PLAN 2040 Conformity Determination Report: Exhibit 1 1

PLAN 2040 Conformity Determination Report

EXHIBIT 1A

Interagency Review of Planning Assumptions

Used in Regional Emissions Analysis

For Atlanta Eight-Hour Ozone Nonattainment Area

Interagency Consultation Meeting

Atlanta Regional Commission

The ARC will be conducting a conformity analysis under the eight-hour ozone standard as part of the 

conformity determination for the PLAN 2040 RTP / FY 2012-2017 TIP for the 20 county nonattainment 

area. 

Below is a detailed listing of the procedures and planning assumptions for the upcoming conformity 

analysis of the PLAN 2040 RTP. 
PLAN 2040 Conformity Determination Report: Exhibit 1 2

Section 1: General Methods and Assumptions 

1) Modeling Methodology: Estimate link-level VMT and congested flow speeds using ARC 20-county 

travel demand model that corresponds to the 20-county eight-hour ozone nonattainment area

2) Conformity Test

a) Nonattainment Classification - Moderate

b) Motor Vehicle Emission Budget (MVEB) Test1

i. NOx: 306.75 tpd

ii. VOC: 172.27 tpd

3) Conformity Analysis Years: 2016, 2020, 2030, 2040

4) Modeling Start Date: March 2011. This start date is defined by the ARC as the initiation of the first 

model run for the Plan 2040 RTP, begun when all datasets needed for the model run were 

completed.

5) Interagency Consensus on Planning Assumptions: January 25, 2011.

 

Section 2: Travel Demand Modeling Assumptions

1) Calibration Year: 2000 (with some 2005 interim validations and benchmarking thereafter)

2) Project Listing: Project listings will be provided in electronic format to Interagency Consultation 

Group for review in the first quarter of 2011.

a) Regionally Significant and Federally Funded

b) Regionally Significant and Non-Federally Funded

3) Demographic Data: Provided as separate attachment

4) Speed Data: Free-flow Speed by Area Type and Facility Type2

 

1 MVEB established as part of Atlanta Early Progress State Implementation Plan for year 2006. Federal Register 

notice of adequacy published April 9, 2007 (72 FR 17550), with an effective date of April 24, 2007. 

2 Within the ARC travel demand and emission modeling process, free flow speeds are adjusted to reflect the 

increase in delay and travel time on a roadway segment as traffic volumes build and congestion levels increase. 

Link-level congested flow speeds are used to estimate NOx and VOC emissions as required by Sections 

93.122(b)(i)(iv) and 93.122(b)(2) of the Transportation Conformity Rule.
PLAN 2040 Conformity Determination Report: Exhibit 1 3

 Area Type

Facility Type

Urban Very 

High 

Density

Urban High 

Density

Urban 

Medium 

Density

Urban 

Low 

Density

Suburban Exurban Rural

Metered 

Ramps

0

Zone Centroid 

Connectors

7 11 11 11 11 14 14

1

Interstate / Freeway 

Free Flow

55 58 58 61 61 63 65

2 Parkway 50 50 55 55 57 60 60

3 HOV Buffer Separated 55 58 58 61 61 63 65

4 HOV Barrier Separated 55 58 58 61 61 63 65

5

High Speed Ramp / CD 

Road

50 50 55 55 57 60 60 15

6 Medium Speed Ramp 50 50 50 50 50 50 50 10

7 Low Speed Ramp 40 40 40 40 40 40 40 10

8 Loop Ramp 30 30 30 30 30 30 30 10

9 Off Ramp w/ Intersection 25 25 25 25 25 25 25

10 On Ramp w/ Intersection 40 40 40 40 40 40 40 5

11 Expressway 40 42 45 48 52 55 60

12 Principal Arterial - Class I 26 30 33 36 42 46 55

13 Principal Arterial - Class II 24 27 30 34 40 44 48

14 Minor Arterial - Class I 22 25 28 31 38 42 45

15 Minor Arterial - Class II 20 23 26 29 34 38 42

16 HOV - Arterial (all classes) 20 27 30 33 36 39 42

17 Major Collector 18 22 25 28 31 34 38

18 Minor Collector 15 18 21 24 27 30 35

19

Planned Ramps w/ 

Intersections

30 30 30 30 30 30 30 5

20

Planned Directional 

Ramps

45 45 45 45 45 45 45 10

5) Transit Modeling

a) Model recalibrated to 2000 transit ridership estimates, provided by transit operators

b) Reflects results from the 2001-2002 Transit On Board Survey, with preliminary adjustments from 

2009 Transit On Board Survey

c) Routes updated to reflect current operating plans
PLAN 2040 Conformity Determination Report: Exhibit 1 4

d) Transit mode split is estimated using the mode choice model 

 i) Estimates individual modal trips from the person trip movements developed in the trip 

distribution model. 

 ii) Composed of three nested logit models: 

(1) Home based work trips, which includes home based university trips; 

(2) Home based other trips, which include home based other, home based shopping and 

home based grade school; and 

(3) Non-home based trips. 

 iii) The mode choice model is organized in terms of seven characteristics: 

(1) Mathematical structure; 

(2) Trip purposes and choice sets;

(3) Limitations on choice sets;

