volume 3 travel demand model documentation and user's guide

Volume 3 Travel Demand Model Documentation

and User’s Guide

February 16, 2010

p r e p a r e d b y

Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation & User’s Guide

i

TABLE OF CONTENTS

1.0 Introduction ........................................................................................................................... 1 1.1 Model Certification Process ......................................................................................... 1 1.2 Datasets Available ......................................................................................................... 2 1.3 Overview of Model Performance and Documentation ........................................... 3

2.0 Data Development and Review ......................................................................................... 5 2.1 Traffic Analysis Zones .................................................................................................. 5 2.2 Socioeconomic Data ...................................................................................................... 9 2.3 Updating Highway Network to 2007 Conditions .................................................... 20 2.4 Traffic Count Data ......................................................................................................... 29 2.5 Screenline Locations ..................................................................................................... 29 2.6 Travel Surveys ............................................................................................................... 33

3.0 External Trips ........................................................................................................................ 35 3.1 External Model .............................................................................................................. 35 3.2 External Validation Adjustments ................................................................................ 39 3.3 External Validation Results ......................................................................................... 39

4.0 Trip Generation..................................................................................................................... 41 4.1 Trip Generation Process ............................................................................................... 41 4.2 Trip Generation Validation Adjustments .................................................................. 42 4.3 Trip Generation Validation Results ............................................................................ 45

5.0 Trip Distribution .................................................................................................................. 47 5.1 Trip Distribution Model Structure .............................................................................. 47 5.2 Trip Distribution Model Development and Validation ........................................... 48 5.3 Trip Distribution Model Results ................................................................................. 51

6.0 Mode Choice .......................................................................................................................... 55 6.1 Mode Choice Model Structure for General Highway Assignment ........................ 55 6.2 Mode Choice Model Structure for Exclusive HOV or Truck Lanes ....................... 56 6.3 Mode Choice Model Structure for Time-of-Day Model .......................................... 57

7.0 Highway Assignment .......................................................................................................... 59 7.1 Highway Assignment Model Structure ..................................................................... 59 7.2 Development and Validation of Highway Assignment Model .............................. 59 7.3 Highway Assignment Validation Results ................................................................. 60

8.0 Summary and Conclusions ................................................................................................. 67 8.1 Summary of 2007 Model Validation Observations .................................................. 67 8.2 Future Model Enhancements....................................................................................... 68


ii

TABLE OF CONTENTS (continued)

Appendix A: Network Project Lists

Appendix B: Technical Memorandum #1

Appendix C: Technical Memorandum #2

Appendix D: Technical Memorandum #3

Appendix E: 2007 Volume-to-Count Ratios

Appendix F: User’s Guide

Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide

i

LIST OF TABLES

2.1 Number of TAZs in TransCAD Model .............................................................................. 5

2.2 Regional Summary of Socioeconomic Data for 2035 LRTP Update............................... 11

2.3 Facility Type Codes ............................................................................................................... 21

2.4 Area Type Codes ................................................................................................................... 21

3.1 Internal-External (IE) and External-External (EE) Percentage Splits ............................. 36

4.1 New Chattanooga Trip Production and Attraction Rates ............................................... 43

4.2 Special Generator Locations ................................................................................................ 44

4.3 Aggregate Trip Rates ............................................................................................................ 45

4.4 2007 Trips per Household by Trip Purpose ...................................................................... 46

4.5 Percent of Trips by Purpose ................................................................................................. 46

5.1 Terminal Times ...................................................................................................................... 48

5.2 2007 Trips Between K-Factor Districts ............................................................................... 49

5.3 2035 Trips Between K-Factor Districts ............................................................................... 50

5.4 Penalties .................................................................................................................................. 50

5.5 Average Trip Length (in Minutes) ...................................................................................... 52

5.6 Intrazonal Trips by Trip Purpose ........................................................................................ 53

6.1 Auto Occupancy Rates ......................................................................................................... 56

6.2 Vehicle Occupancy Allocation by Trip Purpose ............................................................... 57

6.3 Temporal Distribution of Trips ........................................................................................... 58

7.1 Volume Over Count Ratios by Facility Type, Area Type and Number of Lanes ........ 61

7.2 Comparison of Volume-to-Count Ratios by Screenline................................................... 62

7.3 Percent Difference for Daily Volumes (Calculated for Links with Counts) ................. 63

7.4 Root Mean Square Error (RMSE) by Volume Group ....................................................... 64

7.5 Vehicle Miles Traveled by Model Facility Type ............................................................... 65


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LIST OF FIGURES

2.1 TAZ Splits ............................................................................................................................... 7

2.2 Regional Summary of Socioeconomic Data for 2035 LRTP Update............................... 11

2.3 Comparison of Households Between 2030 and 2035 LRTP Models .............................. 12

2.4 Comparison of Households Between All 2035 LRTP Model Years ............................... 12

2.5 Comparison of Population Between 2030 and 2035 LRTP Models ................................ 13

2.6 Comparison of Population Between All 2035 LRTP Model Years ................................. 14

2.7 Comparison of Employees Between 2030 and 2035 LRTP Models ................................ 15

2.8 Comparison of Employment Between All 2035 LRTP Model Years .............................. 15

2.9 Comparison of Hotel-Motel Units Between 2030 and 2035 LRTP Models ................... 16

2.10 Comparison of Hotel-Motel Units Between All 2035 LRTP Model Years .................... 17

2.11 Comparison of School Enrollment Between 2030 and 2035 LRTP Models ................... 18

2.12 Comparison of School Enrollment Between All 2035 LRTP Model Years .................... 18

2.13 Comparison of College Enrollment Between 2030 and 2035 LRTP Models ................. 19

2.14 Comparison of College Enrollment Between All 2035 LRTP Model Years .................. 20

2.15 2007 Model Network by Facility Type ............................................................................... 23

2.16 2007 Model Network by Area Type ................................................................................... 25

2.17 2007 Model Network by Number of Lanes ....................................................................... 27

2.18 Screenline Locations ............................................................................................................. 31

3.1 External Station Locations ................................................................................................... 37

7.1 Correlation of Assigned Versus Observed Volumes ....................................................... 63


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1

1.0 Introduction As part of Chattanooga-Hamilton County/North Georgia (CHCNGA) 2035 Long-Range Transportation Plan (LRTP) Update, the TransCAD travel demand model was updated and revalidated to the base year 2007 with a horizon year 2035. The first phase of the LRTP update includes the development and review of base year 2007 input data and validation of the model to base year conditions. Subsequent phases of this study include the forecasting of future year 2035 external trips, the preparation of an existing-plus-committed (E+C) network, and an evaluation of future travel demand within the CHGNGA Transportation Planning Organization (TPO) boundary. The TPO boundary includes all of Hamilton County in Tennessee and portions of Catoosa, Dade, and Walker Counties in Georgia. The validated 2007 model and CHCNGA 2035 transportation recommendations were utilized in the development of the CHCNGA Transportation Planning Organization’s (TPO) 2035 LRTP. The LRTP was conducted for the TPO housed within the Chattanooga-Hamilton County Regional Planning Agency (RPA) using a consultant team led by Cambridge Systematics. Cambridge Systematics developed and validated the base and future year model, while RPA staff developed the socioeconomic data for input into the travel demand model.

1.1 Model Certification Process

The base year 2007 Chattanooga-North Georgia travel demand forecasting model uses procedures and model accuracy requirements consistent with state and national standards. National standards are documented in the Model Validation and Reasonableness Checking Manual coauthored by Cambridge Systematics for the Federal Highway Administration (FHWA). Effective March 1, 2008, the Tennessee Department of Transportation (TDOT) Long-Range Planning Division, Systems Planning and Policy Office implemented a Division Procedure for the MPO model approval process. On August 20, 2008, the TPO met with its consultants along with TDOT, GDOT, and CARTA to discuss the TransCAD modeling efforts for the CHCNGA 2035 LRTP Update. It was agreed at that time that the following four submittals would be provided to TDOT and GDOT as part of TDOT’s model approval process:

1. Outline of the model, planning assumptions to date, and model validation worksheet template;

2. Year 2007 and 2035 socioeconomic data files (TransCAD and GIS) for the TPO region, including any maps, graphs, charts, or tables developed as part of the TPO’s internal review;

3. Populated validation worksheet upon completion of draft validated model. This worksheet will include statistics for Trip Generation, Trip Distribution, Mode Choice (if applicable), and Traffic Assignment. If the assumptions included in submittal #1 change


2

as part of the validation process, they will be documented and submitted for approval at this time; and

4. Full model documentation report and user’s guide, along with all TransCAD files, after the draft LRTP has been documented.

Submittal #1 was submitted and approved by TDOT in September 2008. Subsequently, Regional Planning Agency (RPA) staff and its consultant, Cambridge Systematics, held a teleconference with the Georgia Department of Transportation (GDOT) and TDOT on June 30, 2009 to discuss the draft socioeconomic data and preliminary validation statistics, as outlined in this submittal.

Submittal #2, which included the 2007 and 2035 socioeconomic data, was submitted to TDOT, GDOT, and the air quality Interagency Consultation Committee (ICC) in July 2009 and approved during the ICC meeting on August 6, 2009.

Preliminary validation statistics were provided to the Interagency Consultation Committee (ICC) for review in advance of the September 3, 2009 ICC meeting. Submittal #3 was submitted to TDOT, GDOT, and the ICC on September 28, 2009. Comments were received by TDOT on October 8, 2009 and addressed via teleconference between TDOT and Cambridge Systematics on October 12, 2009.

This full report constitutes Submittal #4, provided to TDOT and GDOT for review and approval in early December 2009.

1.2 Datasets Available

Several datasets were created for the purpose of developing the 2035 LRTP, as well as for demonstrating air quality conformity for Particulate Matter (PM2.5). Air quality emissions are documented in the Conformity Determination Report (CDR) which constitutes Volume 2 of the three-volume LRTP series. Transportation projects included in each of the model networks are listed in Appendix A of this document. The following model datasets are available:

• 2002 – Used for air quality baseline emissions.

• 2007 – Base year validated model.

• 2009 – Used to compare with emissions in the State Implementation Plan (SIP) for PM2.5.

• 2015 Existing-Plus-Committed (E+C) – Used to determine what congestion would be in the year 2015 if no further transportation improvements were funded above and beyond what currently is in the FY ‘08-‘11 Transportation Improvement Program (TIP). Nonexempt (new road or widening) projects expected to complete construction by the end of calendar year 2011 are included in the E+C transportation network.


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• 2015 Fiscally Constrained LRTP (Tier 1) – Includes all nonexempt projects funded for construction prior to or during year 2015 (Tier 1) of the fiscally constrained LRTP.

• 2025 E+C – Used to determine what congestion would be in the year 2025 if no further transportation improvements were funded above and beyond what currently is in the FY ‘08-‘11 Transportation Improvement Program (TIP). Nonexempt (new road or widening) projects expected to complete construction by the end of calendar year 2011 are included in the E+C transportation network.


• 2035 E+C – Used to determine what congestion would be in the year 2035 if no further transportation improvements were funded above and beyond what currently is in the FY ‘08-‘11 Transportation Improvement Program (TIP). Nonexempt (new road or widening) projects expected to complete construction by the end of calendar year 2011 are included in the E+C transportation network.


The above nine datasets have been provided to TDOT and GDOT as part of this Volume 3 submittal.

1.3 Overview of Model Performance and Documentation

This technical report, which constitutes Volume 3 of the three-volume LRTP series, provides detailed information on the development and validation of the TransCAD travel demand model. Section 2.0 describes the data development and review process, including traffic analysis zones (TAZs) and highway network information. Section 3.0 describes the estimation of base year external trips. Section 4.0 provides information on the trip generation model while Section 5.0 explains the trip distribution model. Section 6.0 describes the mode choice model while Section 7.0 provides information on the highway assignment model. The report concludes with a summary and discussion of next steps and future model enhancements in Section 8.0. Section 8.0 also includes a summary bullet list of the overall model performance. Overall, the 2007 model is performing within acceptable limits with an overall volume-to-count ratio of 0.96 and a Root Mean Square Error (RMSE) of 34.6 percent.


4



5

2.0 Data Development and Review Section 2.0 describes in detail the traffic analysis zone (TAZ) structure, socioeconomic data, highway network, traffic count data, screenline locations, and travel surveys.

2.1 Traffic Analysis Zones

As part of the previous 2030 LRTP Update, the TPO converted the old MINUTP model to TransCAD and refined the TAZ structure significantly resulting in 445 total TAZs for the entire model region. After the 2030 LRTP was adopted, the TPO added more TAZs to Catoosa County as the remaining sliver of Catoosa County not in the previous model was added for the purpose of calculating emissions for air quality conformity. This addition resulted in a total of 450 TAZs for the entire model region. As part of this current 2035 LRTP Update, the TPO has further refined the TAZ structure by splitting internal zones mostly in the outlying regions of the model and within the downtown area of Chattanooga. Previously, the Enterprise South Industrial Park (ESIP) area was included within one TAZ. As part of this update, the ESIP TAZ has been split into eight TAZs based on the ESIP future site plan. In addition to splitting several internal zones, eight more external zones were added to the current model, as indicated in Table 2.1 below. All of these TAZ splits have resulted in a current total of 628 TAZs (590 internal + 38 external) in the entire model region, an increase of 178 TAZs, or 40 percent more zones. Maps illustrating the TAZ splits are attached.

Table 2.1 Number of TAZs in TransCAD Model

2030 LRTP Model Expanded Catoosa

Model 2035 LRTP Model

Internal TAZs 415 420 590

External TAZs 30 30 38

Total TAZs 445 450 628

The following criteria were used to determine if a TAZ should be split, when feasible:

• Greater than 15,000 productions per TAZ in 2030;

• Irregular shaped or large sized TAZs;

• Major existing or planned roads bisecting TAZ; and

• Potential special generator located in TAZ (i.e., isolated TN Aquarium).


6

The following guidelines were used to split the TAZ boundaries, when feasible:

• Existing and future roadways;

• Existing and future land use;

• Railroads;

• Water bodies; and

• Census block group boundaries.


7

Figure 2.1 TAZ Splits


8



9

2.2 Socioeconomic Data

RPA staff developed the 2007 and 2035 socioeconomic data as part of the Chattanooga-Hamilton County/North Georgia 2035 LRTP Update. Historically, the Coosa Valley Regional Development Center (RDC) has developed the socioeconomic data for the Georgia portion of the TPO. However, development of the socioeconomic data for the Georgia side has since become the responsibility of the TPO due to funding limitations. Year 2015 and 2025 socioeconomic data used to develop the Tier 1 and 2 models, respectively, were interpolated using 2007 and 2025 socioeconomic data and then adjusted in the Enterprise South area to reflect build-out of the Volkswagen manufacturing plant by model year 2015. Since model years 2002 and 2009 are used for air quality conformity purposes only, they are documented in the Conformity Determination Report constituting Volume 2 of the three-volume LRTP series.

Variables

The socioeconomic data included in the TransCAD travel demand model can be broken in to four categories, as follows:

• Household Data – Includes total population, school-age children (population between ages 3 and 18), and total housing units.

• Employment – Includes total number of employees and number of employees for each of the five employment categories:

- Agricultural/mining/construction;

- Manufacturing/transportation;

- Retail;

- Service; and

- Government.

• School Enrollment – Includes number of grade school students at the location of the school, number of university students at the location of the university, and total school enrollment (grade school students plus university students). University student enrollment includes community, technical, or vocational colleges and universities.

• Hotel-Motel Units – Includes number of hotel-motel units.

Methodology

The RPA collected the number of building permits issued between 2000 and 2007 for each of the four counties, geocoded their locations, and added the new building permits to the 2000 households by TAZ to achieve 2007 households. Population for the year 2007 was


10

calculated by applying the persons per household ratio in each of the year 2000 zones to the total number of households in 2007. If a zone was split, the persons per household ratio from the parent zone in the year 2000 was applied for each split zone. However, subsequent logic checks determined that some manual adjustments were necessary in Dade and Hamilton Counties to reflect more reasonable persons per household ratios and thus, the overall persons per household ratio for the entire county were applied to those specific zones. The proportion of the total population attributable to school-age children was calculated using 2007 American Community Survey (ACS) data for each of the four counties, with the exception of Dade County, which utilized the same school-aged children factor in Walker County as ACS data was not available for Dade County. Building permit data for Hamilton County were acquired from the municipal building permit files, whereas building permit data for Catoosa and Walker Counties were acquired from The Market Edge, an information reporting service. Since building permits are not required in Dade County, electrical inspection records were acquired from the County as proxy for building permits.

As part of the current 2035 LRTP Update, the RPA evaluated a number of sources for employment data as there were significant discrepancies in the employment control totals between the different data sources within the region. After careful review, it was determined that year 2007 ES202 employment data from the Bureau of Labor Statistics (BLS) be used. Previously, as part of the 2030 LRTP Update, RPA staff utilized the employment control totals from the Bureau of Economic Analysis (BEA) while using Dun & Bradstreet point data to distribute the BEA employment by TAZ. This previous method was used due to some of the suspect employment numbers in the Dun & Bradstreet data. Since then, it has been determined that the ES202 employment data is more comparable to other data sources and the BEA control totals for the year 2000 may have been overestimated. As a result, when comparing the 2000 employment to the 2007 employment, there is a significant decrease in employment from the year 2000 to 2007. However, as mentioned above, it is likely that the 2000 employment was erroneous.

School enrollment data were collected from local school boards, the phone book, Internet, and applying local knowledge.

The number of hotel-motel units were collected from the Visitors Bureau, in-house Geographic Information Systems (GIS) file, a field survey, as well as the phone book and the Internet.

Observations

As indicated in Table 2.2, between the years 2007 and 2035, the Chattanooga region is expected to grow by approximately 39 percent in population and employment. Since the number of school-age children is decreasing in the region, school enrollment is only expected to increase by 16 percent. Although employment decreased from the year 2000 to 2007, as discussed earlier, employment does increase by 39 percent from the year 2007 to 2035, consistent with household and population forecasts. Figure 2.2 compares the regional


11

summary of each socioeconomic variable between the years 2007 and 2035. As expected, all variables increase from the year 2007 and 2035.

Table 2.2 Regional Summary of Socioeconomic Data for 2035 LRTP Update

Variable

Total Region Percent Growth

from 2007 to 2035 2007 2015 2025 2035

Households 178,557 199,570 225,878 252,148 41%

Population 425,724 473,614 533,492 593,335 39%

Employment 218,612 251,377 278,244 305,061 40%

Hotel-Motel Units 9,693 10,274 11,001 11,729 21%

School Enrollment 69,102 72,547 76,851 80,357 16%

College Enrollment 24,459 25,679 27,202 29,520 21%

Figure 2.2 Regional Summary of Socioeconomic Data for 2035 LRTP Update

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

Households Population Employment Hotel-Motel Units

School Enrollment

College Enrollment

2007

2015

2025

2035

Households

Figure 2.3 below compares the number of households between the previous 2030 LRTP (years 2000 and 2030) and the current 2035 LRTP Update (years 2007 and 2035). With the exception of the Georgia counties in the year 2030, the households increase for each year.


