**MEMORANDUM**

SUBJECT: Updates to MOVES for the Tier 3 NPRM Analysis FROM: Megan Beardsley, Environmental Scientist Assessment and Standards Division TO: Docket Number EPA - HQ - OAR - 2011 - 0135 DATE: March 11, 2013 The U.S. Environmental Protection Agency (EPA) is proposing new vehicle emission standards and fuel quality standards to reduce emissions of criteria pollutants. Collectively , these proposed standards are referred to as “Tier 3 vehicle standards” and “Tier 3 fuel standards.” As part of this anal ys is we estimated the impact of the Tier 3 proposal on the nationwide highway vehicle emissions of criteria pollutants, criteria pollutant precursors and selected air toxics. We made these estimates using an updated version of the EPA’ s Motor Vehicle Emission Simulator (MOVES2010). The attached document details how the MOVES default code and databases were updated for the Tier 3 NPRM anal ys is.

# Updates to MOVES for the Tier 3 NPRM Analysis March 2013

Air Quality & Modeling Center Assessment & Standards Division Office of Transportation & Air Quality

U.S. EPA2

I. Introduction ................................ ................................ ................................ ............................. 4 II. Fuel Effect Updates ................................ ................................ ................................ ................. 5 A. Fuel Sulfur Impacts ................................ ................................ ................................ ............. 5 1. New Research of Fuel Sulfur Effects on Emissions ................................ ..................... 5 2. Implementation in MOVES ................................ ................................ .......................... 6 B. Fuel Effects from EPAct Study ................................ ................................ ........................... 7 1. EPAct Fuel Effects on Criteria Pollutants ................................ ................................ .... 7 2. EPAct Fuel Effects on Selected Air Toxics ................................ ................................ .. 9 3. Additional Adjustments for Benzene and 1,3 - Butadiene ................................ ........... 12 C. Additional Fuel - Related Changes to MOVES ................................ ................................ .. 12 III. Evaporative Emission Updates ................................ ................................ ......................... 13 A. Permeation ................................ ................................ ................................ ........................ 13 B. Vapor Venting ................................ ................................ ................................ ................... 14 1. Update of Vapor Venting Algorithms with new DEL TA Model ............................... 14 2. Multiple Day

Diurnals ................................ ................................ ................................ 14 3. Vapor Leaks ................................ ................................ ................................ ................ 15 4. Summary

of Updated MOVES Inputs for Vapor Venting ................................ ......... 18 IV . Update of Air Toxics and HC Speciation ................................ ................................ ......... 21 A. Algorithms for 2003 - and - Earlier Gasoline Vehicles ................................ ........................ 21 B. Estimating Emissions for Additional Air Toxics ................................ .............................. 23 1. Additional Air Toxics: Inputs for Gasoline Vehicles ................................ ................ 24 a) Exhaust ................................ ................................ ................................ .................... 24 b) Evaporative and Permeation ................................ ................................ ................... 28 2. Additional Air Toxics: Inputs for Emissions from Diesel Vehicles .......................... 30 a) Exhaust ................................ ................................ ................................ .................... 30 b) Evaporative ................................ ................................ ................................ ............. 34 C. Hydrocarbon Speciation Factors ................................ ................................ ....................... 35 1. HC Speciation of Exhaust Emissions ................................ ................................ ......... 36 2. HC Speciation of Permeation Emissions ................................ ................................ .... 38 D. Additional Updates to Air Toxics and HC Speciation ................................ ...................... 38 V. Updated Heav y Duty and Diesel Emission Rates ................................ ................................ . 38 A. Changes to Heav y Duty Gasoline Vehicle Rates ................................ .............................. 38 1. Regulatory

Class Definition and Vehicle Composition ................................ ............. 393

2. Estimating Emission Rates ................................ ................................ ......................... 40 B. Changes to Heav y- and Light - Duty Diesel Vehicle Rates ................................ ................ 43 VI . Other Changes ................................ ................................ ................................ ................... 43 A. Changes to Model Year Groups ................................ ................................ ........................ 44 B. Changes to County Allocations ................................ ................................ ........................ 44 C. Repair of Errors ................................ ................................ ................................ ................. 44 D. Chang es to Facilitate Large Numbers of Runs ................................ ................................ . 44 VII. Impact of MOVES Changes ................................ ................................ ............................. 45 References ................................ ................................ ................................ ................................ ..... 464



## I. **Intr oduction**  The U.S. Environmental Protection Agency (EPA) is proposing new vehicle emission standards and fuel quality standards to reduce emissions of criteria pollutants. Collectiv ely , these proposed standards are referred to as “Tier 3 vehicle standards” and “Tier 3 fuel s tandards.” As part of th is anal ys i s we estimated the impact of the Tier 3 proposal on the nationwide highway vehicle emissions of criteria pollutants , criteria pollutant precursors and selected air toxics . We made these estimates using an updated version of the EPA’s Motor Vehicle Emission Simulator (MOVES 2010 ) . This document describes how the MOVES default code and databases were updated for the Tier 3 NPRM analy sis. MOVES 2010 is EPA’s official model for estimating emissions from cars and trucks. At the time of its release, it incorporate d EPA's most up - to - date information on gasoline vehicle emissions. Exhaust emission rates for HC, CO and NOx were developed based on an anal ys is of state inspection/maintenance and roadside remote sensing data from millions of vehicles. 1 Emissions of particulate matter are based on EPA's Kansas City gasoline PM study . 2 , 3 Evaporative emission rates were updated based on extensive evaporative testing conducted b y EPA and the Coordinating Research Council (CRC) 4

. However, since the release of MOVES 2010, we have continued to collect and anal yz e emission data. In particular, we have completed two major studies of fuel effects on emissions in Tier 2 light duty gasoline vehicles, and an important collection of studies on evaporative emissions. Because fuel s and evaporative emissions are affected by Tier 3 standards , it was important to include this data in our anal ys is. Sections below describe this data in detail and explain how it was incorporated into an April 14 , 2011 version of the MOVES model software (MOVESGHGSource20110414a) and a May 12 version of the MOVES default database (MOVESTier3d

b20110512) . Collectively , this memo refers to this software and database as MOVEST3NPRM. When we updated the MOVES fuel effects and evaporative emissions, we also had an opportunity

to improve the model’s emission estimates in other areas. Notably , we updated emission s for the air toxics and h ydrocarbon species addressed in MOVES2010, and we expanded MOVES capabilities to include estimating all the air toxic pollutants in the National Emission Inventory

(NEI) and National Air Toxics Assessm ent (NATA) that are emitted by mobile sources. 5 We also made some updates to heavy duty emission rates for diesel and gasoline vehicles. The sulfate, sulfur dioxide, organic carbon and elemental carbon emission rates for 2007 - and - later heavy duty diesel v ehicles were updated to include information from a recent study that examined the composition of particulate emissions from advanced diesel engines. 6 HC, CO and NOx start and running emission rates for light heav y duty gasoline vehicles were updated to fix an error in these rates for 2007 - and - later emissions, And, we made a number of miscellaneous changes including changes to fleet and activity inputs, repairs of minor errors, and changes to facilitate the large number of parallel runs required for the Tier 3 NPRM anal ys is. D etails on all these changes are provided in the sections below.5



## II. **Fuel Effect	Updates**  **A. Fuel	Sulfur	Impacts**  MOVEST3NPRM include s updates to the effect of fuel sulfur levels below 30ppm on exhaust emissions. In MOVES 2010 these effects were based o n extrapolation from data on sulfur levels above 30 ppm. The updates made for this analy sis were based on significant new data generated through EPA research on low sulfur fuels conduc ted in 2010 and 20 11 .



### 1. **New	Research	of	Fuel	Sulfur	Effects	on Emissions**  The EPA study assess ed the emission reductions expected from the in - use Tier 2 fleet with a reduction in fuel sulfur level from current levels. The study was designed to take into consideration what was known from prior studies on sulfur build - u p in cataly sts over time and the effect of periodic regeneration events that may result from high speed and load operation over the course of day- to - day driving . The study sample consisted of 81 cars and light trucks covering model ye ars 2007 - 9 , each with approximately 20,000 - 40,000 odometer miles. The makes and models targeted for recruitment were chosen to be representative of high sales vehicles covering a range of ty pes and sizes. Test fuels were two non - ethanol gasolines with properties typical of certification fuel, one at a sulfur level of 5 ppm and the other at 28 ppm . All emissions data was collected using the Federal Test Procedure ( FTP ) cycle at a nominal temperature of 75°F. A draft report on this res earch is available . 7 Major findings from this study include:

 Reversible sulfur loading is occurring in in - use fleet of Tier 2 vehicles and has a measureable effect on emissions of NO x , hydrocarbons, and other pollutants of interest .  The effectiveness of high speed/load procedures in restoring catal ys t efficiency is limited when operating on higher sulfur fuel .  Reducing fuel sulfur levels from 28 to 5 ppm is expected to achieve significant reductions in emissions of NOx , hydrocarbons, and other pollutants of interest in the in - use fleet , as summarized in Table 1 , below.6 **Table 1**  **In -**  **use emission reductions from 28 to 5 ppm sulfur** NO X **(p**   ** value)** **THC**

**(p -** **value) CO** 

**(p**   ** value)** **NMHC**

**(p -** **value) CH**  **4**

**(p -**  **value) NO**  **x +NMO** 

**G (p**  **- value)**  **PM**

**‡ Bag 1**  10.7%

(0.0033) 8.5% †

(0.0382) 7.5% †

(0.0552) 7.5%

(< 0.0001) 13.9% †

(< 0.0001) N/A

– **Bag 2** 59.2%

(< 0.0001) 48.8%

(< 0.0001) – **‡** 44.8% † (0.0260) 49.9%

(< 0.0001) N/A

– **Bag 3** 62.1%

(< 0.0001) 40.2%

(< 0.0001) 20.1%

(< 0.0001) 49.9%

(< 0.0001) 29.2%

(< 0.0001) N/A

– **FT P**  **Composite** 23.0% †

(0.0180) 13.0% †

(0.0027) 11.9% †

(0.0378) 10.6% †

(0.0032) 25.8% †

(< 0.0001) 17.3%

(0.0140) – **Bag 1 –**  **Bag 3**  – **‡** 5.2% (0.0063) 4.3%

(0.0689) 5.1%

(0.0107) 4.6%

(0.0514) N/A

– † Model with significant sulfur and mileage interaction term. **‡** Sulfur level not significant at α = 0.10. For THC B ag 1 and CH 4 B ag 1, because the effect of clean - out was not statistically significant, the reduction estimates are based on the esti mates of least squares means.



### 2. **Implementation	in	MOVES** The results shown in Table 1 were applied in MOVEST3NPRM for model year 2004 - and later gasoline vehicles (the nominal start of the Tier 2 phase - in) to estimate sulfur effects below 30 ppm. The sulfur fuel effect applies multiplicatively to other gasoline fuel effects in MOVES, and applies only

for sulfur levels below 30ppm. For sulfur level s above 30 ppm, and for all pre 2004 model year vehicles, the sulfur effect originally used in MOVES 2010 remains in place. Equation 1 shows the generic form of the new sulfur correction . Table 2 shows the specific values for the sulfur coefficients by pollutant, process, and vehicle type.

= 1 . 0 − ∗ ( 30 − ) **Equation 1**  **Low Sulfur Effect Table**  **2 Low Sulfur Coefficients by Vehicle Type, Process and Pollutant**  Veh icle Ty

pe **THC CO**  **N O**  **X PM** 

Starts Running Starts Running Starts Running Starts Running Motorcycle 0 0 0 0 0 0 0 0 Passenger Car, Passenger Truck & Li ght Commercial Truck 0.002237 0.020336 0.001866 0 0 0.024459 0 0 All other Vehicle Ty

pes 0 0.015488 0 0.009436 0 0.027266 0 0 These equ ations were then used to fill in the database table that houses fuel effect equations in the MOVES database (“ GeneralFuelRatioExpression ”) . This table allows the MOVES model7

to compute fuel effects based on the fuel properties of any fuel containe d in the fuel supply and fuel formulation database table s. In addition, in order to properly model fuel sulfur levels below 30 ppm using Equation 1 i n MOVEST3NPRM, we had to modify an existing “floor” to the sulfur correction. In MOVES2010, the MOBILE6 fuel sulfur algorithms, which utilized log - log relationship, were extrapolated for fuels with sulfur level below 30 ppm. To prevent highly non - linear r elationships inherent in log - log equation from dominating the MOVES emission results, a fuel adjustment ‘floor’ of 0.85 was added . This ‘floor’ prevented MOVES 2010 from reducing the emission rate by more than 15 percent from the ‘base’ emission rate as a result of changing the base fuel formulation (30 ppm sulfur) to some other low level (i. e., 0.01 ppm sulfur). The floor is still needed for estimating sulfur reduc tions for model years 2001 - 2003 (which continue to be modeled with the original log - log equation), however, consideri ng the reduction in emissions seen for fuel sulfur levels below 30 ppm in the latest EPA analy sis, it was necessary in MOVEST3NPRM to chang e the sulfur ‘floor’ to 0.40 . 

