EPA-AA-IMS-81-17
Technical Report
DISCUSSION OF THE SELECTION OF COVERAGE AND FREQUENCY
ALTERNATIVES IN INSPECTION AND MAINTENANCE PROGRAMS
Jane A. Armstrong
August 1981
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
-------
Table of Contents
Page
1.0 Introduction 2
2.0 Background 2
3.0 Geographic Coverage 3
4.0 Selection of Vehicle Classes Covered 4
5.0 .Selection of Model Year Covered (Age Exemptions) 9
6.0 Selections of Inspection Frequency 14
-------
3.
3.0 GEOGRAPHIC COVERAGE
The first decisions to be made in selecting the geographic area in which I/M
will be implemented are whether the program should focus only upon maj.or urban
areas, and then, if so, how far beyond the urbanized area boundary the
inspection -requirement should extend. For the densely populated States in the
Northeast, a logical choice is to make the I/M program statewide. This option
has been selected by Massachusetts, Connecticut, Rhode Island, and
New Jersey. Other states are at the opposite end of the spectrum with major
urban centers isolated within hundreds of miles of sparsely populated desert
or mountainous terrain. Here the choice to implement I/M only in the
urbanized area is equally logical. For most states, however, the choice is
not so simple and must include a consideration of pollutant transport,
commuter VMT and ease of administration.
Many of the vehicles which contribute to an urban nonattainment problem
(whether CO or ozone) are not garaged in the urbanized area proper. Vehicles
from suburban developments in nearby counties may have a large percentage of
their VMT occurring during trips for work or recreation to the urban center.
A serious problem of public perception arises when urban residents note that
not only are they the ones who must .live with excessive pollution, but .also
they must comply with vehicle inspection requirements while their suburban
neighbors need not. Thus the coverage area should be large enough to
encompass all areas which significantly contribute to the non-attainment
problem.
Enforcement considerations assume the most important .role in selection of the
exact coverage area. Two types of enforcement systems are possible, each with
unique implications for the decision. They are sticker systems and
registration systems.
Registration systems generally are easiest to enforce, since they require no
extra effort on the part of the police. A certificate is issued to vehicles
which have complied with I/M program 'requirements, and this certificate is
then used to obtain vehicle registration. Selection of county boundaries as
inspection program limits provides a simple mechanism for tying program
enforcement to a vehicle registration system. However, if this leads to the
inclusion of sparsely populated, rural areas, it is relatively easy to
identify subject vehicles by zip codes, city names, or even street names,
provided the registration system is computerized. However, as the coverage
area is decreased the problems associated with public perception increase.
State and county boundaries have been long established. If different
boundaries are set for the I/M program, such as non-attainment area
boundaries, program managers may have to answer complaints from vehicle owners
who reside just within the program limits about the alleged inequity of the
I/M re qui rement.
In sticker enforcement systems, police officers issue citations to vehicles
which should have compliance stickers but do not. The main difficulty
inherent in a sticker system lies in distinguishing between a non-complying
subject vehicle and a non-subject vehicle which is operating in rthe same area
-------
This vehicle class includes nearly all pick-ups and vans (except box-type
vans). Most are non-commercial vehicles. It should also be mentioned that
the limits of 6000 pounds curb weight and 45 square feet frontal area are only
used to refine the basic definition of 8500 pounds GVW. There are few
vehicles below 8500 GVWR which do not meet the other criteria.
Although current, this definition of LDT's has only been in effect since
1979. From the beginning of federal motor vehicle emissions standards (in
1968) through 1974, LDT's were lumped together with LDV's in one large class
of vehicles under 6000 pounds GVW. From 1975 to 1979 LDT's were defined as
"any motor vehicles rated at 6000 pounds GVW or less," with the same uses as
are currently defined. Then, in 1979, some trucks previously classed as
heavy-duty became part of the light-duty class. These are called LDT2's by
EPA to distinguish them from vehicles in the original class (LDTl's).
