[Code of Federal Regulations]
[Title 40, Volume 16]
[Revised as of July 1, 2006]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR80.48]
[Page 654-659]
TITLE 40--PROTECTION OF ENVIRONMENT
CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
PART 80_REGULATION OF FUELS AND FUEL ADDITIVES--Table of Contents
Subpart D_Reformulated Gasoline
Sec. 80.48 Augmentation of the complex emission model by vehicle
testing.
(a) The provisions of this section apply only if a fuel claims
emission reduction benefits from fuel parameters that are not included
in the complex emission model or complex emission model database, or if
the values of fuel parameters included in the complex emission model set
forth in Sec. 80.45 fall outside the range of values for which the
complex emission model is deemed valid.
(b) To augment the complex emission model described at Sec. 80.45,
the following requirements apply:
(1) The petitioner must obtain prior approval from the Administrator
for the design of the test program before beginning the vehicle testing
process. To obtain approval, the petitioner must at minimum provide the
following information: the fuel parameter to be evaluated for emission
effects; the number and description of vehicles to be used in the test
fleet, including model year, model name, vehicle identification number
(VIN), mileage, emission performance (exhaust THC emission level),
technology type, and manufacturer; a description of the methods used to
procure and prepare the vehicles; the properties of the fuels to be used
in the testing program (as specified at Sec. 80.49); the pollutants and
emission categories intended to be evaluated; the precautions used to
ensure that the effects of the parameter in question are independent of
the effects of other parameters already included in the model; a
description of the quality assurance procedures to be used during the
test program; the statistical analysis techniques to be used in
analyzing the test data, and the identity and location of the
organization performing the testing.
[[Page 655]]
(2) Exhaust emissions shall be measured per the requirements of this
section and Sec. 80.49 through Sec. 80.62.
(3) The nonexhaust emission model (including evaporative, running
loss, and refueling VOC and toxics emissions) shall not be augmented by
vehicle testing.
(4) The Agency reserves the right to observe and monitor any testing
that is performed pursuant to the requirements of this section.
(5) The Agency reserves the right to evaluate the quality and
suitability of data submitted pursuant to the requirements of this
section and to reject, re-analyze, or otherwise evaluate such data as is
technically warranted.
(6) Upon a showing satisfactory to the Administrator, the
Administrator may approve a petition to waive the requirements of this
section and Sec. 80.49, Sec. 80.50(a), Sec. 80.60(d)(3), and Sec.
80.60(d)(4) in order to better optimize the test program to the needs of
the particular fuel parameter. Any such waiver petition should provide
information justifying the requested waiver, including an acceptable
rationale and supporting data. Petitioners must obtain approval from the
Administrator prior to conducting testing for which the requirements in
question are waived. The Administrator may waive the noted requirements
in whole or in part, and may impose appropriate conditions on any such
waiver.
(c) In the case of petitions to augment the complex model defined at
Sec. 80.45 with a new parameter, the effect of the parameter being
tested shall be determined separately, for each pollutant and for each
emitter class category. If the parameter is not included in the complex
model but is represented in whole or in part by one or more parameters
included in the model, the petitioner shall be required to demonstrate
the emission effects of the parameter in question independent of the
effects of the already-included parameters. The petitioner shall also
have to demonstrate the effects of the already-included parameters
independent of the effects of the parameter in question. The emission
performance of each vehicle on the fuels specified at Sec. 80.49, as
measured through vehicle testing in accordance with Sec. 80.50 through
Sec. 80.62, shall be analyzed to determine the effects of the fuel
parameter being tested on emissions according to the following
procedure:
(1) The analysis shall fit a regression model to the natural
logarithm of emissions measured from addition fuels 1, 2, and 3 only (as
specified at Sec. 80.49(a) and adjusted as per paragraph (c)(1)(iv) of
this section and Sec. 80.49(d)) that includes the following terms:
(i) A term for each vehicle that shall reflect the effect of the
vehicle on emissions independent of fuel compositions. These terms shall
be of the form DixVi, where Di is the
coefficient for the term and Vi is a dummy variable which
shall have the value 1.0 for the ith vehicle and the value 0 for all
other vehicles.
