UNITED STATES ENVIRONMENTAL PROTECTION AGENCY NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY 2565 PLYMOUTH ROAD ANN ARBOR, MICHIGAN 48105-2498

OFFICEOF AIR AND RADIATION May 26,2005 CCD-05

- 

### 10 

### (JDV/LDT/MDPV/HDV/ICI/LD- AFC) Dear Manufacturer: Subject: Assigned DeteriorationFactors This letter provides revised EPA assigned deterioration factors 

### (ADFs)for determining compliance with chassis-based exhaust and evaporativemission standards. These assigned deterioration factors may be used for small volume manufacturers under the provisions of 40 CFR 86.1826-01, and 

### are applicable for chassis tested vehicles using petroleumbased fuels (gasoline and diesel), alcohol fuels (ethanol and methanol) and gaseous fuels (natural gas and liquifiedpetroleum gas). ADFs 

### are provided for current vehicle standards and, because aftermarket alternative fuels converters and Independent Commercial Importers (ICIs) may convert or modify older model year vehicles, ADFs are also listed for previous model year standards. These ADFs must be used by qualifying small volume manufacturers and ICIs who certify new test groups after October 15,2005. Small volume manufacturers and ICIs may optionallyuse these ADFs immediately. 

### Applicability EPA's regulations at 40 CFR 86.1826-01(a) define the applicabilityof ADFs. These revised deterioration factors (DFs) supercede previous assigned deterioration factors presented in EPA Advisory Circular 51C', guidance letters CCD-00-12 dated August 24, 2000 and CD-95-14 dated September 27, 1995,and the ADFs presented in the most recent version of a template letter sent to prospective new small volume manufacturers and Independent Commercial Importers (ICIS).~ Guidance letter CCD-00-12 continues to be the appropriate source for determiningEPA ADFs for aftermarket conversions of heavy-duty engines for operation on alternative fuels. The new ADFs do not necessarily apply to vehicles certified to comply with California emission standards. Manufacturers who desire to certifyvehicles in Californiaby using ADFs will need to satisfy the current requirements from the California Air Resources Board (CARB). The CARB contact is Duc Nguyen (e-mail: dnguyen@arb.ca.gov).

'The assigned deteriorationfactors contained in Advisory Circular 51C are still applicablefor IC1Tier0 vehicles. The assigned exhaust and evaporativeemission deterioration factors used by new small volume manufacturers and ICIs are based on California Air Resources Board Manufacturer Advisory Correspondence documentsNo. 91-04 and 97-01,respectively. 1

### Background The EPA authority to develop and provide vehicle and engine manufacturerswith ADFs is based on Section 206(a)(1)of the Clean Air Act. EPA subsequently enacted regulations which allowed manufacturersto use ADFs. These provisions were described in $86.084-14 and §86.085-24(e)(2),and 

### ADFs were published in Office of Mobile Sources (OMS) Advisory Circular (NC)letter No. 51C, dated December 4, 1986.3 Effective with the Tier 

### 1 emission standards,

### EPA accepted the 

### use of the deterioration factors contained in the California Air ResourcesBoard (CARB) ManufacturersAdvisory Correspondence

### (MAC) letter 

### No. 91-04. EPA also accepteduse of the evaporative emission assigned deterioration factors in CARB MAC letter 

### No. 97-01. These CARB developed

### ADFs were used in lieu of EPA suppliedindustry-wide ADFs for Tier 1 exhaust emissions and enhanced (Tier 1)evaporative emission standards. These same 

### ADFs were 

### also used by manufacturersfor determining compliancewith the NLEV emission standards, and were also used as EPA 

### ADFs to meet interim non-Tier 2 standards and final Tier 2 emission standards. In the September 21, 1994Federal Register,EPA published emission standards and test procedures for gaseous fueled vehicles and engines. 

