Development of Evaporative Emissions 

Calculations for the Motor Vehicle 

Emissions Simulator MOVES2010

Final Report
EPA-420-R-12-027 

September 2012

Assessment and Standards Division 

Office of Transportation and Air Quality 

U.S. Environmental Protection Agency

Development of Evaporative Emissions 

Calculations for the Motor Vehicle 

Emissions Simulator MOVES2010 

Final Report

NOTICE 

This technical report does not necessarily represent final EPA decisions or 

positions. It is intended to present technical analysis of issues using data 

that are currently available. The purpose in the release of such reports is to 

facilitate the exchange of technical information and to inform the public of 

technical developments.
1

Table of Contents

1 Background.............................................................................................................................. 2

2 List of Data Sources................................................................................................................. 5

3 Design and Analysis ................................................................................................................ 6

3.1 Fuel Tank Temperature Generator.................................................................................... 6

3.2 Permeation ........................................................................................................................ 8

3.3 Tank Vapor Venting ....................................................................................................... 11

3.4 Inspection/Maintenance (I/M) Program effects .............................................................. 18

3.5 Liquid Leaks ................................................................................................................... 21

3.6 Refueling......................................................................................................................... 22

Appendix A - Notes on Evaporative Emission Data ................................................................ 25

Appendix B - CumTVVCoeffs Table....................................................................................... 27

Appendix C - MOVES Operating Modes and Emission Processes.......................................... 29

Appendix D - Evaporative Pollutants ....................................................................................... 29

Appendix E – Evaporative Failure Frequency.......................................................................... 30

References................................................................................................................................. 31
2

1 Background

Vehicles emit hydrocarbon (HC) emissions in addition to exhaust emissions due to driving. HC

emissions “evaporate” from the fuel system while a vehicle is sitting or driving, and are largely

driven by changes in the ambient temperature. For gasoline fueled vehicles, evaporative

emissions can account for a significant portion of the total gaseous hydrocarbon inventory. The

processes are unique from exhaust and require their own modeling approach. In the MOBILE

series of models, and in certification test procedures, evaporative emissions were quantified in

distinct modes based on the test procedures used to measure them:

 Running Loss – vapor lost during vehicle operation.

 Hot Soak – vapor lost while parked, immediately after turning off a vehicle.

 Diurnal / Cold Soak - vapor lost while parked and with a stabilized temperature.

 Refueling Loss - vapor lost and spillage occurring during refueling.

However, for MOVES, a change from this approach was proposed to better account for the

underlying physical processes involved in evaporation of fuels, and thus to better model

evaporative emissions under different ambient temperatures and fuel types. For example,

Ethanol (EtOH) has a unique effect on permeation, which is distributed among the modes listed

above. Instead MOVES groups evaporative emissions based on the evaporative mechanism,

using the following “processes”:

 Permeation – the migration of hydrocarbons through elastomers in the vehicle’s fuel

system.

 Tank Vapor Venting (TVV) – vapor generated in fuel system that is expelled into the

atmosphere.

 Liquid Leaks – liquid fuel leaking from the fuel system, eventually evaporating into the

atmosphere.

 Refueling Emissions – vapor in the fuel system that is displaced into the atmosphere as a

vehicle refuels and spillage.

These processes can occur for each of the modes (Running Loss, Hot Soak, Cold Soak) used in

the MOBILE models. MOVES calculates permeation, tank vapor venting, and liquid leaks in

each of the operating modes. The benefit is that each emission process can be modeled using the

different factors that affect it, independently of how the vehicle is operating. This makes for

easier, more accurate modeling of scenarios that do not perfectly replicate the test procedures.

The emission processes used by MOVES and the operating modes used for evaporative

processes are shown in Appendix C.

The graphic below shows the evaporative emission processes. Permeation of the fuel through

the tank walls, hoses and seals occurs continuously, but is affected by the tank temperature.

Vapor is generated by a change in tank temperature and is intended to be captured by the

charcoal canister. If the canister is not purged enough or if there are leaks in the system, vapors

can be expelled when temperatures rise. Liquid leaks can occur in connections, hoses and the

tank itself. Refueling displaces the vapor in the tank and can result in spillage.
3

Evaporative emissions depend on a number of variables. In MOVES, we model the impact of

the following factors:

 Ambient Temperature

 Fuel Tank Temperature

 Model year group (standard)

 Vehicle age

 Vehicle class

 Fuel Properties

o Ethanol content

o Reid Vapor Pressure (RVP)

 Failure Modes

 Presence of inspection and maintenance programs

Both ambient temperature and engine operation can increase fuel tank temperature. Any

increase in fuel tank temperature will generate vapor in the tank and pressure in the tank.

Charcoal canisters connected to the gas tank are intended to vent these vapors through activated

charcoal and remove the hydrocarbons. When the engine is operated the canister is "purged"

periodically and the captured hydrocarbons are diverted to the intake manifold of the engine and

burned. The emission standards (model year and vehicle class) determine the amount of capacity

the canister system is designed to hold. If the amount of vapors generated exceeds the capacity
4

of the canister, the vapors are vented to the atmosphere. This can occur if a vehicle is not driven

and undergoes several days of ambient temperature rises.

Fuel properties are important for evaporative emissions. Since evaporative emissions are just

fuel, the fuel properties will have a significant effect on the amount and types of hydrocarbons

emitted.

Fuel systems will sometimes generate leaks that allow liquid fuel or vapors to circumvent and

escape the control systems on the vehicle. Inspection and maintenance (I/M) programs

sometimes explicitly include inspections intended to identify vehicle in need of evaporative

system repairs. Stage 2 programs are designed to capture the vapors released during refueling.

The model year groups for evaporative emissions are shown in Table 1. They depend on

evaporative emission standards and related technological improvement designed to control

evaporative emissions.

Table 1 - Model Year Groups used for MOVES

Model year group Emissions standard or technology level

1971-1977 Pre-control

1978-1995 Early control

1996 80% early control, 20% enhanced evap.

1997 60% early control, 40% enhanced evap.

1998 10% early control, 90% enhanced evap.

1999-2003 100% Enhanced evap.

2004 and later Tier 2, LEV II

All evaporative emissions from vehicles derive directly from the fuels used and are not affected

by the combustion process. This means that hydrocarbons not present in the fuels that are a

product of combustion (such as methane) will not appear in evaporative emissions. Appendix D

contains a list of the non-combustion pollutants calculated by MOVES from evaporative

emissions.

The data used for this evaporative analysis was collected on Light-Duty gasoline vehicles but

will also be used in application for Heavy-Duty gasoline vehicles. For diesel vehicles, there are

no evaporative emission losses except for refueling spillage. All other diesel evaporative losses

are considered negligible.
5

2 List of Data Sources

The evaporative emissions in MOVES are based on data from a large number of studies.