12

Growth in Georgia is expected to slow down between the years 2007 and 2035 and it is expected that 2030 households in Georgia were overestimated during the previous LRTP update.

Figure 2.3 Comparison of Households Between 2030 and 2035 LRTP Models

124,

447

760 12

,528

20,3

20

140,

707

839 12

,882

24,1

29

157,

459

1,19

0

16,6

49

43,9

19

200,

351

931 15

,275

35,1

36

0

50,000

100,000

150,000

200,000

250,000

Hamilton Dade Walker CatoosaCounty

2000200720302035

Note: 2030 expanded after 2030 LRTP Update to include all of Catoosa County.

Figure 2.4 Comparison of Households Between All 2035 LRTP Model Years

24,1

29

839

140,

707

12,8

82

27,2

75

866

157,

864

13,5

65

31,2

08

898

179,

351

14,4

2135,1

36

931

200,

806

15,2

75

0

50,000

100,000

150,000

200,000

250,000

Catoosa Dade Hamilton WalkerCounty

2007201520252035


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Population

As indicated in Figure 2.5, population in Hamilton County increases each year, regardless of which LRTP update. However, Dade County population decreased from the year 2000 to 2007, even though the number of households increased. This is as a result of adjusting the number of persons per household ratio to more accurately reflect existing conditions in Dade County, which are more consistent with the other counties in the TPO region. In addition, it is suspected that the year 2030 population in the Georgia counties was overestimated during the previous 2030 LRTP as growth is expected to slow down in Georgia.

Figure 2.5 Comparison of Population Between 2030 and 2035 LRTP Models

307,

897

2,46

0

31,7

49

52,9

55

328,

674

2,14

0

32,6

66

62,2

44

362,

330

3,83

7

42,0

85 114,

556

463,

347

2,35

4

38,5

75 88,0

58

050,000

100,000150,000200,000250,000300,000350,000400,000450,000500,000


2000

2007

2030

2035



14

Figure 2.6 Comparison of Population Between All 2035 LRTP Model Years

62,2

44

2,14

0

328,

674

32,6

66

69,6

16

2,20

2

367,

443

34,3

5378,8

43

2,27

7

415,

905

36,4

6788,0

58

2,35

4

464,

348

38,5

75

050,000

100,000150,000200,000250,000300,000350,000400,000450,000500,000


2007201520252035

Employment

As mentioned earlier, the source of the employment data has changed since the previous LRTP and thus, there is a significant reduction in employees from the year 2000 to 2007 due to suspected overestimation in the year 2000. Year 2007 employment data was based on ES202 records from the BLS and was supplemented by records from the Chamber of Commerce, schools, motel in-house records, and job announcements from the newspaper. Year 2000 data was compiled from the Dun & Bradstreet database and was factored up to BEA employment control totals. BEA derived the employment data in part from the BLS data which accounts for about 80 percent of its employment data. The difference between the BEA data and the BLS data is attributed to BLS only reporting employment covered by the State UI and UCFE programs while BEA also estimates employment for farms, part-time employees, private households, schools, religious organizations, railroads, military, and international organizations. Since BEA data did not include addresses and the 2000 approach would exacerbate errors from misgeocoding and misreporting, the RPA decided to geocode the BLS data and supplement it with the additional sources mentioned above for 2007 employment.

Figure 2.7 compares the new 2007 and 2035 employment control totals to the old 2000 and 2030 employment control totals. Due to the change in data sources, there are significant differences between LRTP datasets. However, it is suspected that the new 2007 employment estimates and 2035 forecasts are more accurate.


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Figure 2.7 Comparison of Employees Between 2030 and 2035 LRTP Models

240,

320

331 21

,465

26,3

02

194,

977

108

8,24

3

15,2

84

308,

469

516 27

,904 56

,598

274,

622

195

8,36

3

20,0

40

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000


2000

2007

2030

2035


Figure 2.8 Comparison of Employment Between All 2035 LRTP Model Years

15,2

84

108

194,

977

8,24

3

16,6

43

132

226,

326

8,27

6

18,3

49

165

251,

404

8,32

6

20,0

40

195

276,

463

8,36

3

0

50,000

100,000

150,000

200,000

250,000

300,000

Catoosa Dade Hamilton Walker

County

2007201520252035


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Hotel-Motel Units

As demonstrated in Figure 2.9, several hotels were constructed in Hamilton County between the years 2000 and 2007. The number of hotel-motel units in 2007 actually surpassed those projected in 2030 as part of the last 2030 LRTP. It is anticipated that the growth in hotel-motel units in Hamilton County will slow down between 2007 and 2035, although it will still increase by 22 percent. Similarly, Walker County hotel-motel units increased in 2007 beyond 2030 forecasted levels. However, it is suspected that the growth in hotel-motels units in Catoosa County was overestimated for the year 2030 during the previous LRTP update and it is expected to slow down by the year 2035, as the RPA is uncertain of future growth in Catoosa County.

Figure 2.9 Comparison of Hotel-Motel Units Between 2030 and 2035 LRTP Models

4,10

5

0 18

570

8,88

5

0 200 60

8

6,85

1

0 37

1,07

3

10,8

76

0 233 620

0

2,000

4,000

6,000

8,000

10,000

12,000


2000

2007

2030

2035



17

Figure 2.10 Comparison of Hotel-Motel Units Between All 2035 LRTP Model Years

608

0

8,88

5

20061

2

0

9,45

3

20961

6

0

10,1

64

22162

0

0

10,8

76

233

0

2,000

4,000

6,000

8,000

10,000

12,000


2007201520252035

School Enrollment

The number of grade school students in Hamilton County decreased from the year 2000 to 2007 as there were a number of school closings. However, school enrollment is expected to increase by the year 2035. As demonstrated in Figure 2.11, the growth in school students in Walker County was faster than expected resulting in far more students in the year 2007 than originally forecasted by the year 2030 as part of the previous LRTP update. Since the RPA is uncertain of future long-term growth, there is only a minimal increase in school students between the years 2007 and 2035 in Walker County. In Catoosa County, it is suspected that the 2030 forecasted school enrollment may have been slightly overestimated and thus, year 2035 forecasts are slightly lower when compared to the year 2030.


18

Figure 2.11 Comparison of School Enrollment Between 2030 and 2035 LRTP Models

51,5

70

0

3,93

1

7,08

3

50,8

35

0

7,04

2

11,2

25

54,0

92

0

5,11

1 14,7

70

58,7

18

0

7,52

3

14,1

16

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000


2000200720302035


Figure 2.12 Comparison of School Enrollment Between All 2035 LRTP Model Years

11,2

25

0

50,8

35

7,04

2

11,7

85

0

53,3

70

7,39

312,4

84

0

56,5

36

7,83

214,1

16

0

58,7

18

7,52

3

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

Catoosa Dade Hamilton Walker

County

2007201520252035


19

College Enrollment

College enrollment in Hamilton County increased by 23 percent between the years 2000 and 2007. However, growth is expected to slow down by the years 2030 and 2035, as indicated in Figure 2.13. Since the last LRTP update, the TPO TransCAD model was expanded to include all of Catoosa County. As a result, Harvest Deaf Bible College in Catoosa County is now included in the model, which accounts for the 27 college students in the year 2007 not previously in the model. In addition, Covenant College in Dade County was not included in the previous LRTP update and has since been added to the model.

Figure 2.13 Comparison of College Enrollment Between 2030 and 2035 LRTP Models

18,7

80

0 0 0

23,0

82

1,35

0

0 27

25,0

59

0 0 0

27,9

32

1,55

3

0 35

0

5,000

10,000

15,000

20,000

25,000

30,000


2000

2007

2030

2035



20

Figure 2.14 Comparison of College Enrollment Between All 2035 LRTP Model Years

27

1,35

0

23,0

82

028

1,41

7

24,2

33

030

1,50

1

25,6

70

035

1,55

3

27,9

32

0

0

5,000

10,000

15,000

20,000

25,000

30,000


2007201520252035

2.3 Updating Highway Network to 2007 Conditions

In order to update the year 2000 model network to the year 2007, a list of capacity-adding transportation improvements completed between the years 2001 and 2007 was developed and distributed to the ICC for review and approval. Maps of these projects and the corresponding list are included in Appendix A. These projects were coded on top of the previously validated 2000 model network to reflect 2007 transportation network conditions.

In addition, several roads were added to the model network to more accurately depict travel patterns and to assist with splitting several of the larger traffic analysis zones (TAZs). TRIMS and Roadway Characteristics (RC) data were obtained from TDOT and GDOT, respectively, to assist with reviewing the link characteristics (facility type and number of lanes) in the model network. To supplement this information, several windshield surveys were conducted to obtain area type, facility type, and number of lanes data for those roads being added to the model.

Maps of the 2007 model network by area type, facility type, and number of lanes are provided in Figures 2.15, 2.16, and 2.17 below. As part of the 2007 model update, a new area type code representing industrial land uses were added to the model. This new area type provided the ability to reduce speeds in areas serving industrial facilities. The TPO conducted a windshield survey in 2008, during which time areas representing industrial


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land uses were noted and revised accordingly in the 2007 model. In addition, topography data was overlayed on top of the 2007 model network to assist with updating the mountainous area type codes added during the previous model/LRTP update. A complete list of facility type and area type codes is included in Tables 2.3 and 2.4, respectively.

Table 2.3 Facility Type Codes

Code Description 1 Interstate

2 Expressway

3 Principal Arterial, Divided

4 Principal Arterial, Undivided

5 Minor Arterial

6 Collector

7 Ramp

8 One-Way

90 External Centroid Connector

99 Internal Centroid Connector

Table 2.4 Area Type Codes

Code Description 1 Central Business District (CBD)

2 Central Business District Fringe

3 Residential

4 Outlying Business District

5 Rural

6 Urban Undeveloped

7 Mountainous

8 Industrial


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23

Figure 2.15 2007 Model Network by Facility Type


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25

Figure 2.16 2007 Model Network by Area Type


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27

Figure 2.17 2007 Model Network by Number of Lanes


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2.4 Traffic Count Data

The validation of any travel demand model relies upon the existence of extensive base year traffic count data. Volume-to-count ratios generated by the model are used to measure the ability of a travel demand highway assignment model to simulate known traffic conditions. Traffic counts are needed for a variety of different roadway categories distributed throughout the study area in order to validate highway assignment performance among screenlines, facility types, area types, and lane configurations.

As part of the 2007 model update and Congestion Management Plan Update, the TPO identified locations along CMP routes and in the 2007 model where additional counts were needed. The TPO collected these supplemental counts in 2008 to assist with validation. As a result, year 2007 traffic counts available from TDOT, GDOT, Hamilton County, and the City of Chattanooga were included in the 2007 traffic count field used to calculate validation statistics. However, a year 2008 traffic count field was added to the model network to include these supplemental traffic counts collected in 2008. Since the base year of the model was 2007, these 2008 counts were not included in the validation statistics. However, they were used to supplement validation efforts and compare to 2007 traffic counts for accuracy.

2.5 Screenline Locations

Screenlines are drawn across the model network throughout various parts of the study area to summarize traffic volumes in subareas and along major corridors. These screenlines are used to report an aggregate volume-to-count ratio for all of the links that comprise any given screenline. This allows for measurement of travel flows between subareas of the study area. Screenlines typically follow natural features, major transportation facilities, or political boundaries. Also, screenlines can be used to cordon off certain portions of the study area in order to measure the flows into and out of those areas (such as measuring the flow of travel demand into and out of central business districts (CBDs) or the external model boundary).

As part of the previous 2030 LRTP update, 10 screenlines were identified and added to the TransCAD model network. These screenlines were checked to ensure that their orientation coincided with traffic count locations. Included in these 10 screenlines is an external cordon line that measures behavior of the external model. Also included is a partial cordon line around downtown Chattanooga and a variety of cut lines to allow for more detail in observing trip flow behaviors. The model network includes a field to indicate screenline codes one through 10, which are illustrated in Figure 2.19.


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31

Figure 2.18 Screenline Locations


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2.6 Travel Surveys

Household Travel Diary Survey

In 2002, a household travel diary survey was conducted to determine trip generation rates, average trip lengths, auto occupancy factors, and other characteristics used in model development and validation. The same rates and parameters derived from the 2002 household travel diary survey for the last model update were used for the 2007 model update as part of this 2035 LRTP. Typically, household travel diary surveys are conducted every 10 years to accurately reflect travel characteristics of the region. Pending funding availability, the TPO intends to conduct a new household travel diary survey in calendar year 2011. The results of the 2011 travel diary survey will be incorporated into the new 2010 base year model for the next LRTP update.

External Origin and Destination Survey

In 2002, a roadside origin-destination intercept survey designed to obtain characteristics of travelers entering, exiting, and passing through the region from locations outside the CHCNGA study area was conducted. During the last 2030 LRTP Update, it was determined that the results from the 2002 external origin and destination survey were biased. It was determined that the percentage of through trips were not reliable as the interstate surveys were conducted on ramps at interchanges and rest areas. Vehicles were not pulled off to the side of the road on the mainline interstate segments where most External-External (EE) trips occur. The vehicles that were surveyed already were stopping at the interchange or rest area. Therefore, the results provide a significant bias towards Internal-External (IE) trips and EE trips were thus underestimated. The percent IE/EE splits from the origin and destination survey were subsequently compared to the old 2000 MINUTP model and it was determined that the old 2000 MINUTP model percent splits appeared more reasonable. The MINUTP splits were used as a starting point for the previous 2000 model validation conducted in 2005 and were later modified during the 2000 model validation process.

As a result, the 2002 roadside origin-destination intercept survey was not used within the TransCAD model for this current 2035 LRTP Update,. With the exception of new external stations, the updated model as part of this 2035 LRTP Update used the same IE/EE splits from the last model. Any new external stations, which are minor roads with low traffic counts, assumed 100 percent IE trips. However, the TPO intends to conduct a new external origin and destination survey during the fall of 2010. In the meantime, the TPO will be designing the sampling plan and survey instrument. The results of the 2010 external origin and destination survey will be used to validate the external model for the 2010 base year validation as part of the next LRTP update.


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3.0 External Trips

3.1 External Model

Initial development of an external model requires that external trips be divided into at least two categories: internal to external (IE) trips and external to external (EE) trips. IE trips are those trips that either have an origin outside of the study area and a destination within the study area or vice versa. EE trips have both an origin and a destination outside of the study area, but pass through the study area. EE trips are preloaded in the CHCNGA model, as it is not usually expected that EE trips will reroute due to congestion. This is because EE trips generally consist of long-distance travelers not familiar with the local street system. There are two input files that describe external trips in the model. These are the TAZ geography file and the EE trips matrix file.

Although the TAZ geography input file is part of the trip generation process, it is integral to generating the IE trips for the external model. As noted in Section 2.6, the percent IE/EE splits for each external zone were initially derived from the old MINUTP 2000 external model and refined during the last model update. The percent IE trips were applied to the 2007 AADT to calculate the total number of IE trips at each external zone for the TAZ geography file.

The EE trips input matrix file (year_EXTERNAL-EXTERNAL.mtx) is generally the residual left after estimating IE trips in the TAZ geography file (TAZ_2007.dbd). The percentage of EE trips was applied to the AADT per external zone and then distributed from each origin zone to each destination zone using distribution patterns from the 2000 model EE trips file. Eight new external stations were added to the 2007 model above and beyond the 30 external stations included in the previous 2000 model. Year 2007 traffic counts at each of the 38 external stations were utilized to determine the total external trips. The same percent distribution of external-external (EE), or through trips, versus internal-external (IE) trips at each of the original 30 external zones used in the 2000 model was used for the 2007 model. Since the eight new external stations in the 2007 model were located along minor facilities, it was assumed that 100 percent of the external trips were attributed to IE trips, or those with one trip end inside the TPO region and one trip end outside the TPO region.

It should be noted that traffic counts for the external stations were coded in to the adjacent link to the external centroid connector in the model network so that the correct area type, facility type, and number of lanes is associated with the link.

Table 3.1 below demonstrates the percentage of IE and EE trips at each of the 38 external stations in the 2007 model.


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Table 3.1 Internal-External (IE) and External-External (EE) Percentage Splits

Zone 2007 Description

Percent Split

IE EE 800 (I-75 S) 67% 33% 801 (US-41 Chattanooga Road) 69% 31% 802 Old Ringgold Road 98% 2% 803 (GA SR 151 Alabama Highway) 81% 19% 804 GA SR 95 100% 0% 805 Ringgold Road 65% 35% 806 (GA SR 1, U.S. 27 S) 58% 42% 807 Straight Gut Rd. 100% 0% 808 (GA SR 341 Cove Road) 93% 7% 809 GA SR 193 92% 8% 810 Lula Lake Road 91% 9% 811 (GA SR 157/ 189 Lookout Mountain Scenic Highway) 97% 3% 812 (GA SR 58 , U.S. 11, Birmingham Pike) 75% 25% 813 I-59 82% 18% 814 I-24 64% 36% 815 TN SR 134 98% 2% 816 U.S. 64, U.S. 72, U.S. 41, TN SR 2 63% 37% 817 TN SR 27 Suck Creek Road 98% 2% 818 (TN SR 8, U.S. 127 Taft Highway) 58% 42% 820 (U.S. 111) 62% 38% 821 Retro Hughes Road 2% 98% 822 (TN SR 309 Leggett Road) 12% 88% 823 (TN SR 29, U.S. 27 N, Rhea Co. Highway) 31% 69% 825 TN SR 58 72% 28% 826 Old State Highway 58 66% 34% 827 TN SR 60 Georgetown Road 23% 77% 828 TN SR 312 Harrison Pike 100% 0% 829 (I-75 N) 71% 29% 830 (U.S. 11, U.S. 64, SR 2 S. Lee Highway) 94% 6% 831 McDonald Road 100% 0% 832 Old Alabama Road SW 100% 0% 833 Candies Creek Road SW 100% 0% 834 Tunnel Hill Road 100% 0% 835 TN SR 317 Weatherly Switch Trail SW 95% 5% 836 Bill Stewart Road 98% 2% 837 TN SR 2 Varnell Road 94% 6%


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Figure 3.1 External Station Locations


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3.2 External Validation Adjustments

Validation adjustments to the external model consisted of modifying the TAZ geography and EE trips files. Several iterations of the external model were executed in order to balance volumes at the external stations in such a manner so the addition of IE and EE trips matched the total AADT of each external station.

Special generator attractions were added to some of the external stations in an attempt to correct overassignments that were occurring in their vicinity. In the south of the model, there was major overassignment on several north-south arteries and the thought was that some of the trips trying to go north into Chattanooga should really be headed towards Dalton and areas to the South. To correct that, attractions were added to some of the external stations, such as I-75 South, to pull the trips in that direction. Similarly, the roads coming off the Cumberland Escarpment (Walden Ridge) into the Tennessee River Valley and I-75 and SR 60 leading into the Cleveland, Tennessee area received the same treatment with attractors being placed to pull some trips in that direction, rather than going into Chattanooga.

3.3 External Validation Results

Model validation results are described later in Section 7.0 on the highway assignment. In particular, a review of the external cordon line and other screenlines close to the model boundary indicate a reasonable match of external travel movements. The external cordon line achieves a volume-over-count ratio of 1.00.