### In a separate rulemaking action on September 

### 30, 1994, EPA published emission standards for Clean-Fuel Vehicles (CFVs) and Engines. These regulationsprompted EPA to publish 

### ADFs for the Clean-Fuel Vehicle program in EPA guidance letter CD-95-14in 1995,and to re-issue this as guidance letter CCD-00-12,in 

### 2000. The ADFs in these guidance letters are identical. The 

### ADFs for gaseous vehicles were not based on data, but instead they were based on an analysis of emission standards values. The current EPA policy regarding ADFs is found in 40 CFR 586.1826-Ol(b)(l)(i). This 

### CFR section discusses using a 70” percentile analysis of industry-wide data to determine

### ADFs for manufacturerswith sales volumes less than 300 vehicles, while 586.1826-01(b)(2)(i)(A) discusses using either 

### a 70” percentile or arithmetic average of a manufacturer’sdeterioration factor data, whichever is less, to determine

### ADFs for a manufacturerwith sales volumes of 301- 14,999 vehicles. 

### In §86.1826-01(b)(l)(ii) and in §86.1826-01(b)(2)(i)(C) the CFR authorizesthe use of “alternativemethods’’to calculate ADFs. It is this flexibility in 586-1826-01which was exercised in developing the revised EPA 

### ADFs in Tables 

### 1and 2. 

### Summary Small volume manufacturersof light-duty vehicles, light-duty trucks, medium-duty passenger vehicles, and heavy-duty chassis tested vehicles should use the 

### ADFs presented in this letter. Aftermarket alternative fuels converters for these same vehicle classes should use the same ADFs, or alternatively, fuels convertersmay use OEM DFs as optionally permitted in EPA guidance document CCD-04-20. Aftermarket alternative fuels converters of heavy-duty engines should continue to use EPA guidancedocument CCD-00-12.

’A/C 51C supercededA/C Nos. 51B and 51-1and was effective beginning with the 1988 model year 2

### Revised 

### ADFs Tables 1and 2 present the new ADFs. Attachment 3 describes the analysis methodology used to develop Tables 

### 1 and 

### 2. Questions concerning the derivation or usage of these factors may be directed to Martin Reineman, 734-2 14-4430,or reineman.martin @epa.gov
Sincerely, 

# -G.$/

# s-=bQMerrylin Zaw-Mon, Director Certification and ComplianceDivision Office 

### of Transportation and Air Quality Attachments: Tables 1 and 2 Attachment 3



### 3

\Table 

### 1to 

### CCD-05-10



### Standards NMOGI 

# co NOx HCHO NMHC 50K 120K 50K 120K 50K 120K 50K 120K Tier 2 1.14 1.37 1.22 1.62 1.27 1.73 1.63 2.34 

### NLEVI 1.14 1.36 1.32 1.78 1.30 1.90 1.54 2.3 1 

### Interim non-Tier2 

### Tier 1 1.09 1.23 1.11 1.27 1.13 1.32 NIA NIA 

### HDV NIA 1.37 

### N/A 1.62 NIA 1.73 NIA 2.344

lOOK ADF 

### = 1

## + (120K ADF 

### - 1)*(96W116K) Where: 

### lOOK ADF = The converted 

### 120,000mile multiplicative 

### ADF 120K ADF = The 

### 120,000mile multiplicative 

### ADF 96K, 116K = 

### 96,000 and 

### 116,000miles, respectively 

### 3) Tier 

### 2 standards have an optional useful life 

### of 150K. Use the following equation to convert 

### 120K ADFs to 

### 150KADFs: 150K ADF 

### = 1

## + (120K 

### ADF 

### - 1)*(146W116K) Where: 

### 150K ADF =The converted 120,000mile multiplicative 

### ADF 120K ADF 

### = The 

### 120,000mile multiplicative 

### ADF 146K, 116K = 

### 146,000and 

### 116,000miles, respectively 

### 4) HCHO standards apply to 

### HDVs effective with the 2008 

### MY.



### 4Table 2 to CCD-05-10



# - 120,000Mile 

### A ditive 

### ADFs4$ Evaworative Emission 

### ADFslJY3

- 

### 24D 

## + HS), 

### g 

### 2 Day (High 

### 24D+ HS),g6 Running 

### Loss, gtmi' ORVR,

Tier 

### 29 0.05 0.004 0.022 LDT2 Tier 1 LDV, LDT1, 

### 0.29 0.33 0.006 0.041 LDT2

~~ LDT31°, 

### 0.47 0.56 0.005 

### 0.026 LDT41°,HDV,Heavy-asLight'' Notes: 

### 1) This table does not apply to diesel vehicles. 2) This table does not apply to alcohol fueled vehicles. 

### ADFs for alcohol fueled vehicles will be assigned on a case-by-case basis based on latest industry wide-information. 3) Evaporative emission test waivers may apply to aftermarket fuels conversions to CNG or LPG if approved in advanceby 