Light-Duty Diesel Trucks (Diesel LDT)^ - diesel-powered vehicles with the same
characteristics as gasoline LDT's. This is a very small class of vehicles,
currently less than 1% of the total LOT fleet.
Heavy-Duty Gasoline Trucks (HDG) - any gasoline-powered motor vehicle rated at
more than 8500 pounds GVW or that has a vehicle curb weight of more than 6000
pounds or that has a basic frontal area in excess of 45 square feet. These
vehicles include large commercial trucks, recreational vehicles and schooltype
buses. Prior to 1979, this class included vehicles rated at more than 6000
GVW (see LDT definition for further\explanation).
Heavy-Duty Diesel Trucks (HDD) - diesel-powered vehicles with the same weight
and frontal area limitations as HDG's. This class of vehicles consists
primarily of heavy tractor rigs; transit buses are also in this class.
Motorcycle (MC) - Any motor vehicle with a headlight, taillight, and stoplight
and having: two wheels or three wheels and a curb mass less than or equal to
680 kilograms (1499 pounds). (40 CFR 86.402-78)
The relative contributions of the various vehicle classes to total mobile
source emissions based on national averages are detailed in Figures 4-1 to
4-4. Percentages are projected by HOBILE2 (EPA's mobile source emission
factor computer model) and assume no I/M implementation. Note that for the
light-duty classes, diesel and gasoline emissions are combined. The vast
majority of vehicles in these classes are gasoline-powered, however.
4.2 Discussion
The vehicle classes inspected, in existing I/M programs are shown in Table
4-1. In deciding which vehicle classes to include in an I/M program, a
planner should focus on program effectiveness, ease of implementation and
equity. Each vehicle class will be discussed separately below, but there are *
two general considerations which should be mentioned first. '
-------
Table 4-1
Vehicle Classes Inspected in I/M Programs
GLDV
Diesel LDV
GLDT
Diesel LOT
I1DG
HDD
MC
New Jersey
yes
no
6000 Ibs.
no
no
yes
no
Oregon
yes
yes
8500 Ibs.
8500 Ibs.
yes
no
no
Arizona
yes
yes
6000 Ibs.
6000 Ibs.
yes
yes
yes
Ca lif ornia
yes
no
8500 Ibs.
no
no
no
no
Nevada
yes
no
6000 Ibs.
no
no
no
no
Rhode Island
yes
no
8500 Ibs
no
no
no
no
New York
yes
no
8500 Ibs
no
no
no
no
Georgia
yes
no
6000 Ibs
no
no
no
no
-------
HDD's - As with light-duty diesels, heavy-duty diesel trucks have no known
potential for HC or CO emissions reductions through I/M. Again, data suggest
that these vehicles do not deteriorate significantly over time in their
exhaust emissions. Approximately 60 percent of HDD VMT is short-haul, and is
accrued mostly in urban areas. Smoke reduction potential does exist, but the
number of excessively smoking diesels has not been quantified by EPA. Smoke
testing requires a loaded test using a dynamometer if it is to be meaningful,
since the smoke level at idle is not a good indication o-f smoke levels under
load. Arizona's mandatory smoke check for diesels is at idle, and very few
fail.
There are also many political and administrative problems involved in testing
heavy-duty diesels. Most .HDD's are interstate vehicles, thus they would be
exempt from testing in all but their home states. Even in-state trucks may be
from an area where I/M is not required.
Motorcycles - Motorcycles have good HC and CO emissions reduction potential
per vehicle through I/M, but a combination of small numbers and their
relatively low vehicle mileage makes the total reduction achievable very
small. As shown in Figures 4-1 to 4-4, motorcycles account for a negligible
fraction (less than.1%) of total mobile source emissions.
