Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 1
Summary
Motor vehicles are a major source of air pollution on urban, regional, and
national scales. Programs to control their emissions have focused on setting
emissions standards for new vehicles, resulting in engineering and design im-
provements in emissions-controT systems.
Inspection and maintenance (~/M) programs have been instituted in many
jurisdictions to ensure that those controls operate properly throughout the life
of a vehicle. These programs are implemented in areas violating federal air-
quality standards (nonattainment areas) and in other areas seeking to improve
air quality. The inspection typically involves regularly scheduled exhaust tests
measuring carbon monoxide (CO), hydrocarbons (HC), and sometimes nitro-
gen oxides (NOx) emissions. I/M tests also include a visual inspection ofthe
components controlling evaporative and exhaust emissions and may include a
functional gas-cap test and a pressure test ofthe evaporative emissions-controT
system. The U. S. Environmental Protection Agency (EPA) has oversight and
developmental responsibility for I/M programs, which are implemented by state
agencies.
Evidence suggests that I/M programs have been less effective than antici-
pated. This concern prompted Congress to request this study in its fiscal ~ 998
appropriations to EPA. In response to this request, the National Research
Council (NRC) convened the Committee on Vehicle Emission Inspection and
Maintenance Programs to conduct this study. Phase ~ ofthe study, presented
in this report, examines the criteria and metho(lology for evaluating I/M pro-
grams and assesses their effectiveness in reducing vehicle emissions. Phase
OCR for page 2
~ Evaluating Vehicle Emissions I/M Programs
2 will evaluate several types of T/M programs in more depth. The study charge
also calls for the committee to make recommendations for improving T/M
programs. The committee recommends some improvements in this report and
will address others in phase 2.
In carrying out its charge for this report, the committee reviewed pas-
senger-car and light-truck emissions (the emissions typically targeted by T/M
programs) within the context of overall emissions from mobile sources and
other anthropogenic sources. Em~ssions-control technologies and testing tech-
niques were considered, together with how changes in these factors might
affect T/M programs. The committee also reviewed methods to estimate emis-
sions reductions, and it examined previous evaluations ofthese reductions and
other criteria important for evaluating such programs.
FINDINGS AND RECOMMENDATIONS
The committee found that I/M programs have generally achieved less
emissions reductions than originally projected by EPA's Mobile Source Emis-
sions Factor (MOBILE) model and the California Air Resources Board Emis-
sions Factor (EMFAC) model. These model-predicted reductions are impor-
tant because they serve as part of the formal basis for crediting emissions
reductions within state implementation plans (SIPs). ~ Independent and state-
sponsoredevaluations of ongoing I/M programs have estimated that the em~s-
sions reductions attributable to these programs are from zero to about one-half
ofthe reductions predicted by the models.2 This figure is estimated using in-
use vehicle emissions data, such as remote-sensing, random roadside vehicle
testing, and T/M emissions testing. The committee concluded that these data
provide the best estimate of T/M's effectiveness. Evaluations that rely on
mode! predictions of emissions reductions using few or no in-use data are not
accurate. This conclusion is based on a small number of peer-reviewed stud-
ies, and the methods used to make these estimates must be improved.
Despite the smaller-than-forecasted benefits from I/M programs, the
iSIPs describe the strategies that regions in noncompliance with National Ambient
Air Quality Standards (NAAQS) use to come into compliance.
2The estimated emissions reductions are dependent on the pollutant and version
of the model used for comparison. They are lowest for test-and-repair idle test
programs and highest for hybrid or centralized transient test programs.
OCR for page 3
Summary
committee still sees a great need for programs that repair or eliminate high-
em~ssions vehicles (commonly called high-em~tting vehicles or high emitters)
from the fleet, given the major influence ofthis small fraction ofthe fleet on
total emissions and air quality. However, I/M programs should improve the
way they identify vehicles in need of repair and verify repairs. Improvements
are also needed in the methods used to evaluate the impacts of these pro-
grams.