### EPA. See

### EPA guidance letter 

### CCD-04-20 dated October 

### 1,2004. 4) Some Tier 

### 1 and Interim non-Tier 

### 2 evaporative emission standards have a useful life of 

### 100K miles. Use the following equation to convert 

### 120K additive 

### ADFs to 

### lOOK additive 

### ADFs: 

### lOOK 

### ADF = (120K ADF)*(96K/116K) Where: 

### lOOK ADF = The converted 

### 120,000mile additive

### ADF 120K ADF 

### =The 

### 120,000mile additive 

### ADF 96K, 116K = 

### 96,000 and 

### 116,000miles, respectively 

### 5) Tier 

### 2 evaporative emission standardshave an optional useful life of 

### 150Kmiles. Use the following equation to convert 

### 120K addltive

### ADFs to 

### 150K additive 

### ADFs: 150K

### ADF = 

### (120K ADF)*(146W116K) Where: 

### 150K ADF 

### = The converted 

### 120,000mile additive

### ADF 120K ADF =The 

### 120,000mile additive

### ADF 146K, 116K 

### = 146,000and 

### 116,000miles, respectively 

### 6) No 2-day standards for dedicated CNG or dedicated 

### LGP vehicles. 7) No running loss standards for dedicated CNG or dedicated LPG vehicles. 

### 8) No 

### ORVR standardsfor dedicated CNG vehicles. 

### 9) 

### ADFs for 

### Tier 2 

### LDT3, LDT4, MDPV, and 

### HDV evaporative 

### standardswill be provided after phase-in starts in the 

### 2008 

### MY. 10) ADFs apply to Tier 

### 1LDT3 and 

### LDT4 vehicles regardless of fuel tank capacity. 

### 1 1) Heavy duty vehicles optionally certifiedunder light-duty provisions. 5Attachment 3 to CCD-05-10 Developmentof Revised EPA Assigned Deterioration Factors
Data Base This analysiswas based on 2001
- 2005 model year vehicle data contained in EPA’s Certification and Fuel Economy Information data base, CFEIS. The certification data include information from passenger cars, light-dutyvehicle trucks (LDT1 through LDT4), medium-dutypassenger vehicles, and optionally chassis certifiedheavy-duty vehicles. Analysis Approach

# - General In addition 

### to needing revised 

### ADFs for the Tier 

### 2 and HDV standards,because ICIs and aftermarket alternative fuels convertersmay certify older model year vehicles, revised exhaust emission ADFs were also developed for manufacturers certifying to Tier 1 and NLEV 

### standard^.^
The development of revised ADFs for exhaust emissions were based on a number of compromiseswhich met an objectivebased on simplicity, applicability and goodjudgment. To satisfythose objectives the following criteria were developed and employed: Simplicity

- Provide sets of multiplicative

### ADFs which can be applied across multiple levels of program specific emission standards. Applicability

## - Develop 

### ADFs for all applicable EPA emission control “program types,” i.e. vehicles certifiedto Tier 1standards,NLEV standards (includes Clean Fuel Vehicle 

### (CFV) standards), Tier 2 standards, and HDV 

### standard^.^ Provide multiplicative

### ADFs for petroleum fuels (gasoline and diesel), alcohol fuels (ethanol and methanol), and gaseous fuels (compressed natural gas and liquifiedpetroleum gas) for intermediate and full useful life standards. Provide multiplicative