4.3 Recommendations
For the present, EPA recommends testing gasoline light-duty vehicles and
gasoline light-duty trucks. The efficacy of testing these vehicle classes has
.been proven,- and it is relatively simple to test gasoline LDT's in addition to
LDV s. Furthermore, there is a large emission reduction benefit to be
obtained from testing these vehicles, as seen in Figures 4-1 to 4-4. Since
most LDT's are used for personal transportation, a serious equity argument
arises if this class is excluded. It is recommended that a definition of less"
than 8500 pounds GVW be placed on LDT's if EPA's exact definition cannot be
met using existing registration procedures.
When more data are available on the emissions reduction potential of
heavy-duty gas trucks, and states and local areas have overcome the start-up
problems in inspecting LDV's and LDT's, they can evaluate the need for testing
these vehicles, and add them if desired. In a centralized program it might be
wise to design some of the inspection lanes to be wide and tall enough to
accommodate these trucks.
5.0 SELECTION OF MODEL YEARS COVERED (AGE EXEMPTIONS)
An I/M program may exempt older model year vehicles from program
requirements. Such exemptions may be considered to be desirable for many
reasons, some of which are discussed below. However, exemptions reduce .the
effectiveness of an I/M program, so they involve a tradeoff.
Olders cars have less sophisticated emissions controls than are currently
available. Pre-1968 vehicles were not subject to Federal emission standards,
although most domestic models have been equipped with PCV valves since 1963.
-------
11
FIXED MODEL TERR RDJUSTMENT FflCTORS
1 . 0
0. 9
0,8 .
0. 7
0. 6
0.5
0.3
0. 2
0. 1
0.0
o
H-
O
UJ
o
HTDROCRRBONS
==«= CRRBON
MONOXIDE
69 70 71 72 73 7U 75 76 77
OLDEST MODEL TERR INSPECTED
78
79
80
Figure 5-1
-------
13
Table 5-1
Moving Model Year Exemption Adjustment
Factors for January 1, 1988 Evaluation
of an I/M Program
Number of Adjustment Factors **
Model Years * HC CO
19 iToo iToo
18 .99 .99
17 .99 .99
16 .98 .98
15 .97 .97
14 .96 • .96
13 .94 .94
12 .93 .92
11 .90 .89
10 .87 .86
9 .82 .81
8. .78 .76
• 7 . .70 .68
6 .63 .60
5 .55 .53
* If AGE=CALENDAR YEAR - MODEL YEAR, cars with AGE greater than "Number of
Model Years" are not inspected.
** Adjustment factors are relative to an I/M program that inspects all model
year vehicles, which in MOBILE1 or MOBILE2 is the same as the most recent 19
model years. Care should be taken when running MOBILE1 or MOBILE2 to input
the model year coverage so that at least 19 model years, ending with the model
year that is the same as the evaluation year, are covered.
5.1 Recommendations
EPA makes no recommendations as to whether to grant age exemptions. But, if a
state desires them, for whatever reasons, EPA recommends:
(1) exemption of pre-1968 vehicles altogether, and
(2) exemption of cars with AGE.greater than 15 years.
Exemption of these vehicles, while accomplishing many of the goals of. age
waivers, preserves most of the program's effectiveness. (For all practical
purposes, in calculating effectiveness, this program is the same as one with
only a 15 model year moving exemption; Table 5-1 can be used to calculate
sffectiveness). The following table illustrates which model years would -be
'.ncluded in the recommended program for the calendar years 1980 through 1987.
-------
15
Change-of-Ovnership
Change-of-owriership inspection is the term used to represent a program where
inspection is required upon transfer of 'title of a used motor vehicle and also
when a used motor vehicle is registered for the first time in a 'specific
political jurisdiction. In the absence of an annual inspection requirement a
change-of-ownership I/M program will provide only a fraction of the emission
reductions benefit that an annual program will provide. This fraction will be
equal to the percent of the local fleet which changes ownership each year
(typically 20%).
Most I/M program managers will be concerned with the impact of adding a
change-of-ownership inspection to the annual cycle. The following discussion
concerns the emission reduction impact associated with a combined program.