The use ofthe MOBILE and EMFAC models to predict emissions-reduc-
tion benefits from I/M programs in the development of air-quality-attainment
plans indicates a flaw in the SIP process. EPA has granted states substantial
emissions-reduction credits for I/M programs without the need to verify the
extent to which the predicted emissions reductions are actually occurring.
That situation creates a regulatory disincentive for states to evaluate the actual
emissions-reduction benefits from T/M programs. Such an evaluation might
reveal a shortfall in a state's emissions-reduction benefits and trigger require-
ments for SIP revisions.
The committee recommends that the crediting of emissions-reduction
benefits for T/M programs, as with other emissions-control strategies, should
be tied to the actual emissions reductions produced by these programs. Em-
phasis on observational data and empirical evidence has been inadequate in
most aspects of I/M program evaluations. Rigorous scientific and technical
analyses have been lacking in supporting decisions related to program imple-
mentation. EPA should expand its use of outside experts and publication of
analyses in peer-reviewed literature to address that deficiency. Improvements
are especially needed in the quantification of I/M program impacts based on
more data-intensive approaches. These evaluation methods and their applica-
tions to estimate emissions benefits of state T/M programs should be reviewed
independently and be disseminated to policy makers and the public.
Prospective Estimates of Emissions
Reductions from [/M Programs
Findings
On the basis of evaluations by states and by independent researchers,
the committeefound thatI/Mprograms provide much lower benef Is than
estimated by the models. The MOBILE model estimates that a filthy imple-
OCR for page 4
4 Evaluating Vehicle Emissions I/M Programs
mented enhanced I/M programs would produce overall emissions reductions
of 28% for HC, 31°/O for CO, and 9% for NOx.4 Reasons for overstating
emissions reductions include the following:
· Overestimation ofthe deterioration of vehicle-em~ssions performance
(which overestimates potential benefits from T/M-induced emissions repairs).
· Inadequate representation ofthe behavior of motorists and mechanics.
· Overestimationofcompliancewiththeprogramandtheeffectiveness
rat .
01 repairs.
· Overestimation of the ability to identity high-emitting vehicles.
· Incomplete implementation of some components of I/M programs
(e.g., effective evaporation tests and inclusion of all older vehicles).
Recommendations
EPA and states should expectlower emissions-reduction benef tsfrom
I/Mprograms as currently configured. In general, models projecting emis-
sions reductions from I/M programs should be improved to reflect actual re-
ductions more accurately. States should perform periodic on-road sampling
and evaluations of emissions reductions and compare those observations with
modeled forecasts used in Sips. To the extent that states are allowed to use
clefault parameters in emissions models to forecast I/M emissions reductions
for SIP credit, the default values of key parameters (e.g., compliance rates and
repair effectiveness) should be more pessimistic (i.e., forecast lower emissions
reductions) than those currently used. That might help to create an incentive
for states to provide evidence that their programs achieve greater emissions
reductions than specified by the default settings in the model.
.
High-Emitting Vehicles
Findings
A small, malfunctioning fraction of the fleet contributes a substantial
proportion of overall vehicle emissions. Typically, less than 10% of the
Enhanced I/M programs are required in areas classified in "serious," "severe," or
"extreme" nonattainment of National Ambient Air Quality Standards.
4The discussion here refers to analysis that was performed in 1992 using the
version of the model known as MOBILE4. 1.
OCR for page 5
Summary 5
Beet contributes more than 50°/ of the emissions for any given pollutant.
Emissions reductions are skewed; a relatively small share of the vehicles
failing an T/M test contributes a large proportion of total excess emissions
remissions above the standard for failing a vehicle), while vehicles with em~s-
sions just above the threshold for test failure (so-called "marginal emitters")
often have only a small reduction in overall emissions after repairs or, in some
cases, actually have an increase in emissions after repairs. Thus, the largest
potential reductions in emissions from T/M programs are associated with a
small number of high-em~tting vehicles.
Studies that combine data for vehicle ownership, high-emitter frequency,
and income levels suggest a strong link between low household income and the
likelihood of owning a high-em~tting vehicle. Studies also show that between
10°/0 and 27% of vehicles that fad! an I/M test never pass the test. Their exact
fate has not been well characterized, although some have been found to be still
in operation in I/M areas in some states more than a year after their last test.