### ADFs at a common 

### full useful life, and provide a means to scale them to a longer 

### or shorter full useful life as necessary.6 Good Judgment

- Exercise other options than using a 70” percentile value, such as

Tier 1 standardswere in effect starting with 1994modelyear passenger cars and light trucks under 6000 lbs GVW, and were phased-in for 100% of 1999model year light trucks with GVW over 6OOO lbs. NLEV standardsbecame effectivewith 1999model year passenger cars and LDTls,and were phased-in for 100%of 2001 modelyear LD’I2.s.
In this analysis,the CFV program is assumed to be an extension of the NLEV program. The standards are similar for passenger cars, LDTl and LDT2. The LDT3 and LDT 4 standardsin the CFV program were used for determining compliancewith Federal standards under the NLEV program, as there are no specificLDT3 and LDT4 standardsunder the EPA NLEV program. For EPA emission purposes, Useful Life is defined as l00K milesfor passengercars and lightlight-duty trucks but 120K miles for the heavy light-duty vehicles under the Tier 1,NLEV, and Clean Fuel Vehicle programs. Useful life is 1 20K, with an optionaluseful life of 150K for all classes of vehicles under the Tier 2 program. 

### 6calculating an average value, to develop 

### ADFs when sample sizes are 

### very small. The resulting ADFs should not be unrepresentatively high or low relative to the CFEIS deterioration factor (DF) data from all 

### manufacturers. MultiplicativeADFs were developedbecause they can be applied across a range of standardsfor 

### a particular

### program type with 

### many exhaust emission categories (for example, the 

### 11 bins of-the Tier 2 program). Providing additive ADFs has the disadvantagethat they should be unique across different emission standards. Providing additive 

### ADFs would yield an undesirable number of 

### ADFs per program type (for example, four sets per pollutant type for Tier 

### 1 vehicles, six sets per pollutant type for NLEV vehicles, 14 sets per pollutant type for Clean Fuel Vehicles, 

### 11 sets per pollutant for Tier 2 vehicles, and two sets per pollutant for Heavy-Duty Vehicles, for a total of 

### 37 

### ADFs for a particular exhaust pollutant). Such a large set of 

### ADFs wasjudged to be too complex, and stratifying the 

### DF data into 

### so many unique groups would result in sample sizes too small to provide either representative70”’percentiles or averages. Providing a reduced number of multiplicativeADFs does not imply that the technology across a particular set of emission standards is the same. For example, the technology to achieve Bin 

### 2 standards vs. Bin 10 standardsunder the Tier 2 program may be considerably different,but using multiplicative

### ADFs assumes the g& of deterioration across the Tier 2 program type is the same. The same reasoning holds for the other EPA program types: Tier 

### 1,NLEV, and HDV where there are multiple sets of standards. By using multiplicative

### ADFs, a much reduced number of exhaust emission 

### ADFs may be applied across different levels of standards. This is the approach taken in Table 1, where 

### ADFs are presented on a program specific basis. The methodology used to analyze and develop evaporative emission 

### ADFs is similar to that described above with the exception that because the vast majority of manufacturer submitted evaporative emission 

### DFs are additive, only additive 

### DFs were analyzed. Instead of the four program types described above for exhaust emissions, there are two evaporative emission program types 

### - the Enhanced Evaporative Emission Standards (Tier 

### l),which has four unique sets of standards, and the Tier 2 Evaporative Emission Standards, also containing four unique sets of standards when heavy duty vehicles are included. Because an additive ADF cannot be applied across different standards, Table 2 provides unique additive 

### ADFs across the different evaporative emission standard levels.



# . Exhaust Emission Analysis Approach A query was constructedto extract the DF data from of the Oracle based EPA CFEIS data system. The 

### CFR requires 

### an analysis using unique 

### DFs.’ Data fields in the 

### CFEIS relationa1 data base which were used to conduct this analysis included the following: Model Year 

### - Identifies the model year of interest, or 2001 

### - 2005 model year data for this



### ’ Unique DFs are associated with a “durabilitygroup,” a basic classification used for grouping vehicles. 

### 7analysis Manufacturer

### - Identifies specific LDV,LDT, MDPV, or HDV vehicle manufacturers through unique manufacturer codes 

### Sales 

### Area


### - Represents different 

### standards (program types), 

### such 

### as Federal 

### vs. California Vehicle Class Code 

### - Distinguishespassenger cars from four categories of light trucks. Differences in class vehicle codes also identify different emission standards. DF TweCode