### B. **Fuel	Effects from	EPA**  **ct Study**  As required b y the Energy Policy Act of 2005 (EPA ct), the EPA conducted an extensive evaluation of the effects of fuel properties other than sulfur on emissions from Tier 2 gasoline vehicles. The EPAct exhaust research program and anal ys is are extensively documented in the “EPAct Test Program Report” 8 and “EPAct Analysis Report.” 9 Information about the study is not repeated here. Because the fuel effects in MOVES were based on analy sis of the Tier 0 and Tier 1 vehicles ty

pical of the 1990s , we felt it was important to incorporate the EPAct study results into our air quality anal ys is. However, given the many months of work needed for this anal ys is, we had to develop the fuel inputs for MOV EST3NPRM before the EPAct anal ys is described the second report was finalized. This section describes the preliminary anal ys is results that were used to generate the fuel effects inputs used in MOVEST3NPRM . Note, information on how the EPAct data was use d to update h ydrocarbon speciation rates is provided in Section IV .C , below. 

### 1. **EPAct	Fuel	Effects	on	Criteria	Pollutants** MOVES estimates emissions immediately following engine starts (“start emissions”) as distinct from those from warmed - up operation (“running emissions”), and allows different fuel effects for these two modes of operation. Two sets of exhaust fuel effect c oefficients were therefore emplo yed in the model; one set of coefficients was applied to represent start emissions and a second set was applied to represent hot - running emissions. In some cases fuel effects estimated for these two processes differed substantially , as the effects of fuel properties on start emissions are dominated by changes in combustion and catal ys t warm - up, while the impact of running emissions is dictated b y catalyst efficiency when full y operational. The MOVES model accounts for the e ffect of fuel properties on vehicle emissions by estimating emissions from vehicles operating on a “base fuel,” and multiplying these “base emissions” by

a fuel adjustment to represent emissions on various in - use fuels. Different fuel adjustments have been developed to represent each pollutant and emission process. The fuel adjustment varies depending on the properties of the in - use fuel. Italso varies depending on the8

ty pe of vehicle, the model year and the age of the vehicle. The fuel effects used in MOVES2010 are documented in an EPA technical report. 10 The paragraphs below explain how these fuel effects were updated for purposes of the current analy sis. MOVES T3NPRM allows a very flexible input data format for incorporating and appl yi ng coefficients w ithin a wide variety of mathematical forms. These “fuel - effect ratio expressions” can include up to 32,000 characters and are stored in a database table dedicated to this purpose (GeneralFuelRatioExpression). The statistical models generated using EPAct results allow estimation of emissions effects related to five fuel properties: ethanol content (%), aromatics content (%), RVP (psi), T50 (°F) and T90 (°F), as well as selected interaction terms among these five parameters. The statistical models generate d from the EPAct exhaust data follow the general structure of Equation 2 below. In this equation, β denotes a model coefficient, Z etOH and Z

T90 denote “standardized” f

uel terms for these properties, and Z etOH×T90 denotes a “standardized” term for an etOH×T90 interaction term. a For simplicity , onl y the terms for ethanol, T90 and their interaction have been shown; linear and interaction terms for the remaining three prop erties are not shown here . Finally , the term s ε2 represents the residual error or “mean square error” for the model. Note that the subsets of the potential terms vary by emission and process, depending on the results of the statistical model fitting. Relative fuel effects are calculated by appl yi ng the models to specific “in - use” fuels and pre - defined “base fuels” and taking the ratio of the emissions on the in - use fuel to those on the base fuel, as shown in Equation 2 .



# e 2 90 T etOH 90 T etOH T90 T90 etOH etOH 0 5 . 0 ] s order term - 2nd other [ ] ms linear ter other [ 

### e (g/mi) Emissions      s Z Z Z                 

###   **X β**  **Equation 2**  **. Generic Form of**  **Statistical Model for Emissions in relation to Selected Fuel**  **Properties.**

base use in e e Effect Fuel **X β**  **X β** 

  **Equation 3**  **Generic Form of Relative Fuel Effect** Table 3 shows the coefficients for models used in Equation 3 Generic Form of Relative Fuel Effect for four individual pollutants, including total hydrocarbons (THC) and the criteria pollutants CO, NO x , and PM. The application of these models has been integrated into MOVEST3NPRM . For imp lementation in MOVES, Equation 1 Equation 3 is input directly into the GeneralFuelRatioE xpression table using sets of coefficients from Table 3 . The table presents two sets of coefficients for each pollutant, representing the effects of the fuel properti es on start

a Note that these coefficients apply to fuel properties that have been “standardized,” i.e., centered on their means and scaled by their standard deviations, based on the fuel - property matrix used to develop the models. To properly apply the models, this process must be applied for the specif ic fuels under consideration . For more information on this technique, please see the EPAct analysis report.9

and running exhaust emissions, respectivel y. b Because these coefficients apply to “standardized” fuel properties, as mentioned above, the magnitude and sign of each term gives a sense of the influence of each term in the estimation of that pollutant relative to the others . F or example, for PM start emissions, changes in aromatics and T90 are very influential, and are positivel y related with PM emissions (e.g., when aromatics increase, PM increases). For THC start emissions, on the other hand, the negative sign of the coefficient indicates that the relationship is inverse, i.e., increases in RVP are associated with decreases in THC. It is also important to note that the values of the coefficients presented in Table 3 represent the status of anal ysis and interpretation of the EPAct results at the time they were applied to this analy sis. Thus, they sometimes differ from values presented the final anal ys is rep ort 9 , which represent the outcome of additional anal ys is and interpretation. **Table 3**  **. Coefficients for Model**  **s representing Regulated Gaseous Emissions and**

**Particulated, from**  **the EPAct**  **Program.** Parameter **THC CO**  **NO X**  **PM**

Start Running Start Running Start Running Start Running Intercept - 0.86577 - 4.90925 1.347166 - 1.38957 - 2.85935 - 4.56921 etOH 0.067934 0.068143 - 0.06967 0 0.067502 0.062989 0.1807 0.1158 aromatics 0.083434 - 0.02281 - 0.01156 0.097982 0.133931 0.044062 0.3792 0.1988 RVP - 0.04669 - 0.03953 0.020631 0.028383 T50 0.148984 0.071538 0.021592 0.024856 0.047821 0.1004 - 0.0037 T90 0.014347 0.066813 - 0.14685 0.041802 0.3034 0.0953 etOH ×etOH 0.040652 0.085346 T50 ×T50 0.075548 0.030543 0.07222 0.0806 etOH ×Arom 0.022971 0.040277 0.062441 - 0.02369 T50 × T90 0.050029 0.028862 0.021773 0.1059 etOH × T50 0.034265 0.111736 etOH × T90 0.047815 0.0647 arom × RVP 0.025524 0.0537 arom × T50 0.033858 0.058589 arom × T90 0.022605 0.038612 0.0665 variance 1.0443



### 2. **EPAct	Fuel	Effects	on Selected	Air	Toxics**  For use in MOVES T3NPRM , inputs were also developed and applied to estimate emissions of selected toxic compounds and ethanol, but the approach differed from that described above for hydrocarbons and the criteria pollutants. Rather than estimating the change in emissions for one compound relative to two different fuels, the approach for toxics estimates the toxic emissions as a fraction of theVOC emissions on the same fuel. The compounds selected for this anal ys is include acetaldeh yde, f ormaldehyde, acrolein, benzene and 1,3 - b For all models, “start” and “running” emissions are represented by results measured on Bags 1 and 2 of the LA92 cycle, respectively.10

butadiene, all identified as national or regional risk drivers in the 2005 National - scale Air Toxics Assessments (NATA). 11 Table 4 shows coefficients for statistical models for ethanol and the five toxics. These models were developed using techniques similar to the models shown in Table 3 , using speciated results obtained from the EPAct exhaust program. The coefficients for the toxics models are interpreted and applied in the same way . However, two differences must be noted : a s reso urces limited the number of tests for which h ydrocarbons could be speciated, some statistical models were developed using smaller subsets of data and are thus simpler in structure, including onl y subsets of the four linear terms etOH, arom, T50 and T90 and no second - order terms. In the table, models fit using reduced data subsets contain no cells for the terms not included, and the ‘ -

-- “ s ymbol indicates that RVP was not included. In addition, as VOC are calculated as non - methane organic gases (NMOG) minu s ethane (H 3 CCH 3 ), it was necessary to develop analogous models for are both NMOG and ethane. Coefficients for these two models are shown in Table 5 . Models for these two compounds were calculated in the same manner as those shown in Table 3 and Table 4 . Note that models for both start and running ethane were developed using reduced data subsets . Thus, if we let **Xβ toxic**  , **Xα NMOG**  and **Xθ ethane**  represent models for a selected toxic compound, NMOG , and ethane, respectivel y, calculated by appl yi ng Equation 2 to each compound for a specified fuel, the toxic emissions as a fraction of VOC emissions is given by

ethane NMOG toxic e e e Fraction Toxic toxic **X θ**  **X α**  **X β** 

   f **Equation 4**  **. General expression for toxic fractions.** Also note that models representing running emissions are not available for three compounds: acrolein, benzene and 1,3 - butadiene. For these compounds, the relevant subsets of data were ina dequate to allow model fitting. Therefore, for these compounds, running emissions were represented as constant fractions of VOC, with values derived from the available data. F or acrolein, benzene and 1,3 - butadiene, the values of the fractions were 0.00077 , 0.047 and 0.0, respectivel y.11

**Table 4**  **. Fuel Effect Coefficients for**  **Selected Toxic Pollutants from EPAct Exhaust**  **Program** Parameter **Acetaldehyde Form**  **aldehyde Acrolein**  **Ethanol Benzene**  **1,3 -**  **Butadiene** Start Running Start Running Start Start Running Start Start Intercept - 5.23229 - 9.41919 - 5.97707 - 8.65741 - 7.93381 - 4.90805 - 9.56335 - 4.1074 - 5.91748 etOH 0.81449 0.190954 0.229862 0.078035 0.247572 1.462653 0.816632 - 0.12725 arom 0.034835 0.028224 0.112172 0.403208 RVP - 0.0417 --- - 0.04718 --- - 0.0645 - 0.06054 --- --- --- T50 0.086703 0.167177 0.188036 0.070291 0.039682 T90 0.038013 0.13018 - 0.08322 0.248876 - 0.09923 etOH^2 - 0.16694 - 0.0831 - 0.49699 T50^2 0.066653 0.052617 0.110804 etOH*arom 0.018402 0.016505 etOH*RVP 0.02194 T50*T90 0.039593 0.034887 0.059859 etOH*T50 - 0.01627 - 0.11858 etOH*T90 0.020043 0.046167 Variance (s ε2 ) 0.2034 0.46902 0.4765 0.45999 0.46611 0.701256 1.927463 0.4635 0.13059 **Table 5**  **. Fuel Effect Coefficients for NMOG and Ethane, from EPAct Exhaust Program** 

Parameter **NMOG Ethane** 

Start Running Start Running Intercept - 0.9574 - 5.5218 - 4.3412 - 7.7241 etOH 0.08783 0.09213 0.05222 arom 0.1037 0.02477 - 0.1925 - 0.1092 RVP - 0.04745 - 0.03752 --- --- T50 0.1535 0.092137 0.1830 0.1452 T90 0.009353 0.1114 0.1270 etOH^2 0.0414 T50^2 0.07934 0.06726 etOH*arom 0.02172 0.07561 etOH*RVP - 0.0303 T50*T90 0.05249 etOH*T50 0.03658 0.04477 etOH*T90 0.04798 Arom*RVP 0.02616 Arom*T50 0.07454 Arom*T90 0.02022 0.03430 RVP*T90 Variance (s ε2 ) 0.1949 1.853 0.2750 2.82212 

### 3. **A dditional	A**  **djustments for	Benzene	and	1,3**  **- Butadiene**  For two compounds, benzene and 1,3 - butadiene, additional refinements were applied to address limitations of the EPAct study design. For benzene, the issue was that the fuel matrix included aromatics generally , but not benzene specificall y. W e co nsidered it inadequate to model benzene in exhaust without explicitly accounting for benzene levels in fuel, so we c hose to develop a post- hoc refinement using data external to the EPAct program. In this case the source was a program conducted in support of the 2007 MSAT2 rule. This program performed measurements on nine Tier 2 certified vehicles on fuels with benzene levels ranging from 0.6 to 1.1 percent b y weight. 12 , 13 With benzene represented as a fraction of VOC (as in Equation 4 ) denoted as f

benzene , a value modified to account for benzene levels in different fuels ( f * benzene ) is calculated as shown in Equation 5 where xbenzene is the benzene level for the fuel modeled (weight percent), A is the mean benzene level in the EPAct exhaust program fuel set (0.66 weight percent), and B is a coefficient, taking a value of 0.24.