(4) Analysis of transit access;

(5) Treatment of HOV lanes;

(6) Stratification by income groups; and

(7) Analysis of alternative transit paths. 

e) Transit Fare Modeling

i) Fare structure and operating plans supplied by the local transit operators

(1) Fares remain constant over time, across all network years

(2) Fares reflect current transit operating plans 

ii) Transit fare structure uses a fare matrix on a zone to zone level with a universal fare structure 

(flat fare) for all bus and rail lines

(1) Changes to the existing fare structure and service frequency are coded directly into the 

model 

(2) Current fare values in the model are weighted according to the percentage of riders 

using a discounted fare pass; changes to these assumptions can be incorporated directly 

into the model 

(3) Peak and off-peak fares are equivalent

f) 2009 Transit On Board Survey interim adjustments

i) Update of regional transit travel targets based on a preliminary expansion of the raw on-board 

survey data

(1) Modifications to express bus and BRT transfer constants

(2) Modifications to travel demand model estimates of zero-car transit work trips

(3) Modifications to travel demand model estimates of kiss-and-ride passenger access and 

use of transit system

(4) Overall evaluation of all modal constants

(5) Refinement to park-and-ride lot assumptions

(6) Updated walk connector and percent walk procedures

ii) Modified transit skimming procedures

iii) Re-calibrated air passenger model

iv) Assessment of travel demand model understanding of market segments and travel patterns 

relative to the on-board survey records
PLAN 2040 Conformity Determination Report: Exhibit 1 5

Section 3: Emissions Modeling Assumptions 

1) Emissions Factor Model: MOBILE6.2.03

2) Eight Hour Ozone Standard MOBILE6.2.03 Inputs (13-county portion)3

a) Average hourly temperature and relative humidity and average daily barometric pressure for 

the 10 highest ozone days, 2000 – 2002

b) Stage II refueling

i) Started in 1992

ii) Three phase in years

iii) 81% efficiency

c) Anti-tampering program

i) Started in 1982

ii) Covers model years 1975 – 1995

iii) All LDG vehicle types are covered

iv) Annual program

v) 97% compliance

vi) Catalyst removal only

d) I/M Program

i) Exhaust and Evaporative (OBD and gas cap pressure test) for 1996 and newer vehicles

(1) Began in 1982

(2) Annual inspection required

(3) Computerized test and repair OBD – Exhaust

(4) Computerized test and repair OBD & GC - Evaporative

(5) Applies to all LDG vehicle types

(6) Three year grace period

(7) 3% waiver rate for all vehicles – Exhaust test

(8) 0% waiver rate for all vehicles – Evaporative test

(9) 97% compliance

ii) Exhaust and Evaporative test for 1975 – 1995 vehicles

(1) Began in 1982

(2) Annual inspection required

(3) Computerized test and repair ASM 2525/5015 Phase-in – Exhaust

(4) Computerized test and repair GC – Evaporative

(5) Applies to all LDG vehicle types

(6) 3% waiver rate for all vehicles – Exhaust

(7) 0% waiver rate for all vehicles – Evaporative

(8) 97% compliance

(9) 25 year and older model years are exempt

e) Fuel - Phase 2 Low Sulfur, Low RVP Georgia Gasoline4

 

3

For the eight-hour ozone standard there are two sets of MOBILE6 input files, one for the 13 counties that make 

up the former one-hour ozone nonattainment area in which a specific set of emission control measures is in place 

and one for the seven “ring” counties. For each set, the input files contain the same assumptions for all analysis 

years (2010, 2020, and 2030).

4

In 2002, Georgia's two-phase gasoline sulfur control program limited average sulfur in gasoline sold in the 13-

county Atlanta area and in 12 surrounding counties to 150 parts per million (ppm). In addition, there was a 
PLAN 2040 Conformity Determination Report: Exhibit 1 6

i) 100% market share of 10% ethanol-blend gasoline (E10) assumed

ii) volatility waiver for E10 allows 1.0 psi RVP increase

f) 2002 regional fleet age distribution

i) Derived from R.L. Polk & Co. registration data for 13-county area

ii) Applied to 15 of the 16 MOBILE6.2.03 composite vehicle classifications – LDV, LDT1, LDT2, 

LDT3, LDT4, HDV2B, HDV3, HDV4, HDV5, HDV6, HDV7, HDV8, HDBS, HDBT, MC

(1) Default for HDV8B

(2) Default VMT fractions

3) Eight Hour Ozone Standard MOBILE6.2.03 Inputs (7-county portion)

a) Average hourly temperature and relative humidity and average daily barometric pressure for 

the 10 highest ozone days, 2000 – 2002

b) No Stage II refueling

c) No anti-tampering program

d) No I/M program

e) Fuel - Phase 2 Low Sulfur, Low RVP Georgia Gasoline

i) 100% market share of 10% ethanol-blend gasoline (E10) assumed

ii) volatility waiver for E10 allows 1.0 psi RVP increase

f) 2002 regional fleet age distribution

i) Derived from R.L. Polk & Co. registration data for 7 county area

ii) Applied to 15 of the 16 MOBILE6.2.03 composite vehicle classifications – LDV, LDT1, LDT2, 

LDT3, LDT4, HDV2B, HDV3, HDV4, HDV5, HDV6, HDV7, HDV8, HDBS, HDBT, MC

(1) Default for HDV8B

(2) Default VMT fractions

 

4) VMT adjustment factors 

a) Calculated for year 2000 

b) HPMS adjustment in base year of calibration in accordance with Section 93.122(b)(3) of the 

Transportation Conformity Rule which recommends that HPMS adjustment factors be 

developed to reconcile travel model estimates of VMT in base year of validation to HPMS 

estimates for the same period

c) Summer (seasonal) adjustment to convert from average annual VMT to summer-season VMT5

d) Factors applied to VMT estimates generated by ARC travel demand model for 13-county portion 

and 7-county portion of 20-county modeling domain, separately.