• CRC E-9 – Measurement of Diurnal Emissions from In-Use Vehicles1

• CRC E-35 – Measurement of Running Loss Emissions in In-Use Vehicles23

• CRC E-41 – Evaporative Emissions from Late-Model In-Use Vehicles45

• CRC E-65 – Fuel Permeation from Automotive Systems6

• CRC E-65-3 – Fuel Permeation from Automotive Systems: E0, E6, E10, and E857

• CRC E-77 – Vehicle Evaporative Emission Mechanisms: A Pilot Study

• CRC E-77-2 – Enhanced Evaporative Emission Vehicles

• CRC E-77-2b – Aging Enhanced Evaporative Emission Vehicles (DRAFT)

• CRC E-77-2c – Aging Enhanced Evaporative Emission Vehicles with E20 Fuel

• BAR Gas Cap Study

• API Gas Cap Study

• EPA Compliance Testing

Appendix A has a summary of the test programs mentioned above.
6

3 Design and Analysis

Fuel tank temperature was empirically found to be the driver of the transient emissions

processes, permeation and vapor venting in the CRC E-77 pilot testing program which included

ten vehicles.8Therefore, determining fuel temperature is critical in predicting emissions in each

operating mode. Fuel tank temperature is dependent on the daily ambient temperature profile,

vehicle operation patterns, and vehicle model year. As standards have tightened, fuel system

materials and connections have become more efficient at containing gaseous HC’s from escaping

to the atmosphere. Purge systems and canister technologies have also advanced resulting in

lower emissions.The calculated fuel tank temperature can be used in modeling permeation and

vapor venting. Because liquid leaks are liquid rather than vapor, they are not dependent on

temperature..

3.1 Fuel Tank Temperature Generator

This section explains how MOVES generates fuel tank temperature over a diurnal ambient

temperature profile and the vehicle trip schedule. Tank temperature is used in later calculation of

permeation and vapor venting, which makes this an instrumental algorithm in modeling

evaporative emissions for MOVES.

3.1.1 Fuel Tank Temperature Calculator General Steps

Define Input Parameters:

 Hourly ambient temperature profile (zoneMonthHour table)

 Key on and key off times (sampleVehicleTrip table)9

 Day and hour of first KeyON (hourDay table)

 Vehicle Type (Light-duty vehicle, Light-duty truck, Heavy-duty gas truck)

 Pre-enhanced or enhanced evaporative emissions control system

Tank temperature is modeled for the three primary operating modes of a vehicle. Operating, hot

soak, and cold soak. Operating vehicles tanks are warmer than ambient due to recirculation from

the engine. Hot soak is the period after a vehicle’s engine ceases to run, and the vehicle begins

to cool to ambient temperature. Cold soak is the period in which a vehicle is not running and is

not hot soaking, therefore the primary driver of tank temperature of a cold-soaking vehicle is the

ambient temperature.

3.1.2 Calculate fuel tank temperature for hot and cold soaks

The following equation is used to model tank temperature as a function of ambient temperature.

)(

air Tank

Tank TTk

dt

dT

 Equation 1

TTank is the fuel tank temperature, Tair is the ambient temperature, and k is a constant

proportionality factor (k = 1.4 hr-1, reciprocal of time constant). The value of k was established

by trial and error using EPA compliance data. Compliance data was available on 77 vehicles that

underwent a 2-day diurnal test and had a 1-hour hot soak. There was no distinction made
7

between hot and cold soak calculations. We assume that during any soak, the only factor driving

change in the fuel tank temperature is the difference between the tank temperature and the

ambient temperature.

As stated before this equation only applies during all parked conditions, which include the

following time intervals:

 From the start of the day (midnight) until the first trip (keyON)

 From a keyOFF time until the next keyON time

 From the final keyOFF time until the end of the day

For more information on the activity data used to determine the time of keyOn and keyOff

events, see the MOVE technical report10 and supporting contractor reports11,12.

Mathematical steps

a) At time t0 = 0 or KeyOFF (start of soak), TTank = Ti. This value will either be the ambient

temperature at the start of the day, or the fuel tank temperature at the end of a trip.

b) Then, for all t > 0 and KeyOFF, the next tank temperature is calculated in this manner:

(Tair – Ttank) is a function of time. Since analytical integration is too complicated (the input

ambient temperature data is in a table), numerical integration is used to perform this step. The

method of numerical integration varies based on the accuracy desired. The above method

represents the Euler method, one of the simplest methods of integration. The smaller the time

step Δt, the more accurate the solution. MOVES uses a Δt of 15 minutes, which is accurate

enough for our modeling purposes without causing tremendous strain on computing resources.

3.1.3 Calculate fuel tank temperature during operation

Vehicle trips are relatively short compared to the length of the day or modeling period.

Therefore, even though the fuel tank temperature profile is not perfectly linear with time,

assuming a linear increase in temperature makes calculations easier without compromising

accuracy.

The convention used in this algorithm is that ΔTtank applies over a 4300 second period. This is

the length of the running loss test performed by manufacturers at certification. To find ΔTtank, we

must first find ΔTtank95, the average increase in tank temperature during a standard 4300 second

95°F running loss test. The increase in fuel tank temperature depends on the temperature of the

tank at the KeyON time. It also depends on vehicle type and technology, due to different

configuration and design that affect heat loss. The different ΔTtank95 temperatures are as follows:

 If the vehicle is evap-enhanced, then ΔTtank95 = 24°F 13

 If the vehicle is pre-enhanced, the vehicle type affects ΔTtank95.

2

i

n

j

T nTank air jTank   TtTTk











  





0

1

)( ( ) Equation 2a

T air nTanktTTkT )( nTank 1 Tank n( )  Equation 2b
8

o If LDV, then ΔTtank95 = 35°F.

o If LDT, then ΔTtank95 = 29°F.

We use these values to calculate to calculate the ΔTtank for other starting fuel tank temperatures

using equation 3.

Equation 3

This equation comes from GM regression analyses of light-duty vehicles driving the running loss

drive cycle with several different starting temperatures.14 The average slope of fuel temperature

increase to starting fuel temperature is -0.352 with a standard error of the mean of 9.5%. This is

to say that the lower the starting fuel tank temperature, the bigger the increase over a drive cycle.

This gives us the increase in tank temperature so we can create a linear function that models fuel

tank temperature for each trip.

keyON Tank KeyON

Tank

Tank Ttt

T

T ,)(

4300 / 3600







Equation 4

The 4300/3600 is in the denominator as a conversion from seconds to hours, maintaining

consistency in the algorithm.

Assumptions:

 The first trip is assumed to start halfway into the hour stated in the first trip’s

HourDayID.

 The effect of a change in ambient temperature during a trip is a negligible compared to

the temperature change caused by operation.

 The KeyON tank temperature is known from calculation of tank temperature from the

previous soak.

3.2 Permeation

Permeation emissions are fuel vapor emissions that escape through micro-pores in pipes, fittings,

fuel tanks, and other vehicle components. They differ from leaks in that they occur on the

molecular level and do not represent a mechanical/material failure in a specific location.

3.2.1 Base Rates

We first determined base rates for permeation. These were determined using the per-hour

emission rate during the last six hours of a 72-96-72°F diurnal test (also known as cold

soak/resting loss) The diurnal tests analyzed are federal cycle (72F-96F) tests from the CRC E-9

and E-41 programs. These two programs together represent a total of 151 vehicles with model

years ranging from 1971 to 1997.1,4,5 In the final six hours of the diurnal; the emissions rate,

ambient temperature, and fuel temperature are relatively stable or constant. This leads us to

believe that permeation is the only process occurring. The rates are broken out by model year

group and age group. The base permeation rates are in Table 2. Model years 1996-1998 are

represented individually to reflect the 20/40/90% phase-in of enhanced evaporative emissions

standards.