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4.0 Trip Generation Just as with the previous 2000 model, the CHCNGA 2007 model uses a cross-classification trip generation process for trip productions along with trip rate equations for trip attractions. Trip productions and attractions are generated by zone using trip production rates derived from the Chattanooga household travel survey and trip attraction rates borrowed from the Knoxville household travel survey. This section discusses the Trip Generation model step.

4.1 Trip Generation Process

During the previous 2030 LRTP Update adopted in 2005, the 2002 Chattanooga Household Travel Survey data was evaluated to determine what variables impact travel patterns the most in the Chattanoga region. As a result, a cross-classification method based on auto availability and children per household was implemented. This same method was used during this 2035 LRTP update. Other potential explanatory variables from the survey, such as household size and income, were evaluated. However, trip rate matrices derived from these variables showed inconsistent patterns. Therefore, both the CHCNGA 2000 and 2007 models used trip rates developed for the four following auto availability categories:

• Zero autos per household;

• One auto per household;

• Two autos per household; and

• Three or more autos per household.

Trip rates for the four auto availability categories are cross-classified by categories, as follows:

• Zero children per household;

• One child per household; and

• Two or more children per household.

Auto availability and children per household data were derived from the 2000 Census.

Trip production rates were developed for the following trip purposes:

• Home-Based Work (HBW);

• Home-Based School (HBSchool);

• Home-Based Shop (HBShop);


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• Home-Based Social/Recreation (HBSR);

• Home-Based Other (HBO); and

• Nonhome Based (NHB).

Trip production rates by purpose are provided in Table 4.1. Trip production rates for hotel-motel units are provided in Table 4.2. Trip attraction rates for HBW, HBSchool, HBShop, HBSR, HBO, and NHB purposes were borrowed from the Knoxville model as these rates were more appropriate for use in Chattanooga than the Northeast Florida Regional Planning Model trip attraction rates used in the previous 2000 model. New trip attraction rates for the CHCNGA model specific to Chattanooga would have required an employer survey in addition to the household travel survey. Trip attraction rates for the light-duty truck, medium-duty truck, and heavy-duty truck trip purposes were derived from the FHWA Quick Response Freight Manual and did not change since the last 2000 model. Trip attraction rates are depicted in Table 4.3. Further detail on adjustments made to trip rates are included in the following section.

The productions and attractions output from the trip generation process are stored by zone by trip purpose in the TAZ geography file (TAZ_2007.dbd). This same master file includes the socioeconomic data for each model year. As a result, the number or density of productions and attractions can be illustrated by TAZ within TransCAD or a GIS.

4.2 Trip Generation Validation Adjustments

Adjustments were made to the trip attraction rates and special generators in order to validate the trip generation step in the travel demand model. Further detail is provided below.

Trip Attraction Rates

As noted above, trip production rates utilized in the 2007 model are the same as those utilized in the 2000 model. However, trip attraction rates were modified in the 2007 model as they were borrowed from the Jacksonville, Florida region for the previous 2000 model. Trip attractions for some purposes, such as HBW, differed appreciably from the trip productions and it was therefore decided to borrow trip attraction rates from the Knoxville model and adjust where appropriate in an attempt to achieve closer matches. Utilizing Knoxville trip attraction rates is likely more appropriate for the Chattanooga region due to potential differences in travel characteristics in the Jacksonville, Florida region. The Knoxville trip attraction rates documented in the Knoxville Regional Travel Demand Model Validation Report of March 2004 were based on their household travel survey using regression analysis. Using the Knoxville attraction rates resulted in some improvement in the unbalanced ratios for most trip purposes in Chattanooga. Adjustments were necessary to some of the trip attraction rates as trip purposes did not correlate perfectly between the


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Knoxville and Chattanooga models. The final Chattanooga 2007 model trip production and attraction rates are listed below.

Table 4.1 New Chattanooga Trip Production and Attraction Rates

Tota

l Hou

seho

lds

Tota

l Em

ploy

men

t

Agr

icul

tura

l/Min

ing/

Con

stru

ctio

n

Man

ufac

turin

g/Tr

ansp

orta

tion

Ret

ail

Serv

ice

Gov

ernm

ent

Scho

ol E

nrol

lmen

t

Tota

l Pop

ulat

ion

Home-Based Work

0.00 0.51 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Home-Based School

0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.72 0.00

Home-Based Shop

0.00 0.00 0.00 0.00 0.78 0.11 0.19 0.00 0.20

Home-Based Social Recreation

0.00 0.00 0.00 0.00 0.48 0.06 0.12 0.00 0.12

Home-Based Other

0.00 0.00 0.00 0.00 1.38 0.19 0.35 0.00 0.36

Nonhome-Based 1.54 0.36 0.00 0.00 3.83 0.31 0.64 0.00 0.00

Light-Truck 0.10 0.00 0.30 0.25 0.25 0.15 0.15 0.00 0.00

Medium-Truck 0.05 0.00 0.10 0.10 0.10 0.05 0.05 0.00 0.00

Heavy-Truck 0.05 0.00 0.05 0.05 0.05 0.05 0.05 0.00 0.00

Special Generators

The addition of special generators is a subjective and iterative process. Ideally, a model should only have special generators where standard trip rate equations would not calculate any trips (e.g., recreational areas and group quarters). However, most models also need special generators to account for locations where trips are significantly under- or over-estimated due to the unique nature of the land use (airports, colleges, universities, and tourist attractions typically fall into this category). Volume-to-count ratios in the areas surrounding each of these potential special generators were reviewed to determine whether or not special generators were needed. Special generator trips are derived by manually calculating trips using special generator trip rates and substituting the manual results for the machine-generated results.


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Although the 2000 TransCAD model included special generators at the airport, the University of Tennessee at Chattanooga, Chattanooga State College, and Chester Frost National Park, no special generators were assumed at the beginning of 2007 model validation effort. During the validation process, several of the special generators included in the 2000 model were added back in to the 2007 model, as well as several new special generators. A complete listing of special generators used in the model is provided in Table 4.2.

Table 4.2 Special Generator Locations

Zone Description 17a UTC Dorms

18 UTC Dorms

19 UTC Dorms

48* UTC Dorms

49 UTC Dorms and students

50 UTC Dorms and students

135 Lovell Field (CHA) Chattanooga Metro Airport

157a Newly added – Hamilton Place Mall

190 Chattanooga State College

197 Chester Frost Park

800a I-75 South External Station

801a U.S. 41/Chattanooga Road External Station

805a Ringgold Road External Station

806a GA SR 1/U.S. 27 South External Station

818a TN SR 8/U.S. 127/Taft Highway External Station

820a U.S. 111 External Station

822a TN SR 309/Leggett Road External Station

823a TN SR 29/U.S. 27/N. Rhea Co. Hwy. External Station

827a TN SR 60/Georgetown Road External Station

829a I-75 North External Station

a Indicates new special generator added to 2007 model.

As noted in Section 3.2, special generator attractions were added to some of the external stations in an attempt to correct overassignments that were occurring in their vicinity. In the south of the model, there was major overassignment on several north-south arteries and the thought was that some of the trips traveling north into Chattanooga should really be traveling towards Dalton and areas to the South. To correct that, attractions were added to


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some of the external stations, such as I-75 South, to attract trips in that direction. Similarly, the roads coming off the Cumberland Escarpment (Walden Ridge) into the Tennessee River Valley and I-75 and SR 60 leading into the Cleveland, Tennessee area received the same treatment with attractors being placed to pull some trips in that direction, rather than going into Chattanooga.

Special generators are contained in the special generator input file in the format of number of productions or attractions by trip purpose by TAZ. The special generators input file is specific to each year and is titled, year_SPGEN.bin.

4.3 Trip Generation Validation Results

Table 4.3 provides comparisons of aggregate trips per household, person, and employee, along with persons per household between the CHCNGA 2007 TransCAD model and the previous 2000 model. There were approximately nine person trips per household in the Chattanooga region in the 2007 model, within TDOT’s target range of 8.5 to 10.5.

Table 4.3 Aggregate Trip Rates

Chattanooga Standards

Unit of Measure 2007 2000 TDOT FHWA

Persons per Household 2.38 2.50 n/a n/a

Internal Trips per Household

9.00 9.44 8.5-10.5 8.0-14.0

Internal Trips per Person 3.78 3.78 n/a 3.5-4.0

HBW Trips per Employee 1.12 0.74 n/a n/a

Employees per Person 0.51 0.73 n/a n/a

Total Population 425,666 395,061

Total Households 178,905 158,055

Total Employment 218,612 287,918

Table 4.4 demonstrates the average number of trips per household by trip purpose in the 2007 model.


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Table 4.4 2007 Trips per Household by Trip Purpose

Trip Purpose 2007 Trips Per Household Home-Based Work 1.37

Home-Based School 0.55

Home-Based Shop 1.05

Home-Based Socrec. 0.64

Home-Based Other 1.87

Non Home-Based 2.75

As indicated in Table 4.5 below, HBW trips represent approximately 16.6 percent of all the trips generated in the Chattanooga region, slightly below TDOT’s target of 18 percent (excludes commercial vehicle and external trips). Approximately 50 percent of trips in the Chattanooga region can be attributed to HBSchool, HBShopping, HBSR, and HBO trips purposes, within TDOT’s target of 47 to 54 percent. NHB trips are slightly higher than the desired range of 22 to 31 percent at 33 percent. Commercial vehicles represent approximately seven percent of the trips in the 2007 model, a reduction compared to the 2000 model. It must be noted, however, that employment in the 2007 model is lower than for the 2000 model, contributing to the reduced commercial vehicles, as demonstrated in technical submittal #2. It should be noted that part of this low-simulation problem is a function of the household travel survey which has shown somewhat surprising results based on previous trip rate analyses of the survey data. The TPO intends to conduct a new household survey when the budget is available so that a new cross classification matrix of trip rates might be calculated.

Table 4.5 Percent of Trips by Purpose

Trip Purpose

Percent Trips

2007 TDOT Target Home-Based Work 17% 17% 18-27%

Home-Based School 7%

50% 47-54% Home-Based Shop 13%

Home-Based Socrec. 8%

Home-Based Other 23%

Non Home-Based 33% 33% 21-31%

Total 100% 100% 100%


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5.0 Trip Distribution Trip Distribution models link trip productions and attractions between pairs of TAZs. These interchanges are typically calculated through application of a Gravity Model. Gravity Models distribute trips among zones directly proportional to the relative attractiveness of each individual zone and inversely proportional to the friction between zones (i.e., distance). The result is a matrix of person trips that is later balanced in order to be defined in terms of origins and destinations (as opposed to productions and attractions). Resulting person trip matrices are processed later in the model chain during mode choice to convert these to balanced vehicle trips.

5.1 Trip Distribution Model Structure

The trip distribution step of the model estimates or predicts the spatial pattern of trips between origin and destination zone pairs. The general distribution process includes the building of highway networks and travel-time skims as well as application of the Gravity Model. This includes updating the travel-time skims with intrazonal and terminal times, distributing trips between zones using a Gravity Model, and producing a set of congested highway skims. The primary input data used for trip distribution is the friction factor (F_FACTORS.bin) file. This file is used by the Gravity Model to measure the effects of spatial separation between zones for the purpose of trip distribution. It is generally assumed that trips are less likely to be allocated to destinations with greater travel times if alternative destinations with lesser travel times and similar attractiveness are available.

Friction factors from the previous CHCNGA 2000 model were used as a starting point for the new CHCNGA 2007 TransCAD model. They were further modified during the model validation process as discussed in Section 5.2.

Intrazonal times represent the travel time within or across a zone. These times are calculated as one-half the travel time from one zone to the nearest adjacent zone. Terminal times represent the time involved at either end of a trip to travel from an origin to a vehicle or from the vehicle to a final destination. More specifically, this accounts for the time necessary to walk to or from the vehicle used for any given trip. Table 5.1 lists the terminal times by area type used in the CHCNGA 2007 TransCAD model. Terminal times inside the study area are typically greatest in central business districts.


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Table 5.1 Terminal Times

Terminal Times Area Types Area Type Descriptions 5 1 Central Business District (CBD)

3 2 Central Business District (CBD) Fringe

1 3 Residential

2 4 Outlying Business District

1 5 Rural

1 6 Urban Undeveloped

1 7 Mountainous

2 8 Industrial

10 9 External Centroid Connector

5.2 Trip Distribution Model Development and Validation

Validation of the CHCNGA 2007 trip distribution model primarily involved modification of the highway network, friction factors, and K-factors. Evaluation of the trip distribution model was accomplished by comparing statistics for average trip length and the percentage of intrazonal trips between the CHCNGA 2007 model and other comparable models in the southeast, including the previous CHCNGA 2000 model.

Network Link Attributes

As part of the model validation process, the TPO conducted an in depth review of the highway network, particularly in downtown Chattanooga and in the Enterprise South Industrial Park. Network characteristics were updated to more accurately reflect the conditions of the roadway system in the CHCNGA study area for the year 2007. In addition to updating existing roadway characteristics, the TPO added a new area type (8-Industrial). Field review also resulted in some changes to network characteristics. The master network, which includes all network years, is titled LRTP_MASTER_NETWORK.dbd.

Friction Factors

Initially, friction factors from the previous 2000 model, which were borrowed from the earlier MINUTP model, were used as part of the validation of the 2007 model. However, upon review of the average trip lengths, it was determined that adjustments to the friction factors were necessary. As a result, the TPO first developed and calibrated new friction factors to match the Chattanooga 2002 Household Travel Diary Survey data. However,


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these new friction factors resulted in unsatisfactory results. Average trip lengths were proving to be shorter than expected and overall validation results were consequently worse. As a result, the original friction factors from the previous 2000 model were iteratively adjusted to achieve better trip length distribution characteristics. Several iterative runs were performed to arrive at the final friction factors used for the remainder of the model validation runs. The final friction factors (F_FACTORS.bin) are included in the complete model dataset that is being provided to TDOT and GDOT as part of this submittal.

K-Factors

K-Factors are sometimes used during the validation process to adjust the trip patterns estimated or predicted by the Gravity Model. K-Factors are typically used at water crossings and between areas with different socioeconomic characteristics, (e.g., rural verses urban conditions). Just as was included in the previous 2000 model, K-factors were necessary between areas north and west of the Tennessee River and areas south and east of the Tennessee River, as well as between Georgia and Tennessee. However, unlike the previous model, the K-factors were not directionally skewed to/from Georgia and Tennessee. K-Factors are stored in a zone-to-zone matrix file (K_FACTORS.mtx) in TransCAD.

Tables 5.2 and 5.3 demonstrate the number of trips between K-Factor districts for the years 2007 and 2035, respectively.

Table 5.2 2007 Trips Between K-Factor Districts

2007 K-Factor District Trip Interchanges

District North of River South of River in Tennessee Georgia

External Stations

North of River 295,216 48,598 13,033 54,204

South of River in Tennessee 124,147 717,149 115,740 110,646

Georgia 13,969 59,732 187,369 40,186

External Stations 12,768 12,938 9,754 34,391


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Table 5.3 2035 Trips Between K-Factor Districts

2035 K-Factor District Trip Interchanges

District North of

River South of River in Tennessee Georgia

External Stations

North of River 412,044 79,091 19,644 77,977

South of River in Tennessee 167,164 1,045,880 156,318 163,274

Georgia 16,718 75,241 252,564 55,793

External Stations 18,603 20,753 13,464 48,564

Penalties and Prohibitors

A turn penalty and/or prohibitor file allows for the adjustment of travel times on specific links by either inducing a time penalty to pass from one link to another or prohibiting the movement all together. Prohibitors are typically confined to ramp intersections. However, since interstates and expressways are dual-line coded in the model network, the need for turn prohibitors at interchanges is eliminated. As a result, no prohibitors were included in the CHCNGA 2007 TransCAD model. Furthermore, K-factor and speed adjustments provided satisfactory distribution results without requiring travel-time penalties.

However, it was found necessary to add penalties, primarily along the Tennessee River bridges, to correct local imbalances. Table 5.4 below lists the locations and amount of the penalties. In addition, there is a penalty along Mountain Creek Road, as this corridor is a winding, narrow roadway with a steep grade. Other characteristics coded into the network fail to fully address the hazards of taking this route, which was dramatically overassigning. Penalties are stored in a binary file titled CHATT_TURN_PENALTY.bin.

Table 5.4 Penalties

Roadway Penalty (minutes)

U.S. 27 Bridge 1.35

N. Market Street Bridge 1.10

Dupont Parkway 0.25

Mountain Creek Road 2.00


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5.3 Trip Distribution Model Results

The two fundamental Gravity Model checks discussed in this section are the average trip length by purpose and the percentage of intrazonal trips. An analysis of volume-to-count summaries along screenlines also can be helpful in establishing the accuracy of trip distribution. However, as screenline summaries apply more significantly to the analysis of traffic assignment, these will be discussed later in Section 7.0.

Average Trip Length by Purpose

Table 5.5 demonstrates the final average trip lengths for each trip purpose in comparison to the old 2000 model. In addition, year 2007 HBW trip lengths were compared to those included in the Census Transportation Planning Package (CTPP) for the year 2000 in Hamilton, Catoosa, and Walker Counties. HBW trip lengths improved in the 2007 model compared to the 2000 model as they are closer to the CTPP trip lengths. However, the 2007 model HBW trip lengths are still slightly shorter when compared to the CTPP trip lengths. This is as a result of the daily nature of the model compared to the highly peak hour-weighted CTPP figure. The modest expansion of the model to include all of Catoosa County since the last LRTP partially explains the reduction in Internal-External trip times. All of the 2007 trip lengths are within acceptable limits provided by the Federal Highway Administration (FHWA). No trip length targets have been established by TDOT at this time.


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Table 5.5 Average Trip Length (in Minutes)

2007 2000

Purpose Chattanooga (TransCAD)

Chattanooga (TransCAD)

CTPP (Hamilton)

CTPP (Catoosa)

CTPP (Walker)

FHWA Target

Home-Based Work 18.26 16.36 21.20 23.70 26.50 11.2-35.4

Home-Based School 13.85 14.48 n/a n/a n/a 8.9-15.9

Home-Based Shop 12.84 13.78 n/a n/a n/a 8.6-18.7


13.55 11.38 n/a n/a n/a 10.4-17.3

Home-Based Other 12.44 14.41 n/a n/a n/a

Nonhome-Based 14.18 15.44 n/a n/a n/a 8.1-17.1

Commercial Vehicles

17.88 19.64 n/a n/a n/a n/a

Light-Truck 17.78 18.79

Medium-Truck 17.20 17.95

Heavy-Truck 20.75 22.17

Internal-External 37.38 41.04 n/a n/a n/a n/a

Total 14.53 18.68 n/a n/a n/a n/a

Intrazonal Trip Distribution

The 2007 model validation effort involved significant splitting of zones, particularly towards the periphery. This reduced the average size of zones. Consequently, as indicated in Table 5.6, the percent intrazonal trips fell slightly to below nine percent as compared to above nine percent for the 2000 model. As expected, given the tendency of individuals to travel further for work purposes, the percent intrazonal trips for HBW are lower than for other purposes at just under two percent. Providing the percent of intrazonal trips by purpose assists with assessing zone size and the attenuation of trips.