VMT Adjustment Factors

Functional Class Name Factor for 13 

County Area

Factor for 7 

County Area

Rural Interstate 0.67 0.89

Rural Principal Arterial 1.02 0.99

 

seasonal (June 1 to September 15) 7.0 pounds per square inch (psi) Reid vapor pressure cap on gasoline sold in this 

Phase 1 area. In 2003, Phase 2 of Georgia's gasoline rule reduced average sulfur to 30 ppm year-round and added 

20 additional counties to the sulfur and RVP control program. 

5

Procedures for Emission Inventory Preparation, Volume IV: Mobile Sources, Section 3.4.2.6, EPA420-R-92-009, 

USEPA Office of Air and Radiation, Office of Mobile Sources, 1992.
PLAN 2040 Conformity Determination Report: Exhibit 1 7

Rural Min. Arterial 1.16 0.98

Rural Major Collector 0.88 1.81

Rural Minor Collector 1.07 1.81

Rural Local 0.64 1.10

Urban Interstate 1.05 0.86

Urban, Other Freeway 2.44 0.85

Urban Principal Arterial 0.67 0.97

Urban Minor Arterial 1.21 0.96

Urbanized Collector 1.21 1.80

Urbanized Local 0.95 1.06

5) Off-Model Calculations

a) Senior I/M Exemption (emissions debit)

i) The Senior I/M Exemption calculated for year 2002 is conservatively high and will be added 

to the regional emission inventories for each analysis year.

6) TCMs

a) No additional credit is taken in the emissions modeling process for SIP TCMs

b) Listed below is a TCM status report

Description ARC Project # GDOT PI # TIP Status

HOV LANES

Sponsor – GDOT

I-85N from Chamblee-Tucker Rd to SR 316 

(HOT Lanes),

I-85 @ SR 316, Interchange Reconstruction

AR 073B 713760 98-00,

99-01

Under 

construction*

GW-AR 053A

GW-AR 053B

110530 01-03

02-04

03-05

05-10

Implemented 

Implemented

ATLANTIC STATION, 17th STREET BRIDGE

Sponsor – City of Atlanta

A – Bridge and Southbound off ramps

C – Northside Dr over Norfolk Southern 

Railroad to Atlantic Station

D – Northbound off ramp to 17th Street Bridge, 

Williams St Relocation

AT-AR 224A

AT-AR 224C

AT-AR 224D

714190

0001297

0001298

00-02

01-03

02-04

03-05

05-10

A – Implemented

C – Implemented

D – Implemented

CLEAN FUEL BUSES

Sponsors – MARTA and CCT

M-AR 232 N/A 94-95 Implemented

EXPRESS BUS ROUTES

Sponsor – MARTA

M-R 160

M-R 162

770632

770632

94-96 Implemented

IMPROVE / EXPAND BUS SERVICE 

Sponsor – MARTA

M-R 161 770633 96-98 Implemented

INTERSECTION UPGRADE, COORDINATION & 

COMPUTERIZATION

Sponsor(s) – GDOT in partnership with local 

AT 089 04Y108 93-95 Implemented

CL 094 770600 94-96 Implemented

CO 249 770601 94-96 Implemented
PLAN 2040 Conformity Determination Report: Exhibit 1 8