- Distinguishes type of aging process used in a manufacturer’sdurability demonstration Fuel 

### Twe

- Identifies the fuels which were analyzed, which include gasoline, diesel, ethanol, and 

### CNG Individual test groups within 

### a durability group were analyzed to extract the following data fields: Emission Name
- Identifiesthe exhaust or evaporative emission pollutants of interest Useful Life 

### - 50K or 120K miles 

### (or lOOK or 

### 150K),specific to the standard and pollutant 

### of interest Result 

### - The low mileage (4K) test result AdditiveDF 

### - The quantity in g/mi (exhaust) or 

### g (evap) added to the low mileage test result to show the effect of deterioration,if any, at 

### 50K or 120K miles’ MultiplicativeDF
- Dimensionless multiplier applied to the low mileage test result to show the effect of deterioration,if any, at 

### 50K or 

### 120K miles’ CertificationLevel

- The emissionresult after either (but not both) the additive DF or the multiplicativeDF is applied to the low mileage test result and compared to the appropriate standards. Emission Standard

- Standardsin g/mi (exhaust) or g (evap) at 

### 50K or 

### 120Kmiles



### - Tier 

### - The specific emissionprogram (or standard)of interest, for example, TI (Tier l), LEV (NLEV), B5 (Tier 2, Bin 

### 5), or HDV The query results were sorted using the relational and filtering capabilities of Microsoft Access and reduced using the statistical analysis capabilitiesof Microsoft Excel. The exhaust emission query results were filtered for: 

### Usable DFs 

### - Unusable entries included

### DFs representing durability demonstrationsusing aged components, which by definition, cannot be used for developing quantitative

By definition, an additive emission DF equals the useful life emission value minus the 4K emission result. By definition, a multiplicative DF is the ratio of emissions at 50K or 120K miles divided by the emissions at low mileage,nominally 4K miles. 8ADFs.lo DF Tvpe Code/DF Twe - The records filtered out in this step included DF Types described as: Aged Components,EPA ADFs, and MFR ADFs. 

### Vehicle Class Code 

## - This code 

### was used 

### for obtaining

### DFs from the 

### vehicles of 

### interest, which included passenger cars, light trucks of the categoriesLDT1

- 

### LDT4, medium-duty passenger vehicles, and optionally chassis certifiedheavy-duty vehicles. Vehicle Manufacturer

### - The DF data from 

### 23 large volume vehicle manufacturerswere selectedfor analysis. Emission Name 

### - This step filtered for the pollutants of interest. They included: 

### HC-NM (non-methanehydrocarbon), OMHCE (alcohol fuel organic material hydrocarbon equivalent), OMNMHCE (alcohol fuel organic material non-methanehydrocarbon equivalent), 

### NMOG (non-methaneorganic gas), HCHO (formaldehyde), CO (carbon monoxide),NOx (nitrogen oxides), and 

### PM (particulate matter). OMHCE and 

### OMNMHCEDFs are associatedwith emission tests on ethanol flex-fueled vehicles and their sample sizes after all screening criteria were applied were extremely small. 

### OMHCE, OMNMHCE, and 

### HC-NM data were combinedto calculate 

### “NMOG’DFs. Sales Area

- The data were filtered to exclude vehicles sold in California due to their unique program requirements and standards. Duplicate Records 

### - $86.1826-01(a)(2)(ii)(A) requires unique records be used for developingADFs. This filtering step removed duplicateDF values which occur because, by definition, multiple test groups may use the DFs developed

### for a unique durability group. EPA emission standards for Tier 1 and NLEV programs have useful life standards for some vehicle classes of 

### lOOK miles, while the Tier 

### 2 program have optional useful life standards

### of 150K miles. To avoid presenting multiple tables of ADFs based on various useful lifes, the analysis converted 

### lOOK and 

### 150KmultiplicativeDFs (MultDFs) to 

### 120K MultDFs. The objective was to create a larger sample size for developing 

### 120K ADFs while avoiding inaccurate results from analyzing small samples of DFs at 

### lOOK or 

### 150K miles. The resulting 

### 120K ADFs developed from 70* percentiles were then scaled by applying adjustment factors that yielded 

### 1OOK and 

### 150K ADFs. The conversion of 

### lOOK MultDFs to 

### 120K MultDFs assumes a linear deterioration rate from 

### 4K to 

### 120K miles, and uses the known emission results at 

### 4K and 

### 1OOK miles. Knowing the slope of the line relating emission level vs. mileage, one can calculate an assumed value for emissions at 