53

Table 5.6 Intrazonal Trips by Trip Purpose

Chattanooga (TransCAD) Percent Intrazonal

Purpose 2007 2000

Home-Based Work 1.93% 7.04%

Home-Based School 6.63% 11.12%

Home-Based Shop 12.51% 9.93%


11.98% 21.08%

Home-Based Other 12.96% 11.16%

Nonhome-Based 9.61% 8.02%

Commercial Vehicles 2.77% 3.06%

Light-Truck 2.74% 2.95%

Medium-Truck 3.46% 4.15%

Heavy-Truck 1.27% 1.19%

Total 8.89% 9.18%


54



55

6.0 Mode Choice Currently, the Chattanooga TransCAD model does not include a transit network/pathbuilding component. At the beginning of the 2035 LRTP Update, the TPO intended to add transit to the TransCAD model contingent upon the availability of existing data to validate the new transit component. However, upon review of the data, it was determined that an on-board transit survey was needed in order to validate a new transit model. The TPO will be developing the survey instrument for the on-board transit survey shortly after the adoption of the 2035 LRTP Update. Subsequently, the TPO will conduct the on-board survey in the fall of 2010, in preparation for the next base year 2010 model for the LRTP Update to be adopted in 2014. The TPO intends to add the transit network/pathbuilding component to the next generation of the TransCAD model in time for the next LRTP update. In the interim, the same auto occupancy model used in the model from the previous 2030 LRTP Update is being used for the current 2035 LRTP Update. Ratios of persons per vehicle were derived from the local household diary survey conducted in the Chattanooga region in 2002. These persons per vehicle ratios by trip purpose were used to convert person trips to vehicle trips.

Although the current model does not include a transit network, it does include a vehicle occupancy allocation component that disaggregates vehicle trips by single occupancy vehicle (SOV) and high-occupancy vehicle (HOV) categories. Trips also are allocated by truck categories. This is useful in evaluating HOV lanes or truck-exclusive lanes.

This section of the report describes the different mode choice structures used to generate the three types of trip tables for input into their respective assignment processes, as follows:

• General Highway Assignment;

• Exclusive HOV or Truck Lane Assignment; and

• Time-of-Day Assignment.

Each of the three mode choice processes are detailed below.

6.1 Mode Choice Model Structure for General Highway Assignment

The CHCNGA 2007 model was validated using the General Highway Assignment process. The CHCNGA 2007 mode choice model first balances the External-External (EE) trip table and then adds these preloaded EE trips to the trip table, including all of the other trip purposes. The six internal passenger vehicle trip purposes (HBW, HBSchool, HBShop, HBSR, HBO, and NHB) are then converted from person trips to vehicle trips using the auto occupancy rates included in Table 6.1. Auto occupancy rates were calculated by purpose


56

from the household travel characteristics survey. The three truck purposes (LDTK, MDTK, and HDTK) and the Internal-External (IE) trip purpose already are in vehicle trips and are therefore not converted during mode choice.

Table 6.1 Auto Occupancy Rates

Purpose Persons/Auto

Home-Based Work 1.12

Home-Based School 1.12

Home-Based Shop 1.48

Home-Based Social/Recreational 1.72

Home-Based Other 1.65

Nonhome-Based 1.68

Auto occupancy rates are only applied when running the General Highway Assignment option. This model option was used to produce the validation summary statistics found in Section 7.0 of this report.

6.2 Mode Choice Model Structure for Exclusive HOV or Truck Lanes

As noted earlier, a vehicle occupancy allocation component is included in the mode choice model in order to evaluate the impact of exclusive HOV or truck lanes. This component disaggregates vehicle trips into the following three categories:

• SOVs;

• HOVs with two persons per vehicle; and

• HOVs with three or more persons per vehicle.

The share of SOV and HOV trips were generated from the Chattanooga household travel diary survey and are provided by trip purpose in Table 6.2 below. An iterative process was used to adjust the factors during the last model update, as the initial run using the factors directly from the survey were significantly overestimating the number of trips in the model. As a result, the factors were adjusted proportionately to achieve the correct number of trips. The same factors used in the final 2000 model were used in the current 2007 model.


57

Table 6.2 Vehicle Occupancy Allocation by Trip Purpose

Vehicle Occupancy

Trip Purpose

HBW HBSchool HBShop HBSR HBO NHB

SOV 80.5% 80.0% 41.0% 25.0% 28.7% 26.6%

HOV 2 14.6% 15.0% 44.3% 56.3% 53.5% 46.4%

HOV 3+ 4.9% 5.0% 14.8% 18.8% 17.8% 27.0%

Total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0%

Based on the Chattanooga external origin/destination survey, approximately 39 percent of external trips were allocated to SOV trips, 24 percent to HOV2 (two persons/vehicle) trips, and 23 percent to HOV3 (three or more persons/vehicle) trips. The remaining 14 percent of external trips were allocated to truck purposes.

Trips also are allocated by truck categories, as described earlier in this report. These trips already are in vehicle trip equivalents so vehicle occupancy conversions are not needed:

• Light-Duty Truck;

• Medium-Duty Truck; and

• Heavy-Duty Truck.

Based on the Chattanooga external origin/destination survey, approximately five percent of external trips were allocated to light-duty truck trips, five percent to medium-duty truck trips, and four percent to heavy-duty truck trips. The share of truck and SOV/HOV trips are only applied when running the HOV Only or Truck Only Assignment processes.

6.3 Mode Choice Model Structure for Time-of-Day Model

Once all trip purposes are converted to vehicle trips, a.m. and p.m. peak hour trip tables can be generated using the peak hour factors derived from the household travel diary survey. As part of the evaluation of the household travel survey, the percent of trips that occur within each hour of the day (peak hour factors) were calculated and are depicted in Table 6.3. The a.m. peak hour occurs between 8:00 a.m. and 9:00 a.m., as the highest percent of trips in the morning occurs during that hour in Chattanooga, at approximately 7.4 percent. The p.m. peak hour occurs between 5:00 p.m. and 6:00 p.m., as the highest percent of trips in the afternoon occurs during that hour, at approximately 8.7 percent.


58

The time-of-day model is an optional step that can only be applied to the General Highway Assignment model and is done by checking the a.m. Assignment and/or p.m. Assignment boxes in the user interface before running the General Highway Assignment.

It should be noted that the time-of-day factors are applied after the trips are assigned and thus, do not account for diversion in trips as a result of peak hour congestion. Therefore, it is not a true time-of-day component. The TPO is exploring the possibility of developing a true time-of-day model for the Chattanooga region that will be validated based on traffic counts by time-of-day. Since time-of-day models are necessary for transit modeling, it will likely be a combined model enhancement effort.

Table 6.3 Temporal Distribution of Trips

Hour Percent of Trips 12:00 to 1:00 a.m. 0.4%

1:00 to 2:00 a.m. 0.1%

2:00 to 3:00 a.m. 0.2%

3:00 to 4:00 a.m. 0.0%

4:00 to 5:00 a.m. 0.1%

5:00 to 6:00 a.m. 0.5%

6:00 to 7:00 a.m. 2.3%

7:00 to 8:00 a.m. 7.0%

8:00 to 9:00 a.m. 7.4%

9:00 to 10:00 a.m. 4.7%

10:00 to 11:00 a.m. 5.3%

11:00 a.m. to 12:00 p.m. 6.1%

12:00 to 1:00 p.m. 6.9%

1:00 to 2:00 p.m. 6.8%

2:00 to 3:00 p.m. 6.6%

3:00 to 4:00 p.m. 8.0%

4:00 to 5:00 p.m. 7.5%

5:00 to 6:00 p.m. 8.7%

6:00 to 7:00 p.m. 8.1%

7:00 to 8:00 p.m. 5.3%

8:00 to 9:00 p.m. 3.5%

9:00 to 10:00 p.m. 2.6%

10:00 to 11:00 p.m. 1.3%

11:00 p.m. to 12:00 a.m. 0.5%

Total 100.0%

Note: Percent of trips based on trips ending during time period.


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7.0 Highway Assignment The purpose of highway assignment models is to load vehicle trips onto the highway network. This results in traffic estimates on individual links that ultimately attempt to simulate general vehicular travel throughout the study area. Supplemental assignment processes were generated for simulating HOV and truck exclusive facilities, and time-of-day simulations.

Validation of the highway assignment involved iterative modifications to centroid locations, verification of counts, and adjustment of speeds, capacities, K-Factors and other parameters related to trip distribution. A number of key evaluation statistics are generated during the assignment phase of the model. Volume-to-count ratios are compared by area type, facility type, laneage, and screenlines. Along with these statistics, the root mean squared error (RMSE) was generated by volume group.

This section describes validation of the highway assignment model. It includes an overview of the model structure, development and adjustment of model parameters, and a review of model results.

7.1 Highway Assignment Model Structure

Trips are loaded onto the network by means of an iterative equilibrium highway load program based on an all-or-nothing capacity restrained assignment. A total of 11 iterations are conducted during base year model execution (maximum iterations are set to 15) and the convergence parameter is set to 0.001. A series of statistical summaries are subsequently generated as a result of code added to the model script to report validation statistics. The supplemental exclusive lane assignment model is used to test scenarios where selected vehicle classes (e.g., single-occupant autos) are restricted from using selected lanes and ramps (e.g., HOV lanes). The time-of-day assignment model is used to obtain assignment volumes for specific time periods. These supplemental models are not normally executed when conducting a general traffic assignment where only total daily traffic volumes are desired.

7.2 Development and Validation of Highway Assignment Model

In total, 23 major model runs were executed in order to validate the CHCNGA 2000 TransCAD model. In addition, several model runs were made inbetween major model runs to iterate minor adjustments. Model validation was accomplished by minimizing the difference between model simulated volumes and observed counts for the year 2007 on network links throughout the study area. As many count locations were accounted for as


60

possible in order to ensure a wide range of coverage geographically as well as to incorporate as many examples of facilities and land uses located within the study area.

Adjustments were made to key elements in the modeling process to achieve this validation. After each run, a summary of the results was compiled and analyzed in order to identify areas for improvement in the model and successful strategies toward validation. Appropriate changes consistent with the discoveries revealed during analysis were then implemented and subsequent runs were executed. This iterative process was continued until validation was achieved.

Changes made to the model during highway assignment validation consisted mainly of iterative adjustments to speeds and highway network editing, including adjustment of centroids and centroid connectors. Other adjustments discussed elsewhere in this report also impacted highway assignment results.

7.3 Highway Assignment Validation Results

In validating traffic assignment, final outcome of a travel demand model, common performance metrics include the following:

• Systemwide volume-to-count ratio;

• Volume-to-count ratios by link group (area type, facility type, and number of lanes);

• Volume-to-count ratios along screenlines;

• Percent difference in model volumes and counts by volume group;

• Systemwide coefficient of determination between assigned volumes and counts;

• Systemwide percent root mean square error; and

• Percent root mean square error by volume group.

Table 7.1 includes the volume-to-count ratios by facility type, area type, and number of lanes. Overall, the model is validating at 0.96, within acceptable limits. This also is an improvement in the overall validation since the 2000 model with a volume-to-count ratio of 0.95. Although the validation of expressways improved in the 2007 model, the validation of undivided principal arterials, minor arterials, and one-way facilities got worse when compared to the 2000 model. This can be attributed to the correction in the network coding in the 2007 model reflecting the 3rd and 4th Street one-way facilities in downtown Chattanooga. Furthermore, additional network detail was included in some portions of the model as a result of further TAZ splits, as well as a significant amount of more traffic counts being provided in the 2007 model. Therefore, although the 2007 model may indicate lower volume-to-count ratios for some facility type categories, it is likely more accurate than the 2000 model due to the additional traffic counts. In addition, no ramp counts were available in the 2000 model and have since been added to the 2007 model validating at a 2007 volume-


61

to-count ratio of 0.99. Four of the six facility type categories that have targets set by TDOT are within acceptable limits.

Although no targets have been established to date by TDOT for volume-to-count ratios by area type, seven of the eight area type categories are validating within +/- 10 percent. In addition, the new industrial area type category is validating at 0.90. The CBD area in downtown Chattanooga is validating at 0.74, which has historically validated lower than other categories in the Chattanooga model. With the exception of one-lane facilities (by direction), the 2007 model is validating better within each lane category compared to the old 2000 model.

Table 7.1 Volume Over Count Ratios by Facility Type, Area Type and Number of Lanes

Chattanooga Volume/Count Ratio 2007 2000 TDOT Targeta Facility Type

1. Interstate 1.02 0.98 +/- 7%

2. Expressway 1.04 0.94 +/- 7%

3. Principal Arterial Divided 0.98 0.98 +/- 10%

4. Principal Arterial Undivided 0.86 0.94 +/- 10%

5. Minor Arterial 0.80 0.88 +/- 15%

6. Collector 0.98 0.98 +/- 25%

7. Ramp 0.99 n/a

8. One-Way 0.49 0.71 n/a

Area Type

1. CBD 0.69 0.88

2. CBD Fringe 0.97 0.92

3. Residential 0.92 0.96

4. OBD 0.95 0.92

5. Rural 1.07 1.10

6. Urban Undeveloped 1.04 1.02

7. Mountainous 1.09 0.95

8. Industrial 0.90

Number of Lanes by Direction 1 0.88 0.93

2 0.99 0.98

3 0.98 0.95

4 1.03 0.92

Total 0.96 0.95


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The 10 screenlines from the previous model were kept and utilized to assist in model validation for the 2007 model. Their positions capture all the major traffic flows in the Chattanooga Region and thus further adjustments and additions were deemed unnecessary. A map of the screenline locations was provided in Section 2.0 (Figure 2.18). Maps of volume-to-count ratios on each link in the model with a count are included in Appendix E. For eight of the 10 screenlines, the volume-to-count ratios fall within the +/- 10 percent target range of TDOT. Table 7.2 compares the volume-to-count ratio for each screenline in the 2007 model against the old 2000 model.

Table 7.2 Comparison of Volume-to-Count Ratios by Screenline

Chattanooga Volume/Count Ratio

Screenline 2007 2000

1 1.00 0.97

2 1.01 0.94

3 0.88 0.97

4 0.99 0.91

5 0.82 0.90

6 0.93 0.99

7 1.10 1.09

8 0.91 1.06

9 1.06 1.02

10 1.00 1.00

Table 7.3 indicates the percent difference in model volumes and observed counts by volume group. All volume groups within the 2007 model achieve the established TDOT targets.


63

Table 7.3 Percent Difference for Daily Volumes (Calculated for Links with Counts)

AADT Chattanooga 2007TransCAD TDOT Targeta

<1,000 48.90% +/- 60%

1,000-2,500 19.20% +/- 47%

2,500-5,000 -2.80% +/- 36%

5,000-10,000 -10.30% +/- 29%

10,000-25,000 -8.90% +/- 25%

25,000-50,000 1.50% +/- 22%

>50,000 -5.90% +/- 21%

The correlation coefficient of observed counts to model volumes (R2) is performing well at 0.95, exceeding TDOT’s target of 0.88, as demonstrated below in Figure 7.1.

Figure 7.1 Correlation of Assigned Versus Observed Volumes

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000

Assigned Volume

2007 AADT

As indicated in Table 7.4, the overall RMSE for the 2007 model is 34.6 percent, within acceptable Federal limits. TDOT has established an overall RMSE target of 30 percent. However, based on discussion with TDOT during the June 30, 2009 teleconference, it was


64

determined that 30 percent was just a target and was not required as Federal standards indicate a RMSE range of 32 to 39 percent is within acceptable limits (according to the FHWA Model Validation and Reasonableness Checking Manual). Although the previous 2000 model indicated an overall RMSE of 23 percent, it is suspected that it was not as accurate due to the reduced amount of traffic counts available at that time. All volume groups within the 2007 model achieved a RMSE value close to or within Federal and/or TDOT targets.

It should be noted that volume-over-count ratio charts relative accuracy and whether there is a systemwide under- or over-assignment, whereas RMSE measures assignment accuracy irrespective of whether these are generally over- or under-assignments. Achieving 0.96 in the 2007 model instead of 0.95 in the 2000 model is indicative of higher traffic assignments overall, which might not impact the overall percent error in a positive manner. The 0.96 overall volume/count ratio is reflective of the possibly low simulation of HBW trips, discussed earlier. Another consideration is that several outlying lower volume roads were added to the model near the boundary which could potentially negatively affect the 2007 RMSE results in particular.

Table 7.4 Root Mean Square Error (RMSE) by Volume Group

Count Range

Chattanooga TransCAD

TDOT Target

FHWA and New FDOT Guidelines

and Standards 2007 2000

0-4,999 83.70% 73.10% 115.76 45-100

5,000-9,999 46.30% 33.60% 43.14 35-45

10,000-14,999 36.40% 18.10% 28.27 27-35

15,000-19,999

25.40% 21.70%

25.38

25-30

20,000-29,999 15-27

30,000-39,999 16.90% 15-25

40,000-49,999 12.10%

4.40% 30.25

50,000-59,999 7.20% 10-20

60,000-69,999

15.50% n/a 19.20 10-19

70,000-79,999

79,999-89,999

Overall 34.60% 23.40% 30.00% 32-39%

Table 7.5 summarizes the vehicle miles traveled (VMT) by model facility type, as well as the percent of VMT that falls within each model facility type compared to TDOT targets. With the exception of minor arterials, all of the facility types fall within or close to TDOT’s targets


65

for percent of VMT by facility type. In addition, the overall ratio of VMT to Highway Performance Monitoring System (HPMS) VMT is 1.06 (excluding external centroid connectors). While this general VMT distribution might be off for freeways and arterials, volume-over-count ratios show a favorable validation of these links. As a result, the only way to better match the VMT distribution would be to worsen the volume-over-count statistics.

Table 7.5 Vehicle Miles Traveled by Model Facility Type

Facility Type Chattanooga 2007 Model VMT TDOT Target

Interstate 4,228,041 (31.4%) 33-38%

Expressway 1,496,818 (11.1%)

Principal Arterial Divided 2,067,224 (15.4%) 27-33%

Principal Arterial Undivided 835,239 (6.2%)

Minor Arterial 1,384,961 (10.3%) 18-22%

Collector 1,465,718 (10.9%) 8-12%

Ramp 215,118 n/a

One-Way 16,672 n/a

External Connectors 921,730 n/a

Centroid Connectors 827,412 n/a

Total 13,458,933

Comparison to Observed Speeds

During November 2008, the TPO conducted travel time runs during the a.m. and p.m. peak-periods along all routes in their Congestion Management Plan (CMP). The results of these travel time runs were used to calculate average peak-period congested speeds. These observed speeds were then compared to the daily congested speeds in the model during the 2007 model validation process. Appendix D includes a map of the observed 2008 a.m. peak-period congested speeds, as well as a map of the daily congested speeds from the 2007 model. As expected, the model speeds compared to the observed speeds are slightly different in some instances since the model speeds are daily and the observed speeds are peak-period. However, there was a significant improvement in congested speeds along interstates in the 2007 model as they were too low in the 2000 model.


66



67

8.0 Summary and Conclusions Section 8.0 provides a bullet list summary of the 2007 model validation observations, as well as details on future model enhancements and data collection efforts planned by the TPO.