Description ARC Project # GDOT PI # TIP Status

Jurisdictions DK 118 770603 94-96 Implemented

FN 086 770605 94-96 Implemented

FS 068 770605 94-96 Implemented

GW 135 170950 94-96 Implemented

R 098 04418 93-95 Implemented

R 098 770391 94-96 Implemented

ITS – ADVANCED TRAFFIC MANAGEMENT 

SYSTEM / INCIDENT MANAGEMENT PROGRAM

Sponsor – GDOT

I-75/I-85 within I-285, Northern portion of I285 between I-75 and I-85

R 098 770391 94-96 Implemented

CLEAN FUELS REVOLVING LOAN PROGRAM

Sponsor – GEFA

R 195 770790, 

770795

96-98 Implemented

HOV LANES

Sponsor – GDOT

I-75 and I-85 within I-285

R 174 320H94 94-96 Implemented

PARK & RIDE LOTS 

Sponsor(s) – Douglas & Rockdale Counties

Douglas County – Chapel Hill @ I-20,

Rockdale County – Sigman @ I-20

DO 211C 94-96 Implemented

REGIONAL COMMUTE OPTIONS & HOV 

MARKETING PROGRAMS

Sponsor(s) – GDOT

R 159 770631 94-96 Implemented

SIGNAL PREEMPTION

Sponsor – MARTA

M-R 164 770636 94-96 Implemented

TRANSIT INCENTIVES PROGRAM

Sponsor - MARTA

M-AR 231A

M-AR 231B

771031

771119

98-00

99-01

00-02

Implemented

TRANSPORTATION MANAGEMENT 

ASSOCIATIONS

Sponsor – ARC

AR 221A

AR 221B

AR 221C

AR 221E

AR 221F

771033

771140

771141

0000570

0000571

98-00

99-01

00-02

01-03

Implemented

UNIVERSITY RIDESHARE PROGRAM

Sponsor - ARC

AR 220A

AR 220B

AR 220C

AR 220D

AR 200E

771032

771113

0000351

0000567

0000568

98-00

99-01

00-02

01-03

02-04

Implemented

* This project was substituted for the HOV lane. The substitution was adopted on November 5, 2009 by 

EPA's concurrence letter. 
PLAN 2040 Conformity Determination Report: Exhibit 1 9

EXHIBIT 1B

Interagency Review of Planning Assumptions

Used in Regional Emissions Analysis

For Atlanta PM2.5 Nonattainment Area

Interagency Consultation Meeting

Atlanta Regional Commission

The ARC will be conducting a conformity analysis under the PM2.5 standard as part of the conformity 

determination for the PLAN 2040 RTP / FY 2012-2017 TIP for the 20 county nonattainment area. 

Below is a detailed listing of the procedures and planning assumptions for the upcoming conformity 

analysis of the PLAN 2040 RTP. 
PLAN 2040 Conformity Determination Report: Exhibit 1 10

Section 1: General Methods and Assumptions 

1) Modeling Methodology

a) Estimate link-level VMT and congested flow speeds using ARC 20-county travel demand model 

that corresponds to the 20 full-county portion of the PM2.5 nonattainment area

b) Estimate VMT for Heard and Putnam partial-county areas using historical traffic count data 

derived from GDOT’s Annual Traffic Count (ATC) program database

i) ATC data provided by county by traffic count station

ii) Traffic count growth trends for each analysis year estimated through linear regression using 

the most recent six years of consecutive traffic count data available

c) Estimate congested flow speeds for Heard and Putnam partial-county areas using VMTweighted speed by HPMS functional class, extrapolated from ARC travel demand model for each 

analysis year

2) Conformity Test

 a) Nonattainment Classification - Basic

 i) No-Greater-Than-Base-Year interim emissions test

(1) 2002 base year

(2) Base year emissions to be developed as part of conformity analysis as provided for in 

preamble to the eight-hour ozone and PM2.5 Transportation Conformity Rule6. Base year 

emissions will be established using the same modeling methodology presented above.

3) Conformity Analysis Years: 2016, 2020, 2030, 2040

4) Modeling Start Date: March 2011. This start date is defined by the ARC as the initiation of the first 

model run for the PLAN 2040 RTP Update and FY 2008-2013 TIP, begun when all datasets needed for 

the model run were completed.

5) Interagency Consensus on Planning Assumptions: January 25, 2011

Section 2: Travel Demand Modeling Assumptions

1) Calibration Year: 2000 (with some 2005 interim validations and benchmarking thereafter)

2) Project Listing: Project listings will be provided in electronic format to Interagency Consultation 

Group for review in the first quarter of 2011.

a) Regionally Significant and Federally Funded

b) Regionally Significant and Non-Federally Funded

3) Demographic Data: Provided as separate attachment

4) Speed Data: Free-flow Speed by Area Type and Facility Type7

 

6

Federal Register, Vol. 69, No.126, July 1, 2004, p. 40015, first column.

7 Within the ARC travel demand and emission modeling process, free flow speeds are adjusted to reflect the 

increase in delay and travel time on a roadway segment as traffic volumes build and congestion levels increase. 

Link-level congested flow speeds are used to estimate NOx and VOC emissions as required by Sections 

93.122(b)(i)(iv) and 93.122(b)(2) of the Transportation Conformity Rule.
PLAN 2040 Conformity Determination Report: Exhibit 1 11

Area Type

Facility Type

Urban Very 

High 

Density

Urban 

High 

Density

Urban 

Medium 

Density

Urban Low 

Density SuburbanExurban Rural Metered Ramps

0

Zone Centroid 

Connectors 7 11 11 11 11 14 14

1

Interstate / 

Freeway Free 

Flow

55 58 58 61 61 63 65

2 Parkway 50 50 55 55 57 60 60

3

HOV Buffer 

Separated 55 58 58 61 61 63 65

4

HOV Barrier 

Separated 55 58 58 61 61 63 65

5

High Speed Ramp 

/ CD Road 50 50 55 55 57 60 60 15

6

Medium Speed 

Ramp 50 50 50 50 50 50 50 10

7 Low Speed Ramp 40 40 40 40 40 40 40 10

8 Loop Ramp 30 30 30 30 30 30 30 10

9

Off Ramp w/ 

Intersection 25 25 25 25 25 25 25

10 On Ramp w/ 

Intersection 40 40 40 40 40 40 40 5

11 Expressway 40 42 45 48 52 55 60

12 Principal Arterial -

Class I 26 30 33 36 42 46 55

13 Principal Arterial -

Class II 24 27 30 34 40 44 48

14 Minor Arterial -

Class I 22 25 28 31 38 42 45

15 Minor Arterial -

Class II 20 23 26 29 34 38 42

16 HOV - Arterial (all 

classes) 20 27 30 33 36 39 42

17 Major Collector 18 22 25 28 31 34 38

18 Minor Collector 15 18 21 24 27 30 35

19Planned Ramps w/ 

Intersections 30 30 30 30 30 30 30 5

20 Planned 

Directional Ramps 45 45 45 45 45 45 45 10
PLAN 2040 Conformity Determination Report: Exhibit 1 12