### 120Kmiles. Using the definition 

### of a 

### MultDF as 

### 120Kemission 

### value 

### divided by 

### 4K emission value, the equation for converting a lOOK MultDF to a 120K MultDF becomes:

Io In the CFEIS data system, manufacturersthat used aged componentsin lieu of submitting additive or multiplicative DFs, often coded the entries differently. For example, manufacturersselecting this durability option sometimes submitted multiplicativeDFs of 1 and an additiveDF of 0.0, others simply left the multiplicative and additive DF fields blank, others have combinations of multiplicative DFs of 1, additive DFs or 0.0,and blank entries. 

### 9

### Eq 1: 

### 120KMultDF = 

### 1 

## + (100KMultDF

- 

### 1)*(116K/96K)" Where: 

### 120K MultDF =The converted 

### 100,000 mile multiplicativeDF 

### 1OOK'MultDF=

### The 100,000

### mile multiplicative

### DF from the 

### CFEIS data 

### base 116K,96K = 

### 116,000 and 

### 96,000 miles,respectively Similar to equation 

### 1, the equation for converting 

### 150K MultDFs to 

### 120K MultDFs is: Eq 

### 2: 120K MultDF 

### = 

### 1 

# + (150K MultDF

- 

### l)*(l16K/146K) Given the substantial number of additive DFs in the data base, the initial analysis approach created "equivalent" multiplicative DFs from the additive DFs using the low mileage test result (Result) and the 

### 50K or 

### 120Kresult (Certification Level). The objective was to able use the additive DFs in order to develop a larger sample size to find the 70* percentile values. An equivalent multiplicativeDF was calculatedby dividing individual CFEIS CertificationLevel values by the correspondlng

### CFEIS Result values. The resulting equivalent multiplicativeDFs were then combined with manufacturerreported multiplicativeDFs in the CFEIS data base (the actual multiplicative DFs) and the combined values ranked from lowest to highest DF, with the 

### 70* percentile value selected as a new ADF. Unfortunately, the viability of using additiveDFs converted to equivalent multiplicativeDFs breaks down when the 

### 4Ktest result is very low. The resulting multiplicativeDF becomes very large, which is why manufactureswere given the option of using additive DFs in lieu 

### of multiplicative DFs. Various options were consideredin order to include "reasonable" converted additive DFs in the analysis. These options included: 

### 1) using converted DFs capped at selected subjective levels (for example those below 

### 3.0); 2) capping the converted DFs at the maximum value of the actual multiplicative

### DFs; and 

### 3) calculatingan average DFbased 

### on using the actual multiplicative DFs together with the converted additive DFs. None of these options were determined to be satisfactory due 

### to their arbitrary nature in the case of the first two options, or the unrepresentatively high ADFs resulting from using the third option. By process of elimination, the approach selectedwas to analyze only the actual multiplicative DFs and ignore the additive DFs. This solution was deemed acceptable as long as there were sufficient data for a particular combination of emission control program, pollutant, and fuel type. This is the analysis approach used for developingthe gasoline fueled vehicle 

### ADFs in Table 

### 1. Because the ADFs in Table 

### 1 are based on 

### 120K multiplicative DFs, manufacturerswho wish to use the multiplicativeADFs in Table 

### 1 for vehicle classes with full useful life of 

### lOOK miles may use the following equation:

I' This equation assumes the low mileage test is conductedat 4K miles. In actuality, the 4K test is conducted at a mileage not exactly equal to 4K miles. 