, 95 95(352.0 )  TTank   TTank KeyON   TTank
9

Table 2 - Base permeation rates at 72°F

Model year group Age

group

Base

permeation

rate [g/hr]

1971-1977

10-14 0.192

15-19 0.229

20+ 0.311

1978-1995

0-3 0.0554

4-5 0.0554

6-7 0.0913

8-9 0.0913

10-14 0.124

15-19 0.148

20+ 0.201

1996

0-3 0.046

4-5 0.046

6-7 0.075

8-9 0.075

10-14 0.101

15-19 0.120

20+ 0.163

1997

0-3 0.037

4-5 0.037

6-7 0.059

8-9 0.059

10-14 0.079

15-19 0.093

20+ 0.125

1998

0-3 0.015

4-5 0.015

6-7 0.018

8-9 0.018

10-14 0.022

15-19 0.024

20+ 0.029

1999 and Newer

0-3 0.0102

4-5 0.0102

6-7 0.0102

8-9 0.0102

10-14 0.0102

15-19 0.0102

20+ 0.0102
10

3.2.2 Temperature adjustment

In the E-65 permeation study, it was found that permeation rates, on average, double for every

18°F (10°C).6This study included permeation testing performed on 10 vehicle fuel rigs at 85°F

and 105°F. The vehicles ranged in model year from 1978-2001. In MOVES the base permeation

rates are calculated at 72°F.

The following equation is derived from that study and used to adjust the base permeation rate:

(0385.0 ) Tank TT base

adj base ePP



 Equation 5

Pbase is the base permeation rate, Ttank is the tank temperature, and Tbase is the base temperature

for a given temperature cycle (e.g. 72°F for a 72-86-72°F diurnal test).

3.2.3 Fuel Adjustment

E10 affects evaporative emissions from gasoline vehicles due to the increased permeation of fuel

vapors through tanks and hoses. The model separates permeation emissions from vapor venting

emissions to allow better accounting of vapor losses for these different processes.

Fuel effects on permeation were developed from CRC’s E-65 and E-65-3 programs, which

measured evaporative emissions from ten fuel systems that were removed from the vehicles on

E0, E5.7, and E10 fuels; and CRC’s E-77-2 and E-77-2b programs, which measured evaporative

emissions from sixteen vehicles. For this analysis, we separated the evaporative enhanced and

Tier 2 vehicles from the pre-enhanced vehicles. Enhanced evaporative vehicles began being

phased in from 1996 through 1999 and needed to meet a 2.0 g standard over a 24-hour diurnal

test. Pre-enhanced vehicles needed to meet 2.0 g over a 1-hour simulated diurnal. We estimated

the ethanol effect by using a mixed model. The vehicle’s evaporative certification, fuel ethanol

content, and fuel RVP were modeled as fixed effects and the particular vehicle modeled as a

random effect. The natural log of the emission rates over the 65-105-65°F diurnal cycle provided

a normally distributed dataset to the model. Due to a relatively small amount of data, in order to

find a significant effect of ethanol within different evaporative certifications (enhanced AND

Tier 2 vs. pre-enhanced), we had to combine E5.7 and E10 results into one category of “Ethanol”

fuel. Ethanol fuel could then be seen to have a significant influence on permeation from a

baseline E0 fuel. The percent difference between the Ethanol rate and the E0 rate was input into

MOVES as the fuel adjustment. Due to the phase in from 1996 to 1999 (20/40/90/100%), the

two fuel adjustments must be properly weighted for those model years. The fuel adjustment in

MOVES is based on a variable called fuelModelYearID. Table 3 shows the fuel adjustments

used for E5 through E85 for the fuelModelYearID’s used in MOVES.
11

Table 3 – Increase in Emissions

Due to ethanol levels of 5% to 85% compared to E0 (gasoline)

Model years

(via fuelModelYearID in

MOVES)

Percent increase due to ethanol

(E5 through E85)

1995 and earlier 65.9

1996 75.5

1997-2000 107.3

2001 and later 113.8

There is more information regarding permeation emissions in the final releases of the CRC E-77-

2b and E-77-2c studies which can be used to update the permeation estimates in future versions

of MOVES.

3.3 Tank Vapor Venting

It is important to understand TVV emissions and their various sources. As tank temperature rises

and vapor is generated within the tank, it is consequently driven from the fuel system due to

increased pressure. Most modern vehicles are equipped with some kind of control strategy, such

as a carbon canister, to try and capture these vapors as they are generated. Later, the vapors are

consumed as they purge to the engine when the vehicle is operated next. However, the canister is

vented to the atmosphere to prevent unwanted pressure build-up within the fuel system allowing

emissions to “bleed” through the carbon, or even freely pass through a completely saturated

carbon bed. Problems with the evaporative control systems such as tampering, mal-maintenance,

and inadequate durability result in evaporative system failures and can also cause the unintended

release of vapors. The inclusion of these problems in the emission estimate and the use of

inspection and maintenance (I/M) programs to make repairs are handled through the cold soak

calculation.

Integral to the understanding of Tank Vapor Venting (TVV) is how to calculate Tank Vapor

Generated (TVG). This is a function of increase in fuel tank temperature, ethanol content,

altitude and RVP. MOVES uses the Wade-Reddy equation for vapor generation.

( )

*RVPB CT CT1 

x  eeAeTVG Equation 615

In Equation 6, T1 is the starting temperature and Tx is the temperature at hour x. Coefficients

A,B,C are required and represent the different altitude and ethanol effects. These coefficients are

shown below in Table 4.

Table 4 – TVG constants for Equation 6

Gasoline E10

Constant Sea Level Denver alt. Sea Level Denver alt.

A 0.00817 0.00518 0.00875 0.00665

B 0.2357 0.2649 0.2056 0.2228

C 0.0409 0.0461 0.0430 0.0474
12

The following explains how vapor venting rates are calculated for each operating mode. For

cold soak, MOVES first finds the amount of vapor generated in the tank as a function of fuel

tank temperature and RVP. Then, it determines how much of this vapor is released into the

atmosphere based on several criteria, such as model year and fill pipe pressure test result. The

temperatures will have been generated by the fuel tank temperature generator, and the RVP will

have been generated by the MOVES tank fuel generator16. This cannot apply for when vapor is

not generated (when fuel tank temperature is not increasing), such as during a hot soak, but is

released. For these situations, we have aggregated TVV rates after subtracting out permeation

and leaks from the test results. Also, due to the availability of test data for running loss and the

short length of trips, we determined TVV rates during operation the same way we did for hot

soak.

3.2.4 Cold Soak

Cold soak vapor emissions are occurring while a vehicle is not operating and therefore only

responding to changes in ambient temperature. These are also commonly referred to as “diurnal”

emissions. To calculate emissions during cold soak, we again use diurnal data from CRC

programs E-9 and E-41. First we need to filter the dataset so that each test meets the following

requirements:

 Vehicle has no vapor leaks

 Vehicle is “As received” (not a retest)

 We only include hours of increasing temperature (no TVG while temperature decreases)

 Pressure test result is pass, fail, or blank (no dashes, slashes, “I”, etc.)