5) Transit Modeling

 a) Model recalibrated to 2000 transit ridership estimates, provided by transit operators

 b) Reflects results from the 2001-2002 Transit On Board Survey, with preliminary adjustments from 

2009 Transit On Board Survey

 c) Routes updated to reflect current operating plans

 d) Transit mode split is estimated using the mode choice model 

i) Estimates individual modal trips from the person trip movements developed in 

 the trip distribution model. 

 ii) Composed of three nested logit models: 

(1) Home based work trips, which includes home based university trips; 

(2) Home based other trips, which include home based other, home based shopping and home 

based grade school; and 

(3) Non-home based trips. 

 iii) The mode choice model is organized in terms of seven characteristics: 

(1) Mathematical structure; 

(2) Trip purposes and choice sets;

(3) Limitations on choice sets;

(4) Analysis of transit access;

(5) Treatment of HOV lanes;

(6) Stratification by income groups; and

(7) Analysis of alternative transit paths. 

 e) Transit Fare Modeling

i) Fare structure and operating plans supplied by the local transit operators

(1) Fares remain constant over time, across all network years

(2) Fares reflect current transit operating plans 

ii) Transit fare structure uses a fare matrix on a zone to zone level with a universal fare 

structure (flat fare) for all bus and rail lines

(1) Changes to the existing fare structure and service frequency are coded directly into the 

model 

(2) Current fare values in the model are weighted according to the percentage of riders using a 

discounted fare pass; changes to these assumptions can be incorporated directly into the 

model 

(3) Peak and off-peak fares are equivalent

f) 2009 Transit On Board Survey interim adjustments

i) Update of regional transit travel targets based on a preliminary expansion of the raw on-board 

survey data

(1) Modifications to express bus and BRT transfer constants

(2) Modifications to travel demand model estimates of zero-car transit work trips

(3) Modifications to travel demand model estimates of kiss-and-ride passenger access and 

use of transit system

(4) Overall evaluation of all modal constants

(5) Refinement to park-and-ride lot assumptions

(6) Updated walk connector and percent walk procedures

ii) Modified transit skimming procedures

iii) Re-calibrated air passenger model

iv) Assessment of travel demand model understanding of market segments and travel patterns 

relative to the on-board survey records
PLAN 2040 Conformity Determination Report: Exhibit 1 13

Section 3: Emissions Modeling Assumptions 

1) Emissions Factor Model: MOBILE6.2.03

2) PM2.5 Standard MOBILE6.2.03 Inputs (13-county portion)8

Annual averages of the hourly average temperature and relative humidity for each hour of each month; 

and annual average of the daily average barometric pressure for each month; 2000 – 2002

a) Stage II refueling

i) Started in 1992

ii) Three phase in years

iii) 81% efficiency

b) Anti-tampering program

i) Started in 1982

ii) Covers model years 1975 – 1995

iii) All LDG vehicle types are covered

iv) Annual program

v) 97% compliance

vi) Catalyst removal only

c) I/M Program

i) Exhaust and Evaporative (OBD and gas cap pressure test) for 1996 and newer vehicles

(1) Began in 1982

(2) Annual inspection required

(3) Computerized test and repair OBD – Exhaust

(4) Computerized test and repair OBD & GC - Evaporative

(5) Applies to all LDG vehicle types

(6) Three year grace period

(7) 3% waiver rate for all vehicles – Exhaust test

(8) 0% waiver rate for all vehicles – Evaporative test

(9) 97% compliance

ii) Exhaust and Evaporative test for 1975 – 1995 vehicles

(1) Began in 1982

(2) Annual inspection required

(3) Computerized test and repair ASM 2525/5015 Phase-in – Exhaust

(4) Computerized test and repair GC – Evaporative

(5) Applies to all LDG vehicle types

(6) 3% waiver rate for all vehicles – Exhaust

(7) 0% waiver rate for all vehicles – Evaporative

(8) 97% compliance

(9) 25 year and older model years are exempt

d) Fuel9

 

8

For the PM2.5 standard there are two sets of MOBILE6 input files, one for the 13 counties that make up the 

former one-hour ozone nonattainment area in which a specific set of emission control measures is in place and 

one for the seven “ring” counties plus the portions of Heard and Putnam counties. For each set, the input files 

contain the same assumptions for all analysis years (2010, 2020, and 2030).