(ii) A linear term in the parameter being tested for each emitter
class, of the form Aix(P1-P1
(avg))xEi, where Ai is the coefficient for the
term, P1 is the level of the parameter in question,
P1 (avg) is the average level of the parameter in question
for all seven test fuels specified at Sec. 80.49(a)(1), and
Ei is a dummy variable representing emitter class, as defined
at Sec. 80.62. For normal emitters, E1 = 1 and E2
= 0. For higher emitters, E1 = 0 and E2 = 1.
(iii) For the VOC and NOX models, a squared term in the
parameter being tested for each emitter class, of the form
Bix(P1-P1 (avg))\2\xEi,
where Bi is the coefficient for the term and where
P1 , P1 (avg), and Ei are as defined in
paragraph (c)(1)(ii) of this section.
(iv) To the extent that the properties of fuels 1, 2, and 3 which
are incorporated in the complex model differ in value among the three
fuels, the complex model shall be used to adjust the observed emissions
from test vehicles on those fuels to compensate for those differences
prior to fitting the regression model.
(v) The Ai and Bi terms and coefficients
developed by the regression described in this paragraph (c) shall be
evaluated against the statistical criteria defined in paragraph (e) of
this section. If both terms satisfy these criteria, then both terms
shall be retained. If the Bi term satisfies these criteria
and the Ai term does not, then both terms shall be retained.
If the Bi term does not satisfy these criteria,
[[Page 656]]
then the Bi term shall be dropped from the regression model
and the model shall be re-estimated. If, after dropping the
Bi term and re-estimating the model, the Ai term
does not satisfy these criteria, then both terms shall be dropped, all
test data shall be reported to EPA, and the augmentation request shall
be denied.
(2) After completing the steps outlined in paragraph (c)(1) of this
section, the analysis shall fit a regression model to a combined data
set that includes vehicle testing results from all seven addition fuels
specified at Sec. 80.49(a), the vehicle testing results used to develop
the model specified at Sec. 80.45, and vehicle testing results used to
support any prior augmentation requests which the Administrator deems
necessary.
(i) The analysis shall fit the regression models described in
paragraphs (c)(2) (ii) through (v) of this section to the natural
logarithm of measured emissions.
(ii) All regressions shall include a term for each vehicle that
shall reflect the effect of the vehicle on emissions independent of fuel
compositions. These terms shall be of the form
DixVi, where Di is the coefficient for
the term and Vi is a dummy variable which shall have the
value 1.0 for the ith vehicle and the value 0 for all other vehicles.
Vehicles shall be represented by separate terms for each test program in
which they were tested. The vehicle terms for the vehicles included in
the test program undertaken by the petitioner shall be calculated based
on the results from all seven fuels specified at Sec. 80.49(a). Note
that the Di estimates for the petitioner's test vehicles in
this regression are likely to differ from the Di estimates
discussed in paragraph (c)(1)(i) of this section since they will be
based on a different set of fuels.
(iii) All regressions shall include existing complex model terms and
their coefficients, including those augmentations that the Administrator
deems necessary. All terms and coefficients shall be expressed in
centered form. The Administrator shall make available upon request
existing complex model terms and coefficients in centered form.
(iv) All regressions shall include the linear and squared terms, and
their coefficients, estimated in the final regression model described in
paragraph (c)(1) of this section.
(v) The VOC and NOX regressions shall include those
interactive terms with other fuel parameters, of the form
Ci(1, j)x(P1-P1 (avg))x(Pj-
Pj (avg))xEi, where Ci(1, j) is the
coefficient for the term, P1 is the level of the parameter
being added to the model, P1 (avg) is the average level of
the parameter being added for all seven addition fuels specified at
Sec. 80.49(a), Pj is the level of the other fuel parameter,
Pj (avg) is the centering value for the other fuel parameter
used to develop the complex model or used in the other parameter's
augmentation study, and Ei is as defined in paragraph (c)(1)
of this section, which are found to satisfy the statistical criteria
defined in paragraph (e) of this section. Such terms shall be added to
the regression model in a stepwise manner.