1) For each diurnal test, fuel tank temperature is calculated at each hour using the fuel tank

temperature algorithm described in section 3.1.

2) We calculate the base permeation rate using the method described in 3.2.1. (Average of last

six hours of HC evaporative emissions). Then, using the temperature adjustment described in

section 3.2.2 we calculate the temperature adjusted permeation rate for each hour of diurnal.

3) Subtract the temperature adjusted permeation rate from the total HC for every hour. Because

the SHED can only measure total HC, it cannot distinguish permeation from TVV, so we

must make this correction.

4) Sum TVV from beginning of diurnal to each hour to get Cumulative TVV.

5) Using Equation 6, calculate TVG in grams per gallon of vapor space, from hour 1 to hour x.

where hour x is the last hour where temperature is increasing.

TVG is the amount of vapor generated in the tank. We establish a relationship between

Cumulative TVV and TVG for inputs into MOVES. This is done by constructing a quadratic

curve of CumTVV vs. TVG for each model year group, age group, and pressure test result.

The curve is set to have a zero-intercept (0,0) to ensure that at 0 TVG, there is no tank vapor

venting, an accurate physical assumption. Figure 1 below illustrates the phase-in of evaporative

enhanced vehicles over the model years 1996-1998. For instance, a given amount of vapor

generated (x-axis) a smaller amount of vapor is vented as the technology phases in. The curves

2 CumTVV 1  2TVGaTVGa Equation 7
13

used in Figure 1 use the combined passing and failing coefficients for the case of vehicles in the

6-7 age group. A complete set of coefficients for Equation 7 can be found in Appendix B. The

aggregate columns are the inputs used in the MOVES model for the I/M and non-I/M coefficient

cases in the cumTVVCoeffs table.

Figure 1 – MOVES Composite Vapor Generation Curves

Model Years 1996-1998

Curves were generated for model year groups 1971-1977 (ages 20+), 1978-1995 (ages 0-19) and

1996-2003 (ages 0-9). The curves are also broken out by pressure test result. In failing vehicles,

there is more vapor vented than in an otherwise equivalent passing vehicle with properly

functioning evaporative controls. Coefficients for remaining age and model year groups are

determined by extrapolation. The coefficients of variation (CVs) are calculated by dividing the

standard error of the sample (calculated by SPSS) by the mean, for each coefficient in the

quadratic equation.

6) Failure frequencies (F) are determined from pressure, gas cap, and OBD test results from the

Phoenix I/M program (See section 3.4 Inspection/Maintenance (I/M) Program effects) This

allows calculation of aggregate coefficients that properly weight the pass and failing vehicles

in the fleet. They are calculated in equation 8.

Equation 8 is repeated with the coefficients for each model year and age group stratification,

to create the curve that accurately represents a given fleet’s pass/fail ratio.

)1(

, , , FaFaa aggx failx passx  Equation 8
14

7) Since the aggregate coefficients are determined using the failure rates, which are essentially

weighting factors, the standard errors of the aggregate coefficients are calculated:

2

,

2 2

,

2

,

, , ,

)1( ay aggx ay failx ay passx sFs  sF Equation 9

As a result, the CV’s for the aggregate coefficients are calculated:

2 2

,

2 2 2

,

2

,

, , ,

)1(

1

aggx afailx failx apassx passx

aggx

a CVaF CVaF

a

CV   Equation 10

Error! Reference source not found.Appendix B shows a selection of the coefficients resulting

from the analysis. Ratios between age groups are used to extrapolate for the 10-14 age group in

the 1971-1977 model year groups, and older age groups where data did not exist are assumed to

have the same coefficients as their preceding age groups. The passing coefficients for the 2004

and later model year group were reduced by 32% from the 1999-2003 model year group, which

reflects a reduction in the evaporative emissions standard from enhanced-evap to Tier 2/LEV II.

Separate model year groups are created for 1996 through 1998 due to the phasing of enhanced

evaporative standards. These three groups are only different weightings of the 1978-1995 and

1999-2003 model year groups based on the 20/40/90% phase-in for 1996/1997/1998. Similarly,

though not shown, is a table developed for non-I/M vehicles using non-I/M failure frequencies

calculated from the Phoenix I/M data set. Figure 2 shows an example of the difference between

I/M areas and non-I/M areas for model year 1998 (6-7) using Equation 7 and the coefficients

shown in Appendix B.

Figure 2 - MOVES Vapor Generation Curves

Model Year 1998
15

3.2.5 Hot Soak

Hot soak vapor emissions refer to the vapor vented immediately after a car ceases operation and

begins to cool; until it reaches the ambient temperature. In MOVES, the TVV apportioned to Hot

Soak is a simpler process than the Cold Soak calculations. Base rates in grams per hour are used

for each model year and age group. Pass and fail results are weighted together to form the

aggregate rate, similarly to Cold Soak. The process for developing the rates is described below:

Data is used from CRC E-41 Late Model In-Use Evap. Emission Hot Soak Study. This study

included 50 vehicles (30 passenger cars and 20 light duty trucks) ranging from model year 1992

to 1997. The driving schedule is a full LA-4, NYCC, NYCC, and LA-4 with a two minute idle

period following the first LA-4, the second NYCC and the final LA-4.

The data must first be filtered by the following criteria:

a. Vehicles are Non-leakers (emissions less than 10.0 grams17; taken from

M6.EVP.009_2.4; Since hot soak emissions are measured after one hour, the total

emissions is “equal” to its g/hr rate)

b. Vehicles are “As received” (no retests)

c. Vehicle pressure test result must be pass, fail, or blank only (no dashes, slashes, “I”,

etc.)

1) First, we find the temperature at the start of the soak for each hot soak test. This is done by

adding the calculated temperature increase experienced during an LA-4 running loss test

cycle (1372 seconds), since the vehicle is put through this test before entering the soak

chamber. The temperature rise depends on the fuel tank temperature at the start of the LA-4

test. To calculate the temperature Tstart, see section 3.1.3 Calculating fuel tank temperatures

during operation. Then we find the average tank temperature in that hour:

This is derived from the average value of a function over an interval (in this case, between 0

and 1 hour after the start of the hot soak). As stated in section 3.1.2, k = 1.4 hrs-1.

2) Similarly to the Cold Soak calculations, permeation HC must be subtracted from the SHED

measurement during the Hot Soak period so that we do not wrongly allocate the measured

HC. The average temperature calculated in Step 2 is used to correct the 72°F base permeation

rate, which is then subtracted from HC for each hour to get the TVV rate.