9

In 2002, Georgia's two-phase gasoline sulfur control program limited average sulfur in gasoline sold in the 13-

county Atlanta area and in 12 surrounding counties to 150 parts per million (ppm). In addition, there was a 
PLAN 2040 Conformity Determination Report: Exhibit 1 14

i) 2002 Base Year: Annual average sulfur and Reid Vapor Pressure (RVP) based on caps in 

Georgia's Low Sulfur, Low RVP gasoline marketing rule (June – September) and on the 

monthly sulfur and RVP values in USEPA's National Mobile Inventory Model (NMIM)10

database (October – May) 

ii) 2010 and later: Phase 2 Low Sulfur (30ppm) Georgia Gasoline year-round; annual average 

RVP based on caps in Georgia’s gasoline marketing rule (June-September) and on the 

monthly RVP values in the NMIM database (October-May) 

iii) Diesel sulfur: average of the monthly values in USEPA's NMIM database for each analysis 

year

e) 2002 regional fleet age distribution

i) Derived from R.L. Polk & Co. registration data for 13-county area

ii) Applied to 15 of the 16 MOBILE6.2.03 composite vehicle classifications – LDV, LDT1, LDT2, 

LDT3, LDT4, HDV2B, HDV3, HDV4, HDV5, HDV6, HDV7, HDV8, HDBS, HDBT, MC

(1) Default for HDV8B

(2) Default VMT fractions

3) PM2.5 Standard MOBILE6.2.03 Inputs (7-county and partial-county portions)

g) Annual averages of the hourly average temperature and relative humidity for each hour of each 

month; and annual average of the daily average barometric pressure for each month; 2000 –

2002

h) No Stage II refueling

i) No anti-tampering program

j) No I/M program

k) Fuel

i) 2002 Base Year11: Annual average sulfur and RVP based on caps in Georgia's Low Sulfur, 

Low RVP gasoline marketing rule (June – September) and on the monthly sulfur and RVP 

values in USEPA's NMIM database (October – May) 

ii) 2010 and later: Phase 2 Low Sulfur (30ppm) Georgia Gasoline year-round; annual average 

RVP based on caps in Georgia’s gasoline marketing rule (June-September) and on the 

monthly RVP values in the NMIM database (October-May)

iii) Diesel sulfur: average of the monthly values in USEPA's NMIM database for each analysis 

year

l) 2002 regional fleet age distribution

i) Derived from R.L. Polk & Co. registration data for 9 counties (Carroll, Bartow, Hall, Barrow, 

Walton, Newton, Spalding, Heard, and Putnam)

ii) Applied to 15 of the 16 MOBILE6.2 composite vehicle classifications – LDV, LDT1, LDT2, 

LDT3, LDT4, HDV2B, HDV3, HDV4, HDV5, HDV6, HDV7, HDV8, HDBS, HDBT, MC

(1) Default for HDV8B 

 

seasonal (June 1 to September 15) 7.0 pounds per square inch (psi) Reid vapor pressure cap on gasoline sold in this 

Phase 1 area. In 2003, Phase 2 of Georgia's gasoline rule reduced average sulfur to 30 ppm year-round and added 

20 additional counties (including Putnam) to the sulfur and RVP control program. Because MOBILE6 shows no 

effect of oxygenate (e.g., ethanol) on PM2.5, ethanol-blend gasoline was not modeled for the PM2.5 regional 

emissions analysis. 

10 http://www.epa.gov/oms/nmim.htm

11 For the 2002 base year only, separate emission factors were run for Putnam County because the Low-Sulfur, Low 

RVP Georgia Gasoline program was not implemented in the county until 2003. This resulted in a fuel blend in 

Putnam County in 2002 that is not low-sulfur and that has a higher average annual RVP.
PLAN 2040 Conformity Determination Report: Exhibit 1 15

(2) Default VMT fractions

4) VMT adjustment factors 

a) Calculated for year 2000 

i) Reflects Section 93.122(b)(3) of the Transportation Conformity Rule which recommends that 

HPMS adjustment factors be developed to reconcile travel model estimates of VMT in base 

year of validation to HPMS estimates for the same period. 

ii) Factors applied to VMT estimates generated by ARC travel demand model for 13-county 

portion and 7-county portion of 20-county modeling domain, separately.

VMT Adjustment Factors

Functional Class Name

Factor for 13 

County Area

Factor for 7 

County Area

Rural Interstate 0.64 0.85

Rural Prin. Arterial 1.00 0.97

Rural Min. Arterial 1.14 0.97

Rural Major Collector 0.87 1.80

Rural Minor Collector 1.06 1.80

Rural Local 0.64 1.09

Urb. Interstate 1.03 0.85

Urb. Other Fwy 2.38 0.85

Urb. Prin. Arterial 0.68 0.97

Urb. Min. Arterial 1.22 0.97

Urbanized Collector 1.24 1.80

Urbanized Local 0.97 1.09

5) Off-Model Calculations

a) Senior I/M Exemption (emissions debit)

i) The Senior I/M Exemption calculated for year 2002 is conservatively high and will be added 

to the regional emission inventories for each analysis year.