8.1 Summary of 2007 Model Validation Observations

Below is a summary of 2007 model validation observations:

• The overall 2007 model is validating at an RMSE of 34.6 percent, within acceptable Federal limits;

• The 2007 model is validating at a systemwide volume-to-count ratio of 0.96, within acceptable limits and improved since the 2000 model;

• The correlation coefficient of observed counts to model volumes (R2) is performing well at 0.95, exceeding TDOT’s target of 0.88;

• Eight of 10 screenlines are validating within acceptable limits;

• The overall ratio of model VMT to HPMS VMT is 1.06;

• Average trip lengths increased for some trip purposes and decreased for others, although HBW trip lengths did improve;

• The percent of intrazonal trips attributed to HBW trips are now within a more reasonable range;

• Congested speeds along the interstate and other higher facilities are improved compared to the 2000 model and observed congested speeds;

• Overall, higher facilities are generally comparable to the 2000 model, however, minor facilities got worse in the 2007 model due to additional traffic count availability and network detail;

• Overall, the 2007 model has more counts with almost 10 percent of the network having counts. As a result, the 2007 model includes improved accuracy and reliability of the model statistics;

• Employment in the 2007 model is lower than in the 2000 model, resulting in lower commercial trips; and

• As with all models, there is always room for improvement. However, this model should be sufficient for updating the 2030 LRTP to the year 2035.


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8.2 Future Model Enhancements

Several enhancements are planned for the next generation of the Chattanooga travel demand model to be used for the next LRTP update scheduled for adoption in 2014. These enhancements, as well as the planned data collection efforts necessary to support these enhancements, are detailed below.

Data Collection

In preparation for the next LRTP Update due for adoption in 2014, the TPO is planning for multiple data collection and compilation efforts over the next two years. Below are some of the data collection efforts planned:

• Socioeconomic Data – Once the Census 2010 population and household data is released, likely in 2012, the TPO will use the data to develop the base year 2010 model socioeconomic data. In the meantime, the TPO will be providing guidelines to the counties and municipalities in the TPO region stating what socioeconomic data is required to assist with compiling the data. Additionally, proprietary employment datasets for the year 2010 may be evaluated for accuracy to determine the most appropriate data source for the Chattanooga region. In addition to year 2010, the TPO will be forecasting socioeconomic data to the horizon year for the next LRTP Update, likely year 2040.

• Traffic Counts – During calendar year 2010, the TPO will be identifying and collecting traffic counts at key locations throughout the TPO to assist with validating the 2010 base year model as part of the next LRTP update. The traffic counts will be collected by vehicle class and 15-minute intervals in order to validate trips at the truck level and to include a new time-of-day component in the model.

• External Origin and Destination Survey – In 2002, a roadside origin-destination intercept survey designed to obtain characteristics of travelers entering, exiting, and passing through the region from locations outside the CHCNGA study area was conducted. During the last 2030 LRTP Update, it was determined that the results from the 2002 external origin and destination survey were biased. As a result, during the last 2030 LRTP Update, as well as this current 2035 LRTP Update, the 2002 roadside origin-destination intercept survey was not used within the TransCAD model. Therefore, the TPO intends to conduct a new external origin and destination survey during the fall of 2010. In the meantime, the TPO will be designing the sampling plan and survey instrument. The results of the 2010 external origin and destination survey will be used to validate the external model for the 2010 base year validation as part of the next LRTP update.

• On-Board Transit Survey – As mentioned earlier, the TPO intends to conduct an on-board transit survey in order to validate a new mode choice/transit component in the TransCAD travel demand model. The TPO will be designing the sampling plan and


69

survey instrument in the spring/summer of 2010 with the survey being conducted in the fall of 2010.

• Household Travel Diary Survey – In 2002, a household travel diary survey was conducted to determine trip generation rates, average trip lengths, auto occupancy factors, and other characteristics used in model development and validation. Typically, household travel diary surveys are conducted every 10 years to accurately reflect travel characteristics of the region. Pending funding availability, the TPO intends to conduct a new household travel diary survey in calendar year 2011. The results of the 2011 travel diary survey will be incorporated into the new 2010 base year model for the next LRTP update.

• Bicycle and Pedestrian Counts – If a nonmotorized component is added to the travel demand model prior to validating the 2010 base year model for the next LRTP Update, the TPO will collect bicycle and pedestrian counts. Currently, the TPO owns three bicycle and pedestrian counters and has begun collecting counts in key locations.

Travel Demand Model Enhancements

The above mentioned data collection efforts will be used to incorporate several enhancements to the current CHCNGA TPO TransCAD model. These enhancements could potentially include the following additions to the TransCAD model prior to the next LRTP Update:

• Updated external model based on 2010 external data;

• Updated trip generation structure based on 2011 household travel diary survey data;

• New mode choice/transit component not previously included in the model to be used to forecast transit ridership;

• New nonmotorized component not previously included in the model to be used to forecast bicycle and pedestrian trips;

• New time-of-day component used to disaggregate daily trips into three to four time periods. This will improve the accuracy in calculating air quality emissions and is typically necessary for transit models; and

• Validate truck trips in addition to total trips, whereas in the past, only total trips were validated.


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Appendix A: Network Project Lists

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Sha

llow

ford

Rd.

S

R 3

171.

2W

iden

ing

Wid

en fr

om 4

to 6

lane

s20

0520

07 &

200

9

No

Yes

Yes

Cha

ttano

oga

I-75

SR

317

1.1

mile

sou

th o

f SR

2/U

S 1

13.

1W

iden

ing

Wid

en fr

om 4

to 8

lane

s20

0720

07 &

200

9

No

Yes

Yes

3301

5C

hatta

noog

aI-7

5N

ew In

terc

hang

e at

Mile

9

(Ent

erpr

ise

Sou

th)

New

In

terc

hang

eN

ew In

terc

hang

e at

Mile

9 (E

nter

pris

e S

outh

)20

0720

07 &

200

9

No

Yes

Yes

107*

STP

-M-9

202(

52)

Cha

ttano

oga

3rd

St./

4th

St.

Lind

say

Bro

ad S

t./G

eorg

ia A

ve.

0.5

Wid

enin

gW

iden

from

2 to

4 la

nes

2003

2007

& 2

009

No

Yes

Yes

21c

TN07

-LO

C01

Cha

ttano

oga

Ent

erpr

ise

Blv

d.E

nter

pris

e P

kwy.

For

kE

nter

pris

e S

outh

Blv

d. c

ul-d

e-sa

c1.

1N

ew

Con

stru

ctio

nC

onst

ruct

new

4-la

ne ro

adw

ay fr

om E

nter

pris

e P

kwy

to e

xist

ing

cul-d

e-sa

c20

0820

09N

oY

esY

es

21d

3304

110

7637

.02

Cha

ttano

oga

SR

317

C

onne

ctor

(P

ropo

sed)

I-75

Ent

erpr

ise

Sou

th

Inte

rcha

nge

Api

son

Pik

e @

Old

Lee

Hw

y.0.

6N

ew

Con

stru

ctio

nN

ew 4

-lane

faci

lity

2009

2009

No

Yes

Yes

58TN

01-M

C01

110

1432

Cha

ttano

oga

Sha

llow

ford

Rd.

Sta

ndife

r Gap

Wes

t of C

ente

r St.

1.2

Wid

enin

gW

iden

ing

from

2 to

5 la

nes

(4 th

ru la

nes)

2008

2009

No

Yes

Yes

96S

TP-9

9-2

6504

40C

atoo

sa C

ount

yS

R 1

46La

kevi

ew D

r.I-7

51.

3W

iden

ing

Wid

en fr

om 2

to 4

lane

s, in

clud

ing

brid

ge

reco

nstru

ctio

n

2009

(rem

ove

from

20

09 n

etw

ork

for a

ir qu

ality

)

2009

(c

onst

ruct

ion

won

't be

co

mpl

ete

until

20

10)

No

Yes

Yes

98S

TP-9

8-3

6422

10C

atoo

sa C

ount

yS

R 1

46I-7

5 S

R 3

/US

41

0.6

Wid

enin

gW

iden

from

2 to

4 la

nes

2009

(rem

ove

from

20

09 n

etw

ork

for a

ir qu

ality

)

2009

(c

onst

ruct

ion

won

't be

co

mpl

ete

until

20

10)

No

Yes

Yes

102

TN01

-MC

002

(TN

)/S

TP-9

9-1

(GA

)10

1029

(TN

)/65

0430

(GA

)E

ast R

idge

(TN

)/Cat

oosa

C

ount

y (G

A)

Rin

ggol

d R

d.C

R 4

0 Fr

awle

y R

d.0.

03W

iden

ing

Wid

en fr

om 2

to 5

lane

s (4

thro

ugh

lane

s)20

0820

09N

oY

esY

es

111*

STP

-M-9

202

(36)

/TN

01-M

C00

610

1557

Cha

ttano

oga

Ash

land

Ter

race

Nor

cros

s R

d.

Kno

llwoo

d D

rive

1.3

Wid

enin

gW

iden

from

2 to

4 la

nes

2008

2009

No

Yes

Yes

Mod

el

Net

wor

k Ye

arLe

ngth

(m

iles)

Type

of

Proj

ect

Full

Des

crip

tion

Con

stru

ctio

n C

ompl

etio

n Ye

arEx

empt

?M

odel

ed?

Reg

iona

lly

Sign

ifica

nt?

LRTP

ID

TIP/

STIP

ID

DO

T PI

NJu

risdi

ctio

nR

oadw

ayFr

omTo

2015

Mod

el N

etw

ork

Proj

ects

(Sin

ce 2

009)

City

(Cou

nty)

Stat

eFr

omTo

15C

hatta

noog

aTN

SR 3

17/B

onny

Oak

s D

rive

SR 1

7I-7

5W

iden

ing

Wid

en fr

om 2

to 4

lane

s (a

lread

y fo

ur la

nes

eith

er d

irect

ion

of li

sted

te

rmin

i spe

cific

ally

from

Silv

erda

le

Roa

d ea

st to

I-75

and

from

Pr

eser

vatio

n D

rive

wes

t to

SR 1

7)4.

920

1020

11 E

+C &

20

15N

oYe

sYe

s

17a

3304

2C

hatta

noog

a/C

olle

geda

leTN

SR 3

17/A

piso

n Pi

keO

ld L

ee H

wy.

SR 3

21W

iden

ing

Wid

en fr

om 2

to 4

lane

s2.

1720

1020

11 E

+C &

20

15N

oYe

sYe

s

21b

8190

8.2

Cha

ttano

oga

TNEn

terp

rise

Pkw

y.En

terp

rise

Pkw

y./I-

75

Inte

rcha

nge

Ente

rpris

e Bl

vd./P

kwy.

Fo

rkN

ew

Con

stru

ctio

n

Con

stru

ct n

ew 4

-lane

road

way

(E

nter

pris

e Pk

wy.

) fro

m E

nter

pris

e Pk

wy.

/I-75

Inte

rcha

nge

to

Ente

rpris

e Bl

vd./P

kwy.

For

k20

1020

11 E

+C &

20

15N

oYe

sYe

s

101

3302

0C

hatta

noog

aTN

I-75

1.1

Mi s

outh

of S

R

2/U

S 11

0.

2 M

i nor

th o

f SR

2/U

S 11

Wid

enin

gW

iden

from

4 to

8 la

nes

1.3

2010

2011

E+C

&

2015

No

Yes

Yes

108

TN01

-MC

007

Cha

ttano

oga

TNSh

allo

wfo

rd R

d. G

unba

rrel

Rd.

Jenk

ins

Rd.

Wid

enin

gW

iden

ing

from

2 to

5 la

nes

(4 th

ru

lane

s)1.

120

1020

11 E

+C &

20

15N

oYe

sYe

s

3C

hatta

noog

a (H

amilt

on C

o.)

TNU

S 27

Nor

th o

f Ten

ness

ee

Riv

er B

ridge

SR 8

/Sig

nal M

ount

ain

Blvd

.W

iden

ing

Wid

en fr

om 4

to 8

lane

s2.

720

15N

oYe

sYe

s

4Fo

rt O

glet

horp

eG

AD

eitz

Rd.

SR 1

46/C

loud

Spr

ings

R

d.R

eeds

Brid

ge

Rd.

/Boy

nton

Rd.

Wid

enin

g/

Rea

lignm

ent

Wid

en fr

om 2

to 4

lane

s2.

120

15N

oYe

sYe

s

562

1530

Rin

ggol

d (C

atoo

sa

Co.

)G

ASR

151

/Ala

bam

a H

wy.

Hol

com

b R

d.U

S 41

/Nas

hvill

e St

.W

iden

ing

Wid

en fr

om 2

to 4

lane

s w

ith tu

rn

lane

s as

nee

ded

1.7

2015

No

Yes

Yes

10C

hatta

noog

a (H

amilt

on C

o.)

TNG

add

Rd.

Nor

cros

s R

d.

SR 1

53W

iden

ing

Wid

en fr

om 2

to 4

lane

s0.

220

15N

oYe

sYe

s

11C

hatta

noog

a (H

amilt

on C

o.)

TNC

entra

l Ave

. Ext

ensi

on3r

d St

.R

iver

side

Driv

eN

ew R

oadw

ay

(Ext

ensi

on)

2-la

ne e

xten

sion

0.6

2015

No

Yes

Yes

17a

3304

2

Cha

ttano

oga/

Col

lege

dale

(H

amilt

on C

o.)

TNSR

317

/Api

son

Pike

Old

Lee

Hw

y.SR

321

Wid

enin

gW

iden

from

2 to

4 la

nes

2.1

2015

No

Yes

Yes

17b

3304

3C

olle

geda

le

(Ham

ilton

Co.

)TN

SR 3

17/A

piso

n Pi

keSR

321

East

Bra

iner

d R

d.W

iden

ing

Wid

en fr

om 2

to 4

lane

s4.

020

15N

oYe

sYe

s

21e

Cha

ttano

oga

(Ham

ilton

Co.

)TN

Ente

rpris

e Pa

rkw

ayH

icko

ry V

alle

y R

oad

1 m

ile s

outh

of H

ighw

ay

58N

ew A

lignm

ent

0.6

2015

No

Yes

Yes

Juris

dict

ion

Con

stru

ctio

n C

ompl

etio

n Ye

arLe

ngth

(m

iles)

Mod

eled

?

Mod

el

Net

wor

k Ye

arEx

empt

?R

egio

nally

Si

gnifi

cant

?LR

TP

IDTy

pe o

f Pr

ojec

tPr

ojec

t Des

crip

tion

In

FY '0

8-'1

1 TI

P (A

men

ded

Feb

'09)

Term

ini

Roa

d N

ame

e(

ato

Co

)te

pse

aay

co

ya

eyoa

d58

eg

et

06

05

oes

es23

Fort

Ogl

etho

rpe

GA

Lake

view

Dr.

Page

Rd.

Cro

ss S

t.W

iden

ing

Wid

en fr

om 2

to 4

lane

s0.

720

15N

oYe

sYe

s

8833

025

Cha

ttano

oga

(Ham

ilton

Co.

)TN

US

27/I-

124

I-24

Sout

h of

Ten

ness

ee

Riv

erW

iden

ing

Wid

en fr

om 4

to 8

lane

s1.

520

15N

oYe

sYe

s91

Cat

oosa

Co.

GA

Thre

e Kn

otch

Rd.

Boyn

ton

Rd.

SR 2

Wid

enin

gW

iden

from

2 to

4 la

nes

0.3

2015

No

Yes

Yes

9433

045

Cha

ttano

oga

(Ham

ilton

Co.

)TN

SR 3

20/E

ast B

rain

erd

Rd.

East

of G

rays

ville

Rd.

Be

l Air

Rd.

Wid

enin

gW

iden

from

2 to

4 la

nes

1.9

2015

No

Yes

Yes

108

TN01

-MC

007

Cha

ttano

oga

(Ham

ilton

Co.

)TN

Shal

low

ford

Rd.

Gun

barr

el R

d.Je

nkin

s R

d.W

iden

ing

Wid

enin

g fro

m 2

to 5

lane

s (4

thru

la

nes)

1.0

2015

No

Yes

Yes

126

Cha

ttano

oga

(Ham

ilton

Co.

)TN

Hic

kory

Val

ley

Rd.

Ente

rpris

e Pa

rkw

ay

Exte

nsio

nH

ighw

ay 5

8W

iden

ing

Wid

en fr

om 2

to 4

lane

s1.

120

15N

oYe

sYe

s

128*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

ASt

reet

ASt

reet

CN

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

720

15N

oYe

sYe

s

129*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

BSt

reet

ASt

reet

AN

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

120

15N

oYe

sYe

s

130*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

CSt

reet

ASt

reet

EN

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

420

15N

oYe

sYe

s

131*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

DI-2

4C

hest

nut

New

Roa

dway

New

two

lane

col

lect

or ro

ad0.

620

15N

oYe

sYe

s

132*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

ESt

reet

FBr

oad

stN

ew R

oadw

ayN

ew tw

o la

ne c

olle

ctor

road

0.4

2015

No

Yes

Yes

133*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

FSt

reet

DW

28t

h st

.N

ew R

oadw

ayN

ew tw

o la

ne c

olle

ctor

road

0.3

2015

No

Yes

Yes

134*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

GSt

reet

FSt

reet

HN

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

120

15N

oYe

sYe

s

135*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

HSt

reet

DSt

reet

FN

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

220

15N

oYe

sYe

s

136*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

ISt

reet

DW

28t

h st

.N

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

220

15N

oYe

sYe

s

137*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

JSt

reet

DSt

reet

EN

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

120

15N

oYe

sYe

s

138*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

KSt

reet

DC

hest

nut

New

Roa

dway

New

two

lane

road

0.2

2015

No

Yes

Yes

139*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

LC

hest

nut

W 2

6th

st.

New

Roa

dway

New

two

lane

road

0.1

2015

No

Yes

Yes

140*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

MSi

ndey

St

Broa

d st

.N

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

120

15N

oYe

sYe

s

141*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

NM

iddl

e St

reet

Mid

dle

Stre

etN

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

320

15N

oYe

sYe

s

142*

**C

hatta

noog

a (H

amilt

on C

o.)

TNSt

reet

OSt

reet

NSt

reet

NN

ew R

oadw

ayN

ew tw

o la

ne ro

ad0.

120

15N

oYe

sYe

s

170*

***

Cha

ttano

oga

(Ham

ilton

Co.

)TN

SIA

Roa

d fo

r VW

(In

dust

rial A

cces

s R

d.)

Ente

rpris

e Bo

ulev

ard/

Dis

cove

ry

Dr.

SR 5

8N

ew R

oadw

ayIn

dust

rial a

cces

s ro

ad fo

r Vo

lksw

agen

2.3

2015

No

Yes

Yes

178

3302

7C

hatta

noog

a (H

amilt

on C

o.)

TNU

S 27

/Olg

iati

Brid

geR

iver

front

Pkw

y.M

anuf

actu

rer's

Rd.

Wid

enin

gW

iden

from

4 to

6 la

nes

2015

No

Yes

Yes

2025

Mod

el N

etw

ork

Proj

ects

(Sin

ce 2

015)

City

(Cou

nty)

Stat

eFr

omTo

5Y

esR

ingg

old

(Cat

oosa

C

o.)

