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2. THE STANDARDS, CERTIFICATION AND TESTING
2.1 Numerical Values of Standards
Section 202 of the Clean Air Amendments of 1970 requires the
Administrator of the EPA to prescribe emission standards for light-duty
motor vehicles together with measurement techniques on which such stan-
dards are to be based.* Such standards require that the emissions of
carbon monoxide and unburned hydrocarbons from light-duty vehicles and
engines manufactured during or after model year 1975 be reduced by at
least 90 percent from these required of 1970 vehicles; also, emissions
of oxides of nitrogen from light-duty motor vehicles and engines manu-
factured during or after model year 1976 are to be at least 90 percent
below the average of those actually measured from light-duty vehicles
manufactured during model year 1971 which are not subject to any fed-
eral or state emission standards. The 1975 model year standards are:
0.41 grams per vehicle mile for hydrocarbons (HC)
3.4 grams per vehicle mile for carbon monoxide (CO)
3.1 grams per vehicle mile for oxides of nitrogen (NOx).
Standards for 1976 model year vehicles are:
0.41 grams per vehicle mile for hydrocarbons
3.4 grams per vehicle mile for carbon monoxide
and 0.4 grams per vehicle mile for oxides of nitrogen.
The Clean Air Amendments call for vehicle compliance with the above
standards for five years or 50,000 miles, whichever occurs first.
2 2 Procedures for Certification, CVS-CH Test
e
The numerical values of the standards must be defined in terms
of a specific method of measurement and a specific driving cycle. The
EPA Administrator is required by Section 206 to test any motor vehicle
The Federal Register of November 15, 1972, contains a complete descrip-
tion of the regulations concerning the standards, test procedures,
allowable maintenance, etc.
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or class of motor vehicles to determine whether they meet the standards
set forth in Section 202(b) of the Clean Air Amendments. A certificate
of conformity is to be issued for classes of motor vehicles that comply
with the standards, thus permitting the manufacture and sale of these
classes of vehicles. The emissions test to be used for certification of
1975 and 1976 vehicles, referred to as the CVS-CH test, consists of a
12-hour wait at a temperature between 60° and 86°F, a cold-engine startup,
a continuous sequence of different driving modes simulating an average
trip over a 23-minute route in an urban area, a ten-minute shutdown
followed by a hot-engine restart, and a repeat of the fi rst 505 seconds
of the 23-minute cycle. This test is performed wi th the vehicle on a
chassis dynamometer. Exhaust-gas sampling begins immediately after
the key is turned on (whether the engine starts or not). Diluted
exhaust emissions are collected during the first 505 seconds in one
bag, those during the remainder of the 23-minute cycle in a second bag,
and those from the hot-restart phase in a third bag. Contents of the
three bags are then analyzed and weighted in accordance with the EPA
test procedure to get the final mass emissions, in grams per mile, of
HO, CO, and NOx.
To obtain a certificate of conformity for a class of vehicles,
the automobile manufacturer must also demonstrate the effectiveness
of the vehicles' emission-control system over the "useful life" of a
vehicle. The regulations require a manufacturer to test two separate
fleets of prototype vehicles representing models to be sold to the
public. The "emission data" fleet is intended to determine the emissions
of relatively new vehicles. The vehicles in this fleet are driven 4,000
miles to break in the engine and stabilize emissions. The emissions are
then measured, using the CVS-CH test procedure. Allowable maintenance
on emission-data vehicles is limited to the adjustment of engine idle
speed at the 4,000-mile test point.
The second fleet, the ''durability-datat' fleet, is designed to
detains the capability of the emission-control system to keep emissions
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below the standards over the expected useful life of the vehicle. The
vehicles in this fleet are driven for 50,000 miles and tested for
emissions every 4,000 miles. The procedure for mileage accumulation
is the Durability Driving Schedule over a modified AMA route. The
maximum speed is 70 mph, and the average is 30 mph. One ma jor engine
tuneup to manufacturer's specifications may be performed on durability
vehicles at 24, 000 miles (on vehicles with 150-CID or less, at 12, 000,
24,000, and 36, 000 miles) . The replacements and ad justments allowed
are detailed in the regulations. Emissions tests must be run before
and after any vehicle maintenance that may be reasonably expected to
affect emissions. As the first step in determining compliance of a
new light-duty vehicle, emission-deterioration factors are determined
from the durability-data fleet emission test results. Separate factors
are determined for HO, CO, and NOx and for each engine/control-system
combination. A straight line is fitted, by the method of least squares,
to each of the plots of emissions versus me leage for the endurance
fleet. For each of the three pollutants, deterioration factors are
determined from these curves as the ratio of emissions at 50,000 miles
to those at 4,000 miles. The emission test results, at 4,000 miles,
for each emission-data fleet vehicle are then multiplied by the
appropriate deterioration factor to give adjusted emissions for each
vehicles These adjusted emissions are then compared to the standards.
Every test vehicle from an engine family must comply with the standards
before any vehicle in that family can be certified.
2. 3 Prod''c:t i on-T.i no Ten t ins
To ascertain whether vehicles are being manufactured in accor-
dance with the regulations with respect to which a certificate of
conformity was issued, Section 206(b) authorizes EPA to test new
vehicles and engines. Such tests can be conducted by EPA or by the
manufacturer in accordance with conditions specified by EPA. According
to Section 206(b)~21(A), if:
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"based on tests on a sample of new vehicles
or engines covered by a certificate of conformity,
the Administrator determines that all or part of
the vehicles or engines so covered do not conform
with the regulations with respect to which the
certificate of conformity was issued, he may sus-
pend or revoke such certificate in whole or in
part "
The Act sets forth a procedure for reissuance of the certificate and
for hearings on its suspension or revocation.