(3) The model described in paragraphs (c) (1) and (2) of this
section shall be developed separately for normal-emitting and higher-
emitting vehicles. Each emitter class shall be treated as a distinct
population for the purposes of determining regression coefficients.
(4) Once the augmented models described in paragraphs (c) (1)
through (3) of this section have been developed, they shall be converted
to an uncentered form through appropriate algebraic manipulation.
(5) The augmented model described in paragraph (c)(4) of this
section shall be used to determine the effects of the parameter in
question at levels between the levels in Fuels 1 and 3, as defined at
Sec. 80.49(a)(1), for all fuels which claim emission benefits from the
parameter in question.
(d)(1) In the case of petitions to augment the complex model defined
at Sec. 80.45 by extending the range of an existing complex model
parameter, the effect of the parameter being tested shall be determined
separately, for each pollutant and for each technology group and emitter
class category, at levels between the extension level and the nearest
limit of the core of the data used to develop the unaugmented complex
model as follows:
[[Page 657]]
------------------------------------------------------------------------
Data core limits
Fuel parameter -------------------
Lower Upper
------------------------------------------------------------------------
Sulfur, ppm......................................... 10 450
RVP, psi............................................ 7 10
E200, vol %......................................... 33 66
E300, vol %......................................... 72 94
Aromatics, vol %.................................... 18 46
Benzene, vol %...................................... 0.4 1.8
Olefins, vol %...................................... 1 19
Oxygen, wt %........................................
As ethanol........................................ 0 3.4
All others:....................................... 0 2.7
------------------------------------------------------------------------
(2) The emission performance of each vehicle on the fuels specified
at Sec. 80.49(b)(2), as measured through vehicle testing in accordance
with Sec. Sec. 80.50 through 80.62, shall be analyzed to determine the
effects of the fuel parameter being tested on emissions according to the
following procedure:
(i) The analysis shall incorporate the vehicle testing data from the
extension fuels specified at Sec. 80.49(b), the vehicle testing results
used to develop the model specified at Sec. 80.45, and vehicle testing
results used to support any prior augmentation requests which the
Administrator deems necessary. A regression incorporating the following
terms shall be fitted to the natural logarithm of emissions contained in
this combined data set:
(A) A term for each vehicle that shall reflect the effect of the
vehicle on emissions independent of fuel compositions. These terms shall
be of the form Di x Vi, where Di is the
coefficient for the term and Vi is a dummy variable which
shall have the value 1.0 for the ith vehicle and the value 0 for all
other vehicles. Vehicles shall be represented by separate terms for each
test program in which they were tested. The vehicle terms for the
vehicles included in the test program undertaken by the petitioner shall
be calculated based on the results from all three fuels specified at
Sec. 80.49(b)(2).
(B) Existing complex model terms that do not include the parameter
being extended and their coefficients, including those augmentations
that the Administrator deems necessary. The centering values for these
terms shall be identical to the centering values used to develop the
complex model described at Sec. 80.45.
(C) Existing complex model terms that include the parameter being
extended. The coefficients for these terms shall be estimated by the
regression. The centering values for these terms shall be identical to
the centering values used to develop the complex model described at
Sec. 80.45.
(D) If the unaugmented VOC or NOX complex models do not
contain a squared term for the parameter being extended, such a term
should be added in a stepwise fashion after completing the model
described in paragraphs (d)(2)(i)(A) through (C) of this section. The
coefficient for this term shall be estimated by the regression. The
centering value for this term shall be identical to the centering value
used to develop the complex model described at Sec. 80.45.
(E) The terms defined in paragraphs (d)(2)(i)(C) and (D) of this
section shall be evaluated against the statistical criteria defined in
paragraph (e) of this section.
(ii) The model described in paragraph (d)(2)(i) of this section
shall be developed separately for normal-emitting and higher-emitting
vehicles, as defined at Sec. 80.62. Each emitter class shall be treated
as a distinct population for the purposes of determining regression
coefficients.
(e) Statistical criteria. (1) The petitioner shall be required to
submit evidence with the petition which demonstrates the statistical
validity of the regression described in paragraph (c) or (d) of this
section, including at minimum:
(i) Evidence demonstrating that colinearity problems are not severe,
including but not limited to variance inflation statistics of less than
10 for the second-order and interactive terms included in the regression
model.