#   

#   benzene benzene benzene * benzene 

### f

f B A x f 

    **Equation 5**  **. Benzene Correction** Similarly, given the importance of olefins to estimation of emissions for 1,3 - butadiene, and the fact that the E PAct exhaust program study design did not incorporate olefins as a factor, we develop ed a post - hoc adjustment explicitly accounting for olefin level. This adjustment was derived b y varyi ng olefin levels in the Complex Model 14 and fitting a pol ynomial trend to the results. 15 Starting with an unadjusted toxic fraction for 1,3 - butadiene ( f buta), the modified fraction f * buta is calculated using Equation 6 , in which x olefin is the olefin level, and A , B , C and D are coefficients, taking values of 0.000008, 0.0002, 0.0069 and 0.008823, respectivel y. 

###          D C

Bx Ax f f olefin 2 olefin buta * buta **Equation 6**  **. 1,3 -**  **Butadiene Correction** To estimate emissions for other gaseous air toxics, additional updates were i ncorporated into MOVES for this analy sis. Additional compounds includ e 2,2,4 - trimethylpentane, ethylbenzene, n - hexane, methyl - tert - butyl ether, propionaldehyde, styrene, toluene, and x yl enes. For these pollutants, toxic - to - VOC ratios were derived from spe ciation profiles and applied to VOC as estimated b y M OVES . These ratios varied between pre - 2004 and 2004 and later vehicles, and also among E0, E10 and E15 blends. For more information, see Section IV.B. below. 

### C. **Additional Fuel** **- Related	Changes	to**  **MOVES** Quantifying emissions from the proposed Tier 3 rule required a number of other minor changes to the MOVES2010 fuel databases and fuel effects code. Because MOVES2010 models distinct fuel supplies only through 2012, we updated the fuel supply support tables to supporting tables to allow distinct fuel supplies for calendar years13

through 2050. Also, as described in Section III.A below , we updated the permeation calculation to allow modeling of E15 fuels. c Additional fuel related chang es to the MOVES model include the addition of T50 and T90 as fuel parameters in the FuelFormulation table (these parameters will be calculated from E200 and E300 if not present, otherwise the MOVES model will default to using T50 and T90 values ); a correction to an error in the fuel effects generator ; and a correction to ensure that ethanol emissions are modeled as zero in counties where ethanol fuel blends are not present. Other fuel related changes included replacing the “NULL” values in the default fuel descriptions with actual values, and deleting most fuels from the MOVES default database, since they were provided in county- specific databases. We also changed the operation of the fuel importer to require users to import all fuel formulations needed fo r a given county , year, and month. 

## III. **Eva porati** **ve Emission	Updates**  Evaporative emissions account for a significant portion of th e gaseous h ydrocarbon inventory . For MOVEST3NPRM, the evaporative emission calculations were updated significantl y. We changed the calculation of permeation emissions to account for the E15 fuels modeled in the reference and control scenarios. More importantly , we updated the calculation of vapor venting emissions to account for results from a multi - year research program that improved our understanding of the vapor venting process, the emission consequences of long - duration parking (“multi - day

diurnals”) and the prevalence of vapor leaks. These updates are detailed in the sections below. We made no changes to the modeling of liq uid leaks. 

### A. **Permeation** MOVES 2010 already included effects of E10 on permeation emissions for newer technology vehicles, based on data collected b y Coordinating Research Council ( CRC ) in the E - 65.3 program and as part of the more recent CRC E - 77 series of evaporative emissions programs. 16 These data showed a significant change in the relative impact of E10, from a 65 percent increase for pre - enhanced vehicles, to a 213 percent increase for newer technology vehicles. 17 Th e CRC E - 77 anal ys is also confirmed th e E - 65.3 finding that there is no significant difference between emission effects on E5.7 and E10. The use of E15 in the reference and control fuel supplies modeled for the Tier 3 NPRM required that MOVES model E15 permeation effects as well . The E - 77 p rogram evaluated permeation emissions on E20 as well as E10, and found that there was not a significant difference in permeation emissions between these two blends. These data, in conjunction with the E - 65.3 data discussed above, suggest that any l evel of ethanol in the fuel results in large increases in permeation emissions, but that the magnitude of increases are largel y insensitive to

c We also began to add tables and code to the MOVES model to facilitate the modeling of flexible fuel vehicles (FFVs) operating on E85. When it became clear that FFV usage was negligible in the scenarios to be modeled for the NPRM, this work was not comple ted. Thus, while some portions of the MOVEST3NPRM appear to provide the capability to model E85 emissions, the model should not be used for that purpose.14

how much ethanol is in the fuel. As a result, in MOVEST3NPRM, we applied the E10 permeation effects to E15 as well. These data also indicated significant impacts on toxics that differed from other ty pes of evaporative emissions. The toxics impacts were not analyzed in time for inclusion in MOVES2010, but were included in MOVEST3NPRM , as explained in S ection IV .B.1.b) , below. 

### B. **Vapor	Venting** When a vehicle’s fuel s ystem warms (due to ambient temperature rise while a vehicle is parked, or from vehicle operation), fuel vapors are generated. These may escape into the atmosphere if the capacity of the evaporative control sy s tem is exceeded, or through s ys tem leaks. In particular, a s a vehicle sits, without driving, through multiple diurnal cycles, the carbon canister accumulates vapor every day . It can only

adsorb vapor until it reaches its finite cap acity; then it begins to vent to the atmosphere. A canister with degraded/damaged carbon may have reduced capacity, but eventually every canister will vent to the atmosphere when the carbon reaches saturation. Upon reaching saturation, a canister acts in a relatively predictable manner. During cooling hours, the canister backpurges to the fuel tank and regains some of its capacity. Then, during the subsequent warming period , that capacity is re - filled with vapor and any excess vapor generated will escape to the atmosphere. MOVES2010 has a specific Tank Vapor Venting emission module to account for vapor venting emissions, but does not account for soaking periods of longer than 24 hours. Based on new research findings, updates to MOVES were required to account for longer duration diurnal events, to improve the distinction between evaporative canister breakthrough and vapor leaks, and to reflect new vapor venting emissions data from the CRC E - 77 program.



### 1. **Update	of	Vapor	Venting Algorithms	with	new	DELTA	Model**  MOVES2010 estimates vapor venting emissions by calculating vapor generated as a function of temperature rise and fuel RVP, and a test - data - based relationship between the amount of vapor vented compared to the amount generated based on available diurnal emission test data. The MOVES2010 evaporative emissions estimates were based on in - use data collected between 1994 and 1996 . 18 This dataset provides SHED evaporative emission s (in grams) for a large set of vehicles undergoing a single diurnal cycle . Although the data used in MOVES 2010 provided a large and robust dataset for one day of emissions, and the resulting emissions rates provided a good estimate of average overall venting emissions, we wanted to improve our ability to model emissions in situations where the cannister capacity might be exceeded, such as when vehicle uses high RVP fuels (e.g. E15) or parks for multiple days. To improve MOVES’ ability to model this breakthrough effect, the “Diurnal Emissions L ost to Atmosphere” ( DELTA ) model was develope d. 19 This model applied theoretical vapor generation models to data from the CRC E - 77 program on 9 and 10 RVP fuel, to produce vapor venting emission rates for MOVES.



### 2. **Mult iple	Day	Diurnals**  The DELTA model described above provided a way for us to estimate emissions for long duration parking (multi - day diurnals) episodes, but did not address the question of the frequency of such events. While there have been many activity studies that track vehicle operation, very15

few have focused on the question of vehicle inactivity . The onl y source of data we found to address this question was a study performed by Georgia Tech , which instrumented vehi cles for two ye ar time periods, and also surveyed participating households on the driving patterns of all vehicles in a household20

. It was found that 16 percent of all household vehicles surveyed drove less than 3,000 miles per year21 . W e lack information to know how many of these vehicles are driven on frequent short trips or very infrequent longer trips, but assuming that at least half of these vehicles have long soaks or drive without purging the canister, we use d this value to estimate that at a given time 8 percent of the fleet has been soaking for 5 day s or longer (the maximum soak length we’ve included in MOVES) . For implementation in MOVES , the number of vehicles experiencing day 2 through 5 of a diurnal are modeled as a percent of the vehicles that have been soaking since the beginning of the day. The resulting estimate of the percent of vehicles soaking for multiple day s, by time of day , is shown in below.

**Figure 1**  **Percentage of Vehicles Soaking By Time of Day** Although a relativel y small number of vehicles soak beyond one day , they are important because the ir emissions are disproportionatel y high. The MOVEST3NPRM code was modified to incorporate the DELTA model and to model the complex processes of backpurge and canis t er capacity over multiple day s. 

### 3. **Vapor Leaks**  MOVES was also updated to reflect the prevalence of vehicles with evaporative leaks based o n field research conducted in Denver between 2008 and 2010 . 22 In MOVES 2010 , emissions for properl y functioning and leaking vehicles were averaged into a single rate. In MOVEST3NPRM , we have distinguished the emission rate for a properly functioning evaporative control sy stem from the rate for vehicle s with leak s . A leaking vehicle essentiall y 'b ypasses' the canister s y stem, and generated vapor will escape through the leak location.16

In th e Denver field studies , a remote sensing device (RSD) was used to recruit vehicles which were prepped and measured in a PSHED (Portable Sealed Housing for Evaporative Determination) . Th e vehicles ’ hydrocarbon emissions were recorded for 15 minutes and leaking vehicles were inspected to identify the cause/source of the vapor leak. Using the individual vehicle data along with the data on the population of vehicles passing the RSD, the prev alence of vapor leaks in the fleet was estimated (see Figure 2 ) . We have classified a “ vapor leaker” as any vehicle that would fail the enhanced evaporative standard of 2 grams. The standard sums the emissions from the worst day of a 3 - day diurnal test and the hot soak. To develop a surrogate standard for a 15 minute hot soak test, we use d knowledge of certification testing to attribute 0.4g of the 2g standard to the hot soak portion , and , 0.3 grams of 0.4 grams to the first 15 minutes of the hour - long hot soak test. This approach results in 0.3g as a surrogate standard for a 15 minute hot soak.

**Figure 2**  **Estimated Distribution of PSHED value**  **s in the Ken Caryl Fleet by Model Year Group**  When observing the difference between two points in the above figure, one can determine how many

vehicles fall into a particular emission range. For example, in model year group 1981 - 1995, 2.6% of vehicle s are leaking at more than 20g/ 15min and 6.5% of vehicles are leaking at 0.0 0.1 0.2 0.3 0.4 0.5 0.6

1 10 100



### High-PSHED Definition (g/Qhr)**E s** **t i** **m a** **t e** **d F** **r a** **c t** **i o** **n o** **f K** **e n** **C a** **r y** **l F** **l e** **e t** **w i** **t h** **H i** **g h** **P S** **H E** **D** 1961-1970 1971-1980 1981-1995 1996-2003 2004-201017

more than 10g/ 15min . Subtracting these two values yields that 3.9% of vehicles in the model ye ar group have a leak between 10g/ 15min and 20g/ 15min . This process reveals that older vehicles not only

have more leaks, but larger leaks. Because the detailed, b y model year, data only contain prevalence rates for PSHED measurements as low as 1.0g/15min, failure rates are extrapolated to 0.3g/15min. Using aggregate data from the Ken Caryl s tation, it is found that 0.3g/15min PSHED measurements are 50% more prevalent than 1.0g/15min PSHED measurements. Linear extrapolation and interpolation is used to model vapor leak prevalence for ages and model years not represented in this cross - sectional study . We assume newer cars will have lower leak prevalence than older cars. We also divide model year groups at the year new technology was introduced. However, because we know vapor leaks also occur due to tampering, mal - maintenance, and other non - durability related issues, technology is not the only factor in a vehicle having a vapor leak. The older model year re gressions alway s have a more severe deterioration than newer model ye ars. Failure rates at different severities are included below for two of the different age groups (see Figures 3 and 4).