More study of this issue is needed to determine how serious this problem is
and what policies will improve it.
Recommendations
I/Mprograms shoul~focus primarily on identity cation, diagnosis, and
repair of the highest-emitting vehicles along with verification of those
repairs. A number oftesting or identification regimes can identify high-emit-
ting vehicles, including traditional I/M programs testing all vehicles, programs
targeting certain vehicles for more or less frequent testing, and remote sensing.
States should be given flexibility to choose a regime that meets their em~ssions-
reduction goals at the lowest cost to the public.
The focus on high-emitting vehicles should extend to promoting policies
that seek effective repair or removal of all such vehicles. However, any pro-
gram designed to repair high-emitting vehicles might raise serious fairness
concerns, because high emitters are more likely to be owned by persons of
limited economic means. The committee recommends that policies be ex-
plored to provide financial or other incentives for motorists of high-emitting
vehicles to seek repairs or vehicle replacement. Clearly, further research is
needed to design the means to reduce high emitters in ways that are effective
as well as socially and politically acceptable. States would have to evaluate
which policies are the most cost-effective and acceptable ways of obtaining
emissions reductions from high-emitting vehicles.
OCR for page 6
6 Evaluating Vehicle Emissions I/M Programs
The committee is aware that identification of high-emitting vehicles is
problematic and that the designation is relative. The sense ofthe committee is
that more needs to be known about the cost-effectiveness of setting different
emissions cutpoints,5 including the value of repairing vehicles with emissions
only marginally higher than current cutpoints, to determine optimal cutpoints for
vehicle tests.
Evaluating I/M Emissions Reductions
Findings
Off cial biennial evaluations of enhanced I/M programs required by
the Clear, Air Act Amendments of 1990 have not been completed by the
majority of states required to perform them. The guidelines clevelope(1 by
EPA for performing these evaluations are limited to a single method, which
compares an I/M program with a benchmark I/M program. These guidelines
are being revised and expanded. Most past evaluations have been performed
by state agencies in response to state requirements for estimates of emissions-
reductions benefits or by independent researchers interested in the same issue.
The primary data sources for evaluation of emissions-reduction benefits
are test data from I/M programs, remote sensing of on-road vehicles, and
roadside testing of on-road vehicles. Vehicle registration data are also impor-
tant for estimating changes in the fleet over time. There are three approaches
for using those data to determine emissions-reduction benefits. The "reference
method" compares vehicle emissions in the program area with those in some
reference area, which can be a benchmark T/M program or a non-~/M area.
The "step method" compares emissions of vehicles tested under a newly
instituted I/M program with emissions of vehicles in the same area that have
yet to be tested under the new program. The "comprehensive method" tracks
changes in emissions for vehicles that pass the test, those that initially fail and
then pass, and those that fait and never pass.
Each data source and evaluation method has inherent advantages and
disadvantages. For example, simple comparison of emissions data in one area
with those in a reference area needs to correct for physical and socioeconomic
-
sThe emissions levels that define whether a vehicle passes or fails are called
cutpoints.
OCR for page 7
Summary
7
differences between regions in which emissions would be expected to vary
regardless of the presence or absence of an I/M program. In addition, using
data on repaired vehicles collected as part ofthe I/M program to estimate the
em~ssions-reduction benefits might not account fully for noncompliance with
the program or for repairs made in anticipation of the I/M test.
Recommendations
EPA shoul~provide additionalguidancefor carrying out]/Mevalua-
tions. The agency is commended for beginning this work, and the committee
recommends that it be expanded to include additional methods of evaluation.
EPA's guidance should be based on sound measurement and statistical evalua-
tion methods and be peer reviewed. The agency should address comments
gathered during the review of these evaluation methods. In addition, EPA
should publish aspects ofthese evaluations in professional journals so that they
can be reviewed further and disseminated.
The committee recommends that EPA and states ensure that some
programs undergo comprehensive, long-term evaluations using multiple
data sources and analytic techniques. I/M programs that undergo repeated,
in-depth evaluations using multiple data sources and methods can potentially
help improve the design of I/M programs and evaluation process nationally.
