[Code of Federal Regulations]

[Title 40, Volume 31]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 40CFR1065.12]



[Page 677-679]

 

                   TITLE 40--PROTECTION OF ENVIRONMENT

 

         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)

 

PART 1065_ENGINE-TESTING PROCEDURES--Table of Contents

 

             Subpart A_Applicability and General Provisions

 

Sec.  1065.12  Approval of alternate procedures.



    (a) To get approval for an alternate procedure under Sec.  

1065.10(c), send the Designated Compliance Officer an initial written 

request describing the alternate procedure and why you believe it is 

equivalent to the specified procedure. We may approve your request based 

on this information alone, or, as described in this section, we may ask 

you to submit to us in writing supplemental information showing that 

your alternate procedure is consistently and reliably at least as 

accurate and repeatable as the specified procedure.

    (b) We may make our approval under this section conditional upon 

meeting other requirements or specifications. We may limit our approval, 

for example, to certain time frames, specific duty cycles, or specific 

emission standards. Based upon any supplemental information we receive 

after our initial approval, we may amend a previously approved alternate 

procedure to extend, limit, or discontinue its use. We intend to 

publicly announce alternate procedures that we approve.

    (c) Although we will make every effort to approve only alternate 

procedures that completely meet our requirements, we may revoke our 

approval of an alternate procedure if new information shows that it is 

significantly not equivalent to the specified procedure.

    If we do this, we will grant time to switch to testing using an 

allowed procedure, considering the following factors:

    (1) The cost, difficulty, and availability to switch to a procedure 

that we allow.

    (2) The degree to which the alternate procedure affects your ability 

to show that your engines comply with all applicable emission standards.

    (3) Any relevant factors considered in our initial approval.



[[Page 678]]



    (d) If we do not approve your proposed alternate procedure based on 

the information in your initial request, we may ask you to send the 

following information to fully evaluate your request:

    (1) Theoretical basis. Give a brief technical description explaining 

why you believe the proposed alternate procedure should result in 

emission measurements equivalent to those using the specified procedure. 

You may include equations, figures, and references. You should consider 

the full range of parameters that may affect equivalence. For example, 

for a request to use a different NOX measurement procedure, 

you should theoretically relate the alternate detection principle to the 

specified detection principle over the expected concentration ranges for 

NO, NO2, and interference gases. For a request to use a 

different PM measurement procedure, you should explain the principles by 

which the alternate procedure quantifies particulate mass similarly to 

the specified procedures. For any proportioning or integrating 

procedure, such as a partial-flow dilution system, you should compare 

the alternate procedure's theoretical response to the expected response 

of the specified procedures.

    (2) Technical description. Describe briefly any hardware or software 

needed to perform the alternate procedure. You may include dimensioned 

drawings, flowcharts, schematics, and component specifications. Explain 

any necessary calculations or other data manipulation.

    (3) Procedure execution. Describe briefly how to perform the 

alternate procedure and recommend a level of training an operator should 

have to achieve acceptable results.

    Summarize the installation, calibration, operation, and maintenance 

procedures in a step-by-step format. Describe how any calibration is 

performed using NIST-traceable standards or other similar standards we 

approve. Calibration must be specified by using known quantities and 

must not be specified as a comparison with other allowed procedures.

    (4) Data-collection techniques. Compare measured emission results 

using the proposed alternate procedure and the specified procedure, as 

follows:

    (i) Both procedures must be calibrated independently to NIST-

traceable standards or to other similar standards we approve.

    (ii) Include measured emission results from all applicable duty 

cycles. Measured emission results should show that the test engine meets 

all applicable emission standards according to specified procedures.

    (iii) Use statistical methods to evaluate the emission measurements, 

such as those described in paragraph (e) of this section.

    (e) We may give you specific directions regarding methods for 

statistical analysis, or we may approve other methods that you propose. 

Absent any other directions from us, use a t-test and an F-test 

calculated according to Sec.  1065.602 to evaluate whether your proposed 

alternate procedure is equivalent to the specified procedure. We 

recommend that you consult a statistician if you are unfamiliar with 

these statistical tests. Perform the tests as follows:

    (1) Repeat measurements for all applicable duty cycles at least 

seven times for each procedure. You may use laboratory duty cycles to 

evaluate field-testing procedures.

    Be sure to include all available results to evaluate the precision 

and accuracy of the proposed alternate procedure, as described in Sec.  

1065.2.

    (2) Demonstrate the accuracy of the proposed alternate procedure by 

showing that it passes a two-sided t-test. Use an unpaired t-test, 

unless you show that a paired t-test is appropriate under both of the 

following provisions:

    (i) For paired data, the population of the paired differences from 

which you sampled paired differences must be independent. That is, the 

probability of any given value of one paired difference is unchanged by 

knowledge of the value of another paired difference. For example, your 

paired data would violate this requirement if your series of paired 

differences showed a distinct increase or decrease that was dependent on 

the time at which they were sampled.



[[Page 679]]



    (ii) For paired data, the population of paired differences from 

which you sampled the paired differences must have a normal (i.e., 

Gaussian) distribution. If the population of paired difference is not 

normally distributed, consult a statistician for a more appropriate 

statistical test, which may include transforming the data with a 

mathematical function or using some kind of non-parametric test.

    (3) Show that t is less than the critical t value, tcrit, tabulated 

in Sec.  1065.602, for the following confidence intervals:

    (i) 90% for a proposed alternate procedure for laboratory testing.

    (ii) 95% for a proposed alternate procedure for field testing.

    (4) Demonstrate the precision of the proposed alternate procedure by 

showing that it passes an F-test. Use a set of at least seven samples 

from the reference procedure and a set of at least seven samples from 

the alternate procedure to perform an F-test. The sets must meet the 

following requirements:

    (i) Within each set, the values must be independent. That is, the 

probability of any given value in a set must be unchanged by knowledge 

of another value in that set. For example, your data would violate this 

requirement if a set showed a distinct increase or decrease that was 

dependent upon the time at which they were sampled.

    (ii) For each set, the population of values from which you sampled 

must have a normal (i.e., Gaussian) distribution. If the population of 

values is not normally distributed, consult a statistician for a more 

appropriate statistical test, which may include transforming the data 

with a mathematical function or using some kind of non-parametric test.

    (iii) The two sets must be independent of each other. That is, the 

probability of any given value in one set must be unchanged by knowledge 

of another value in the other set. For example, your data would violate 

this requirement if one value in a set showed a distinct increase or 

decrease that was dependent upon a value in the other set. Note that a 

trend of emission changes from an engine would not violate this 

requirement.

    (iv) If you collect paired data for the paired t-test in paragraph 

(e)(2) in this section, use caution when selecting sets from paired data 

for the F-test. If you do this, select sets that do not mask the 

precision of the measurement procedure. We recommend selecting such sets 

only from data collected using the same engine, measurement instruments, 

and test cycle.

    (5) Show that F is less than the critical F value, Fcrit, tabulated 

in Sec.  1065.602. If you have several F-test results from several sets 

of data, show that the mean F-test value is less than the mean critical 

F value for all the sets. Evaluate Fcrit, based on the following 

confidence intervals:

    (i) 90% for a proposed alternate procedure for laboratory testing.

    (ii) 95% for a proposed alternate procedure for field testing.