It is impractical to determine the emissions from a large
fraction of production vehicles by the CVS-CH procedure. Each test
involves a twelve-hour wait at room temperature followed by a 41-
minute test, with expensive and complex instrumentation required . In
addition, measurements of exhaust emissions show poor repeatability.
Data from the automobile manufacturers and several independent labora-
tories taken on 1972 model year vehicles using the 1975 Federal CVS-CH
test show coefficients of variation of 10 to 20 percent. When the
CVS-CH test is applied to 1975-76 prototype vehicles, the probable
percentage error increases, since emission levels have decreased from
1972. Only limited data were available of test reproducibility using
the CVS-CH test with dual-catalyst-equipped vehicles near the 1976
emission levels. Coefficients of variation for these limited data,
consisting of 16 repetitive tests on a vehicle, were as great as 50
percent for CO. Test on three-valve carbureted stratified-charge
engines, which meet 1975 standards, have yielded much lower coefficients
of variation.
Some of the reasons for the lack of repeatability of measure-
ments are the difficulty of following the speed-time curve specified
in the CVS-CH procedure, lack of repeatability of some of the engine
functions having an effect on emission control (such as the choke
time), and the fact that the 1975-76 pollutant levels give such low
concentrations in the sample bags that the resolution capabilities of
the instruments are approached. The variation of test results during
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the cold portion of the test is the largest part of total test varia-
tion, with a large percentage o f CO and HO emissions occurring during
the first two minutes of the CVS-CH test. An individual measurement
using the CVS-CH test on a 1975-76 car can vary from the true value
by 50 percent and thus little significance should be attached to a
single test. Since a hot-start test does not include the emissions
that dominate the results obtained with the CVS-CH test, no short hot-
start test will pass and fail exactly the same vehicles as the CVS-CH
test. It thus is evident that 100 percent production-line testing with
any procedure except CVS-CH test (impractical on production line)
cannot determine if all vehicles are being manufactured in accordance
with the regulations with respect to which a certificate of conformity
was issued.
In terms of overall air quality, it is the average emissions
from a group of cars that determines the automotive contribution to
air pollution. This fact and the variability of test results men-
tioned above shows a need for regulations that control the manufacture
and operation of vehicles to ensure that the emissions on the average
meet the standards. It is only necessary to test a quality audit
sample of production-line vehicles to demonstrate that the average
emissions of production vehicles compare satisfactorily with the
certification standard, taking into account a prescribed useful life
deterioration factor and a tolerance factor reflecting the difference
between production vehicles and pre-production prototypes. The logical
test to choose for this quality audit is the CVS-CH procedure.
The Committee recommends, as in the CAVE January 1, 1972 report,
that only the emis signs of the average of each engine-vehicle combina-
tion on the production line be required to meet the standards. A
requirement that all vehicles meet the emission standards is too
restrictive and is unnecessary to meet air quality needs.
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2.4 Compliance after Sale, Warranty
The recommendation covering production-line averaging has an
impact on the warranty provisions of the law, contained in Sections
207(a) and (b) of the Clean Air Amendments. Section 207(a) requires
that the manufacturer of each new motor vehicle and engine shall warrant
to the purchaser that it is (1) designed, built, and equipped so as to
conform at the time of sale with (the applicable standards), and (2)
free from defects in materials and workmanship which cause such vehicle
or engine to fail to conform with (the standards) for its "useful life."
Section 207(b) deals with warranties for vehicles throughout
their useful life. This section states that manufacturers could
ultimately be required to warrant compliance of the emission control
system of a vehicle throughout its useful life if it is maintained
and operated in accordance with the manufacturer's instructions and
if the nonconformity results in the car owner "having to bear any
penalty or other sanction . . . under State or Federal law." Before
such a useful-life warranty can be imposed however, the Administrator
must first determine that there are available testing methods and
procedures to ascertain whether a vehicle, when in actual use, complies
with the emission standards and that such methods and procedures are
reasonably capable of being correlated with tests conducted by EPA
preparatory to issuance of a certificate of conformity (meaning the
full CVS-CH procedure). These warranty provisions apply to each
vehicle. However, if it is concluded that there is no short test
or procedure that reasonably correlates with the CVS-CH test, the
problem of possible conflict in implementing the warranty requirement
is eliminated. After consideration of this point, the Committee
concludes that no short test is available now, or Likely to be
available in the near future, that will pass and fail the same vehicles
as the full CVS-CH test.
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Section 207(c) of the Clean Air Act deals specifically with
recall of vehicles which, although properly maintained, do not conform
with the standards. According to Section 207 (c)~1), "If the Administrator
determines that a substantial number of any class or category of vehicles
or engines, although properly maintained and used, do not conform to the
regulations prescribed under Section 202, when in actual use throughout
their useful life (as determined under Section 202(d)), he shall imme-
diately notify the manufacturer thereof of such nonconformity, and he
shall require the manufacturer to submit a plan for remedying the non-
confonmity of the vehicles or engines with respect to which such notifi-
cation is given."
Since the purpose of the Clean Air Amendments is to control the
automotive contribution to air pollution, the Committee believes that
a surveillance audit of a statistical sample of vehicles is adequate
to determine if each family of cars meets the standards. The full OVS-
CH test would be run for the surveillance audit. Such surveillance tests
could be used not only to determine emissions Fran each car family, but
also to evaluate deterioration of emission control systems in actual use,
to evaluate the effectiveness of prescribed maintenance procedures, to
develop information on failure modes, and to establish the need for re-
call of a class of vehicles.
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Representative terms from entire chapter:
useful life