**Figure 3**  **Extrapolated Prevalence Rat es for Binning Leaks in MOVES, Age 0**  **- 3** 18

**Figure 4**  **Extrapolated Prevalence Rates for Binning Leaks in MOVES, Age 20+** 

### 4. **Summary	of	Updated	MOVES	Inputs	for	Vapor	Venting** The MOVES cumtvvcoeffs table in the default database was updated to include the new inputs required to more accurately model cold soak vapor venting emissions and separate non leaking from leaking vehicles. The new fields are described below in Table 6 .19 **Table 6**  **New Columns in ‘cumtvvcoeffs’ Table** Column Name Brief Explanation How it’s used backPurgeFactor The percent of canister

capacity regained during the diurnal cooling cycle. For example: A canister with a gasoline vapor capacity of 200 grams fills to 100 grams in the first day . With a backPurgeFactor of 35% 23 , i t will begin day 2 filled to 65 grams. averageCanister This is the sales - weighted

average Gasoline Working Capacity . Canisters have ty picall y increased in size over time and with new regulations. When vapor generated > **averageCanister** capacity , emissions are released to the environment. This is also the maximum value to which **backPurgeFactor** can be applied. tvvEquation An equation representing how

much vapor is vented per unit vapor generated for non leaking vehicles These emissions are weighted with the leaking vehicle emissions estimated with **leakEquation** . leakEquation A linear equation representing

how much vapor is vented per unit vapor generated for leaking vehicles These emissions are weighted with the vapor venting emissions estimated with **tvvEquation** . leakFraction The fraction of vehicles

leaking. Used to weight together **tvvEquation** and **leakEquation** . The leak fraction is a function of model ye ar and age. weightedLine = leakFraction*leakEquation+(1 - leakFraction)*tvvEquation tankSize The Sales - weighted average

size of gas tank. The **tankSize** is a key factor in calculating how much vapor is generated. A larger tank with the same **tankFillFraction** as a smaller tank will generate more vapor due to a larger headspace. tankFillFraction The average fill level of gas

tank s . This is applied to the **tankSize** to calculate how much headspace is available for vapor generation. A key improvement facilitated by these new coefficients is the development of tvvEquation and leakEquation . The emission curves that were previousl y i n the model were drawn in grams of vapor generated per gallon of headspace, and onl y intended for one day of emissions. The new curves use total grams as the unit and are intended to model the complex processes o f backpurge, canister capacity , and multiple day s. The tvvEquations are complex exponential curves created using data from the E - 77 programs 24 using the DELTA model 25 . The leak equations are linear equations developed using emission rates of known leakers. The data on leaking vehicles comes from the E - 77 program and Colorado High Evap program 26 . These two curves are generated in the database for each source type, model ye ar group, and age group. Each20

set of curves has a leak fraction (representing the percent of leaking vehicles in that population) that is used to weight the two curves together to produce a composite curve. We model mission rates for vapor leaks as a linear relationship between total tank vapor generated (TVG) and tank vapor vented (TVV). TVG is calculated using the Wade - Reddy equation which determines TVG as a function of fuel RVP, fuel ethanol content, temperature rise, and tank fill level. There are two datasets used to develop vapor leak emission rates. The E 77 program supplied information on high emitting vehicles, with known fuel properties and i mplant ed leaks, that were tested on the California diurnal cycle. The Colorado program provided inf

ormation on 16 leaking vehicles. They performed a 6 - hour SHED test consisting of a contro lled heat rise from 72F - 96F. This test provides us with enough information to calculate TVG. For both programs, the Sealed Housing for Evaporative Determination (SHED) emission measurements along with calculated TVG obtain enough information to apply a linear regression model of the relationship between fuel vapor generated and fuel vapor vented . Vapor leak emissions span many orders of magnitude given their diverse lo cations and sizes. Since our leak prevalence estimates were measured at high altitude in Denver, we must use a correction factor for the way we bin the leaking vehicles. Using the Wade - Reddy equation, we can calculate that Denver E10 fuel generates 1.41 times as much vapor as Sea Level gasoline. For example , a vapor leak at the rate of .3g/ 15min in Denver will equate to a .21g/ 15min leak at Sea Level. The bins used to categorize vapor leak severity as well as the average vapor leak emission rate for that bin are listed in the table below. **Table 7**  **Vapor leak emission rates by bin** Denver bins (grams/ 15min) Sea Level bins Grams vented / grams generated 0.3 - 2 0.21 - 1.42 0.1191 2 - 5 1.42 - 3.55 0.2686 5 - 10 3.55 - 7.09 0.6492 >10 >7.09 1.3273 The hot s oak measurements from the E - 77 programs and the PSHED (Portable SHED) measurements from the Denver program are used to bin each vehicle . In addition, the corresponding diurnal test provides information necessary to determining the leak emission rate. For each model ye ar and age group combination, the vapor leak prevalence for each severity bin is applied to the corresponding vapor leak emission rate. The result is a vapor leak emission rate representative of all vapor leaks greater than 0.3g/15min. This representative leak emission rate is then weighted b y the leak prevalence with the non - leaking emission rate. See Figure 5.21

**Figure 5**  **Example of how leak emission rates are calculated using prevalence rate bins** 

## IV. **Update of	Air	T** 

**oxics and	HC	Speciation**  The calculation of air toxics and the speciation of hydrocarbons was updated in the version of MOVES used for the Tier 3 NPRM analy sis. As described in Section II.B above, the EPAct anal ys is led to changes in the fuel effects for some major air toxics. Other changes to MOVES included the capability

to estimate emissions for many air toxics not available in MOVES2010a (but now available in MOVES2010b) . The section below details these change s. Also, the documentation of toxic calculations for MOVES 2010 did not include details on the calculation of some toxics for 2003 - and - earlier gasoline vehicles. These calculations are unchanged from MOVES 2010 , but are documented here for completeness. 

### A. **Alg orithms	for	2003**  **- and** **- Earlier	Gasoline	Vehicles**  For 2003 - and - earlier model year gasoline vehicles, the algorithms for calculating emissions of major air toxics are unchanged from MOVES2010a. The algorithms used for benzene, 1,3 - butadiene, formaldeh yde, an d acetaldeh yde are documented in this subsection for completeness. For 2003 - and - earlier light - duty cars and trucks, all heavy- duty gasoline vehicles and all motorcycles, algorithms used to calculate toxic ratios are the same as in MOBILE6.2. In MOBILE6.2 toxic ratios between light - duty gasoline vehicles and heav y- duty gasoline vehicl es differed; however, since the only available data for heavy- duty gasoline vehicles were extremely limited, and mostly

from vehicles with either no emission controls or earl y oxidation catalysts, > 10g / Qhr > 5g / Qhr > 2g / Qhr > 0. 3g / Qhr < 0. 3g / Qhr 

### Non- leak mea su rem ents mean mea n mean mea n x x x x 5% 10% 25% 60% 

### weig hted leak ra te mea n nonleak ra te x x 5% 95%



### MOVES Em is si on Ra te Lea k Meas ur ements22

for MOVES we decided to apply toxic to VOC ratios from light - duty gasoline vehicles to VOC emissions for this vehicle class. Toxic to VOC ratios for benzene, 1,3 - butadiene, formaldehyde, and acetaldehyde exhaust emissions from light - duty gasoline vehicles with three - way or three - way

plus oxidation catalysts were estimated using algorithms developed for the Complex Model for Reformulated Gasoline. 27 For MTBE, a draft fuel effects model based on the Complex Model database was used. 28 This model is based on algorithms from underl yi ng data of nearl y 900 observations. However, instead of using model algorithms directl y, MOBILE6.2 was run at different fuel MTBE levels and a curve of fuel MTBE to MTBE/VOC ratios was developed. This curve was then used in MOVES. It should be noted that the sulfur effects terms in the algorithms were not used; instead, sulfur impacts on toxic emissions were assumed to be proportional to the sulfur impacts on total VOC estimated by MOVES. The Complex Model algorithms are based on data from vehicles representing a 1990 model year fleet. For benzene, 1,3 - butadiene, formaldeh yd e, and acetaldeh yde, the algorithms are based on about 1800 observations. The algorithms are applied by stratifying the light - duty gasoline fleet into ten Technology

Groups and appl yi ng the algorithms individual ly to each group (this is known as the unconsolidated Complex Model). The ten groups are formed as a combination of fuel sy stem, catal ys t type, air injection (y /n toggle), EGR, and Normal / High emitter status. Thes e groups are listed in Table 8 . The first nine groups represent onl y normal emitting vehicles. The tenth group represents all of the high emitters, regardless of technology. Separate toxic ratios are calculated for each of the groups and weighted together by the fraction of the fleet attributable to each technology group in MOBILE6. **Table 8**  **Technology groups in the Complex Model for Reformulated Gasoline Technol**  **ogy Group Definitions Technology Group**  **Fuel System Catalyst**  **Air Injection EGR**  1 PFI 3WAY NO AIR EGR 2 PFI 3WAY NO AIR NO EGR 3 TBI 3WAY NO AIR EGR 4 PFI 3WAY + OX AIR EGR 5 PFI 3WAY AIR EGR 6 TBI 3WAY AIR EGR 7 TBI 3WAY + OX AIR EGR 8 TBI 3WAY NO AIR NO EGR 9 CARB 3WAY + OX AIR EGR High Emitters ALL ALL ALL ALL PFI = port fuel Injection, TBI = throttle body injection, CARB = carburetor, 3WAY = three way catalyst, 3WAY + OX = three way plus oxidation catalyst, ERG = exhaust gas recirculation For light - duty

gasoline vehicles with oxidation cataly sts only or no cataly sts, toxic to VOC ratios for these pollutants are determined using algorithms derived from a more limited data set23

of about 50 vehicles tested on a baseline fuel and a small number tested on reformulated fuels. Data were not available to develop algorithms for ETBE and TAME blends; thus, the algorithms for ethanol ox ygenated gasoline were used for ETBE blends, and the algorithms for MTBE oxygenated gasoline were used for MTBE blends . For vehicles running on 1 0 percent ethanol, 2.39 percent of exhaust VOC was estimated to be ethanol. This estimate is based on tests on nine vehicles from four test programs . 29 , 30 , 31 , 32 MOVES also has ethanol to VOC ratios for E5 and E8, based on linear interpolation from the E10 value (0.01195 for E5 and 0.01912 for E8). 

### B. **Estimating	Emissions	for	Additional	Air	Toxics** The version of MOVES used for the Tier 3 NPRM analy sis was e xpanded to include all air toxic pollutants in the National Emission Inventory (NEI) and National Air Toxics Assessment (NATA) that are emitted by mobile sources. This list of pollutants is provided in Table 9 . These pollutants are organized into four categories: 1) Gaseous h ydrocarbons 2) Polycyclic aromatic h ydrocarbons (PAHs)

– These hydrocarbons which contain fused aromatic rings can be found in the gas phase, particle phase, or both, depending on properties of the compound, particle ch aracteristics, and atmospheric condi tions 3) Dioxins and furans

– polychlorinated organic compounds which are persistent and bioaccumulative d 4) Metals Emissions for gaseous HAPs and PAHs are reported in anal ys es for the Tier 3 regulatory anal ys is. The pollutant “xylenes” represents the sum of emissions from three isomers of x yl ene : o - xylene, m - xylene, and p - xylene. Emissions of metals and dioxins and furans are not reported, since MOVES estimates these using straight emission rates which do not change with f uel properties or criteria pollutant emission levels. Thus, scenarios being evaluated will have no impact on inventories for these pollutants .

d MOVEST3NPRM should not be used for dioxin modeling. The dioxin rates in MOVEST3NPRM were entered u sing incorrect units. This error does not affect our analysis which did not consider dioxin emissions.24 **Table 9**  **A ir toxics included in MOVESTier3NPRM**  **Pollutant MOVES Pollutant**  **ID CA** **S Number Gaseous Hydrocarbons**  1,3 - Butadiene 24 106990 2,2,4 - Trimethy lpentane 40 540841 Acetaldehyde 26 75070 Acrolein 27 107028 Benzene 20 71432 Ethanol 21 64175 Eth yl Benzene 52 100414 Form aldeh yd e 25 50000 Hexane 55 110543 Methyl Tert Butyl Ether (MTBE) 22 1634044 Propionaldehyde 58 123386 Styrene 60 100425 Toluene 61 108883 Xy lenes 62 1330207 **PA Hs**  Acenaphthene 41 83329 Acenaphthylene 42 208968 Anthracene 44 120127 Benz(a)anthracene 45 56553 Benzo(a)pyrene 46 50328 Benzo(b)fluoranthene 47 205992 Benzo(g,h,i)perylene 48 191242 Benzo(k)fluoranthene 49 207089 Chrysene 50 218019 Dibenzo(a,h)anthracene 51 53703 Fluoranthene 53 206440 Fluorene 54 86737 Indeno(1,2,3,c,d)pyrene 56 193395 Naphthalene 23 91203 Phenanthrene 57 85018 Py rene 59 129000 

### 1. **Add i**  **tional	Air	Toxics:		Inputs	for	Gasoline	Vehicles** Data methodologies and sources are provided for gasoline vehicles running on E0, E10, E15 and E20 gasoline. 