TVV rates are averaged by model year group, age group, and pressure test results, shown in

the table below.

air

k

avg start air TeTT

k

T 



( )1)(

1

Equation 11
16

Table 5 - Average hot soak tank vapor venting rates

Model year

group

Age

group

Pressure test

result

TVV

rate

(g/hr)

Number

of Cases

1971-1977 20+ F 6.17 5

20+ P 2 4

1978-1995

0-5 Unknown 1.25 5589

0-5 P 0.56 901

0-9 F 2.37 170

6-9 Unknown 1.75 202

6-9 P 1.38 255

10-14 Unknown 5.13 2

10-14 F 3.41 31

10-14 P 1.76 64

15-19 F 4.51 5

15-19 P 2.99 14

1996-2003 all Unknown 0.1073 83

3) As with cold soak, aggregate rates are found using failure rates involving pressure, gas cap,

and OBD tests for non-I/M and I/M. Table 6 reflects the most updated I/M analysis explained

in section 3.4 Inspection/Maintenance (I/M) Program effects (unlike the cold soak

coefficients in Table 5) or the enhanced evaporative phase-in.
17

Table 6 - Hot soak tank vapor venting rates

Model year

group

Age

group

Non-I/M

TVV rate

[g/hr]

I/M

TVV rate

[g/hr]

Pre-1971 20+ 5.455 5.116

1971-1977 10-14 3.099 2.957

15-19 5.149 4.881

20+ 5.455 5.116

1978-1995

0-3 0.627 0.612

4-5 0.627 0.612

6-7 1.451 1.43

8-9 1.471 1.455

10-14 2.082 1.963

15-19 3.492 3.225

20+ 3.817 3.49

1996-2003

0-3 0.124 0.099

4-5 0.124 0.1

6-7 0.15 0.1

8-9 0.168 0.103

10-14 0.25 0.113

15-19 0.383 0.137

20+ 0.611 0.198

2004 and later

0-3 0.06 0.035

4-5 0.06 0.036

6-7 0.086 0.036

8-9 0.105 0.039

10-14 0.187 0.05

15-19 0.323 0.074

20+ 0.553 0.137

3.3.3 Running Loss

Running Loss is the process of vapor venting that occurs during vehicle operation. Data for

developing running loss emission rates came from CRC E-352,3 and CRC E-414,5. Between these

two programs 200 vehicles were testing with model years ranging from 1971-1997.

1) For each vehicle, we calculated fuel tank temperature at the end of the running loss test using

the fuel tank temperature algorithm (see section 3.1.2). The running loss test performed in E41 was the typical 4375-second LA-4 – NYCC – NYCC – LA-4 sequence, with two minute

idle periods following the first LA-4, the second NYCC, and the final LA-4.

2) We found the average temperature during the test by assuming a linear increase in

temperature during the test. Thus, the average was calculated by averaging the start

temperature of the test and the final temperature of the test found in step 1.

3) We used this average temperature to determine the average permeation rate during the hot

soak via the permeation temperature adjustment using the 72°F base permeation rates

determine by model year, age.
18

4) We calculated gram/hour rates by dividing total emissions by the duration of the running loss

test (4300 seconds)

5) We filtered/reduced the data set such that each test met the following requirements:

a. Non-liquid-leakers (emissions less than 137.2 g/hour17; taken from M6.EVP.009,

Section 2.4, Table 2-1)

b. “As received” vehicles (no retests)

c. Pressure test result must be pass, fail, or blank only (no dashes, slashes, “I”, etc.)

6) Subtract permeation from HC for each hour to get tank vapor venting (TVV) rate

7) After analysis of TVV data, we found that the best way to stratify running loss TVV was by

model year only. The table below shows the results of the analysis.

Table 7 - Final average running loss tank vapor venting emission rates

Model year

group

TVV mean

[g/hr]

Pre-1971 12.59

1971-1977 12.59

1978-1995 11.6

1996-2003 0.72

2004 and later 0.234

8) Since model year group is the only stratification available in the data, the running loss TVV

rates for I/M and non-I/M rates are the same.

3.4 Inspection/Maintenance (I/M) Program effects

Our assumption in MOVES is that tank vapor venting is the only evaporative process where the

benefits of I/M are realized. The types of evaporative tests performed in I/M programs (gas cap

test, fill pipe pressure test, OBD scans) do not affect permeation or liquid leaks.

In order to develop I/M and non-I/M tank vapor venting rates, we used available data from I/M

programs to determine the failure frequencies of evaporative control systems. These frequencies

were then used to combine the rates for failing vehicles and those for passing vehicles. Details of

each of the four programs in our dataset are in the table below.

Table 8- Description of evaporative characteristics of available I/M programs 18

Gas cap

test OBD Pressuretest Frequency Network Calendar years

Colorado Y Advisory only N Biennial Hybrid 2003-2006

N. Carolina N Y N Annual Decentralized 2002-2006

Phoenix Y Y Y Biennial Centralized 2002-2006

Tucson Y Y N Annual Centralized 2002-2006
19

Since the Phoenix program contained the most extensive amount of data, we used it to develop

the reference I/M evaporative failure frequency. The Tucson, Colorado, and North Carolina data

were used to adjust the Phoenix numbers for differences in I/M programs.

The Phoenix evaporative I/M program used gas cap tests on all vehicles, OBD scans on OBDequipped vehicles, and fill pipe pressure tests on pre-OBD vehicles. The OBD codes used to

determine evaporative failures were P0440, P0442, P0445, P0446, and P0447 for all vehicle

makes and additionally P1456 and P1457 for Honda and Acura vehicles. Vehicles that had one

or more of these faults were flagged as failing vehicles, analogous to pre-OBD vehicles that

failed the pressure test. Very few vehicles failed both the gas cap test and the pressure/OBD test.

Therefore, our total number of failures was the sum of gas cap and pressure/OBD failures.

To determine failure frequencies for I/M areas, from the Phoenix data, we looked at the initial

and final results for each vehicle in a given I/M cycle. For passing vehicles, the initial test and

the final tests are one and the same. We averaged the initial and final failure frequencies

(weighted equally) to calculate an overall I/M failure frequency by model year group and age

group. Using the initial failure frequencies alone would neglect the effect of repair that most

failing vehicles would be required to undergo, and using the final failure frequencies alone

would neglect the existence of the failing vehicles driving around in the fleet in the first place.

To determine non-I/M failure frequencies, we restricted our sample in the Phoenix data to those

vehicles with license plates from states that do not have an I/M program anywhere. Figure 3

gives an example of how failure frequencies increase with age. Shown are frequencies for model

years 1978-1995, where data was extrapolated for the youngest age groups.

Figure 3 – Evaporative failure frequencies for I/M and non-I/M vehicles in the Phoenix

area showing model years 1978 to 1995.

The Tucson data was used to determine the effect of program frequency (annual vs. biennial).

For OBD vehicles, Tucson performs gas cap and OBD tests annually, while Phoenix performs

them biennially. Therefore, we were able to develop failure frequencies for annual programs by

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

0-3 4-5 6-7 8-9 10-14 15-19 20+

MOVES age group

Failure frequency

I/M vehicles

Non-I/M vehicles
20

analyzing the Tucson data. We applied the ratio between Tucson and Phoenix to determine the

failure frequencies for where we did not have data (e.g. pre-OBD vehicles).

The North Carolina data was used to determine non-I/M failure frequencies for OBD tests. In

North Carolina, expansion of I/M program has led to counties where many vehicles were tested

under the I/M program for the first time. Vehicles were flagged as non-I/M tests if they were

tested:

• before the official start of the I/M program,

• in a new I/M county and were registered in that same county, or

• in a new I/M county and were registered in a non-I/M county or a county that did not

start I/M within the last year.

