failure mode at the Smog Check station could not be
accurately determined. One more vehicle was eliminated because ARE
apparently lost or never received the data from the after repair test
performed at the Smog Check station. (In this case, it was not clear
whether a waiver had been issued or not.)
* The total number of vehicles deleted from the full sample was the
same in the draft version of this report. However, the availability
of a revised and cleaned-up data base from ARE enabled a more accurate
classification of the status of the vehicles that were deleted from
the sample because they were, or may have been, underhood-only
failures, or because they received waivers.
-9-
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Due to the adjustments listed above, the sample size was reduced from
290 to 138. Recalculation of the emission reductions and post-I/M
deterioration for these 138 vehicles is shown in Table 3.
Table 3
Changes in Emissions by Model Year Group
For Successfully Repaired Vehicles
Failing California Idle and/or 2500 Standards
(Immediate and Deteriorated)
HC Emissions ( g/mi )
before I/M
after repair
deteriorated
% Emission Changes
initial
deteriorated
CO Emissions ( g/mi )
before I/M
after repair
deteriorated
% Emission Changes
initial
deteriorated
NOx Emissions ( g/mi )
before I/M
after repair
deteriorated
% Emission Changes
initial
deteriorated
Mean Mileages
baseline
deteriorated
A Mileage
Canvn1 P Si Zfi
Pre-1975
10.07
5.65
8.23
-44.0%
-18.3%
80.10
64.37
65.57
-19.6%
-18.1%
3.08
2.89
2.77
- 6.0%
-10.1%
109,042
113,671
4,629
34
75-79
4.81
2.77
2.95
-42.4%
-38.5%
53.07
37.40
38.49
-29.5%
-27.5%
2.82
2.47
2.59
-12.2%
- 8.2%
86,748
93,514
6,766
47
Post-197?
1.87
1.06
1.27
-43.6%
-32.2%
30.59
16.23
19.04
-46.9%
-37.7%
1.26
1.28
1.36
+ 1.8%
+ 8.0%
50,290
58,859
8,569
57
> All
4.89
2.77
3.56
-42.0%
-26.1%
50.44
35.30
37.13
-30.0%
-26.4%
2.24
2.08
2.12
- 6.9%
- 5.1%
77,182
84,166
6,984
138
Weighted
Composite
3.69
2.04
2.58
-44.7%
-30.1%
41.97
27.16
29.40
-35.3%
-30.0%
1.82
1.73
1.80
- 4.9%
- 1.1%
-10-
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results from Table 3 are compared to the full 290 vehicle sample
in Table 4. When vehicles receiving waivers and vehicles failing
only an underhood inspection are excluded from the sample, the average
emission reduction for the remaining repaired vehicles is higher for
HC and CO and lower for NOx. The initial hydrocarbon emission
reduction for repaired vehicles increases from 37.3% to 44.7% when
waivers and underhood-only failures are excluded. After experiencing
some deterioration in customer service, the hydrocarbon emission
reduction for repaired vehicles increases from 28.4% to 30.1% when
waivers and underhood-only failures are excluded.
Table 4
Effect of Eliminating Underhood-Only Failures
and Waiver Vehicles on I/M Emission Reductions
Emission Change
HC CO NOx
All Repaired Vehicles
initial -37.3% -26.9% -8.8%
deteriorated -28.4% -25.8% -5.5%
Excluding Waivers
& Underhood-Only Failures
Idle and/or 2500 Failures
initial -44.7% -35.3% -4.9%
deteriorated -30.1% -30.0% -1.1%
A similar trend is shown for carbon monoxide. The initial CO emission
reduction for repaired vehicles increases from 26.9% to 35.3% when
waivers and underhood-only failures are excluded. After experiencing
some deterioration in customer service, the CO emission reduction for
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repaired vehicles increases from 25.8% to 30.0% when waivers and
underhood-only failures are excluded.