GA

SR

151

/Ala

bam

a H

wy.

Hol

com

b R

d.U

S 4

1/N

ashv

ille

St.

Wid

enin

g

Wid

en fr

om 2

to 4

la

nes

with

turn

lane

s as

nee

ded

1.7

2025

No

Yes

Yes

6R

ingg

old

TN/G

A

SR

321

(TN

)/SR

151

(G

A)/O

olte

wah

-Rin

ggol

d R

d.Le

e H

wy.

US

41/

US

76

Wid

enin

gW

iden

from

2 to

4

lane

s12

.120

25N

oY

esY

es

15Y

esC

hatta

noog

a (H

amilt

on C

o.)

TNS

R 3

17/B

onny

Oak

s D

rive

SR

17

I-75

Wid

enin

g

Wid

en fr

om 2

to 4

la

nes

(alre

ady

four

la

nes

eith

er d

irect

ion

of li

sted

term

ini

spec

ifica

lly fr

om

Silv

erda

le R

oad

east

to

I-75

and

from

P

rese

rvat

ion

Driv

e w

est t

o S

R 1

7)5.

120

25N

oY

esY

es

18C

hatta

noog

a (H

amilt

on C

o.)

TNU

S 1

1/U

S 6

4/Le

e H

wy.

McC

utch

eron

Rd.

SR

317

Wid

enin

gW

iden

from

2 to

4

lane

s1.

620

25N

oY

esY

es

20C

hatta

noog

a (H

amilt

on C

o.)

TNS

now

Hill

Rd.

I-75

SR

312

/Mah

an G

ap R

d.W

iden

ing

Wid

en fr

om 2

to 4

la

nes

6.7

2025

No

Yes

Yes

33C

hatta

noog

a (H

amilt

on C

o.)

TNW

auha

tchi

e P

ike

US

11

US

41/

US

64

Wid

enin

gW

iden

from

2 to

4

lane

s2.

820

25N

oY

esY

es

39C

hatta

noog

a (H

amilt

on C

o.)

TNE

ast B

rain

erd

Rd.

Ban

ks R

d.S

R 3

21/O

olte

wah

-R

ingg

old

Rd.

Wid

enin

gW

iden

from

2 to

4

lane

s1.

620

25N

oY

esY

es

64C

hatta

noog

a (H

amilt

on C

o.)

TNJe

nkin

s R

d.S

tand

ifer G

apS

hallo

wfo

rd R

d.W

iden

ing

Wid

en fr

om 2

to 4

la

nes

0.8

2025

No

Yes

Yes

71C

hatta

noog

a (H

amilt

on C

o.)

TNM

ahan

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Appendix B: Technical Memorandum #1

Memorandum

TO: Bob Rock, TDOT Jerry Yuknavage, TDOT Tyrhonda Edwards, GDOT

CC: Angie Midgett, TDOT

FROM: Melissa Taylor, CHCNGA TPO Keli Paul, AICP, Cambridge Systematics

DATE: September 18, 2008

RE: Model Certification Submittal #1: Outline of TransCAD Model Assumptions Chattanooga-Hamilton County/North Georgia 2035 LRTP Update

Effective March 1, 2008, the Tennessee Department of Transportation (TDOT) Long Range Planning Division, Systems Planning and Policy Office, implemented a Division Procedure for the MPO model approval process. On August 20, 2008, the RPA met with its consultants along with TDOT, GDOT, and CARTA to discuss the TransCAD modeling efforts for the CHCNGA 2035 LRTP Update. It was agreed at that time that the following four submittals would be provided to TDOT and GDOT as part of TDOT’s model approval process:


2. Year 2007 and 2035 socioeconomic data files (TransCAD and GIS) for the TPO region, including any maps, graphs, charts, or tables developed as part of the RPA’s internal review;

3. Populated validation worksheet upon completion of draft validated model. This worksheet will include statistics for Trip Generation, Trip Distribution, Mode Choice (if applicable), and Traffic Assignment. If the assumptions included in submittal #1 change as part of the validation process, they will be documented and submitted for approval at this time; and


This technical memorandum constitutes Submittal #1 defined above. Below is an outline of modeling inputs and structure for each step of the traditional four-step modeling process. Further details addressing each output statistic or map required as a result of the TDOT Division Procedure are attached, both for the previous 2000 model and what is anticipated as part of the 2007 model. The attached table also incorporates recommendations from the report developed by the University of Tennessee, Center for Transportation Research, titled “Minimum

2457 Care Dr ive, Sui te 101 Tal lahassee, FL 32308

te l 850 219 6388 www.camsys.com fax 850 219 6389

Travel Demand Model Calibration and Validation Guidelines for State of Tennessee.” This report is also referenced in the TDOT Division Procedure.

1.0 TRIP GENERATION (includes Network data)

1.1 Network Data – The base year model network is being updated from year 2000 to 2007.

1.1.1 Network Refinement - Several roads are being added to the model network to more accurately depict travel patterns and to assist with splitting several of the larger traffic analysis zones (TAZs). TRIMS and Roadway Characteristics (RC) data were obtained from TDOT and GDOT, respectively, to assist with reviewing the link characteristics (facility type and number of lanes) currently in the model network. In addition, several windshield surveys were conducted to obtain area type, facility type, and number of lanes data for those roads being added to the model.

1.1.2 Traffic Counts – Daily traffic counts will also be updated in the 2007 network

using available count data from TDOT, GDOT, Hamilton County and the City of Chattanooga. Count data was not available from Catoosa, Dade, or Walker Counties. Supplemental 24-hour count data by vehicle classification will be collected in late September 2008 to supplement model validation efforts and assist with evaluating existing conditions for the Congestion Management Plan (CMP). Transportation Projects – Several lists of capacity-adding transportation projects included in each model year are being or will be developed as part of the LRTP update process. Each of these project lists will be provided upon completion to TDOT and GDOT, as well as the entire Interagency Consultation Committee (ICC). They are as follows:

• Year 2007 Projects - Projects that completed construction between the years

2000 and 2007 (currently being developed)

• Existing-Plus-Committed (E+C) Projects - Projects that are expected to complete construction between the years 2008 and 2011 (i.e. those in the Transportation Improvement Program (TIP)) (currently being developed)

• Year 2035 Financially Feasible Plan Projects – Projects funded in LRTP

• Year 2025 Funded Projects – Interim year 2025 funded projects

• Year 2015 Funded Projects – Interim year 2015 funded projects

1.2 Socioeconomic Data – The Regional Planning Agency (RPA) is currently developing the 2007 and 2035 socioeconomic data for the entire TPO region. Upon completion, Cambridge Systematics (CS) will conduct a thorough review of the data at the TAZ level, including the development of population, household, employment, hotel-motel, and school enrollment density maps. The TransCAD and GIS files, as well as the maps and any tables, charts, or graphs, will be provided to TDOT and GDOT for review as part of Submittal #2.

- 2 -

1.3 TAZ Refinement – The RPA is taking this opportunity to refine the TAZ structure in the

current TransCAD model. Many of the TAZs are rather large in the outlying areas. Additional network detail being added to the model will also effect the TAZ structure, including external zones.

1.4 Travel Survey Data – During the 2030 LRTP Update adopted in 2005, the Chattanooga

Household Travel Diary Survey conducted in 2002 was used to determine trip production rates for person trips. The Federal Highway Administration (FHWA) Quick Response Freight Manual (QRFM) was used to supply trip production rates for the truck trip purposes. Trip attraction rates were borrowed from the Northeast Regional Planning Model (NERPM) in Jacksonville, FL, as local data was not available. These same trip production and attraction rates will be used for this model update. Although the percent split of Internal-External (IE)/External-External (EE) trips at each external station was developed from the Chattanooga Urban Area Origin-Destination Study conducted in 2002, it was found that the original MinUTP model had more reasonable IE/EE splits due to how the O-D study was conducted. With the exception of new external stations, the updated model as part of the 2035 LRTP Update will use the same IE/EE splits from the MinUTP model. Any new external stations, which will likely be minor roads with low traffic counts, will likely assume 100 percent IE trips.

1.5 Trip Generation Method – During the 2030 LRTP Update adopted in 2005, the 2002

Chattanooga Household Travel Survey data was evaluated to determine what variables impact travel patterns the most in the Chattanoga region. As a result, a cross-classification method based on auto availability and children per household was implemented. This same method will be using during this update.

1.6 Trip Purposes – The current TransCAD model includes the following trip purposes,

which will remain the same during this update:

• Home-Based Work (HBW)

• Home-Based School (HBSchool)

• Home-Based Shop (HBShop)

• Home-Based Social/Recreation (HBSR)

• Home-Based Other (HBO)

• Non-Home Based (NHB)

• Light-Duty Truck (LDTK)

• Medium-Duty Trucks (MDTK)

• Heavy-Duty Trucks (HDTK)

1.7 Special Generators – The current TransCAD model includes special generators at the

airport, the University of Tennessee at Chattanooga, Chattanooga State College, and

- 3 -

Chester Frost National Park. No special generators will be assumed at the beginning of 2007 model validation effort, however, it is anticipated that some special generators may eventually be necessary.

2.0 TRIP DISTRIBUTION

2.1 Friction Factors - The friction factor file used in the new CHCNGA 2000 TransCAD model is similar to the file used in the CHCNGA 2000 MINUTP model. The key difference is the number of trip purposes. Since separate friction factors were not available for the expanded home-based other purposes, the same home-based other friction factors were used for home-based school, home-based shop, and home-based social recreation trips. Gamma functions from the Quick Response Freight Manual were used for truck purposes. These same friction factors will be assumed for the 2007 model and future years. If time permits, the friction factors may be calibrated.

2.2 Terminal Times – Terminal times were used in the 2000 model and will also be used in

the 2007 model. 2.3 K-Factors – K-Factors were used in the 2000 model. To improve the

Georgia/Tennessee State Line screenline in the 2000 model, a 0.25 K-Factor was added from zones in Georgia to zones in Tennessee. To improve the Tennessee River Crossing screenline, a 0.25 K-Factor was added to zones from the north side of the bridges to the rest of the model region. No K-Factors will be assumed at the beginning of the 2007 model validation process, however, they may be added if necessary.

3.0 MODE CHOICE The current TransCAD model for Chattanooga does not include a mode choice/transit component. Instead, it includes an auto occupancy model that converts person trips to vehicle trips using auto occupancy factors by trip purpose derived from the 2002 Household Travel Diary Survey conducted in the Chattanooga region. Dependent upon available data, the RPA was considering adding a mode choice/transit pathbuilding component to the TransCAD model as part of the 2035 LRTP Update. However, since the August 20, 2008 modeling workshop referenced above, it was determined that there is not enough data currently available to validate a mode choice/transit pathbuilding model. As a result, the RPA, in coordination with CARTA, is considering conducting an on-board transit survey in the Spring of 2009 with the intention of building a mode choice model in the Summer and Fall of 2009. However, it will not be included as part of the 2035 LRTP Update. Therefore, the current auto occupancy model will remain in place for the 2035 LRTP Update. 4.0 TRIP ASSIGNMENT

4.1 Time-of-Day – Currently, the Chattanooga model does not include a true time-of-day component. Instead, peak hour factors based on the temporal distribution from the 2002 Household Travel Diary Survey are applied to the daily volumes after the assignment process to achieve AM and PM peak hour volumes. There is the potential

- 4 -

- 5 -

for adding a true time-of-day component to the Chattanooga 2007 model, but not in time for the 2035 LRTP Update.

NEXT STEPS Below is a list of the next information to be provided to TDOT and GDOT for review and approval upon completion: • 2007 and 2035 socioeconomic data (currently expected in November 2008)

• List and corresponding map of capacity-adding transportation projects added to the 2000 model to update to 2007

• Populated validation worksheet once validation complete

As noted earlier, once the modeling efforts and draft LRTP document have been completed, full model documentation, including a user’s guide and all model files, will be provided to TDOT and GDOT. As discussed during the modeling workshop held on August 20, 2008, please provide any comments back to the RPA within 10 days, if not sooner. We thank you in advance for understanding our time constraints and look forward to coordinating with you throughout the development of our model and LRTP. If you have any questions about the model, please do not hesitate to contact Melissa Taylor at the RPA via email at [email protected] or phone at (423) 757-0077. Attachments: Table of TDOT Validation Requirements Empty Validation Worksheet

mailto:[email protected]

Attachment #1

Model Validation Documentation Requirements

Specified in TDOT Division Procedure: MPO Model Approval

and

“Minimum Travel Demand Model Calibration and Validation Guidelines for State of Tennessee,” University of Tennessee, Center for Transportation Research

Attachment #1: MPO Model Certification RequirementsCHCNGA 2035 LRTP

Socioeconomic DataTAZ Maps with corresponding existing and futureSE data, including external stations PDF Maps TDOT*

Person trips/household by purposeValidation Worksheet U Tenn**

Travel Survey Data

Source, year, and type of travel survey information

Text (overview provided in

Submittal #1) TDOT*

Household travel diary survey (2002) used to determine trip generation rates, average trip lengths, auto occupancy factors, and

other characteristics used in 2000 model development and validation.Percent IE/EE splits were calculated from the Chattanooga Urban Area Origin-Destination Study conducted in 2002. However, it was

determined that these percentages were not reliable as the interstate surveys were conducted on ramps at interchanges and rest areas. Vehicles were not pulled off to the side of the road on the mainline interstate segments where most EE trips occur. The vehicles that

were surveyed were already stopping at the interchange or rest area. Therefore, the results provide a significant bias towards IE trips and EE trips are underestimated. The percent IE/EE splits from the origin and destination survey were subsequently compared to the old 2000

MINUTP model and it was determined that the old 2000 MINUTP model percent splits appeared more reasonable.

Will need to modify TAZ structure to

account for new minor roads

added that may represent external stations; if so, will assume 100% IE

split.

If no survey, provide source of trip data


Submittal #1) TDOT* QRFM used for truck trip production rates; NERPM for attraction ratesNetwork DataProvide files (networks, turn penalties/prohibitors, speed/cap, FT codes) Files TDOT*Table of significant projects added to network by model year Excel Table TDOT*Explanation of how MPO dealing with cross-border traffic Text TDOT* K-factor and screenline at state line

Determine during validation

Trip Generation

Description of trip generation method (P/A, O/D, Special Generators; Cross-Class, Regression, or Discrete Choice)


Submittal #1) TDOT*

Cross-Classification method based on auto availability and children per household; Trip production rates for HBW, HBSCHOOL,

HBSHOP, HBSR, HBO, and NHB calculated using 2002 HH Travel Diary Survey; Truck production rates from QRFM; Attraction rates

from NERPM; Special generators included same

Description of trip purposes


Submittal #1) TDOT*HBW, HBSCHOOL, HBSHOP, HBSR, HBO, NHB, LTTK, MDTK,

HDTK same

Description of how EE and EI trips addressed Text TDOT*

The MINUTP splits were used as a starting point and were later modified during the validation process.

The percent IE trips were applied to the 2000 AADT to calculate the total number of IE trips at each external zone for the TAZ geography file. The EETRIPS input matrix file is generally the residual left after estimating IE trips in the TAZ geography file. The percentage of EE trips was applied to the AADT per external zone and then distributed

from each origin zone to each destination zone using distribution patterns from the old MINUTP 2000 model EETRIPS file. For externalzones added to the TransCAD model, and not in the MINUTP model,

it was assumed that 100 percent of these trips were EE trips since these were low volume roadways.

Adding new external stations;

For external zones added to the TransCAD model, assume that 100 percent of these trips are

EE trips since these were low

volume roadways.Whether trip rates developed for vehicle and/or person trips Text TDOT* Person trips same

Special generators (how and where) Text TDOT* Yes; Airport, UTC, Chatt State College, Chester Frost National ParkDetermine during

validationTrip DistributionFiles (friction factors, terminal time, and K-factors) Files TDOT*Trip length by trip purpose for base and future year

Validation Worksheet TDOT*

Comparison of HBW mean trip length compared to Census JTW mean trip length


Trip Length Frequency Distribution (TLFD) by Trip Purpose Compared to Census JTW and Household Travel Survey (Charts)

Validation Worksheet (add

charts) U Tenn**Area-to-Area Flow of Trips Map U Tenn**

2007 ModelTDOT's MPO Model Approval Requirements (Effective 3/1/08)

Source of Requirement

Type of Submittal 2000 Model

Attachment #1: MPO Model Certification RequirementsCHCNGA 2035 LRTP

2007 ModelTDOT's MPO Model Approval Requirements (Effective 3/1/08)

Source of Requirement

Type of Submittal 2000 Model

Were friction factors in gravity model kept constant between base and future years?


Submittal #1) TDOT*

Yes. The friction factor file used in the new CHCNGA 2000 TransCAD model is similar to the

file used in the CHCNGA 2000 MINUTP model. The key difference is the number of trip

purposes. Since separate friction factors were not available for the expanded home-based

other purposes, the same home-based other friction factors are used for home-based

school, home-based shop, and home-based social recreation trips. Also, as discussed,

gamma functions from the Quick Response Freight Manual were used for truck purposes. same

Were terminal times used?


Submittal #1) TDOT* Yes same

Were K-factors used and if so, what was the basis?


Submittal #1) TDOT*

Yes; To improve the Georgia/Tennessee State Line screenline in the CHCNGA 2000 TransCAD model, a 0.25 K-Factor was added from

zones in Georgia tozones in Tennessee. To improve the Tennessee River Crossing

screenline, a 0.25 K-Factor was added to zones from the north side ofthe bridges to the rest of the model region.

Determine during validation

Mode Split TDOT*Description of mode split and choice analysis method (i.e. nested logit?) Text (n/a) TDOT* n/a n/aWere vehicle occupancy factors by trip purpose used to convert person trips to vehicle trips? Were they kept constant between years? Source?


Submittal #1) TDOT* Yes; Yes; Source is HH Travel Survey sameWhat network model coding logic was used to code access to transit in the network? Text (n/a) TDOT* n/a n/aTrip AssignmentFiles (loaded network, summary table including estimated link vols & costs, text file with user inputs and model outputs) Files TDOT*Comparison of screenline vols with counts (2 N/S, 2 EW)


Comparison of cutline, screenline, and cordon line vols with counts


Was time-of-day assignment performed? If so, details.


Submittal #1) TDOT* No sameIf no time-of-day assignment, how were 24-hour vols converted to peak hour vols? What conversion factors used? Relationship between peak hour & 24-hour vol?


Submittal #1) TDOT*Peak hour factors applied to achieve temporal distribution based on

2002 Household Travel Diary Survey sameFraction of total VMT assigned to IZ and centroid connector trips? Is it reasonable?