We compared those failure frequencies to those for vehicles tested in older I/M areas, where

vehicles were previously tested. From the North Carolina data, the average ratio of non-I/M to

I/M OBD failure frequencies is 1.6. This ratio was then applied to the Phoenix OBD and

pressure test failure frequencies to determine non-I/M failure frequencies.

The Colorado data was used to determine non-I/M failure frequencies for gas cap tests. In

Colorado, the I/M data comes mostly from the Denver and Boulder metropolitan areas. Many

residents are new to this area, with many having moved in from non-I/M areas in Colorado or

non-I/M states. Vehicles were flagged as non-I/M tests if their registration state was a 100%

non-I/M state, or if the registration county was a non-I/M county in Colorado. We compared the

failure rates of the flagged vehicles to those of the full tested fleet. The ratio of these two

frequencies was then applied to the Phoenix gas cap failure frequencies to determine non-I/M

failure frequencies. Colorado OBD data was not used, since OBD in Colorado is only advisory,

and does not pass or fail a vehicle.

From the Colorado data, the average ratio of non-I/M to I/M gas cap failure frequencies is 2.2.

This ratio was then applied to the gas cap failure frequencies to determine non-I/M failure

frequencies.

The IM factor lets MOVES interpolate and extrapolate the non-I/M emission rates and the I/M

emission rates depending on the characteristics of the I/M program in each county. Our

reference program, Phoenix, was given an IM factor of 1. The non-I/M rates were given an IM

factor of 0. For each model year group and age group stratification, we used the failure

frequencies determined from the analysis described above to calculate IM factors for the diverse

types of evaporative I/M programs. Figure 4 illustrates how the I/M factor is influenced by the

types of evaporative tests conducted in I/M programs. We modeled the estimated failure

frequency linearly with the I/M factor, with Phoenix, our reference program, always receiving a

value of 1, and our non-I/M failure frequency always receiving a value of 0. Different programs

move along the line, as determined by the analysis from above, based on which evaporative tests

they choose to use. The figure is an example using model year group 1999-2003 and age group

4-5. For these vehicles, Tucson’s OBD and gas cap tests are annual, compared to Phoenix’s

biennial requirement, which gives Tucson a lower failure frequency and a higher I/M factor.

Colorado’s frequency is biennial, like Phoenix’s, but its OBD test is non-enforcing. As a result,

their data shows a higher failure frequency, which results in a lower I/M factor.
21

Figure 4 – Example of how we calculated the I/M adjustment factor. This figure applies

for model years 1999-2003 ages 4-5. The Phoenix and non-I/M results were used to

construct the line.

A table showing the resulting evaporative failure frequency values by age group for all model

years can be found in Appendix E.

3.5 Liquid Leaks

Liquid leaks are the final evaporative emissions process discussed in this document. Liquid leaks

include any non-vapor form of fuel escaping the fuel system. To calculate the average leaking

rate, we used the leaking vehicles excluded from the previous analysis for tank vapor venting.

We estimated permeation and tank vapor venting on these vehicles using the calculation methods

described in Section 3.2 Permeation and Section 3.3 Tank Vapor Venting. We assumed the

remainder of emissions to be caused by liquid leaks. We averaged these emissions by the three

different modes, shown in Table 9.

Table 9 – Emission rates [g/hr] for liquid leakers by mode.

Model year

group

Liquid leak

rate

Cold Soak 9.85

Hot Soak 19.0

Operating 178

The rates in Table 9 must be multiplied by the percentage of leakers in the fleet to get an average

liquid leaking emission rate. For this we relied on the studies by BAR and API. Our estimates

of the percentage of liquid leakers are shown in the table below. On average, we assume that

most leaks do not occur until vehicles are 15 years or older.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.50% 2.00% 2.50% 3.00% 3.50% 4.00%

Failure frequency [%]

I/M factor

Phoenix (reference I/M)

Colorado

Tucson

Non-I/M
22

Table 10 – Percentage of liquid leakers by age.

Age group Percentage of leakers in

fleet

0-9 0.09 %

10-14 0.25 %

15-19 0.77 %

20+ 2.38 %

Combining Table 9 and Table 10, we get Table 11, which shows the liquid leaking rate of the

entire fleet. We assume that this rate does not change with model year nor is it affected by I/M.

Table 11 – Final liquid leak rates in g/hr by age group and mode

Age group Cold soak Hot soak Operating

0-9 0.009 0.017 0.158

10-14 0.025 0.048 0.450

15-19 0.075 0.145 1.36

20+ 0.235 0.452 4.23

3.6 Refueling

Refueling emissions are the fuel vapors pushed out of the fuel tank when liquid fuel is added to

the tank. The calculation of vapor losses includes any liquid fuel that is spilled during refueling

and evaporates. Refueling emissions are determined on the basis of the total gallons of fuel

dispensed based on average daily vehicle miles traveled and the estimated fuel consumption

rates. Both the spillage and the vapor displacement associated with refueling events are in terms

of grams spilled per gallon of fuel dispensed. Diesel fueled vehicles are assumed to have

negligible vapor displacement, but fuel spillage is used to calculate grams of refueling loss for

diesel vehicles.

Uncontrolled and unadjusted refueling emissions are the displaced grams per gallon of dispensed

fuel, plus a small amount of grams (0.31) per gallon for spillage. AP-42 Volume I Section

5.2.2.319 lists the spillage as 0.7 lb/1000 gallons, which is 0.31g/gallon of fuel dispensed. The

vapor displaced by refueling of gasoline fueled vehicles is calculated accounting for temperature

and gasoline volatility using the Reid Vapor Pressure (RVP):

DISPL = -5.909 - 0.0949* TDFDIF + 0.0884*DFTEMP + 0.485*RVP Equation 12

Where: DISPL = grams of displaced vapor (all non-methane).

DFTEMP = dispensed gasoline temperature in degrees Fahrenheit.

RVP = gasoline Reid Vapor Pressure in pounds per square inch (psi).

TDFDIF = tank gasoline temperature (0.418*DFTEMP-16.6).
23

Temperatures are limited to those between 20 degrees and 95 degrees Fahrenheit. The TDFDIF

value is not allowed to be greater than 20 degrees. For dispensed fuel temperature (DFTEMP)

and the difference in temperature of the fuel in the vehicle and that of the dispensed fuel

(TDFDIF), values that are outside the limits are set equal to the limits. The temperature limits

reflect the range of the underlying data. The equation that determines the difference in

temperature of the fuel in the vehicle and that of the dispensed fuel comes from a study done by

Amoco20. In that study, the difference in temperature of the fuel in the vehicle and that of the

dispensed fuel was never greater than 20 degrees.

Two additional factors affect the fuel lost during refueling. First, there exist programs designed

to capture refueling vapors at the pump, often referred to as "Stage 2" or "Stage II" vapor control

programs. Second, most modern vehicles have onboard refueling vapor recovery (ORVR)

systems on gasoline fueled vehicles that capture vapors released during refueling in the vehicle's

evaporative emissions canister.

The effectiveness of Stage 2 programs vary depending on the scope of the program, which

affects how much of the gasoline fuel dispensed is affected by the control technologies, the

technology employed to capture refueling emissions, the effectiveness of the technology in

capturing all of the refueling emissions and reducing spillage and the state of repair

(functionality) of the equipment. These factors will vary from area to area. MOVES uses two

factors, to make adjustments to the refueling losses to account for Stage 2 programs.