(ii) Evidence demonstrating that the regression residuals are
normally distributed, including but not limited to the skewness and
Kurtosis statistics for the residuals.
(iii) Evidence demonstrating that overfitting and underfitting risks
have been balanced, including but not limited to the use of Mallow's
Cp criterion.
(2) The petitioner shall be required to submit evidence with the
petition which demonstrates that the appropriate terms have been
included in the regression, including at minimum:
[[Page 658]]
(i) Descriptions of the analysis methods used to develop the
regressions, including any computer code used to analyze emissions data
and the results of regression runs used to develop the proposed
augmentation, including intermediate regressions produced during the
stepwise regression process.
(ii) Evidence demonstrating that the significance level used to
include terms in the model was equal to 0.90.
(f) The complex emission model shall be augmented with the results
of vehicle testing as follows:
(1) The terms and coefficients determined in paragraph (c) or (d) of
this section shall be used to supplement the complex emission model
equation for the corresponding pollutant and emitter category. These
terms and coefficients shall be weighted to reflect the contribution of
the emitter category to in-use emissions as shown at Sec. 80.45.
(2) If the candidate parameter is not included in the unaugmented
complex model and is not represented in whole or in part by one or more
parameters included in the model, the modification shall be accomplished
by adding the terms and coefficients to the complex model equation for
that pollutant, technology group, and emitter category.
(3) If the parameter is included in the complex model but is being
tested at levels beyond the current range of the model, the terms and
coefficients determined in paragraph (d) of this section shall be used
to supplement the complex emission model equation for the corresponding
pollutant.
(i) The terms and coefficients of the complex model described at
Sec. 80.45 shall be used to evaluate the emissions performance of fuels
with levels of the parameter being tested that are within the valid
range of the model, as defined at Sec. 80.45.
(ii) The emissions performance of fuels with levels of the parameter
that are beyond the valid range of the unaugmented model shall be given
in percentage change terms by 100 - [(100 + A) x (100 + C) / (100 + B)],
where:
(A) ``A'' shall be set equal to the percentage change in emissions
for a fuel with identical fuel property values to the fuel being
evaluated except for the parameter being extended, which shall be set
equal to the nearest limit of the data core, using the unaugmented
complex model.
(B) ``B'' shall be set equal to the percentage change in emissions
for the fuel described in paragraph (f)(3)(i) of this section according
to the augmented complex model.
(C) ``C'' shall be set equal to the percentage change in emissions
of the actual fuel being evaluated using the augmented complex model.
(g) EPA reserves the right to analyze the data generated during
vehicle testing, to use such analyses to determine the validity of other
augmentation petitions, and to use such data to update the complex model
for use in certifying all reformulated gasolines.
(h) Duration of acceptance of emission effects determined through
vehicle testing:
(1) If the Agency does not accept, modify, or reject a particular
augmentation for inclusion in an updated complex model (performed
through rulemaking), then the augmentation shall remain in effect until
the next update to the complex model takes effect.
(2) If the Agency does reject or modify a particular augmentation
for inclusion in an updated complex model, then the augmentation shall
no longer be able to be used as of the date the updated complex model is
deemed to take effect, unless the following conditions and limitations
apply:
(i) The augmentation in question may continue to be used by those
fuel suppliers which can prove, to the Administrator's satisfaction,
that the fuel supplier had already begun producing a fuel utilizing the
augmentation at the time the revised model is promulgated.
(ii) The augmentation in question may only be used to evaluate the
emissions performance of fuels in conjunction with the complex emission
model in effect as of the date of production of the fuels.
(iii) The augmentation may only be used for three years of fuel
production, or a total of five years from the date the augmentation
first took effect, whichever is shorter.
(3) The Administrator shall determine when sufficient new
information
[[Page 659]]
on the effects of fuel properties on vehicle emissions has been obtained
to warrant development of an updated complex model.
[59 FR 7813, Feb. 16, 1994, as amended at 59 FR 36962, July 20, 1994]