NOx emission reduction percentages are affected in the opposite
manner. The initial NOx emission reduction for repaired vehicles
decreases from 8.8% to 4.9% when waivers and underhood-only failures
are excluded. After deterioration in customer service, the NOx
emission decrease for repaired vehicles changes from 5.5% to 1.1% due
to the exclusion of these vehicles.
Finally, it was necessary to repeat the analysis after removing
vehicles that only failed the 2500 rpm test. There were fourteen such
vehicles in the sample, reducing the total sample size to 124. These
results are shown in Table 5. When the results shown in Table 5 are
compared to the previous results, it is apparent that the exclusion of
vehicles that fail only the 2500 rpm test has no significant effect on
the percent emission reductions achieved from repaired vehicles.
However, after deterioration in customer service, the NOx emission
effect for repaired vehicles changes from a decrease of 5.5% to an
increase of 1.1% due to the exclusion of these vehicles.
The performance of the fourteen vehicles that were 2500 rpm-only
failures is shown in Table 6. After mileage accumulation in customer
service, these vehicles (all post-1979 models) had 8.9% lower NOx
emissions than their "before I/M" levels. This compares to 12.6%
higher NOx emissions for the post-1979 models that failed the idle
test (see Table 5) .
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Table 5
Changes in Emissions by Model Year Group
For Successfully Repaired Vehicles
Failing California Idle Standards Only
(Immediate and Deteriorated)
HC Emissions ( g/mi )
before I/M
after repair
deteriorated
% Emission Changes
initial
deteriorated
CO Emissions (g/mi)
before I/M
after repair
deteriorated
% Emission Changes
initial
deteriorated
NOx Emissions ( g/mi )
before I/M
after repair
deteriorated
% Emission Changes
initial
deteriorated
Mean Mileages
baseline
deteriorated
A Mileage
Sample Size
Pre-1975
10.07
5.64
8.23
-44.0%
-18.3%
80.10
64.37
65.57
19.6%
-18.1%
3.08
2.89
2.77
- 6.0%
-10.1%
109,042
113,671
4,629
34
75-79
4.81
2.77
2.95
-42.4%
-38.5%
53.07
37.40
38.49
-29.5%
-27.5%
2.82
2.47
2.59
-12.2%
- 8.2%
86,748
93,514
6,766
47
Post-1979
2.13
1.20
1.41
-43.5%
34.1%
34.40
19.16
21.60
-44.3%
-37.2%
1.23
1.23
1.39
- 0.2%
+12.6%
52,208
60,158
7,950
43
All
5.32
3.01
3.86
-43.4%
-27.4%
54.01
38.47
40.06
-28.8%
-25.8%
2.34
2.16
2.22
- 7.8%
- 5.0%
80,883
87,474
6,591
124
Weighted
Composite
3.77
2.13
2.67
-43.5%
-29.2%
44.49
29.10
31.10
-34.6%
-30.1%
1.80
1.71
1.82
- 5.0%
+ 1.1%
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Table 6
Changes in Emissions by Model Year Group
For Sucessfully Repaired Vehicles
Failing 2500 RPM Only
(Immediate and Deteriorated)
Weighted
Pre-1975 75-79 Post-1979 All Composite
HC Emissions (g/mi)
before I/M --- --- 1.08 1.08
after repair 0.64 0.64
deteriorated 0.90 0.90
% Emission Changes
initial --- --- -40.7% -40.7%
deteriorated -16.7% 16.7%
CO Emissions (g/mi)
before I/M --- --- 18.82 18.82
after repair --- --- 7.22 7.22
deteriorated --- --- 11.18 11.18
% Emission Changes
initial --- --- -61.6% -61.6%
deteriorated -40.6% -40.6% —
NOx Emissions (g/mi)
before I/M --- --- 1.35 1.35
after repair 1.37 1.37
deteriorated — 1.23 1.23 —
% Emission Changes
initial --- --- + 1-5% + 1.5%
deteriorated --- --- - 8.9% - 8.9%
Mean Mileages
baseline 44,402 44,402
deteriorated --- --- 54,867 54,867
A Mileage --- --- 10,465 10,465
Sample Size 0 0 14 14
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