6) TCMs

a) No additional credit is taken in the emissions modeling process for SIP TCMs

b) Listed below is a TCM status report

Description ARC Project # GDOT PI # TIP Status

HOV LANES

Sponsor – GDOT

AR 073B 713760 98-00,

99-01

Under 

construction*
PLAN 2040 Conformity Determination Report: Exhibit 1 16

Description ARC Project # GDOT PI # TIP Status

I-85N from Chamblee-Tucker Rd to SR 316 

(HOT Lanes),

I-85 @ SR 316, Interchange Reconstruction

GW-AR 053A

GW-AR 053B

110530 01-03

02-04

03-05

05-10

Implemented 

Implemented

ATLANTIC STATION, 17th STREET BRIDGE

Sponsor – City of Atlanta

A – Bridge and Southbound off ramps

C – Northside Dr over Norfolk Southern 

Railroad to Atlantic Station

D – Northbound off ramp to 17th Street Bridge, 

Williams St Relocation

AT-AR 224A

AT-AR 224C

AT-AR 224D

714190

0001297

0001298

00-02

01-03

02-04

03-05

05-10

A – Implemented

C – Implemented

D – Implemented

CLEAN FUEL BUSES

Sponsors – MARTA and CCT

M-AR 232 N/A 94-95 Implemented

EXPRESS BUS ROUTES

Sponsor – MARTA

M-R 160

M-R 162

770632

770632

94-96 Implemented

IMPROVE / EXPAND BUS SERVICE 

Sponsor – MARTA

M-R 161 770633 96-98 Implemented

INTERSECTION UPGRADE, COORDINATION & 

COMPUTERIZATION

Sponsor(s) – GDOT in partnership with local 

Jurisdictions

AT 089 04Y108 93-95 Implemented

CL 094 770600 94-96 Implemented

CO 249 770601 94-96 Implemented

DK 118 770603 94-96 Implemented

FN 086 770605 94-96 Implemented

FS 068 770605 94-96 Implemented

GW 135 170950 94-96 Implemented

R 098 04418 93-95 Implemented

R 098 770391 94-96 Implemented

ITS – ADVANCED TRAFFIC MANAGEMENT 

SYSTEM / INCIDENT MANAGEMENT PROGRAM

Sponsor – GDOT

I-75/I-85 within I-285, Northern portion of I285 between I-75 and I-85

R 098 770391 94-96 Implemented

CLEAN FUELS REVOLVING LOAN PROGRAM

Sponsor – GEFA

R 195 770790, 

770795

96-98 Implemented

HOV LANES

Sponsor – GDOT

I-75 and I-85 within I-285

R 174 320H94 94-96 Implemented

PARK & RIDE LOTS 

Sponsor(s) – Douglas & Rockdale Counties

Douglas County – Chapel Hill @ I-20,

Rockdale County – Sigman @ I-20

DO 211C 94-96 Implemented

REGIONAL COMMUTE OPTIONS & HOV 

MARKETING PROGRAMS

Sponsor(s) – GDOT

R 159 770631 94-96 Implemented

SIGNAL PREEMPTION

Sponsor – MARTA

M-R 164 770636 94-96 Implemented

TRANSIT INCENTIVES PROGRAM

Sponsor - MARTA

M-AR 231A

M-AR 231B

771031

771119

98-00

99-01

00-02

Implemented
PLAN 2040 Conformity Determination Report: Exhibit 1 17

Description ARC Project # GDOT PI # TIP Status

TRANSPORTATION MANAGEMENT 

ASSOCIATIONS

Sponsor – ARC

AR 221A

AR 221B

AR 221C

AR 221E

AR 221F

771033

771140

771141

0000570

0000571

98-00

99-01

00-02

01-03

Implemented

UNIVERSITY RIDESHARE PROGRAM

Sponsor - ARC

AR 220A

AR 220B

AR 220C

AR 220D

AR 200E

771032

771113

0000351

0000567

0000568

98-00

99-01

00-02

01-03

02-04

Implemented

* This project was substituted for the HOV lane. The substitution was adopted on November 5, 

2009 by EPA's concurrence letter.
PLAN 2040 Conformity Determination Report: Exhibit 1 18

EXHIBIT 1C

Interagency Review of

Population & Employment Planning Assumptions

Used in Regional Emissions Analysis

For Atlanta Eight-Hour Ozone and PM2.5 Nonattainment Areas

Interagency Consultation Meeting

Atlanta Regional Commission

Final IAC Approval: 3/1/11
PLAN 2040 Conformity Determination Report: Exhibit 1 19

The ARC will be conducting a conformity analysis under the PM2.5 standard as part of the conformity 

determination for the PLAN 2040 RTP / FY 2012-2017 TIP for the 20 county nonattainment area. 

Below is a detailed listing of the procedures and planning assumptions for the upcoming conformity 

analysis of the PLAN 2040 RTP. 

ARC periodically revises its population and employment forecasts based on best available current 

information. Each revision is a two-step process. First, new region-level forecasts are produced. These 

then become region-level controls for census tract and traffic analysis zone (TAZ) forecasts.

The most current region-level control forecasts (PLAN 2040) were completed in spring of 2009. The 

accompanying table summarizes the new population and employment controls for the updated, 20-

county study area.