Questions about the fate of vehicles that fail their I/M test, the durability of
vehicle repairs, or the impact of T/M programs on vehicle registration and
ownership patterns can be answered only through well-(lesigned, comprehen-
sive evaluations using a number of data sources.
Independent researchers should perform parts of these comprehensive
evaluations. As stated previously, these full evaluations should be peer re-
viewed independently by experienced researchers, and EPA should pursue
publishing some aspects ofthese evaluations inprofessionaljournals. Because
such evaluations are resource-intensive, EPA should select several programs
for such treatment and should support a portion of this work.
The committee recognizes that not ad jurisdictions wiR be able to
devote the resources needed to perform comprehensive evaluations using
multiple sources of primary data. The committee recommends that
guidelines for a shortened evaluation method also be developed and peer
reviewed. The method should not rely on the MOB TLE mode! but should be
based on the best evidence from ongoing full evaluations and should include
OCR for page 8
8 Evaluating Vehicle Emissions I/M Programs
estimates of all components of emissions reductions achieved by I/M pro-
grams. These shortened evaluations will likely have to rely primarily on I/M
program data and other local data for primary data sources, although on-road
data would be valuable. States should be urged to collect at least the amount
of on-road data required under the rules for implementing enhanced I/M (O. ~ %
ofthe fleet). Evidence from full evaluations done in other locations might have
to be incorporated to account for factors such as repair deterioration; ineffec-
tive, incomplete, or fraudulent repairs; pretest repairs; and program avoidance
by changing vehicle registration.
A review committee should be established to advise EPA in the selection
of shortened evaluation methods and in the selection of what information can
be drawn from full evaluations to inform the shortened evaluation. The com-
mittee is concerned about the need for states to complete overdue evaluations
and urges EPA to continue to develop these evaluation methods in a timely
manner. Assumptions used in the shortened evaluation can then be continually
improved as more evidence becomes available.
Both the comprehensive and the shortened program evaluations
should include a consistent set of performance indicators, such as the
number of high-emitting vehicles driven in an I/Mprogram area that are
avoiding testing. Although such indicators do not incorporate direct estima-
tion of emissions reductions, they can help back the performance of a program
overtime and provide relatively concise indicators of program success. These
performance indicators could include the following:
inspections.
· An estimate ofthe total number of vehicles driven in the I/M region,
the share of those vehicles that are eligible for inspection, ant! the share of
those that are inspected.
Estimates of the actual number of high emitters on the road.
Failure rates by model year at the program cutpoints.
Estimates ofthe average emissions of vehicles that pass and that fad!
Share of failing vehicles that actually get repaired to below program
cutpoints and their average emissions rates before and after repair.
· Share offailing vehicles that do not ever pass the T/M test, their aver-
age emissions rates, and estimates of the number of those still driven in the
area.
· The rate of repeat failures from one T/M cycle to the next.
OCR for page 9
Summary 9
Research Issues in I/M Evaluation
Findings
Many criticalfactors that have large effects on the emissions-rearuc-
tion benef is from I/M programs are still unknown. An example is the
length oftime that repairs remain effective for a vehicle initially failing an I/M
test. Estimates of the average effective duration for such repairs range from
most ofthe benefits disappearing in less than 6 months to remaining for 2 years
or more. Without better understanding of repair duration and other unknown
factors, the full effect of I/M programs on vehicle emissions will remain uncer-
tain. Full evaluations of at least a few I/M programs would shed light on many
such issues.
Recommendations
Comprehensive evaluations of ]/M programs should be used to re-
search aspects thought to have major impacts or' the emissions-reduction
benef is from I/Mprograms. These include the following aspects:
I/M test.
· The distribution ofthe duration of repairs for vehicles that fail an initial
· The extent of pre-inspection repairs.
· The extent to which temporary repairs and test fraud result in vehicles
registering low emissions only for the purpose of passing an I/M test (the
"clean for a day" phenomenon).
· The fate of vehicles that fail their initial T/M test and never pass (unre-
solved failures).