Definition: refuelingVaporProgramAdjustment

The refuelingVaporProgramAdjustment is a number between zero and one which indicates the

reduction in full refueling displacement vapor losses that result from state or local programs

(such as Stage 2 recovery programs).

Definition: refuelingSpillProgramAdjustment

The refuelingSpillProgramAdjustment is a number between zero and one which indicates the

reduction in full refueling spillage losses that result from state or local programs (such as Stage 2

recovery programs).

The program adjustments in MOVES are stored and applied on a county basis. Each county has

a separate value for vapor and spillage program adjustments. The program adjustment values for

each county in each calendar year are stored in the default MOVES database CountyYear table.

MOVES uses another factor to address the phase in for on-board refueling vapor recovery

(ORVR) systems on vehicles. MOVES applies a 98 percent reduction in refueling vapor losses

and 50 percent reduction in refueling spillage losses from uncontrolled levels for ORVR

equipped vehicles. The effects of ORVR technology is phased in over several model years

beginning in model year 1998.
24

Table 12 - Phase In of Onboard Refueling Vapor Recovery (ORVR) Systems

Model Year Passemger Cars

Light Trucks

<6,000 lbs

GVWR

Light Trucks

6,000-8,500 lbs

GVWR

Heavy Duty

Trucks

1998 40% 0% 0% 0%

1999 80% 0% 0% 0%

2000 100% 0% 0% 0%

2001 100% 40% 0% 0%

2002 100% 80% 0% 0%

2003 100% 100% 0% 0%

2004 100% 100% 40% 40%

2005 100% 100% 80% 80%

2006 and Newer 100% 100% 100% 100%

Definition: refuelingTechAdjustment

The refuelingTechAdjustment is a number between zero and one which indicates the reduction in full

refueling spillage losses that result from improvements in vehicle technology (such as the Onboard

Refueling Vapor Recovery rule). The technology adjustment is applied the same in all locations.

The technology adjustment values are stored in the default MOVES database

SourceTypeTechAdjustment table.

MOVES applies both the program adjustment and the technology adjustment to all model years. This

means that Stage 2 programs are assumed to affect vehicles not affected by the technology adjustment

(ORVR) and any refueling emissions that are not captured by the ORVR systems. MOVES does not

account for the interaction between ORVR systems and the vapors stored at gasoline dispensing stations

equipped with Stage 2 equipment.

The vapor losses (processid=18) and spillage losses (process=19) from refueling are reported by MOVES

as separate emission processes.
25

Appendix A - Notes on Evaporative Emission Data

Parameters: Vehicle Numbers, Test #, Ambient Temperature, RVP, Model Year, Fuel System,

Purge, Pressure, Canister, Gram HC, Retest

E-41 CRC Late Model In-Use Evap. Emission Hot Soak Study (1998)

 50 vehicles (30 passenger cars and 20 light duty trucks)

 Model years 1992 to 1997

 Average RVP: 6.5 psi

 Diurnal Temperature: 72 to 96°F

 Fuel System: Port Fuel Injection, Throttle Body Injection

 Vehicle fuel tank drained and refilled to 40% of capacity with Federal Evaporative

Emission Test Fuel

 Driving schedule will be a full LA-4-NYCC-NYCC-LA4 sequence, with two minute idle

periods following the first LA-4, the second NYCC, and the final LA-4.

 Hydrocarbon readings will be taken continuously throughout the running loss test.

 Cumulative mass emissions will be reported at one minute intervals.

 Ambient Temperature in running loss enclosure: 95°F

E-9 CRC Real Time Diurnal Study (1996)

 151 vehicles (51 vehicles MY 1971-1977, 50 vehicles MY 1980-1985, 50 vehicles MY

1986-1991)

 Odometers range from 39,000 to 439,000 miles

 Fuel tank volume was 15% of the rated capacity

 RVP: 6.62 psi (average sum of 47 vehicles)

 Diurnal temperature: 72 to 96°F

 Fuel System: Port Fuel Injection, Carburetor, Throttle Body Injection

CRC E-35 Running Loss Study (1997)

 150 vehicles (50 vehicles MY 1971-1977, 50 vehicles MY 1980-1985, 50 vehicles MY

1986-1991)

 Ambient Temperature in running loss enclosure: 95°F

 RVP: 6.8 psi

 Fuel System: Port Fuel Injection, Carburetor, Throttle Body Injection

EPA Compliance Data

 2-Day Test

 Length of the hot soak: 1 hour

 77 vehicles

 RVP: average 8.81 psi

 Ambient Temperature:

 Federal Standard (72 to 96°F) Diurnal

 Cal. (65 to 105°F) Diurnal

 Hot Soak: 81.67°F
26

 Fuel System: Port Fuel Injection

Unleaded Cert Fuel CARB Phase II Fuel

MSOD (Mobile Source Observation Database):

Hot Soak: 1 hour hot soak evaporative test

FTP: Federal test procedure (19.53 mph), also referred to as the UDDP schedule

NYCC: New York City Cycle Test (7.04 mph)

BL_1A: 1 hour Breathing Loss Evap. Test – Gas Cap left “On”

BL_1B: 1 hour Breathing Loss Evap. Test – Canister as recd.

ST01: Engine Start cycle test

4HD: 4 hour Diurnal test

24RTD: 24 Hour Real Time Diurnal

33RTD: 33 Hour Real Time Diurnal

72RTD: 72 Hour Real Time Diurnal

3Rest: 3 Hour Resting Loss Evap. Emission Test (follows 1 HR Hot Soak)

CY6084: Real time diurnal temperature pattern: range 60 to 84 F

CY7296: Real time diurnal temperature pattern: range 72 to 96 F

CY8210: Real time diurnal temperature pattern: range 82 to 102 F

DIURBL: Standard temperature rise for 1 hour diurnal or breathing loss evaporative

emission test

F505: Bag 1 of federal test procedure (25.55 mph)

ASM: Acceleration Simulation Mode Test Procedure

ATD: Ambient Temperature diurnal evaporative Test, shed temp constant, vehicle begins

24 degree cooler

S u lf u r R V P D a te

w t %

0 .0 0 4 8 9 .0 4 J u l- 9 8

0 .0 0 4 5 9 .2 D e c - 9 8

0 .0 0 6 3 9 .0 4 A u g - 9 9

0 .0 0 4 8 8 .9 9 M a y - 0 0

0 .0 0 4 2 9 .0 5 S e p - 0 1

0 .0 0 3 9 .1 2 D e c - 0 1

0 .0 0 3 9 .1 2 D e c - 0 2

0 .0 0 3 1 8 .8 M a y - 0 3

0 .0 0 3 5 8 .9 1 A p r - 0 4

0 .0 0 2 7 8 .9 5 J u n - 0 4

Sulfur RVP Date

wt %

0.0023 6.92 Aug-99

0.0023 6.92 May-00

0.0038 6.92 Jan-01

0.0033 6.92 Oct-02

0.0036 6.77 Mar-04
27

Appendix B - CumTVVCoeffs Table

Cumulative Tank Vapor Vented Coefficients

(Equation 7)

a1

(TermB)

a1

(TermB)

a2

(TermC)