ARC staff was assisted in the development of these regional forecasts by a Technical Advisory 

Committee (TAC) of nationally known, local experts on the Atlanta Regional Economy. Chair of the 

Committee was Dr. Donald Ratajczak, Regents Professor Emeritus of Economics at Georgia State 

University. Dr. Ratajczak served as director of the Economic Forecasting Center in the J. Mack Robinson 

College of Business at Georgia State University from 1973 until June 2000 and as a professor of 

economics in the Andrew Young School of Policy Studies until he retired in 2000. The committee 

recommended the final adopted forecasts for use by the Commission in 2009.

The second step in the forecasting process uses mathematical models to disaggregate the region-level 

control population and employment forecasts to “small areas”: the Superdistrict, census tract and traffic 

analysis zone (TAZ) level. TAZs are nested within census tracts. Census tracts nest within superdistricts. 

The mathematical models underlying the region-level controls have evolved and become more complex, 

but ARC’s basic approach is the same today as in 1975. 

The TAZ Disaggregator (TAZ-D) model has been used in Plan2040 to disaggregate the regional controls to 

small areas. This model runs annually and iteratively (unlike the five-year iterative sequence of the 

previous model small area model, DRAM/EMPAL). The process is fully integrated with the ARC travel 

demand model, as impedances (travel costs) from the travel model are a significant influence layer for 

spatial allocation of population and job growth. 

Population and job levels from each successive single-year forecast become the base for forecasts in the 

next model year. First, the Cube/TP+ model analyze base year traffic patterns and produces accessibility 

measures (impedances or travel costs) within the 20-county forecasted area. Then, the TAZ-D model 

uses the composite impedances; Superdistrict-level distribution of base-year population, employment 

and land use; and other spatial influence layers (e.g. like land use, interchange locations, major arterials, 

transit stations, etc.) to develop grid-level forecasts one year into the future. The size of the grid areas in 

the TAZ-D model vary by geographic area of the region, as do the weights assigned to various spatial 

influence factors for growth. The Unified Growth Policy Map (UGPM) was used by the TAZ-D as the 

baseline source to generate household and job density and/or intensity levels to allocate future growth. 

The grid-level forecasts are then aggregated back up to the TAZ, tract, and superdistrict levels. The TAZ-
PLAN 2040 Conformity Determination Report: Exhibit 1 20

level forecasts then become the input used by the Cube/TP+ model to produce the impedances measure 

that drives the next iteration of the integrated model run.

All these models are carefully calibrated based on the best and most current data available. Data used in 

the current effort include 2000 United States Census results, ARC annual estimates of population (using 

the building permit method from 2000 Census base) for superdistricts and census tracts, ARC annual 

estimates of employment by industry for superdistricts, tracts and TAZs from the state of Georgia 

unemployment insurance base file. National forecasts of employment and population were derived from 

the REMI Policy Insight+ model. The results of ARC travel surveys included the SMARTRAQ household 

travel survey, transit on-board survey, Hartsfield air passenger survey, travel time studies, speed studies, 

and others. Highway projects and the schedule for their completion (primary inputs to the Cube/TP+ 

model) are developed as part of an extensive discussion between ARC staff, local planners, Georgia 

Department of Transportation and various federal agencies.

The area modeled by ARC for transportation/air quality purposes expanded from ten (10) to twenty (20) 

counties over the last 15 years. The 2010 Census and federal conformity analysis requirements may 

result in further expansion of the nonattainment area. To meet current and future data needs, ARC 

produced employment estimates by county and census block group for the state of Georgia beginning in 

2008, and continues to produce these estimates annually. The counties covered by land-use data 

produced in the LandPro program is expanded as needed. ARC’s population estimates’ program area will 

be expanded as required, from the current 20 counties, using the 2010 Census as a data baseline.

ARC produced tract-level 2010 estimates of population and 2009 small-area estimates of employment 

for the 20-county study area to support initial iterations of the TAZ-D model. Development of the annual 

estimates and of the year 2000 calibration database for the nonmember counties was coordinated with 

the affected county governments and the Regional Development Centers of which they are members.

Post processing adjustments are made to the ARC forecasts to account for expected large scale changes 

and policy priorities that would not be reflected in historical data. Events such as expected construction 

of a new highway or policy input restricting development within the region are accounted for directly in 

the models with the spatial influence layers or density limitations. Factors such as expected job and 

household growth from the completion of a major development project (i.e. Atlantic Station) or transitoriented development are incorporated as post processing adjustments to the model output.

The forecasts will be used as part of the 2011 RTP (Plan2040/FY 2012-2017 TIP), scheduled for adoption 

in August 2011.
PLAN 2040 Conformity Determination Report: Exhibit 1 21

3,063,026 

3,609,225 

4,263,255 

4,944,939 

5,473,846 

5,925,900 

6,453,347 

6,929,253 

7,377,951 

7,829,905 

8,256,323 

1,940,175 

2,284,122 

2,797,292 

3,003,487 

2,699,950 

2,985,928 

3,304,406 

3,546,530 

3,835,118 

4,158,004 

4,472,567 

 -

 1,000,000

 2,000,000

 3,000,000

 4,000,000

 5,000,000

 6,000,000

 7,000,000

 8,000,000

 9,000,000

1990 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040

Chart 1. ARC's Population and Employment Forecasts

1990 - 2040

Population Employment