### a) **Exhaust** Exhaust i nputs developed for the additional air toxics do not vary by temperature or operating mode. While empirical data suggest toxic to VOC and toxic to PM ratios differ for start versus running emissions, we decided not to vary these inputs in the model by operating25

mode for two key reasons. First, for advanced technology vehicles, HAP emissions during running operation are often below levels of quantitation in test programs. Thus, using data from running operation onl y would necessitate heav y reliance on imputed data. Second, with the large number of toxics modeled, applying separate inputs would be place additional computational demands on the model. Ambient temperature also affects these ratios, but we assumed toxic emission of gaseous toxics and PAHs change proportionally with VOC and PM as temperature varies. In general, data are inadequate to account for temperature effects on toxic to VOC and toxic to PM ratios. Emission rates for metals are assumed to be independent of operating mode and temperature; very

little data exis t to account for impacts of these parameters. For 2003 and earlier vehicles, toxic to VOC ratios for E0 an E10 were developed by Sierra Research 33 using estimates from EPA’s SPECIATE 4.2 database ( Table 10 ) . Toxic to VOC ratios for MTBE blends, however, were obtained from the National County Database in the National Mobile Inventory Model (NMIM ) . 34 NMIM uses the toxic to VOC ratios described i n the documentation for the 1999 NEI for HAPS, version 3, and summarized in Volume 1, Appendix D, Table 1 of the documentation. 35 Ratios for LDG vehicles were used for all gasoline vehicle classes. These ratios were based on older speciation profiles than the E0 and E10 data. Separate ratios are used for each of the following four categories of gasoline blends: 1. Baseline Gasoline. All cases that do not fall into categories 2 - 4 below. 2. 10 perecent Ethanol Gasoline - Used where the fuel contains ethanol which is greater than or equal to 5 percent by

volume or ETBE greater than or equal to 5 percent by volume. 3. Winter Oxygenate MTBE/TAME Gasoline (MTBE1) - Used where the fuel contains MTBE which is greater than or equal to 12 percent by volume or T AME greater than or equal to 13 percent by

volume. 4. RFG/MTBE/TAME (MTBE2) - Used where the fuel is RFG and where the fuel contains oxygenate greater than 5percent b y volume and where the fuel contains MTBE which is less than 12percent by

volume or TAME less than 13 percent b y volume. **Table 10**  **Toxic to VOC ratios for selected air toxics from Tier 1 and earlier gasoline vehicles and trucks**  **P ollutant**  **Name E0**  **E10 MTBE1**  **MTBE2** 2,2,4 - Trimethylpentane 0.01823 0.01849 0.04327 0.04327 Acrolein 0.0006 0.0006 0.0006 0.0006 Ethyl Benzene 0.02147 0.01932 0.01398 0.01484 Hexane 0.01570 0.01593 0.00861 0.00888 Propionaldehyde 0.00086 0.00086 0.00073 0.00073 Styrene 0.00108 0.00097 0.00328 0.00340 Toluene 0.09619 0.08657 0.09873 0.10494 Xylene 0.07814 0.07032 0.05557 0.05910 For 2004 - and - later vehicles running on E0 and E10, and for all vehicles running on E15, ratios for additional gaseous HAPs for E0, E10 and E15 were obtained from Phase 1 of the26

EPAct test program. These profiles were based on tests from 3 vehicles. 36 Toxic to VOC ratios for E10 are used in MOVES for all gasoline above 5 percent ethanol b y volume. Ratios are provided in Table 11 . **Table 11**  **Toxic to VOC ratios for selected air toxics from Tier 2 gasoline vehicles and trucks**  **P ollutant**  **Name E0**  **E10 E15**  2,2,4 - Trimethylpentane 0.03188 0.01227 0.0220 Ethyl Benzene 0.01683 0.01660 0.0157 Hexane 0.00279 0.02911 0.0110 Propionaldehyde 0.00122 0.00054 0.0006 Styrene 0.00085 0.00083 0.0046 Toluene 0.07542 0.07440 0.0727 Xylene 0.06127 0.06047 0.0690 In the NMIM model, PAH emissions were estimated as ratios to PM. This approach was used, even though PAHs are found in the gas, semi - volatile and particle phase, because there is generall y reasonable correlation between PAH and PM emissions. 37 , 38 However, for MOVESTier 3NPRM , PAH mass emissions are apportioned into the gas and particle phase, and gas phase PAHs are estimated using toxic/VOC ratios and particle phase PAHs were estimated using toxic to OC 2.5 (organic carbon less than 2.5 microns) ratios. Although partitioning of PAHs into the gas and particle phases depends on concentrati on, temperature and other factors, MOVES applies one set of allocation factors under all conditions in order to streamline data processing. These allocation factors were developed by Sierra Research 39 using estimates from EPA’s SPECIATE 4.2 database 40 and i nformation on compounds’ phy sical and chemical properties. Table 12 provides molecular weights and allocation factors. The allocations from SPECIATE were based on m edium duty diesel engine data. 41 Using PAH and VOC emissions data from Norbeck et al. (1998) 42 and the allocation factors in Table 12 , the toxic/VOC ratios in Table 14 were developed. Norbeck et al. data were also used to develop toxic/PM 10 ratios. These ratios were then converted to toxic/OC 2.5 ratios for start and running operation. These conversions were made using assumptions that 90 percent of PM 10 is PM 2.5 43 , 87.3 percent of running PM 2.5 is OC, and 66.6 percent of start PM 2.5 is OC. OC percentages of PM2.5 were obtained from MOVES runs. PAH to VOC and PAH to OC 2.5 ratios do not vary between E0 and E10 fuels.27 **Table 12**  **PAH gas/particle phase allocation factors** PAH Species M olecular

W eight Allocation Fraction

PM Phase Gaseous Phase Acenapthene 154 0 1 Acenaphthylene 152 0 1 Anthracene 178 0.466 0.534 Benz(a)anthracene 228 0.723 0.277 Benzo(a)pyrene 252 1 0 Benzo(b)fluoranthene 252 1 0 Benzo(g,h,i)perylene 276 0.773 0.227 Benzo(k)fluoranthene 252 1 0 Chrysene 228 0.823 0.177 Dibenzo(a,h)anthracene 278 1 0 Fluoranthene 202 0.516 0.484 Fluorene 166 0.215 0.785 Indeno(1,2,3 - cd)pyrene 276 1 0 Phenanthrene 178 0.335 0.665 Pyrene 202 0.552 0.44828 **Table 13**  **PAH/VOC and PAH/PM ratios for gasoline vehicles and trucks. PAH**  **Start Fraction of**  **OC 2.5**  **Running**

**Fraction of OC**  **2.5 Fraction of** 

**VOC** Benzo(a)anthracene 0.0001237 0.0000944 0.0000007 Benzo(a)pyrene 0.0001711 0.0001306 0.0000000 Benzo(b)fluoranthene 0.0002032 0.0001551 0.0000000 Benzo(k)fluoranthene 0.0002032 0.0001551 0.0000000 Chrysene 0.0001408 0.0001075 0.0000005 Dibenz(a,h)anthracene 0.0000000 0.0000000 0.0000000 Indeno(1,2,3 - cd)pyrene 0.0001283 0.0000979 0.0000000 Acenaphthene 0.0000000 0.0000000 0.0000185 Acenaphthalene 0.0000000 0.0000000 0.0001040 Anthracene 0.0006577 0.0005020 0.0000114 Benzo(ghi)perylene 0.0003306 0.0002524 0.0000015 Fluoranthene 0.0007834 0.0005980 0.0000111 Fluorene 0.0005425 0.0004141 0.0000300 Naphthalene 0.0000000 0.0000000 0.0022928 Phenanthrene 0.0014184 0.0010827 0.0000427 Pyrene 0.0011450 0.0008740 0.0000141 

### b) **Evaporative and Permeation** Toxic to VOC ratios for evaporative non - permeation emissions of benzene, ethanol, MTBE and naphthalene remain unchanged from those in MOVES2010. Insummary , b enzene and MTBE ratios are estimated using algorithms originally developed for MOBILE 6.2. However, evaporative emissions processes for MOVES differ from those in MOBILE6.2. Thus, algorithms for hot soak in MOBILE6.2 are used for vapor venting and refueling vapor loss in MOVES, and algorithms for running loss are used for fuel leaks and refueling spillage los s ( Table 14 ). Ratios for naphthalene and ethanol are given in Table 15 . Ratios for the additional air toxics found in evaporative non - permeation emissions ( 2,2,4 - trimethylpentane, ethyl benzene, hexane, propionaldehyde, toluene and x yl enes ) were obtained from profiles developed for EPA by Environ Corporation, using data from the Auto/Oil test program conducted in the earl y 1990’s. 44 These rat ios are also given in Table 15 . Conventional gasoline ratios are also used for MTBE ox ygenated gasoline. Since no emissions data exist for evaporative and permeation emissions from E15 vehicles, E15 and E10 fuel speciation data from the EPAct test program were used to adjust the E10 evaporative emissions speciation. 45 For all pollutants except benzene and MTBE, ratios are the same for all ty pes of non - permeation evaporative emissions. The ratios for 10 percent ethanol are used for all fuels with greater than or equal to 5 percent ethanol and less than 12 percent .29

**Table 14**  **Toxic/VOC algorithms for benzene and MTBE gasoline vehicle evaporative emissions**  **Pollutant Process**  **Toxic Fraction Equation (Toxic/VOC)** Benzene Vapor Venting/Refueling Vapor

Fuel Leaks/Spillage ( - 0.03420*OXY - 0.080274*RVP + 1.4448)*BNZ/100 ( - 0.03420*OXY - 0.080274*RVP + 1.4448)*BNZ/100 MTBE Vapor Venting/Refueling Vapor

Fuel Leaks/Spillage (24.205 - 1.746*RVP)*MTBE/1000 (17.8538 - 1.6622*RVP)*MTBE/1000 Note: OXY = wt percent oxygen RVP = Reid vapor pressure in psi BNZ = vol percent benzene MTBE = vol percent MTBE **Table 15**  **Evaporative Toxic/VOC ratios for other toxics fr om** **gasoline vehicles (Auto/Oil)**

**Pollutant E0**  **E10 E15**  Ethanol 0.00000 0.11896 0.193458 Naphthalene 0.00040 0.00040 0.000000 2,2,4 - Trimethylpentane 0.01984 0.03354 0.053129 Ethyl Benzene 0.02521 0.01721 0.016616 Hexane 0.02217 0.02536 0.007478 Toluene 0.09643 0.14336 0.140632 Xylene 0.07999 0.06423 0.057348 The composition of permeation emissions differs significantl y from other types of evaporative emissions. Work to better characterize these permeation emissions was recently conducted b y Southwest Research Institute for EPA and the Coordinating Research Council. 46 Data from 3 - day

diurnal tests on vehicles meeting Tier 1 and near zero evaporative emission standards were used. Toxic to VOC ratios for E0 and E10 were estimated by averaging data from gasolines of different RVPs. Resulting ratios are provided i n Table 16 , for all compounds except benzene, MTBE and naphthalene. For benzene, the diurnal emissions algorithm from MOBILE6.2 was used instead, sin ce this algorithm account for impacts of changing oxygenate, RVP and fuel benzene levels. However, a study of permeation emissions suggests that the ratio of benzene from permeation to total VOC is about 1.77 times higher than the ratio associated with ev aporation. 47 Thus the diurnal emissions algorithm was multiplied by 1.77. This algorithm is:30 1.77[ ( - 0.02895*OXY - 0.080274*RVP + 1.3758)*BNZ/100 ] **Equation 7**  **Diurnal Emissions of Benzene** In the absence of data on permeation emissions for MTBE, the resting loss algorithm from MOBILE6.2 was used: (22.198 - 1.746RVP)*MTBE/1000 **Equation 8**  **Diurnal Emissions of MTBE** For naphthalene, the toxic to VOC ratio for non - permeation evaporative emissions was also a pplied to permeation. For E15, model inputs were developed b y interpolating between E10 and E20 permeation toxic/VOC ratios. The E10 and E20 ratios were obtained from the CRC E - 77 - 2b and CRC E - 77 - 2c test programs. 48 , 49 Inputs are provided in Table 16 . **Table 16**  **Gasoline vehicle permeation toxic/VOC ratios for air toxi cs except benzene**  **,**

**naphthalene and MTBE (CRC E**  **- 77**  **- 2**  **b) Pollutant**  **E0 E10**  2,2,4 - Trimethy lpentane 0.036 0.024 Eth yl Benzene 0.003 0.001 Hexane 0.050 0.065 Toluene 0.110 0.101 Xy lene 0.016 0.011 Ethanol 0.202 

### 2. **Add itional	Air	Toxics**  **:		Inputs	for	Emissions from	Diesel**  **Vehicles** Toxic/VOC ratios, PAH/VOC ratios, PAH/PM ratios and metal emission factors were developed for exhaust emissions from heavy- duty diesel vehicles and applied to all diesel vehicle categories. There are no separate emission ratios or factors for diesel engin es running on biodiesel fuels or s ynthetic diesel fuels, due to very limited data.