Validation Worksheet (add) TDOT*

Traffic counts on 10% of regionwide highway segments by functional calss (freeways and principal arterials at a minimum & screenlines) Table U Tenn**Percent Differences in Daily Volume by FT and screenline

Validation Worksheet U Tenn**

Percent Difference in Peak Hour Volume by FTValidation

Worksheet (add) U Tenn**

Percent RMSE by Link Volume GroupValidation Worksheet U Tenn**

Scatter Plot of Assigned vs. Observed Link Traffic Volume

Validation Worksheet (add

chart) U Tenn**

Correlate coefficient by link volumesValidation

Worksheet (add) U Tenn**Overall PerformanceVMT, VHT, and average speed for entire system and by FT


VMT per capita (VMT/population)Validation

Worksheet (add) TDOT*Final Files (complete datasets) Files TDOT*Final Documentation (complete model validation report, including user's guide)

PDF of Final Report TDOT*

Attachment #2

Model Validation Worksheets

(Template – Not Populated with 2007 Statistics)

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mends +/- 5% target for screenlines with greather than 70,000 AADT.

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for AADT 30,000-50,000 (FDOT)

*11 Summarized from 10-20% for AADT 50,000 - 65,000, 5-15%

for AADT 65,000-75,000, and 5-10% for AADT 75,000+

(FDOT).

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7


Appendix C: Technical Memorandum #2

2457 Care Dr ive, Sui te 101 Tal lahassee, FL 32308


Memorandum

TO: Bob Rock, TDOT Jerry Yuknavage, TDOT Tim Kassa, GDOT

CC: Chattanooga Interagency Consultation Committee (ICC)

FROM: Melissa Taylor, CHCNGA TPO Yuen Lee, Chattanooga-Hamilton County Regional Planning Agency (RPA) Keli Paul, AICP, Cambridge Systematics

DATE: July 8, 2009

RE: Model Certification Submittal #2: Draft 2007 & 2035 Socioeconomic Data Chattanooga-Hamilton County/North Georgia 2035 LRTP Update

Effective March 1, 2008, the Tennessee Department of Transportation (TDOT) Long Range Planning Division, Systems Planning and Policy Office, implemented a Division Procedure for the MPO model approval process. On August 20, 2008, the RPA met with its consultants along with TDOT, GDOT, and CARTA to discuss the TransCAD modeling efforts for the CHCNGA 2035 LRTP Update. It was agreed at that time that the following four submittals would be provided to TDOT and GDOT as part of TDOT’s model approval process:


2. Year 2007 and 2035 socioeconomic data files (TransCAD and GIS) for the TPO region, including any maps, graphs, charts, or tables developed as part of the RPA’s internal review;

3. Populated validation worksheet upon completion of draft validated model. This worksheet will include statistics for Trip Generation, Trip Distribution, Mode Choice (if applicable), and Traffic Assignment. If the assumptions included in submittal #1 change as part of the validation process, they will be documented and submitted for approval at this time; and


This technical memorandum constitutes Submittal #2 defined above. Submittal #1 was submitted and approved by TDOT in September 2008. Subsequently, Regional Planning Agency (RPA) staff and its consultant, Cambridge Systematics, held a teleconference with GDOT and TDOT on June 30, 2009 to discuss the draft socioeconomic data and validation statistics, as outlined in this submittal. Below is a summary of each socioeconomic variable by

- 2 -

County for each base and horizon year, both from the previous 2030 LRTP Update in comparison to the current 2035 LRTP Update. RPA staff created the socioeconomic data, while its consultant reviewed the socioeconomic data above and beyond the RPA’s internal review. In addition, several traffic analysis zone (TAZ) splits were made within the TransCAD travel demand model and are documented below.

1.0 TAZ SPLITS As part of the previous 2030 LRTP Update, the RPA converted the old MinuTP model to TransCAD and refined the TAZ structure significantly resulting in 445 total TAZs for the entire model region. After the 2030 LRTP was adopted, the RPA added more TAZs to Catoosa County as the remaining sliver of Catoosa County not in the previous model was added for the purpose of calculating emissions for air quality conformity. This addition resulted in a total of 450 TAZs for the entire model region. As part of this current 2035 LRTP Update, the RPA has further refined the TAZ structure by splitting internal zones mostly in the outlying regions of the model and within the downtown area of Chattanooga. Previously, the Enterprise South Industrial Park (ESIP) area was included within one TAZ. As part of this update, the ESIP TAZ has been split into eight TAZs based on the ESIP future site plan. In addition to splitting several internal zones, eight more external zones were added to the current model, as indicated in Table 1 below. All of these TAZ splits have resulted in a current total of 628 TAZs (590 internal + 38 external) in the entire model region, an increase of 178 TAZs, or 40 percent more zones. Maps illustrating the TAZ splits are attached.

Table 1. Number of TAZs in TransCAD Model

2030 LRTP Model

Expanded Catoosa

Model

2035 LRTP Model

Internal TAZs 415 420 590 External TAZs 30 30 38 Total TAZs 445 450 628

The following criteria were used to determine if a TAZ should be split, when feasible:

Greater than 15,000 productions per TAZ in 2030;

Irregular shaped or large sized TAZs;

Major existing or planned roads bisecting TAZ; and

Potential special generator located in TAZ (i.e. isolated TN Aquarium).

The following guidelines were used to split the TAZ boundaries, when feasible:

Existing and future roadways;

Existing and future land use;

Railroads;

Water bodies; and

Census block group boundaries.

- 3 -

Figure 1. TAZ Splits

- 4 -

2.0 SUMMARY OF SOCIOECONOMIC DATA RPA staff developed the 2007 and 2035 socioeconomic data as part of the Chattanooga-Hamilton County/North Georgia 2035 LRTP Update. Historically, the Coosa Valley Regional Development Center (RDC) has developed the socioeconomic data for the Georgia portion of the TPO. However, development of the socioeconomic data for the Georgia side has since become the responsibility of the TPO due to funding limitations. Variables The socioeconomic data included in the TransCAD travel demand model can be broken in to four categories, as follows:

• Household Data – Includes total population, school-age children (population between ages 3 and 18), and total housing units.

• Employment – Includes total number of employees and number of employees for each of the five employment categories:

o Agricultural/mining/construction;

o Manufacturing/transportation;

o Retail;

o Service; and

o Government.

• School Enrollment – Includes number of grade school students at the location of the school, number of university students at the location of the university, and total school enrollment (grade school students plus university students). University student enrollment includes community, technical, or vocational colleges and universities.

• Hotel-Motel Units – Includes number of hotel-motel units.

Methodology The RPA collected the number of building permits issued between 2000 and 2007 for each of the four counties, geocoded their locations, and added the new building permits to the 2000 households by TAZ to achieve 2007 households. Population for the year 2007 was calculated by applying the persons per household ratio in each of the year 2000 zones to the total number of households in 2007. If a zone was split, the persons per household ratio from the parent zone in the year 2000 was applied for each split zone. However, subsequent logic checks determined that some manual adjustments were necessary in Dade and Hamilton Counties to reflect more reasonable persons per household ratios and thus, the overall persons per household ratio for the entire county were applied to those specific zones. The proportion of the total population attributable to school-age children was calculated using 2007 American Community Survey (ACS) data for each of the four counties, with the exception of Dade County, which utilized the same school-aged children factor in Walker County as ACS data was not available for Dade County. Building permit data for Hamilton County were acquired from the municipal building permit files, whereas building permit data for Catoosa and Walker Counties were acquired from The Market Edge, an information reporting service. Since building permits are not

- 5 -

required in Dade County, electrical inspection records were acquired from the County as proxy for building permits. As part of the current 2035 LRTP Update, the RPA evaluated a number of sources for employment data as there were significant discrepancies in the employment control totals between the different data sources within the region. After careful review, it was determined that year 2007 ES202 employment data from the Bureau of Labor Statistics (BLS) be used. Previously, as part of the 2030 LRTP Update, RPA staff utilized the employment control totals from the Bureau of Economic Analysis (BEA) while using Dun & Bradstreet point data to distribute the BEA employment by TAZ. This previous method was used due to some of the suspect employment numbers in the Dun & Bradstreet data. Since then, it has been determined that the ES202 employment data is more comparable to other data sources and the BEA control totals for the year 2000 may have been overestimated. As a result, when comparing the 2000 employment to the 2007 employment, there is a significant decrease in employment from the year 2000 to 2007. However, as mentioned above, it is likely that the 2000 employment was erroneous. School enrollment data were collected from local school boards, the phone book, internet, and applying local knowledge. The number of hotel-motel units were collected from the Visitors Bureau, in-house Geographic Information Systems (GIS) file, a field survey, as well as the phone book and the internet. Observations As indicated in Table 2, between the years 2007 and 2035, the Chattanooga region is expected to grow by approximately 39 percent in population and employment. Since the number of school-age children is decreasing in the region, school enrollment is only expected to increase by 16 percent. Although employment decreased from the year 2000 to 2007, as discussed earlier, employment does increase by 39 percent from the year 2007 to 2035, consistent with household and population forecasts. Figure 2 compares the regional summary of each socioeconomic variable between the years 2007 and 2035. As expected, all variables increase from the year 2007 and 2035.

Table 2. Regional Summary of Socioeconomic Data for 2035 LRTP Update

Total Region Variable 2007 2035 % Growth

Households 179,079 252,087 41%Population 427,223 594,203 39%Employment 218,430 303,220 39%Hotel-Motel Units 9,693 11,729 21%School Enrollment 69,102 80,353 16%College Enrollment 24,459 29,520 21%

- 6 -

Figure 2. Regional Summary of Socioeconomic Data for 2035 LRTP Update

Regional Summary

179,079

427,223

218,430252,087

594,203

303,220

80,353

24,45969,102

9,69329,520

11,7290

100,000

200,000

300,000

400,000

500,000

600,000

700,000

Households Population Employment Hotel-Motel Units SchoolEnrollment

CollegeEnrollment

20072035

3.0 HOUSEHOLDS Table 3 below compares the number of households between the previous 2030 LRTP (years 2000 and 2030) and the current 2035 LRTP Update (years 2007 and 2035). With the exception of the Georgia counties in the year 2030, the households increase for each year. Growth in Georgia is expected to slow down between the years 2007 and 2035 and it is expected that 2030 households in Georgia were overestimated during the previous LRTP update.

Table 3. Comparison of Households Between 2030 and 2035 LRTP Models

Households County 2000 2007 2030* 2035

Hamilton 124,447 141,229 157,459 200,748Dade 760 839 1,190 931Walker 12,528 12,882 16,649 15,272Catoosa 20,320 24,129 43,919 35,136GA Total 33,608 37,850 61,758 51,339 Region 158,055 179,079 219,217 252,087

* 2030 expanded after 2030 LRTP Update to include all of Catoosa County

- 7 -

Figure 3. Comparison of Households Between 2030 and 2035 LRTP Models

Households by County

760 83912,882

157,459

43,919

200,748

93120,320

12,528

124,447

24,129

141,229

1,19016,649

35,13615,272

0

50,000

100,000

150,000

200,000

250,000

Hamilton Dade Walker Catoosa

County

2000 2007 2030* 2035

4.0 POPULATION As indicated in Table 4, population in Hamilton County increases each year, regardless of which LRTP update. However, Dade County population decreased from the year 2000 to 2007, even though the number of households increased. This is as a result of adjusting the number of persons per household ratio to more accurately reflect existing conditions in Dade County, which are more consistent with the other counties in the TPO region. In addition, it is suspected that the year 2030 population in the Georgia counties was overestimated during the previous 2030 LRTP as growth is expected to slow down in Georgia.

Table 4. Comparison of Population Between 2030 and 2035 LRTP Models

Population County 2000 2007 2030* 2035

Hamilton 307,897 330,173 362,330 465,215Dade 2,460 2,140 3,837 2,354Walker 31,749 32,666 42,085 38,576Catoosa 52,955 62,244 114,556 88,058GA Total 87,164 97,050 160,478 128,988 Region 395,061 427,223 522,808 594,203


- 8 -

Figure 4. Comparison of Population Between 2030 and 2035 LRTP Models

Population by County

307,897

52,955

330,173

2,140

362,330

114,556

465,215

2,354

38,57631,749

2,46062,244

32,66642,085

3,837

88,058

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

450,000

500,000


County

2000 2007 2030* 2035

5.0 EMPLOYMENT As mentioned earlier, the source of the employment data has changed since the previous LRTP and thus, there is a significant reduction in employees from the year 2000 to 2007 due to suspected overestimation in the year 2000. Year 2007 employment data was based on ES202 records from the BLS and was supplemented by records from the Chamber of Commerce, schools, motel in-house records, and job announcements from the newspaper. Year 2000 data was compiled from the Dun & Bradstreet database and was factored up to BEA employment control totals. BEA derived the employment data in part from the BLS data which accounts for about 80 percent of its employment data. The difference between the BEA data and the BLS data is attributed to BLS only reporting employment covered by the State UI and UCFE programs while BEA also estimates employment for farms, part-time employees, private households, schools, religious organizations, railroads, military, and international organizations. Since BEA data did not include addresses and the 2000 approach would exacerbate errors from mis-geocoding and misreporting, the RPA decided to geocode the BLS data and supplement it with the additional sources mentioned above for 2007 employment. Table 5 compares the new 2007 and 2035 employment control totals to the old 2000 and 2030 employment control totals. Due to the change in data sources, there are significant differences between LRTP datasets. However, it is suspected that the new 2007 employment estimates and 2035 forecasts are more accurate.

- 9 -

Table 5. Comparison of Employees Between 2030 and 2035 LRTP Models

Employment County 2000 2007 2030* 2035

Hamilton 240,320 194,795 308,469 274,622Dade 331 108 516 195Walker 21,465 8,243 27,904 8,363Catoosa 26,302 15,284 56,598 20,040GA Total 48,098 23,635 85,018 28,598 Region 288,418 218,430 393,487 303,220


Figure 5. Comparison of Employees Between 2030 and 2035 LRTP Models

Employment by County

240,320

33121,465 26,302

194,795

108 8,243

308,469

516

56,598

195 8,363 15,28427,904

274,622

20,040

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000


County

2000 2007 2030* 2035

6.0 HOTEL-MOTEL UNITS As demonstrated in Table 6, several hotels were constructed in Hamilton County between the years 2000 and 2007. The number of hotel-motel units in 2007 actually surpassed those projected in 2030 as part of the last 2030 LRTP. It is anticipated that the growth in hotel-motel units in Hamilton County will slow down between 2007 and 2035, although it will still increase by 22 percent. Similarly, Walker County hotel-motel units increased in 2007 beyond 2030 forecasted levels. However, it is suspected that the growth in hotel-motels units in Catoosa County was overestimated for the year 2030 during the previous LRTP update and it is

- 10

expected to slow down by the year 2035, as the RPA is uncertain of future growth in Catoosa County.

Table 6. Comparison of Hotel-Motel Units Between 2030 and 2035 LRTP Models

Hotel-Motel Units County 2000 2007 2030* 2035

Hamilton 4,105 8,885 6,851 10,876Dade 0 0 0 0Walker 18 200 37 233Catoosa 570 608 1,073 620GA Total 588 808 1,110 853 Region 4,693 9,693 7,961 11,729


Figure 6. Comparison of Hotel-Motel Units Between 2030 and 2035 LRTP Models

Hotel Motel Units by County

4,105

0 18570

8,885

0 200608

6,851

0 37

1,073

10,876

0 233620

0

2,000

4,000

6,000

8,000

10,000

12,000


County

2000 2007 2030* 2035

- 11

7.0 SCHOOL ENROLLMENT The number of grade school students in Hamilton County decreased from the year 2000 to 2007 as there were a number of school closings. However, school enrollment is expected to increase by the year 2035. As demonstrated in Table 7, the growth in school students in Walker County was faster than expected resulting in far more students in the year 2007 than originally forecasted by the year 2030 as part of the previous LRTP update. Since the RPA is uncertain of future long-term growth, there is only a minimal increase in school students between the years 2007 and 2035 in Walker County. In Catoosa County, it is suspected that the 2030 forecasted school enrollment may have been slightly overestimated and thus, year 2035 forecasts are slightly lower when compared to the year 2030.

Table 7. Comparison of School Enrollment Between 2030 and 2035 LRTP Models

School Enrollment County 2000 2007 2030* 2035

Hamilton 51,570 50,835 54,092 58,715Dade 0 0 0 0Walker 3,931 7,042 5,111 7,522Catoosa 7,083 11,225 14,770 14,116GA Total 11,014 18,267 19,881 21,638 Region 62,584 69,102 73,973 80,353


Figure 7. Comparison of School Enrollment Between 2030 and 2035 LRTP Models

School Enrollment by County

03,931

0

7,042

0

5,111

14,770

58,715

0

7,083

51,570

11,225

50,83554,092

14,1167,522

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000


County

2000 2007 2030* 2035

- 12

8.0 COLLEGE ENROLLMENT College enrollment in Hamilton County increased by 23 percent between the years 2000 and 2007. However, growth is expected to slow down by the years 2030 and 2035, as indicated in Table 8. Since the last LRTP update, the TPO TransCAD model was expanded to include all of Catoosa County. As a result, Harvest Deaf Bible College in Catoosa County is now included in the model, which accounts for the 27 college students in the year 2007 not previously in the model. In addition, Covenant College in Dade County was not included in the previous LRTP update and has since been added to the model.

Table 8. Comparison of College Enrollment Between 2030 and 2035 LRTP Models

College Enrollment County 2000 2007 2030* 2035

Hamilton 18,780 23,082 25,059 27,932Dade 0 1,350 0 1,553Walker 0 0 0 0Catoosa 0 27 0 35GA Total 0 1,377 0 1,588 Region 18,780 24,459 25,059 29,520


Figure 8. Comparison of College Enrollment Between 2030 and 2035 LRTP Models

College Enrollment by County

0 0 0

23,082

1,3500 27

25,059

0 0 0

27,932

1,5530 35

18,780

0

5,000

10,000

15,000

20,000

25,000

30,000


County

2000 2007 2030* 2035

- 13

NEXT STEPS Below is a list of the next information to be provided to TDOT and GDOT for review and approval upon completion:

List and corresponding map of capacity-adding transportation projects added to the 2000 model to update to 2007; and

Populated validation worksheet once validation complete.

As noted earlier, once the modeling efforts and draft LRTP document have been completed, full model documentation, including a user’s guide and all model files, will be provided to TDOT and GDOT. As discussed during the modeling workshop held on August 20, 2008, please provide any comments back to the RPA within 10 days, if not sooner. We thank you in advance for understanding our time constraints and look forward to coordinating with you throughout the development of our model and LRTP. If you have any questions about the model, please do not hesitate to contact Melissa Taylor at the RPA via email at [email protected] or phone at (423) 757-0077. Attachments: Year 2007 and 2035 Density Maps by Variable Map of TAZ splits TAZ boundary shapefile with 2007 and 2035 socioeconomic data

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Appendix D: Technical Memorandum #3

2457 Care Dr ive , Su ite 101 Ta l lahassee, FL 32308


Memorandum

TO: Bob Rock, TDOT Jerry Yuknavage, TDOT Tim Kassa, GDOT

CC: Chattanooga Interagency Consultation Committee (ICC)

FROM: Melissa Taylor, CHCNGA TPO Keli Paul, AICP, Cambridge Systematics Sheldon Harrison, Cambridge Systematics

DATE: September 28, 2009

RE: Model Certification Submittal #3: Draft 2007 TransCAD Model Validation Chattanooga-Hamilton County/North Georgia 2035 LRTP Update

Effective March 1, 2008, the Tennessee Department of Transportation (TDOT) Long-Range Planning Division, Systems Planning and Policy Office implemented a Division Procedure for the MPO model approval process. On August 20, 2008, the RPA met with its consultants along with TDOT, GDOT, and CARTA to discuss the TransCAD modeling efforts for the CHCNGA 2035 LRTP Update. It was agreed at that time that the following four submittals would be provided to TDOT and GDOT as part of TDOT’s model approval process:

• Outline of the model, planning assumptions to date, and model validation worksheet template;

• Year 2007 and 2035 socioeconomic data files (TransCAD and GIS) for the TPO region, including any maps, graphs, charts, or tables developed as part of the RPA’s internal review;

• Populated validation worksheet upon completion of draft validated model. This worksheet will include statistics for Trip Generation, Trip Distribution, Mode Choice (if applicable), and Traffic Assignment. If the assumptions included in submittal #1 change as part of the validation process, they will be documented and submitted for approval at this time; and

• Full model documentation report and user’s guide, along with all TransCAD files, after the draft LRTP has been documented.