· Consequences of I/M programs for nontailpipe HC reductions.
In addition, many ofthese unresolved issues relate to human responses to
I/M programs, but only a few studies have attempted to examine those as-
pects. Comprehensive evaluations can shed light on the type and magnitude
of behavioral responses, but separate behavioral studies are likely to be needed
to provide additional important insight.
OCR for page 10
10 Evaluating Vehicle Emissions I/M Programs
NOx and Particulate Matter (PM) Emissions
Findings
Future air-quality improvement programs are likely to place greater
emphasis on controlling NOx andPMemissions. I/M programs traditionally
have focused on inspecting vehicles for high CO or HC emissions or both.
Loaded-mode emissions testing procedures6 that are needed to measure NOx
emissions have been introduced widely in only the past 5 years. Apart from
smoking-vehicle complaint programs and some testing of heavy-duty diesel-
truck smoke opacity, little effort has been made to identify and repair vehicles
with high emissions of exhaust PM.
Currently, there are few assessments of I/M program effectiveness in
reducing emissions of NOx and PM pollutants. Although diesel engines are a
minor source of CO and HC, they are significant contributors to mobile-source
NOX and PM emissions.
Recommendations
I/M programs should clearly state which pollutants they are seeking
to reduce. Different types of repair actions and different mechanic train-
ingprograms are neededfor 1/M programs thatfocus on reducing NOX
and PM emissions. Because heavy-duty diesel vehicles are a significant
source of NOx and PM, I/Mprograms that target these pollutants might
have to incorporate heavy-duty diesel vehicles to a greater extent.
Remote Sensing
Findings
Remote-sensing measurements are art excellent source offeet-aver-
age CO and HC emissions data. Remote sensing can also be a usefu!
screening too! to identify vehicles likely to pass orfai! conventional bed
6A loaded-mode test involves testing vehicle emissions while the vehicle is on a
dynamometer that simulates the load a vehicle is under during on-road driving.
OCR for page 11
Summary 1 1
program tests. Although use of remote sensing is increasing, its capabili-
ties remain underutilized in I/Mprograms.
Combined remote-sensing and roadside pullover studies have shown that
a high proportion of vehicles iclentif~ed by remote sensing as high emitters of
CO, HC, or both also failed roadside tests given immediately after the remote-
sensing test. However, the fraction of high-emitting vehicles that escaped
detection by remote sensing in these studies and the number that do not partici-
pate in conventional T/M programs are unknown.
Recommendations
Remote sensing should have an increased role in assessing motor
vehicle emissions and I/M program effectiveness, determining the extent
of pre-inspection repairs, andf estimating the extent of certain types of
noncompliance. Remote sensing is also effective for identifying high emit-
ters; however, its implementation into an I/M testing program should be an
area of further research.
Greater attention must be paid to site selection and quality-assurance and
quality-control issues in remote-sensing studies. Some prior studies have
focused too heavily on the number of vehicles and sites sampled and have
sacrificed quality in seeking large quantities of data.
To determine the ability of remote sensing to identify vehicles with high
NOX emissions, combined remote-sensing ant! roadside pullover studies that
focus on this pollutant should be con(luctecl. An intercomparison ofthe ability
of different remote sensors to measure NOx emissions accurately should also
be performed.
An important research priority is the development and evaluation of
remote-sensing capabilities for exhaust PM emissions. Further research is also
needed to increase the number and types of roadside sampling sites where
remote-sensing equipment can be deployed.
On-Board Diagnostics
Findings
The committee found that the current data set for evaluating the ef-
fectiveness of OLD ~ for I/M testing is inadequate. Contemporary on-
OCR for page 12
12 Evaluating Vehicle Emissions I/M Programs
board diagnostic (OBD) equipment, included on ~ 996 and newer model-year
vehicles, represents a technological innovation for monitoring the performance
of em~ssions-controT equipment on light-duty vehicles. Current OBD technol-
ogy, known as OBDII, provides rapid verification of the operation of both
exhaust and evaporative emissions-controT components but does not measure
emissions. it alerts motorists to potentialproblems by illuminating amalfi~nc-
tion indicator light (MIL) end provides mechanics with diagnostic information
about the source of malfunctions, including malfunctions that are intermittent
in nature (e.g., a misfire). OBDII also represents a potentially improved meth-
od for assessing evaporative em~ssions-contro! components. Given its current
specifications for MIL warnings however, it is not clear whether OBDII can
fulfill both objectives of alerting vehicle owners to potential vehicle malfunc-
tions and serving as a testing device in I/M programs. In addition, it is not
known how motorists will react to MIL illumination, especially when the vehi-
cles are no longer under warranty.