The I/M benefits which are calculated by EPA's computer model MOBILE2 are
based on the assumption that each vehicle is inspected on the anniversary of
its initial sale to its first owner. This would be true if registrations were
good for one year and vehicles never changed ownership, for example. In
reality, vehicles change ownership and this may make annual inspection only on
the anniversary of initial sale undesirable or impractical. To illustrate,
consider a vehicle which has been inspected annually each April because it was
first bought from a new car dealer in April 1979. If this vehicle changes
ownership in September 1985, there are four possible schedules it may be
required to follow as a result:
(i) No -inspection in September 1985; inspection in each April thereafter.
(ii) Inspection in September 1985 as a precondition to the change in
ownership; inspection in April 1986 and each April thereafter.
(iii) Inspection in September 1985; and each September thereafter.
(iv) No inspection in September 1985; inspection in each September
thereafter.
Which of these schedules will apply depends on the individual state's systems
of vehicle registration and I/M- enforcement. A state may already find itself
locked into just one of the schedules under existing statute, with no latitude
to choose another schedule via agency regulations. Or a state may be able to
choose from among two or more of the schedules when the responsible agency
promulgates regulations.
Schedule (i) is exactly the schedule assumed in the MOBILE2 model, so no
adjustments to MOBILE2 benefits are needed. This schedule would be observed
in a state where the registration cycle is tied to the vehicle (either by
relating to the date of initial purchase or to a vehicle identifier such as
the VIN) and there is no change-of-ownership inspection.
-------
17
Random Roadside Checks
Due to limited resources, random roadside checks are not usually extensive
enough to yield any significant emission reduction from the vehicles, that are
failed by the checks and forced to get repairs. The emission benefit
resulting from a roadside check program, if any, presumably comes from its
deterrent effect. Because they fear being failed in a roadside check, owners
might take better care of their vehicles and refrain from misadjusting them
between regular inspections. The magnitude of this tendency depends on the
likelihood of being caught and the "penalty" an owner suffers for failing a
roadside check. This penalty can range from merely being required to get the
failed vehicle repaired and reinspected to having to pay a fine.
It is unlikely that any state would establish a fine so large that enough
owners would continue to get precautionary repairs to result in the required
reductions from a roadside check program alone. Therefore, a random roadside
check program by itself is not a substitute for regular, periodic inspections.
Random roadside checks could be added, however, to an annual I/M program.
There are many possible reasons why. a vehicle which passed its regular
inspection might fail '& subsequent roadside check. Natural deterioration in
the engine since the last inspection is one possibility. In a decentralized
program, the garage may have incorrectly certified the vehicle as passing its
last inspection. Or, the owner or a mechanic may have tampered or misadjusted
the car since the last inspection. Penalizing owners who fail roadside checks
is fair only if the owner is responsible (e.g., if the owner misadjusted the
vehicle or • asked a mechanic to do so). Since it would be impossible to
determine when owners are responsible for the failures, no fine would be
completely fair. EPA therefore recommends that roadside check data only be
used for program assessment and that no penalties be imposed as a result of
roadside check failures.
Random roadside checks can have indirect benefits in addition to the small
direct benefits that come from repair of vehicles which fail the checks and
from the mild deterrent effect. Roadside checks can be used to monitor
program operation and pinpoint problems that need special corrective
attention. For example in a decentralized program, roadside checks showing
that recently inspected cars have a much higher failure rate than being
reported by licensed garages for regular inspections would indicate widespread
error by garages in inspecting cars. Or, it might be found that cars recently
inspected at specific garages have a much higher roadside failure rate than
other cars. Either situation means the state should increase its garage
surveillance and quality assurance programs.
Inspection Window
Under any inspection schedule, there is a window in time within which each
vehicle must pass inspection. Most states with operating I/M programs define
this period as two or three months prior to the compliance deadline, which
provides sufficient time for owners to obtain any needed repairs.
6.3 Recommendations
The recommended program consists of annual, staggered inspections. The
recommended inspection window is 2 or 3 months prior to registration
------- |