a2

(TermC) Non-I/M Case I/M Case

model year

group

age

group pass fail pass fail tvvtermb tvvtermc tvvtermbim tvvtermcim

1960-1970 20+ 5.406 9.254 2.331 3.117 6.59 2.573 6.127 2.479

1971-1977 10-14 1.227 11.314 2.175 0.402 2.457 1.959 1.941 2.049

1971-1977 15-19 5.406 9.254 2.331 3.117 6.093 2.472 5.835 2.419

1971-1977 20+ 5.406 9.254 2.331 3.117 6.59 2.573 6.127 2.479

1978-1995 0-3 1.578 3.073 0.44 1.338 1.599 0.452 1.589 0.446

1978-1995 4-5 1.578 3.073 0.44 1.338 1.631 0.471 1.604 0.455

1978-1995 6-7 1.578 3.073 0.44 1.338 1.642 0.478 1.61 0.459

1978-1995 8-9 1.578 3.073 0.44 1.338 1.666 0.492 1.623 0.466

1978-1995 10-14 0.849 11.314 2.095 0.402 1.692 1.959 1.283 2.025

1978-1995 15-19 3.743 9.254 2.246 3.117 4.458 2.359 4.12 2.305

1978-1995 20+ 3.743 9.254 2.246 3.117 4.955 2.438 4.376 2.346

1996 0-3 1.339 3.073 0.344 1.338 1.369 0.36 1.354 0.352

1996 4-5 1.339 3.073 0.344 1.338 1.401 0.368 1.362 0.357

1996 6-7 1.339 3.073 0.344 1.338 1.419 0.385 1.376 0.365

1996 8-9 1.339 3.073 0.344 1.338 1.447 0.403 1.392 0.374

1996 10-14 0.756 9.666 1.668 0.589 1.477 1.582 1.124 1.624

1996 15-19 3.071 8.017 1.789 2.762 3.707 1.911 3.399 1.853

1996 20+ 3.071 8.017 1.789 2.762 4.122 1.958 3.53 1.879

1997 0-3 1.1 3.073 0.248 1.338 1.14 0.268 1.12 0.259

1997 4-5 1.1 3.073 0.248 1.338 1.171 0.278 1.129 0.264

1997 6-7 1.1 3.073 0.248 1.338 1.196 0.297 1.146 0.273

1997 8-9 1.1 3.073 0.248 1.338 1.228 0.316 1.163 0.283

1997 10-14 0.663 8.018 1.241 0.776 1.263 1.203 0.976 1.222

1997 15-19 2.399 6.781 1.332 2.406 2.957 1.465 2.686 1.402

1997 20+ 2.399 6.781 1.332 2.406 3.29 1.512 2.791 1.428

1998 0-3 0.502 3.073 0.009 1.338 0.567 0.042 0.538 0.027

1998 4-5 0.502 3.073 0.009 1.338 0.596 0.055 0.553 0.035

1998 6-7 0.502 3.073 0.009 1.338 0.639 0.078 0.575 0.046

1998 8-9 0.502 3.073 0.009 1.338 0.681 0.1 0.596 0.057

1998 10-14 0.429 3.897 0.174 1.244 0.727 0.267 0.589 0.223

1998 15-19 0.719 3.691 0.189 1.516 1.081 0.35 0.907 0.273

1998 20+ 0.719 3.691 0.189 1.516 1.207 0.394 0.959 0.296

1999-2003 0-3 0.383 3.073 -0.039 1.338 0.453 -0.003 0.422 -0.019

1999-2003 4-5 0.383 3.073 -0.039 1.338 0.481 0.011 0.438 -0.011

1999-2003 6-7 0.383 3.073 -0.039 1.338 0.528 0.035 0.461 0.001

1999-2003 8-9 0.383 3.073 -0.039 1.338 0.572 0.057 0.483 0.012

1999-2003 10-14 0.383 3.073 -0.039 1.338 0.619 0.082 0.508 0.025

1999-2003 15-19 0.383 3.073 -0.039 1.338 0.706 0.126 0.552 0.048

1999-2003 20+ 0.383 3.073 -0.039 1.338 0.791 0.17 0.595 0.07

2004 & later 0-3 0.124 3.073 -0.013 1.338 0.17 0.008 0.151 -0.001
28

Cumulative Tank Vapor Vented Coefficients

(Equation 7)

a1

(TermB)

a1

(TermB)

a2

(TermC)

a2

(TermC) Non-I/M Case I/M Case

model year

group

age

group pass fail pass fail tvvtermb tvvtermc tvvtermbim tvvtermcim

2004 & later 4-5 0.124 3.073 -0.013 1.338 0.189 0.017 0.161 0.004

2004 & later 6-7 0.124 3.073 -0.013 1.338 0.215 0.029 0.175 0.01

2004 & later 8-9 0.124 3.073 -0.013 1.338 0.24 0.04 0.187 0.016

2004 & later 10-14 0.124 3.073 -0.013 1.338 0.269 0.053 0.203 0.023

2004 & later 15-19 0.124 3.073 -0.013 1.338 0.319 0.077 0.229 0.035

2004 & later 20+ 0.124 3.073 -0.013 1.338 0.368 0.099 0.255 0.047
29

Appendix C - MOVES Operating Modes and Emission Processes

opModeID Operating mode description

150 Hot Soaking

151 Cold Soaking

300 Engine Operation

processID Emission process description

11 Evap permeation

12 Evap vapor venting losses

13 Evap liquid leaks

18 Refueling displacement vapor losses

19 Refueling fuel spillage

Appendix D - Evaporative Pollutants

pollutantID pollutantName NEIPollutantCode shortName

1 Total FID Hydrocarbons HC THC

20 Benzene 71432 Benzene

21 Ethanol ETOH

22 Methyl tert-butyl ether 1634044 MTBE

40 2,2,4-Trimethylpentane 540841 2,2,4-Trimethylpentane

41 Ethyl Benzene 218019 Ethyl Benzene

42 Hexane 206440 Hexane

45 Toluene 85018 Toluene

46 Xylene 123386 Xylene

79 Non-Methane Hydrocarbons NMHC NMHC

80 Non-Methane Organic Gases

NMOG NMOG

86 Total Organic Gases TOG TOG

87 Volatile Organic Compounds VOC VOC

185 Naphthalene gas 91203 Naphthalene Gas
30

Appendix E – Evaporative Failure Frequency

Non-I/M Evaporative Failure Frequency

Age Group 1960-1977 1978-1997 1998-2003 2004 and Later

0-3 0.026 0.026 0.016

4-5 0.035 0.035 0.022

6-7 0.043 0.043 0.031

8-9 0.059 0.059 0.039

10-14 0.122 0.081 0.081 0.049

15-19 0.179 0.130 0.120 0.066

20+ 0.308 0.220 0.152 0.083

Base I/M Evaporative Failure Frequency

Age Group 1960-1977 1978-1997 1998-2003 2004 and Later

0-3 0.014 0.014 0.009

4-5 0.017 0.017 0.013

6-7 0.021 0.021 0.017

8-9 0.030 0.030 0.021

10-14 0.071 0.041 0.041 0.027

15-19 0.111 0.068 0.063 0.036

20+ 0.187 0.115 0.079 0.044
31

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