The OBDII system could operate as designed by automobile manufactur-
ers and still indicate OBD I/M test failures on vehicles with low emissions.
The current specification is that the MIL will illuminate if aproblemis detected
that results in or could potentially result in emissions higher then ~ .5 times the
vehicle's emissions certification standard. Studies have shown that if OBDIT
were used to decide whether vehicles passed or failed an inspection, most
OBDTI failing vehicles would have emissions less than ~ .5 times the standard.
Current I/M programs typically have much higher cutpoints than ~ .5 times the
vehicle's certification standard. The OBDTI failure point might be too stringent
for a cost-effective and publicly acceptable I/M program especially for older
OBDII vehicles. An alternative approach, such as tailpipe testing, might be
nee(led for those vehicles.
Recommendations
An independent evaluation should be established, with appropriate
funding, using researchers outside the agencies to review the effective-
ness arid cost-effectiveness of OBD testing programs before moving
forward with fuR implementation of OBDI] rule requirements. The rule
allows states up to 3 years to phase in OBD T/M, which is required to begin
January 2002. The recommended evaluation should study the issues of inter-
mittent failures and the value of repairing vehicles with low emissions to pre-
OCR for page 13
Summary 13
vent an increase of emissions in the future. Failing a large number of vehicles
with emissions below ~ .5 times the certification standards could undermine the
commitment to find high-emitting vehicles and ensure that they are repaired.
An alternative to using OBDT! as a failure criterion in T/M testing is to use it
as an advisory too!to inform motorists of potential emissions problems. This
option can be used while phasing in an OBDII I/M program. It may also be
considered! for OBDIT vehicles when they become older. No matter how
OBDII is used, a substantial effort by EPA is needled to help the public thor-
oughly understand this system. Besides the issues of intermittent failures and
the value of failing marginal-em~tting vehicles with malfunctioning sensors or
monitors, studies of other issues related to OBD TI should be done. Such issues
include the following:
· The fraction of vehicles appearing in I/M lanes with MILs illuminated.
· The fraction of vehicles with MILs illuminated that do not fail the
exhaust test or any evaporative test.
· The fraction of vehicles without MILs illuminated that fad! the I/M test.
· The response rates of consumers to MILE illumination in both the ab-
sence and the presence of an I/M program and in the absence of a warranty.
· The use of OBDII diagnostic information to identify vehicle repairs
that have a high-emissions-reduction potential and repairs that have only a
marginal impact on emissions.
The possibility for changes in the cutpoint settings on OBDII systems
to allow OBDIT to focus on high-emitting vehicles.
· In the long-term, the promotion of actual emissions readings in future
OBD systems.
· Methods for measuring actual emissions-reduction benefits from
OBDII.
Use of the MOBILE Mode!
Findings
The SIP process mandated by the Clean Air Act and its amendments
requires that modeling be used to predict emissions inventories and esti-
mate benef is from ]/Mprograms in future years. Based on comparisons
with I/Mprogram evaluations, predictions from the current version of the
OCR for page 14
14 Evaluating Vehicle Emissions I/M Programs
MOBITE mode! have greatly overestimated the emissions benef ts from
I/Mprograms. '
These findings and the 2000 report Modeling Mobile-Source Emissions
by the National Research Council suggest that there has been inadequate
emphasis on data and empirical evidence in modeling I/M benefits.