### a) **Exhaust** The composition of VOCs for heav y- duty diesel engines without model year 2007 - and - later emission controls versus those engines with such controls varies significantly . Thus, we developed one set of toxic to VOC ratios for pre - 2007 diesel engines and another set for 2007 and later engines. Since extended idle emissions associated with auxiliary power units (APUs) are not subject to 2007 standards, toxic to VOC ratios for pre - 2007 diesel engines were used for31

them. Since light - duty diesels comprise a very small portion of the fleet, the same ratios were applied to all diesel vehicle classes to streamline modeling EPA relied on a database compiled for the Coordinating Research Council (CRC E - 75) and National Renewable Energy L aboratory

(NREL) to develop toxic to VOC ratios for pre - 2007 engines. 50 This database was developed from a literature survey and included data from 13 different studies. The studies included in this database were conducted in a number of different countries, included heavy- duty and light - duty engines, a variety of diesel and biodiesel fuels, and a number of different operating modes and cycles. For 2,2,4 - trimethylpentane, hexane, pro pionaldeh yde, and toluene, toxic to VOC ratios developed b y Sierra Research from CRC E 75 data were used. The methodology they used to develop ratios is described in detail in their technical report. 51 Data from tests using non - conventional diesel fuel (F ischer - Tropsch, bioDiesel, ethanol - Diesel blends, emulsified fuel, European blends, and other obvious research fuels) were excluded, as were data from non - heavy duty engines. The ratios are provided in Table 10. Toxic to VOC ratios for benzene, 1,3 - butadiene, formaldehyde, acetaldehyde, acrolein, naphthalene, ethylbenzene, sty rene and xylenes were developed by EPA from the E - 75 database. We relied on United States data from heav y- duty diesel engines running on conventional diesel fuels, collected on tes t - cycles representative of real world operation. Some studies measured emissions over distance, while other studies measure emissions relative to brake horsepower. For studies which measured emissions relative to distance, we calculated mean emissions per mile for toxics and VOC, then calculated a ratio of toxics to VOC. For studies which measured emissions relative to brake horsepower - hour, we calculated mean emissions per brake horsepower - hour for toxics and VOC, then calculated a second ratio of toxic s to VOC. We then calculated a composite ratio using sample size to weight the two ratios. The resulting ratios are provided in Table 17 .

**Table 17**  **Toxic to VOC Ratios for pre -**  **2007 diesel engines (CRC E -**  **75) Pollutant**  **Toxic/VOC** 1,3 - Butadiene 0.002918 2,2,4 - Trimethylpentane 0.001808 Acetaldeh yd e 0.035559 Acrolein 0.006622 Benzene 0.007835 Ethyl Benzene 0.002655 Formaldeh yd e 0.078225 Hexane 0.00197 Propionaldehyde 0.00468 Sty rene 0.001312 Toluene 0.00433 Xylenes 0.00378432

For 2007 and later heav y - duty diesels, and 2004 and later light - duty diesels which meet Tier 2 vehicle standards, advanced emission controls change the composition of VOCs. For these engines, we relied on speciated emissions data from the Advanced Collaborative Emissions Study (ACES), directed by

the Health Effects Institute and Coordinating Research Council, with participation from a range of government and private sector sponsors. 52 Detailed emissions data from the study

were provided to EPA at the request of the Coordinating Research Council. The data were collected on four engines on several test cycles with low sulfur diesel fuel. EPA used data from a 16 - hour transient cycle. Toxic to VOC ratios obtained from the ACES data are provided in Table 18 .

**Table 18**  **Toxic to VOC Ratios for 2007 and later diesel engines Pollutant**  **Toxic/VOC** 1,3 - Butadiene 0.00080 2,2,4 - Trimethylpentane 0.00782 Acetaldeh yd e 0.06934 Acrolein 0.00999 Benzene 0.01291 Ethyl Benzene 0.00627 Formaldeh yd e 0.21744 Hexane 0.00541 Propionaldehyde 0.00314 Sty rene 0.00000 Toluene 0.02999 Xylenes 0.03800 As with gasoline vehicles, PAH mass emissions from diesel engines were apportioned into the gas and particle phase, using a single set of allocation factors for all conditions. Gas phase PAHs were estimated using toxic/VOC ratios and particle phase PAHs were estimated using toxic to OC 2.5 ratios. Toxic to VOC and toxic to PM 2.5 ratios for pre - 2007 diesel engines were developed b y EPA from the E - 75 database. Toxic to PM 2.5 ratio s were converted to toxic to OC 2.5 ratios using OC 2.5 to PM 2.5 percentages from MOVES. We relied on United States data from heav y- duty

diesel engines running on conventional diesel fuels, collected on test - cycles representative of real world operation. It should be noted that for some PAHs, there were substantially

more data than for others; thus the level of confidence in emission factors varies among individual compounds. For instance, while data from 66 tests were available for acenaphthene, data from only two tests were available for dibenz(a,h)anthracene. Table 19 provides VOC and PM ratios for PAHs from these older technology engines.33 **Table 19**  **PAH/VOC and PAH/ OC2.5 ratios for pre -**  **2007 diesel engines**

**PAH Start**  **Fraction of OC**  **2.5 Running** 

**Fraction of OC**  **2.5 Fraction of** 

**HC** Benzo(a)anthracene 0.0002100 0.0005806 0.0000445 Benzo(a)p yr ene 0.0000789 0.0002180 0.0000000 Benzo(b)fluoranthene 0.0000234 0.0000648 0.0000000 Benzo(k)fluoranthene 0.0000033 0.0000091 0.0000000 Chry sene 0.0001327 0.0003667 0.0000235 Dibenz(a,h)anthracene 0.0000032 0.0000087 0.0000000 Indeno(1,2,3 - cd)p yrene 0.0000060 0.0000166 0.0000000 Acenaphthene 0.0000000 0.0000000 0.0003210 Acenaphthalene 0.0000000 0.0000000 0.0005009 Anthracene 0.0001058 0.0002924 0.0002353 Benzo(ghi)perylene 0.0000038 0.0000104 0.0000276 Fluoranthene 0.0004058 0.0011217 0.0006108 Fluorene 0.0001818 0.0005025 0.00059 14 Naphthalene 0.0000000 0.0000000 0.0090464 Phenanthrene 0.0004187 0.0011574 0.0019446 Py rene 0.0005865 0.0016213 0.0007577 For 2007 and later diesels, advanced emission controls change the composition and reduce the total mass of PAHs. For these engines, we relied on speciated emissions data from the ACES study . Table 20 provides provides VOC and OC 2.5 ratios for PAHs from these newer technology

engines.34

**Table 20**  **PAH/VOC and PAH/PM ratios for 2007 and later diesel engines**

**PA H**  **Start Fraction of**  **OC 2.5**  **Running**

**Fraction of OC**  **2.5 Fraction of** 

**HC** Benzo(a)anthracene 0.0000015 0.0000010 0.0000003 Benzo(a)p yr ene 0.0000061 0.0000042 0.0000000 Benzo(b)fluoranthene 0.0000026 0.0000018 0.0000000 Benzo(k)fluoranthene 0.0000026 0.0000018 0.0000000 Chry sene 0.0000046 0.0000031 0.0000005 Dibenz(a,h)anthracene 0.0000018 0.0000013 0.0000000 Indeno(1,2,3 - cd)p yrene 0.0000009 0.0000006 0.0000000 Acenaphthene 0.0000000 0.0000000 0.0000526 Acenaphthalene 0.0000000 0.0000000 0.0000853 Anthracene 0.0000488 0.0000334 0.0000304 Benzo(ghi)perylene 0.0000004 0.0000003 0.000000 2 Fluoranthene 0.0000896 0.0000613 0.0000457 Fluorene 0.0000990 0.0000677 0.0001963 Naphthalene 0.0000000 0.0000000 0.0163278 Phenanthrene 0.0007886 0.0005395 0.0008507 Py rene 0.0000859 0.0000588 0.0000379



### b) **Evaporative** MOVES estimates evaporative emissions associated with spillage for diesel vehicles. Since there are no speciated emissions of diesel spillage emissions, we developed toxic to VOC ratios based on a diesel headspace profile, profile number 4547 from the SPE CIATE database. These ratios are provided in Table 21 .

**Table 21**  **Toxic to VOC ratios for diesel spillage emissions Pollutant**  **Toxic/VOC** 2,2,4 - Trimethylpentane 0.0097 4 Ethyl Benzene 0.0032 4 Hexane 0.01076 Toluene 0.0141 9 Xylene 0.01222 Benzene 0.004 1035



### C. **Hydrocarbon Speciation**  **Factors** MOVES provides estimates of hydrocarbon emissions in a number of different grouping s or “hydrocarbon speciations.” The choice depend s on application . The following metrics are commonly

used in EPA and produced b y the MOVES model as documented in a MOVES technical report : 53 Total hydrocarbons (THC) -- Organic compounds in exhaust, as me asured by a flame ionization detector (FID). A FID does not accurately measure all of the mass of oxygenated organic gases, such as ethanol, acetaldehyde, and formaldeh yde . Non - methane h ydrocarbons (NMHC)

– THC minus the mass of methane. Total organic gases (TOG) -- A ll organic gas compounds emitted to the atmosphere , including all of the mass of ox ygenated organic gases. Non - methane organic gases (NMOG)

– TOG minus the mass of ethane. Volatile organic compounds (VOC)

– Organic gas compo unds that participate in atmospheric photochemical reactions. Does not include the mass of methane and ethane. Does include organic compounds not measured b y the FID. Basic exhaust emission rates in MOVES are expressed as TH C. NMHC is then estimated by applying a methane adjustment provided in the MOVES database . The following equation is used to calculate NMHC in MOVES:

= − **Equation 9**  **Calculating NMHC**  **from THC** The methane estimates used in the NMHC calcu lation were updated from MOVES2010 to MOVES2010a as described in an EPA technical report. 54 The methane estimates for gasoline vehicles of model ye ar 2004 - and - later were further updated for MOVEST3NPRM as described in S ection IV .C.1 below. NMOG, TOG, and VOC are other MOVES outputs. These metrics are obtained by applying NMHC - to -NMOG and NMHC - to - VOC speciation factors. A lthough TOG emissions were not calculated for the Tier 3 NPRM analy sis, this version of MOVES changed the way TOG is calcul ated, setting it to equal NMOG plus methane. NMHC to VOC factors are calculated using the following equation:

**Equation 10**  **NMHC to VOC** NMHC NMHC NMHC EtOH EtOH acetald acetald ethane ethane NMHC NMHC EtOH EtOH acetald acetald HCHO HCHO FID VOC MPC X )] FID X (CF FID X CF + ) FID X CF [( ) MPC X CF ( - ) MPC X (CF MPC X CF + ) MPC X CF ( + ) MPC X CF ( = NMHC VOC = Factor Speciation

 

) ( ) (36

NMHC to NMOG factors are calculated using the following equation:

Where: CF = carbon fractio n MPC = mass per carbon FID X = FID response factor **Equation 11**  **NMHC to NMOG** The FID does not measure any of the mass of formaldeh yde; thus for that pollutant a FID response factor of zero was used. The FID measures roughly half the mass of acetaldehyde; thus a FID response of 0.5 was used. For ethanol, a FID response of 0.74 was used, based on anal ys es done at Southwest Research Institute for the EPAct test program. 55



### 1. **HC	Speciation	of	Exhaust	Emissions** Exhaust s peciation factors for pre - Tier 2 gasoline vehicles remain unchanged from MOVES2010. However, since exhaust hydrocarbon emissions from Tier 2 - and - later vehicles are substantiall y different in composition from pre - Tier 2 vehicles, new speciation factors were developed, based on EPAct Phase 3 data . 56 The new factors are summarized in Table 23 below. The EPA ct data also was used to update methane/total hydrocarbon ratios for 2004 - and - later gasoline light - duty cars and trucks . Separate ratios were calculated for running a nd starts, keeping the age effect in MOVES2010 . e Updated methane to THC ratios for light - duty cars and trucks for model ye ars 2004 - and - later are provided in Table 22 . In the process of updating these rates , we also identified and fixed some errors and missing values found in these ratios for pre 2004 gasoline vehicles .

e Simple ratios between methane and THC were calculated for LA92 Bag 1 and Bag 2 from EPAct data, for starts and running, respectively. Gasoline light - duty cars and trucks were analyzed separately. Since the vehicles from EPAct program were less than four years old, for age groups four and later, the age trend in MOVES2010, w hich assumes that the proportion of methane declines as vehicles age, were appli ed. As a means of verification, calculated ratios from EPAct were compared to the ratios from the In - Use Verification Program (IUVP) and the results showed similar results. NMHC NMHC NMHC EtOH EtOH acetald acetald NMHC NMHC EtOH EtOH acetald acetald HCHO HCHO FID NMOG MPC X )] FID X (CF FID X CF + ) FID X CF [( MPC X (CF MPC X CF + ) MPC X CF ( + ) MPC X CF ( = NMHC NMOG = Factor Speciation

 

) ( ) ) (37

**Table 22**  **Methane/THC ratios for gasoline light -**  **duty cars and trucks (MY2004 and later)** 

**Light -**  **Duty Cars (LDV) Light**  **- Duty Trucks (LDT)**  **Age Group Running**  **Starts Running**  **Starts** 0

– 3 0.454054 0.082814 0.520114 0.107257 4

– 5 0.235549 0.050193 0.269818 0.066915 6

– 7 0.207525 0.04565 0.237717 0.059709 8

– 9 0.17483 0.040697 0.200266 0.053998 10

– 14 0.11926 0.030697 0.136611 0.04364 15

– 19 0.101667 0.028455 0.116458 0.040392 20 + 0.100044 0.028016 0.1146 0.038834 More recent and extensive data were available for pre - 2007 diesel engines than those used in earlier versions of MOVES, and for 2007 - and - later diesel engines, data were available from the Advanced Collaborative Emissions Study (ACES). 57 , 58 The new diesel s peciation factors and the speciation factors f

or gasoline vehicles are summarized in Table 23 . **Table 23**  **Exhaust hydrocarbon speciation factors Engine Type**  **Fuel Subtype Ope**  **rating Mode Speciation Factor**  **NMHC to VOC** Gasoline Tier 2 E0 to E10 Start 0.9787 + (0.0068 * wt. % ox ygen) Gasoline Tier 2 E0 to E10 Running 0.9148 - (0.0013 * wt. % ox ygen) Gasoline E15 Start 1.0162 Gasoline E15 Running 0.9049 Diesel

– pre - 2007 All Start and Running 1.1243 Diesel

– 2007+ All Start and Running 1.3058 **NMHC to NMOG** Gasoline Tier 2 E0 to E10 Start 1.0078 + (0.0082 * wt. % ox ygen) Gasoline Tier 2 E0 to E10 Running 1.0149 + (0.0028 * wt. % ox ygen) Gasoline E15 Start 1.0495 Gasoline E15 Running 1.0318 Diesel

– pre - 2007 All Start and Running 1.1455 Diesel

– 2007+ All Start and Running 1.343138 

### 2. **HC	Speciation	of Permeation**  **Emissions** Since no methane or ethane are found in evaporative or permeation emissions, THC is equivalent to NMHC, and VOC is equivalent to NMOG and TOG. Thus, speciation factors are on ly needed to convert THC to VOC , to account for the mass of ethanol not measured b y the FID :

**Equation 12**  **VOC speciation for permeation** For evaporative emissions, THC to VOC factors are unchanged from earlier versions of MOVES. However, factors were developed for permeatio n emissions, based on data from the CRC E - 77 test program. 59 , 60 These factors are provided in Table 24 . **Table 24**  **Gasoline Vehicle Permeation hydrocarbon THC to V**  **OC speciation factors**

**Fuel Subtype Speciation Factor**  E0 to E10 1.0000+(0.0360* wt. % oxygen) E15 1.1755 

### D. **Additional	Updates to	Air	Toxics	and	HC	Speciation**  We made a number of other small changes to air toxics and HC speciation for MOVEST3NPRM. We updated the General Fuel Expression Ratio table to fix a bug in acrolein running and start emissions for model years 1960 through 2003. W e fixed a small bug in the calculation of ethanol emissions , and we fixed an error in the HC speciation factors for diesel and biodiesel running , start and extended idle emissions . 

## V. **Updated Hea** **vy Duty**  **and	Diesel Emission**  **Rates A.**  **Changes	to	Heavy	Duty	Gasoline	Vehicle	Rates** The “2007 Heavy

Duty rule” 61 reduced both start and running emissions from heav y duty on gasoline vehicles. The reduction to running rates was inadvertently omitted from the MOVES2010 model. This subsection documents the detailed anal ys is that was conducted to include this rule in MOVEST3NPRM , and also reflect the requirement that Medium Duty Passenger Vehicles (MDPVs) be certified under Tier 2 regulations. 62 While the 2007 Heav y THC THC THC EtOH EtOH THC THC EtOH EtOH FID VOC MPC

X )] FID X (CF FID X CF ) MPC X (CF MPC X CF = NMHC VOC = Factor Speciation

 

) ( ) (39

Duty rule affects emissions in all Heavy Duty (HD) gasoline categories, f there are very few gasoline vehicles in the largest classes. As a result, revisions were made only to MOVES regulatory

class 41, which are commonl y called light HD or Medium Duty vehicles (8,500 to 14,000 pound GVWR).



### 1. **Regulatory	Class	Definition	and	Vehicle	Compositi on**  Gasoline vehicles in MOVES regulatory class 41 are a mixture of engine certified HD vehicles, chassis certified HD vehicles, and MDPVs. Each has separate set regulations governing their emissions, which are summarized below ( Table 25 ). **Table 25**  **Useful Life FTP Standards** MDPV (Tier 2 Bin 5) 8.5k

– 10k

(Class 2B) 10k- 14k

(Class 3) Engine

Certified Units g/mile g/mile g/mile g/bhp - hr Fully Phased in MY 2009 2008 2008 2010 HC 0.09 NMOG 0.195NMHC 0.230 NMHC 0.14 NMHC CO 4.2 7.3 8.1 14.4 NOx 0.07 0.2 0.4 0.2 The relative proportions of the vehicles within this weight class vary each year depending on economic demand. Consequently , we estimated proportions based on existing data and engineering judgment. MOBILE6 documentation indicates that MDPVs are approximately 16 percent of the gasoline 8,500 to 10,000 truck class. 63 Based on the estimate that MDPV sales have increa sed since the 2003 release of the MOBILE6 report, we project that MDPVs are 15 percent of total MOVES regulatory class 41. The MOBILE6 document 64 further asserts that more than 95 percent of class 2B trucks are chassis certified. Consequentl y, we estimate that 5 percent of all vehicles in the 41 regulatory class are engine certified. Based on anal ys is from the recent medium and heavy duty greenhouse gas rulemaking, we assume that sales of 2B class trucks vehicles were triple that of 3 class trucks ( Table 26 ). 65 This is roughly consistent with recent model ye ar sales totals, and yields the sales fractions below. 66 **Table 26**  **Populat ion Percentage** 

percent of Reg Class 41 MDPV 15% Class 2B 60% Class 3 20% Engine Certified 5%

f MOVES regulatory classes 41 (8,500 to 14,000 pounds GVWR), 42 (14,000 to 19,500 pounds GVWR), 46 (19,500 to 33,000 GVWR) and 47 (GVWR above 33,000 pounds).40 

### 2. **Estimating E**  **mission R** **ates** We weighted the individual FTP standards together using the proportions shown in Table 26 , which yields an aggregate MOVES gasoline FTP useful life standard shown below. While we do not expect the model to produce these rates, it is a useful benchmark for the modeled rate s. The distinction between NMHC and NMOG was ignored in calculating the aggregate FTP, and would have yi elded onl y minor variation in the final aggregate FTP ( Table 27 ). **Table 27**  **Aggregate Useful Life**  **FTP**

Reg Class 41 g/mile NMOG 0.18 CO 7.49 NOx 0.22 We then compared this aggregate FTP standard to the emissions calculated by MOVES 2010a. The Ph ys ical Emission Rate Estimator (PERE), 67 modified to produce Scaled Tractive Power (STP) distributions, was used to generate the bin mix of a regulatory class 41 vehicle on the federal test pro c edure (FTP) drive cycle. The STP modification required shifting the vehicle weight to match Source Ty pe 32 in MOVES (2.06 Tons). We pulled rates by hour from the MOVES DB for the age 0 - 3 group, and added in a cold start (operating mode 108) and a hot start (operating mode 102) from the MOVES database. The modified version of PERE produced the operating mode distribution shown in Table 28 .

. **Table 28**  **Operating Mode Bin Mix for a MD FTP** 

STPpbin N percent vspbin N percent **0** 160 12% **25** 41 3% **1** 258 19% **27** 49 4% **11** 94 7% **28** 17 1% **12** 68 5% **29** 13 1% **13** 70 5% **30** 15 1% **14** 36 3% **33** 13 1% **15** 48 3% **35** 12 1% **16** 141 10% **37** 13 1% **21** 68 5% **38** 17 1% **22** 44 3% **39** 15 1% **23** 97 7% **40** 6 0% **24** 77 6% Total 1372 100% Using this operating mode distribution, we constructed a simulated FTP out of four components (bag 1/3 running, cold start, hot start, and bag 2 running). We con s tructed bag 1 (cold start + bag 1/3 running) and bag 3 (hot start + bag 1/3 running) and weighted the resulting41

components together according to the FTP formula, g and compared the 2007 and later rates in MOVES to the aggregate standard shown in Table 29 . The MOVES 2010a estimates at age 3 are 2.5x to 11x the standard, which indicates that the average vehicle is significantly out of compliance with the 2010 standard.

**Table 29**  **Comparison between MOVES DB FTP and Aggregate FTP**

MOVES FTP Aggregate FTP MOVES /Aggregate FTP NMOG 0.45 0.18 2.51 CO 16.21 7.37 2.20 NOx 2.53 0.23 11.06 Based on this analy sis, we reviewed In Use Verification Program (IUVP) data from MYs 2004 - 2008 vehicles with estimated test weights of 7,500 pounds - or - above to determine the average in use compliance ratio. Non - sales weighted, and after accounting for the individual standards applicable to each v ehicle, this yielded average ratios of FTP to the standard of 0.42 (NMOG) and 0.23 (NOx) ( Table 30 and Figure 6 ). MOVES , which includes all vehicles and is a broader sample than the IUVP program, would be expected to yi eld somewhat higher emissions. Further, while the Heavy Duty 2007 rule does not fully

phase - in until 2010, we would anticipate that manufacturers would achieve similar compliance ratios as in past MYs.