### 10Eq 3: lOOK ADF 

### = 1

## + (120K ADF 

### - 1)*(96W116K) Similarly,the following equation allows a manufacturer to use Table 1 to calculate an exhaust 

### ADF appropriate for a useful life of 150K

### miles: Eq 4: 150KADF = 1 

## + (120K ADF
- 1)*(146W116K) Evaporative EmissionAnalysis Approach The analysis of evaporative emission data required an analysis of additive DFs, but the general approach to developing the evaporative emissions ADFs was similar to the methodology used in the development of the exhaust emission ADFs. Specifically, the same 2001 

### - 2005 

### MY CFEIS data source was used, the same 23 largest manufactures, the same vehicle classes 

### (LDV, LDT1-4, 

### MDPVs, HDVs), the same sales area (no California data), and duplicate DFs were excluded. For sample sizes of 10 or less the additive ADF was calculatedusing the average of the DFs. This occurred only once during the analysis of the Tier 2 running loss data. Similar to exhaust emission DFs, evaporativeemission DFs are based on full useful life mileage. To account for differencesin mileage, an assumption of linear deterioration was used to convert lOOK DFs to 120KDFs. Due to the differencein definition of additiveDF (AddDF) vs. multiplicative DF, the equation used to convert lOOK additive DFs to 120K additive DFs becomes the following: Eq 5: 120K AddDF 

### = (100K AddDF)*(116W96K) Where: 120K AddDF 

### =The converted 100,000mile additiveDF lOOK AddDF 

### =The 100,000mile additiveDF from the CFEIS data base 116K, 96K 

### = 116,000and 96,000 miles, respectively Similarly, any 150K additive DFs were convertedto 120K additive DFs using the equation: Eq 6: 120K AddDF 

### = (150K AddDF)*(116W146K)
Because the ADFs in Table 2 are based on additive DFs, manufacturersmay use the following equation to convert 120K evaporativeemission ADFs to lOOK ADFs: Eq. 

### 7: lOOK ADF = (120K ADF)*(96W116K) Similarly, manufacturersmay use the following equation to convert 120Kevaporative emission ADFs to 150KADFs: 

### Eq. 

### 8: 150K ADF = (120K ADF)*(146W116K) Discussion

### of Tables 

### 1 and 2

11Table 

### 1

### - Table 

### 1 presents multiplicative

### ADFs at 

### 50K and 

### 120K miles for four exhaust emission types (NMOG/NMHC, COY NOx, HCHO) as a function of program type, or standards. The results presented in Table 

### 1 are based on a ranlung of multiplicative

### DFs from lowest to highest and then selectingthe 70" percentile value. The sample sizes used in developingthe values in Table 

### 1 varied from 

### 30 unique 

### DF values for Tier 

### 1 vehicles,to 

### 110 values for 

### NLEV vehicles, to 85 values for Tier 2 vehicles. Owing to the very small sample sizes for fuel types other than gasoline, the ethanol, methanol, 

### CNG, and 

### LPG fuel types will use the 

### DFs derived from analysis of gasoline

### DFs. This is based on the conservative assumption that multiplicative 

### ADFs for vehicles fueled on other fuel types shouldbe no worse than the 

### DFs for vehicles operatingon gasoline. An exception is diesel vehicles where it may be unreasonable to use gasoline 

### ADFs as a surrogate for diesel 

### ADFs. EPA will address manufacturers' needs for diesel 

### ADFs on a case-bycase basis using knowledge of the vehicle control system and current industry wide data to assign representative

### ADFs. Inadequate sample sizes prevent use of a statistical approach to determine representative

### DFs from heavy-duty vehicles. Until more data are available and a revised set of 

### ADFs are published, EPA will permit manufacturers to use the Tier 

### 2 

### ADFs in Table 

### 1 in absence of 

### HDV ADFs based on actual data. Table 

### 2

- Table 

### 2 presents evaporative emission ADFs for three types of evaporative emission tests 

### (3 Day, 

### 2 Day, Running

### Loss), and the onboard refueling vapor recovery test (ORVR). The 

### ADFs are presented as a function 

### of vehicle class. The Tier 1 sample sizes from which the 

### 70* percentile values were selected varied from a high of 

### 165 3 Day 

### DFs to a low of 

### 85 running loss 

### DFs.. Tier 

### 2 sample sizes ranged from a high of 

### 46 ORVR DFs to a low of 

### 2 running loss 

### DFs.

12