Recommendations
The methodology used in MOBllEfor estimatingI/Mbenef ts should
be reevaluated. MOBILE should allow its users to readily incorporate data
from current I/M program evaluations into assessments for future years. Key
parameters (e.g., compliance rates, repair effectiveness, and OBDII I/M
benefits) used to forecast I/M emissions-reduction benefits should have pessi-
mistic default estimates resulting in Tower expected reductions. States might
then have an incentive to demonstrate, through evaluation, that their programs
are better than the default. Further, embedded assumptions in the model
should be simplified as much as possible so that assumed parameter values are
transparent to users, and users can incorporate the latest available data into
parameters.8 In the long-term, the overall [/M estimation methodology in
MOBILE should be substantially revised. Empirical data show that the under-
Tying I/M modeling approach is flawed.
The committee recognizes the need to continue using models to estimate
I/M program benefits in future years. it is important, however, to reiterate that
evaluations of current program performance should rely as extensively as
possible on empirical data (e.g., on-road vehicIe-emissions measurements)
rather than on models such as MOBILE.
Importance of Cost-Effectiveness and Public Response to I/M
Findings
Although emissions reductions are central to any evaluation of EM
programs, costs are inextricably linked to emissions reductions, making
7EPA is currently working on MOBILE6, which is expected to be less optimistic in
its I/M benefit predictions.
~Naturally, these input data should undergo some type of evaluation and approval
process so that the resulting emissions estimates are credible.
OCR for page 15
Summary 15
cost-effectiveness a critical evaluation criterion. For example, costs influ-
ence the behavior of vehicle owners and repair technicians, thereby affecting
the emissions reductions achieved. Both the emissions reductions and the
associated costs must be considered! in the design and improvement of I/M
programs, and in the determination of whether effort is best directed at I/M or
at alternative ways of reducing emissions.
Another important consideration is public concern about new technologies,
such as OBDII or remote sensing, that are increasingly used in T/M programs.
For example, confusion about what the MIL is conveying to drivers could
impede the use of OBDIT in T/M tests. Confusion about new technologies
could reduce public and political support for their introduction into I/M pro-
grams and/or reduce their effectiveness.
Recommendations
I/M programs can be improved by identifying ways to make them
more cost-effective and more readily understood and by easing the testing
burden for vehicle owners. States should be encouraged to develop and
implement cost-effective means for finding and repairing high-emitting vehi-
cles. Analysis of cost-effective measures, however, must take account ofthe
effect of I/M program requirements on owners' behavior. Some ofthe issues
that deserve further research include the following:
· The roles of repair cost waivers in I/M programs. I/M programs typi-
cally devote considerable money and effort to finding failing vehicles. Once
a vehicle is identified as a very-high-emitting vehicle, that vehicle should be
repaired, sold out of the area, or scrapped. Vehicle scrappage programs and
repair assistance programs are examples of policies that could be used to
accomplish such a goal. The most cost-effective policies may differ by region.
~ The use of emissions profiles for determining testing frequency.
There is already growing evidence that reducing the frequency of testing
vehicles with a low probability offaiTure, including exemption of recent model-
year vehicles from regular testing, is very cost-effective. On the other hand,
increasing the inspection frequency of vehicles with a high probability offailure
and/or those with high repair deterioration should be investigated to determine
its cost-effectiveness for identifying high emitters.
~ The durability of emissions-control systems. Encouraging the pro-
duction of vehicles with more robust emissions-control systems through the use
OCR for page 16
~ 6 Evaluating Vehicle Emissions I/M Programs
of extended warranties and new-vehicle compliance programs may be an
alternative approach to maintaining low emissions throughout a vehicle's life-
time.
· Understanding and quantifying owners ' responses to I/M reguZa-
tions. For example, not enough is known about the extent of old-vehicle
scrapping in response to T/M or of program avoidance and other types of
noncompliance among different socioeconomic groups.
· The cost and emissions consequences of enforcement efforts.
Greater enforcement of existing regulations may be a cost-effective way to
improve program performance.
· More effective means of public outreach and education. New
approaches to providing information to the public about new technologies that
may be incorporated in I/M programs should be developed and studied. Prior-
ity should be given to concerns regarding remote sensing and OBDIT.
Representative terms from entire chapter:
vehicle emissions