**Table 30**  **Average Compliance Margin and Headroom** Average Average Ratio FTP/Standard Headroom NMOG 0.42 0.5 8 Nox 0.2 3 0.77

g FTP =( (Bag 1 + Bag 2)*0.43+ (Bag 3+ Bag 2)*0.57)/ 7.4542 **Figure 6**  **Distribution of IUVP FTP Tests** To produce s imilar compliance ratios in MOVES, we applied the following ratios to the r unning and start rates, incorporating the assumption that it is much more difficult to reduce start emission than running emissions. **Table 31**  **Ratios applied to MOVES Rates** 

HC CO Nox Running 0.2 0.2 0.05 Start 0.4 0.4 0.3 Applying these ratios against the MOVES 2010 default rates yi elds the new regulatory class 41 rates. These are shown compared against the aggregate FTP from Table 27 .43 **Table 32**  **Comparison of FTPs using**  **Preliminary New MOVES Rates**

MOVES FTP Aggregate FTP MOVES /Aggregate FTP NMOG 0.10 0.18 0.56 CO 4.72 7.37 0.64 NOx 0.13 0.23 0.58 This process yi elded a number of medium duty rates, which by operating mode, were lower than the L ight Duty Tier 2 Bin 8 rates. Specifically, most of the higher power modes such as 27 - 30 and 37 - 40 were reduced to below the Bin 8 rates. These operating modes are likel y the least affected b y the MY 2010 HD Gas stand ards, which include no SFTP component. To account for the lack of SFTP control on these vehicles we bounded the emission rates so that rates for individual operating mode could be lower than Bin 8 rates * 1.2, and no higher than the MD rates currently

in MOVES. This yielded rates that are slightl y higher than the unbounded rates, with NOx is slightly over the Aggregate FTP standard. These rates were phased in at a rate of 25 percent per year between MY 2007 and 2010 and placed in the MOVES emission rate database.

**Table 33**  **Comparison of Outputs**  **after accounting for SFTP emissions** 

MOVES FTP Aggregate FTP MOVES /Aggregate FTP NMOG 0.13 0.18 0.74 CO 5.31 7.37 0.72 NOx 0.28 0.23 1.20 

### B. **Changes	to	Heavy -**  **and	Light -**  **Duty Diesel**  **Vehicle Rates**  We updated sulfate, sulfur dioxide, organic carbon and elemental carbon emissions for 2007 - and - later diesel vehicles based on data from the ACES study . In 2007 - and - later diesel vehicles, more of the fuel sulfur is converted to SO4 and less t o SO2 compared with earlier diesel vehicles . However, in this update, total PM is unchanged, so organic carbon is reduced. T he details of the data , its analy sis, and its application in MOVES are explained in a separate memo. , 68 

## VI. **Other	Changes** Other changes made for MOVEST3NPRM did not impact MOVES results, but improved our ability to generate the necessary emission rates for air quality modeling. For example, we made finer divisions in MOVES model year groups to allow the phase - in of emission standards . More important in this category of changes were changes to allow MOVES to run a cloud computing environment. This was necessary because evaporative emissions were expected to be important in this analy sis, so we wanted to be sure to capture fine distin ctions in fuel characteristics and44

ambient temperatures. Instead of running MOVES to generate state - level inventories as we did for the recent Heav y Duty Greenhouse Gasoline rule anal ys is , 69 we ran MOVES in emission rate mode and calculated rates for “representative counties.” As explained in the RIA for this proposal, these rates were then applied to other similar counties. This approach allowed us great precision in modeling temperatures, but it required more than 14,000 runs for each scenario -- an unprecedented requirement for computing power. To meet this requirement, we adapted MOVES to run in a cloud computing environment with a Linux operating sy stem. We improved MOVES error handli ng and the ability to distribute MOVES functions among computers. We truncated the IMCoverage table to facilitate the input of local inspection and maintenance data for each county. We adjusted the zoneroadty

pe and sccroadty

pedistribution table to assure that all roadty pes could be modeled in all counties. We also made changes to reduce the runtime for each run. 

### A. **Changes	to	Model	Year	Groups** MOVES2010a grouped emissions for 2021 - and - later model years together with a single emission rate. Because the Tier 3 anal ys is had to estimate the impact of phasing in a new emission standard in this time period, MOVES was revised to use ye ar - by- ye ar model year groups for all ye ars 2021 through 20 3 0. We also introduced a new model year group of 2031 - 2050. This chang e required modification of many MOVES tables, but had no impact on emission estimates for the baseline and reference case . 

### B. **Changes	to	County	Allocations** In the tables zoneroadtyp e and sccroadtypedistribution, zeros were replaced with the value 10 - 15 . Thi s facilitates our approach of using representative counties; it allows the model to calculate emission rates on roadty pes that do not exist in a given county so they can be applied to a similar county

that does have that roadtyp e. 

### C. **Repair of**  **E**

**rrors** An error was found in the algorithm for aggregating Inspection /Maintenance effects to the state - level. This was fixed, facilitating the use of the MOVES model at the national level for inventory calculations. We also updated the modelyear groups used for ammonia extended idle emissions to allow the model to correctly generate these emissions. And we updated model year groups for sulfate, NO and NO2 to allow the model to correctl y estimate emissions for model ye ar 2021. 

### D. **Changes	to F** 

**acilitate L**  **arge N** **umbers	of R**  **uns** For air quality

modeling, we ran MOVES for a very large number of counties. To facilitate this, we adapted MOVES to improve the model’s operation in diverse computing environments, including large computer clusters and services available over the Intern et from c ommercial providers. The MOVES air quality runs were performed with IMCoverage tables for each county. This change avoided conflicts between the default and the input data.45

MOVES now provides a message when users create a user input database with the same name as an existing database, and we added the ability to omit roadtypes when modeling evap orative processes, thus facilitating faster production of RatePerProfile and RatePerVehicle output. We improved the use of indices to speed model runs . We made many changes to the MOVES code to facilitate running MOVES on Linux operating s ys tems, to allow the operation of MOVES with local My SQL , to allow separate processing of “TODO” and “Done” files, to better manage independent “worker” computers, to improve the MOVES log file, and to allow longer names for MOVES worker and master computers None of the changes described in this subsection changed MOVES emission results. 

## VII. **Impact	of	MO VES	Changes**  To assess the overall impact of the MOVES changes described above in emissions with the updated version of MOVES were evaluated b y conducting a national run with MOVES2010 a and the updated MOVES version, using the reference case fuels described the Tier 3 RIA for 2017. The results are shown in Table 34 Impact of MOVES updates to U.S. emissions in 2017 (annual tons ) . **Table 34**  **Impact of MOVES updates to U.S. emissions in 2017 (annual tons )** 

MOVES2010a MOVEST3NPRM Percent Change NOx 3,584,299 3,452,314 - 4% VOC 1,922,560 1,614,384 - 16% CO 23,663,807 20,915,593 - 12% PM 111,928 115,098 3% Benzene 39,567 39,695 0% 1,3 - Butadiene 6,950 6,022 - 13% Acetaldeh yd e 23,433 23,918 2% Formaldeh yd e 25,496 29,446 15% Acrolein 1,193 1,814 52% Ethanol 66,563 111,629 68% Naphthalene 4,786 3,953 - 17% As illustrated in the table, the revision to air toxics inputs had a major impact on the emissions of these compounds. Moreover, the changes between MOVES2010 and MOVEST3NPRM led to a substantial reduction in the e missions of CO and VOC . These reductions will be seen in both the reference and control cases of the Tier 3 NPRM analy sis.46



## Re **fer ences**  1 U.S. EPA, 2008. Development of MOVES Rates for HC, CO and NOx Exhaust Emissions from Light - duty Vehicles for use in the RFS2 NRPM, Memorandum from James Warila, U. S. EPA, November 2008. 2 U.S. EPA. 2008. Kansas City Characterization Study: Final Report (EPA420 - R- 08 - 009) http://www.epa .gov/otaq/emission - factors - research/420r08009.pdf 3 U.S. EPA. 2008. Analysis of Particulate Matter Emissions from Light - Duty Vehicles in Kansas City (EPA420 - R 08 - 010) http: //www.epa.gov/otaq/emission - factors - research/420r08010.pdf 4 U.S. EPA, 2008. Modeling Evaporative Emissions in MOVES for the RFS2 NPRM. Memorandum from Prashanth Gururaja, U.S. EPA, November 2008. 5 U. S. EPA. 20011. 2005 National - Scale Air Toxics Asse ssment. http://www.epa.gov/ttn/atw/nata2005 . 6 Khalek, I., Bougher, T., and Merritt, P. M. 2009. Phase 1 of the Advanced Collaborative Emissions Study. Prepared by Southwest Research Institute for the Coordinating Research Council and the Health Effects Institute, June 2009. Available at www.crcao.org . 7 U.S. EPA. 2013. "The Effects of Fuel Sulfur Level on Emissions from Tier 2 Vehicles in the In - Use Fleet, Draft Report". 8 U.S. EPA, 2013 “ EPAct/V2/E - 89: Ass essing the Effect of Five Gasoline Properties on Exhaust Emissions from Light - Duty Vehicles certified to Tier - 2 Standards : Final Report on Program Design and Data Collection .” EPA 420 - R- 13 - 004. Assessment and Standards Division, Office of Transportation and Air Quality, Ann Arbor, MI. March, 2013. 9 U.S. EPA. 2013 “ Assessing the Effect of Five Gasoline Properties on Exhaust Emissions from Light - Duty Vehicles certified to Tier - 2 Standards: Analysis of Data from EPAct Phase 3 (EPAct/V2/E - 89).” EPA - 420 - R - 13 - 002. Assessment and Standards Division, Office of Transportation and Air Quality, Ann Arbor, MI. March, 2013. 10 U.S. EPA, 2011. MOVES2010 Fuel Adjustment and Air Toxic Emission Calculation Algorithm

– Development and Results (EPA - 420 - R- 11 - 009) http://www.epa.gov/otaq/models/moves/documents/420r11009.pdf 11 U. S. EPA. 2005 National - Scale Air Toxics Assessment. http://www.epa.gov/ttn/atw/nata2005/. 12 U. S. EPA. 2007. Fina l Regulatory Impact Analysis: Control of Hazardous Air Pollutants from Mobile Sources; EPA420 - R - 07 - 002; U.S. Environmental Protection Agency; Office of Transportation and Air Quality: Ann Arbor, MI. Chapter 6.11. http://www.epa.gov/otaq/toxics.htm. 13 U. S. EPA. 2011. Spreadsheet “Benz Buta Adjustments.xlsx.” EPA Docket EPA - HQ - OAR- 2011 - 0135. 14 U. S. EPA. 1993. Final Regulatory Impact Analysis for Reformulated Gasoline. December 13, 1993. http://www.epa.gov/otaq/regs/fuels/rfg/ 15 U. S. EPA. 2011. Spreadsh eets “Olefins versus Butadiene.xls” and Benz Buta Adjustments.xls.” EPA Docket EPA - HQ - OAR - 2011 - 0135. 16 U.S. EPA 2012. Final Report: Development of Evaporative Emissions Calculations for the Motor Vehicle Emissions Simulator MOVES2010 , EPA - 420 - R - 12 - 027, http://www.epa.gov/otaq/models/moves/documents/420r12027.pdf . 17 CRC E - 77 reports: Haskew , H., Liberty, T. (2008), Vehicle Evaporative Emission Mechanisms: A Pilot Study, CRC Project E - 77; Haskew, H., Liberty, T. (2010), Enhanced Evaporative Emission Vehicles (CRC E - 77 - 2); Haskew, H., Liberty, T. (2010), Evaporative Emissions from In - Use Vehic les: Test Fleet Expansion (CRC E - 77 - 2b); Haskew, H., Liberty, T. (2010). Study to Determine Evaporative Emission Breakdown, Including Permeation Effects and Diurnal Emissions Using E20 Fuels on Aging Enhanced Evaporative Emissions Certified Vehicles, CRC E - 77 - 2c. 18 U.S. EPA 2009. 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and Thomas F. Liberty, Harold Haskew and Associates, Inc.; submitted to U. S. EPA, December, 2009. Available at www.crcao.org . 49 Haskew, H. M., Liberty, T. F. 2010. Study to Determine Evaporative Emission Breakdown, Including Permeation Effects and Diurnal Emissions, Using E20 Fuels on Aging Enhanced Evaporative Emissions Certified Vehicles. December 2010. CRC Project E - 77 - 2c. http://www.crcao.org. 50 Hsu ,Y., and Mullen, M. 2007. Compilation of Diesel Emissions Speciation Data. Prepared by E. H. Pechan and Associates for the Coordinating Research Council. CRC Contract No. E - 75 , October, 2007. www.crcao.org . 51 Sierra Research, 2010. Development of Emission Rates for the MOVES Model. Prepared for the U. S. Environmental Protection Agency by Sierra Research, Sacramento, CA, July 2, 2010. Sie rra Research Report No. SR2010 - 07 - 01. 52 Khalek, I., Bougher, T., and Merritt, P. M. 2009. Phase 1 of the Advanced Collaborative Emissions Study. Prepared by Southwest Research Institute for the Coordinating Research Council and the Health Effects Institute, June 2009. Available at www.crcao.org . 53 U.S. EPA 2011. MOVES2010 Fuel Adjustment and Air Toxic Emission Calculation Algorithm

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