This technical memorandum constitutes Submittal #3 defined above. Submittal #1 was submitted and approved by TDOT in September 2008. Subsequently, Regional Planning

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Agency (RPA) staff and its consultant, Cambridge Systematics, held a teleconference with GDOT and TDOT on June 30, 2009 to discuss the draft socioeconomic data and preliminary validation statistics, as outlined in this submittal. Submittal #2, which included the 2007 and 2035 socioeconomic data, was submitted to TDOT, GDOT, and the ICC in July 2009 and approved during the ICC meeting on August 6, 2009. Preliminary validation statistics were provided to the Interagency Consultation Committee (ICC) for review in advance of the September 3, 2009 ICC meeting. In addition, this technical memorandum will be discussed at the October 1, 2009 ICC meeting.

As part of this submittal #3, below is a summary of the year 2007 model network, 2007 model validation, statistics and observations for each step of the modeling process, a comparison of model congested speeds to observed speeds, and next steps. In addition, a bullet list summary of the model validation results and observations is provided at the end of this technical memorandum. Overall, the 2007 model is performing within acceptable limits with an overall volume-to-count ratio of 0.96 and a Root Mean Square Error (RMSE) of 34.6 percent.

1.0 Year 2007 Model Network

In order to update the year 2000 model network to the year 2007, a list of capacity-adding transportation improvements completed between the years 2001 and 2007 was developed and distributed to the ICC for review and approval. Maps of these projects and the corresponding list are included in Appendix A. These projects were coded on top of the previously validated 2000 model network to reflect 2007 transportation network conditions.

Maps of the 2007 model network by area type, facility type, and number of lanes also are included in Appendix B. As part of the 2007 model update, a new area type code representing industrial land uses were added to the model. This new area type provided the ability to reduce speeds in areas serving industrial facilities. The TPO conducted a windshield survey in 2008, during which time areas representing industrial land uses were noted and revised accordingly in the 2007 model. In addition, topography data was overlayed on top of the 2007 model network to assist with updating the mountainous area type codes added during the previous model/LRTP update.

As part of the 2007 model update and Congestion Management Plan Update, the TPO identified locations along CMP routes and in the 2007 model where additional counts were needed. The TPO collected these supplemental counts in 2008 to assist with validation. As a result, year 2007 traffic counts available from TDOT, GDOT, Hamilton County, and the City of Chattanooga were included in the 2007 traffic count field used to calculate validation statistics. However, a year 2008 traffic count field was added to the model network to include these supplemental traffic counts collected in 2008. Since the base year of the model was 2007, these 2008 counts were not included in the validation statistics. However, they were used to supplement validation efforts and compare to 2007 traffic counts for accuracy.

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2.0 Year 2007 Model Validation

2.1 External Trips

As noted in technical submittal #2, eight new external stations were added to the 2007 model above and beyond the 30 external stations included in the previous 2000 model. Year 2007 traffic counts at each of the 38 external stations were utilized to determine the total external trips. The same percent distribution of external-external (EE), or through trips, versus internal-external (IE) trips at each of the original 30 external zones used in the 2000 model was used for the 2007 model. Since the eight new external stations in the 2007 model were located along minor facilities, it was assumed that 100 percent of the external trips were attributed to IE trips, or those with one trip end inside the TPO region and one trip end outside the TPO region.

2.2 Trip Generation

Trip production rates utilized in the 2007 model are the same as those utilized in the 2000 model, as trip production rates were developed using local data from the Chattanooga 2002 Household Travel Diary Survey. However, trip attraction rates were modified in the 2007 model as they were borrowed from the Jacksonville, Florida region for the previous 2000 model. Trip attractions for some purposes, such as Home-Based Work (HBW), differed appreciably from the trip productions and it was therefore decided to borrow trip attraction rates from the Knoxville model and adjust where appropriate in an attempt to achieve closer matches. Utilizing Knoxville trip attraction rates is likely more appropriate for the Chattanooga region due to potential differences in travel characteristics in the Jacksonville, Florida region. The Knoxville trip attraction rates documented in the Knoxville Regional Travel Demand Model Validation Report of March 2004 resulted in some improvement in the unbalanced ratios for most trip purposes in Chattanooga. Adjustments were necessary to some of the trip attraction rates as trip purposes did not correlate perfectly between the Knoxville and Chattanooga models. The final Chattanooga 2007 model trip production and attraction rates are listed below.

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Table 1. New Chattanooga Trip Production and Attraction Rates

To

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ho

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on

Home-Based Work 0.00 0.51 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Home-Based School 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.72 0.00

Home-Based Shop 0.00 0.00 0.00 0.00 0.78 0.11 0.19 0.00 0.20


0.00 0.00 0.00 0.00 0.48 0.06 0.12 0.00 0.12

Home-Based Other 0.00 0.00 0.00 0.00 1.38 0.19 0.35 0.00 0.36

Nonhome-Based 1.54 0.36 0.00 0.00 3.83 0.31 0.64 0.00 0.00

Light-Truck 0.10 0.00 0.30 0.25 0.25 0.15 0.15 0.00 0.00

Medium-Truck 0.05 0.00 0.10 0.10 0.10 0.05 0.05 0.00 0.00

Heavy-Truck 0.05 0.00 0.05 0.05 0.05 0.05 0.05 0.00 0.00

As demonstrated in Table 2, there were approximately nine person trips per household in the Chattanooga region in the 2007 model, within TDOT’s target range of 8.5 to 10.5, also comparing favorably with other cities in the region. Other aggregate trip rates are shown in Table 2 below.

Table 2. Aggregate Trip rates

Chattanooga Standards

Unit of Measure 2007 2000 TDOT FHWA

Persons per Household 2.38 2.50 n/a n/a

Internal Trips per Household 9.00 9.44 8.5-10.5 8.0-14.0

Internal Trips per Person 3.78 3.78 n/a 3.5-4.0

HBW Trips per Employee 1.12 0.74 n/a n/a

Employees per Person 0.51 0.73 n/a n/a

Total Population 425,666 395,061

Total Households 178,905 158,055

Total Employment 218,612 287,918

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As indicated in Table 3 below, Home-Based Work (HBW) trips represent approximately 13 percent of all the trips generated in the Chattanooga region, slightly below TDOT’s target of 18 percent. Approximately 40 percent of trips in the Chattanooga region can be attributed to Home-Based School, Shopping, Social Recreation, and Other trips purposes. This is comparable to Nashville, Tennessee and Montgomery, Alabama at approximately 39 percent. Nonhome-Based (NHB) trips are within the desired range of 22 to 31 percent at 27 percent. Commercial vehicles represent approximately seven percent of the trips in the 2007 model, a reduction compared to the 2000 model. It must be noted, however, that employment in the 2007 model is lower than for the 2000 model, contributing to the reduced commercial vehicles, as demonstrated in technical submittal #2.

Table 3. Percent of Trips by Purpose

Chattanooga

Purpose 2007 2000 TDOT Target

Home-Based Work 13.23% 12.72% 18-27%




6.22% 5.57%


47-54%

Nonhome-Based 26.64% 26.06% 21-31%





Internal-External 11.08% 13.85%

External-External 1.86%

Total 100.00% 100.00%

2.3 Trip Distribution

Initially, friction factors from the previous 2000 model, which were borrowed from the earlier MINUTP model, were used as part of the validation of the 2007 model. However, upon review of the average trip lengths, it was determined that adjustments to the friction factors were necessary. As a result, the TPO first developed and calibrated new friction factors to match the Chattanooga 2002 Household Travel Diary Survey data. However, these new friction factors resulted in unsatisfactory results. Average trip lengths were proving to be shorter than expected and overall validation results were consequently worse. As a result, the original friction factors from the previous 2000 model were iteratively adjusted to achieve better trip

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length distribution characteristics. Several iterative runs were performed to arrive at the final friction factors used for the remainder of the model validation runs. The final friction factors are included in the complete model dataset that is being provided to TDOT and GDOT as part of this submittal.

Just as was included in the previous 2000 model, K-factors were necessary between areas north and west of the Tennessee River and areas south and east of the Tennessee River, as well as between Georgia and Tennessee. However, unlike the previous model, the K-factors were not directionally skewed to/from Georgia and Tennessee. In addition to the K-factors (0.8 for each), it was found necessary to add penalties, primarily along the Tennessee River bridges to correct local imbalances. Table 4 below lists the locations and amount of the penalties.

Table 4. Penalties

Roadway Penalty (minutes)

U.S. 27 Bridge 1.35

N. Market Street Bridge 1.10

Dupont Parkway 0.25

Mountain Creek Road 2.00

Table 5 demonstrates the final average trip lengths for each trip purpose in comparison to the old 2000 model. In addition, year 2007 Home-Based Work (HBW) trip lengths were compared to those included in the Census Transportation Planning Package (CTPP) for the year 2000 in Hamilton, Catoosa, and Walker Counties. HBW trip lengths improved in the 2007 model compared to the 2000 model as they are closer to the CTPP trip lengths. However, the 2007 model HBW trip lengths are still slightly shorter when compared to the CTPP trip lengths. This is as a result of the daily nature of the model compared to the highly peak hour weighted CTPP figure. The modest expansion of the model to include all of Catoosa County since the last LRTP partially explains the reduction in Internal-External trip times. All of the 2007 trip lengths are within acceptable limits provided by the Federal Highway Administration (FHWA). No trip length targets have been established by TDOT at this time.

The 2007 model validation effort involved significant splitting of zones, particularly towards the periphery. This reduced the average size of zones. Consequently, as indicated in Table 6, the percent intrazonal trips fell slightly to below nine percent as compared to above nine percent for the 2000 model. As expected, given the tendency of individuals to travel further for work purposes, the percent intrazonal trips for HBW are lower than for other purposes at just under two percent.

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Table 5. Average Trip Length (in Minutes)

2007 2000

Purpose Chattanooga (TransCAD)

Chattanooga (TransCAD)

CTPP (Hamilton)

CTPP (Catoosa)

CTPP (Walker)

FHWA Target

Home-Based Work 18.26 16.36 21.20 23.70 26.50 11.2-35.4

Home-Based School 13.85 14.48 n/a n/a n/a 8.9-15.9

Home-Based Shop 12.84 13.78 n/a n/a n/a 8.6-18.7


13.55 11.38 n/a n/a n/a

Home-Based Other 12.44 14.41 n/a n/a n/a

10.4-17.3

Nonhome-Based 14.18 15.44 n/a n/a n/a 8.1-17.1

Commercial Vehicles 17.88 19.64 n/a n/a n/a n/a

Light-Truck 17.78 18.79

Medium-Truck 17.20 17.95

Heavy-Truck 20.75 22.17

Internal-External 37.38 41.04 n/a n/a n/a n/a

Total 14.53 18.68 n/a n/a n/a n/a

Table 6. Intrazonal Trips by Trip Purpose

Chattanooga (TransCAD) Percent Intrazonal

Purpose 2007 2000

Home-Based Work 1.93% 7.04%




11.98% 21.08%


Nonhome-Based 9.61% 8.02%





Total 8.89% 9.18%

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2.4 Mode Choice

Currently, the Chattanooga TransCAD model does not include a transit network/pathbuilding component. At the beginning of the 2035 LRTP Update, the RPA intended to add transit to the TransCAD model contingent upon the availability of existing data to validate the new transit component. However, upon review of the data, it was determined that an on-board transit survey was needed in order to validate a new transit model. The RPA will be developing the survey instrument for the on-board transit survey shortly after the adoption of the 2035 LRTP Update. Subsequently, the RPA will conduct the on-board survey in the Fall of 2010, in preparation for the next base year 2010 model for the LRTP Update to be adopted in 2014. The RPA intends to add the transit network/pathbuilding component to the next generation of the TransCAD model in time for the next LRTP update. In the interim, the same auto occupancy model used in the model from the previous 2030 LRTP Update is being used for the current 2035 LRTP Update. Ratios of persons per vehicle were derived from the local household diary survey conducted in the Chattanooga region in 2002.

2.5 Traffic Assignment

In validating traffic assignment, final outcome of a travel demand model, common performance metrics include the following:

• Systemwide volume-to-count ratio;

• Volume-to-count ratios by link group (area type, facility type, and number of lanes);

• Volume-to-count ratios along screenlines;

• Percent difference in model volumes and counts by volume group;

• Systemwide coefficient of determination between assigned volumes and counts;

• Systemwide percent root mean square error; and

• Percent root mean square error by volume group.

Table 7 includes the volume-to-count ratios by facility type, area type, and number of lanes. Overall, the model is validating at 0.96, within acceptable limits. This is also an improvement in the overall validation since the 2000 model with a volume-to-count ratio of 0.95. Although the validation of expressways improved in the 2007 model, the validation of undivided principal arterials, minor arterials, and one-way facilities got worse when compared to the 2000 model. This can be attributed to the correction in the network coding in the 2007 model reflecting the 3rd and 4th Street one-way facilities in downtown Chattanooga. Furthermore, additional network detail was included in some portions of the model as a result of further TAZ splits, as well as a significant amount of more traffic counts being provided in the 2007 model. Therefore, although the 2007 model may indicate lower volume-to-count ratios for some facility type categories, it is likely more accurate than the 2000 model due to the additional traffic counts. In addition, no ramp counts were available in the 2000 model and have since been added to the 2007 model validating at a 2007 volume-to-count ratio of 0.99. Four of the six facility type categories that have targets set by TDOT are within acceptable limits.

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Although no targets have been established to date by TDOT for volume-to-count ratios by area type, seven of the eight area type categories are validating within +/- 1 ten percent. In addition, the new industrial area type category is validating at 0.90. The CBD area in downtown Chattanooga is validating at 0.74, which has historically validated lower than other categories in the Chattanooga model. With the exception of one lane facilities (by direction), the 2007 model is validating better within each lane category compared to the old 2000 model.

Table 7. Volume Over Count Ratios by Facility Type, Area Type and Number of Lanes


2007 2000 TDOT Targeta

Facility Type

1. Interstate 1.02 0.98 +/- 7%

2. Expressway 1.04 0.94 +/- 7%

3. Principal Arterial Divided 0.98 0.98 +/- 10%

4. Principal Arterial Undivided 0.86 0.94 +/- 10%

5. Minor Arterial 0.80 0.88 +/- 15%

6. Collector 0.98 0.98 +/- 25%

7. Ramp 0.99 n/a

8. One-Way 0.49 0.71 n/a

Area Type

1. CBD 0.69 0.88

2. CBD Fringe 0.97 0.92

3. Residential 0.92 0.96

4. OBD 0.95 0.92

5. Rural 1.07 1.10

6. Urban Undeveloped 1.04 1.02

7. Mountainous 1.09 0.95

8. Industrial 0.90

Number of Lanes by Direction

1 0.88 0.93

2 0.99 0.98

3 0.98 0.95

4 1.03 0.92

Total 0.96 0.95

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The 10 screenlines from the previous model were kept and utilized to assist in model validation for the 2007 model. Their positions capture all the major traffic flows in the Chattanooga Region and thus further adjustments and additions were deemed unnecessary. A map of the screenline locations is provided in Appendix C. Maps of volume-to-count ratios on each link in the model with a count are included in Appendix D. For eight of the 10 screenlines, the volume-to-count ratios fall within the +/- 10 percent target range of TDOT. Table 8 compares the volume-to-count ratio for each screenline in the 2007 model against the old 2000 model.

Table 8. Comparison of Volume-to-Count Ratios by Screenline


Screenline 2007 2000

1 1.00 0.97

2 1.01 0.94

3 0.88 0.97

4 0.99 0.91

5 0.82 0.90

6 0.93 0.99

7 1.10 1.09

8 0.91 1.06

9 1.06 1.02

10 1.00 1.00

Table 9 indicates the percent difference in model volumes and observed counts by volume group. All volume groups within the 2007 model achieve the established TDOT targets.

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Table 9. Percent Difference for Daily Volumes (Calculated for Links with Counts)

AADT Chattanooga 2007TransCAD TDOT Targeta

<1,000 48.90% +/- 60%

1,000-2,500 19.20% +/- 47%

2,500-5,000 -2.80% +/- 36%

5,000-10,000 -10.30% +/- 29%

10,000-25,000 -8.90% +/- 25%

25,000-50,000 1.50% +/- 22%

>50,000 -5.90% +/- 21%

The correlation coefficient of observed counts to model volumes (R2) is performing well at 0.95, exceeding TDOT’s target of 0.88, as demonstrated below in Figure 1.

Figure 1. Correlation of Assigned Versus Observed Volumes

0

10000

20000

30000

40000

50000

60000

70000

0 10000 20000 30000 40000 50000 60000 70000

2007 AADT

2007

Ass

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ed V

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As indicated in Table 10, the overall RMSE for the 2007 model is 34.6 percent, within acceptable federal limits. TDOT has established an overall RMSE target of 30 percent. However, based on discussion with TDOT during the June 30, 2009 teleconference, it was determined that 30 percent was just a target and was not required as federal standards indicate a RMSE range of 32-39 percent is within acceptable limits. Although the previous 2000 model indicated an overall RMSE of 23 percent, it is suspected that it was not as accurate due to the reduced

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amount of traffic counts available at that time. All volume groups within the 2007 model achieved a RMSE value close to or within federal and/or TDOT targets.

Table 10. Root Mean Square Error (RMSE) by Volume Group

Chattanooga TransCAD

Count Range 2007 2000 TDOT Target

FHWA & New FDOT Guidelines

and Standards

0-4,999 83.70% 73.10% 115.76 45-100

5,000-9,999 46.30% 33.60% 43.14 35-45

10,000-14,999 36.40% 18.10% 28.27 27-35

15,000-19,999 25-30

20,000-29,999 21.70%

15-27

30,000-39,999

25.40%

16.90%

25.38

40,000-49,999 4.40% 15-25

50,000-59,999 12.10%

7.20% 30.25

10-20

60,000-69,999

70,000-79,999 10-19

79,999-89,999

15.50% n/a 19.20

Overall 34.60% 23.40% 30.00% 32-39%

Table 11 summarizes the vehicle miles traveled (VMT) by model facility type, as well as the percent of VMT that falls within each model facility type compared to TDOT targets. With the exception of minor arterials, all of the facility types fall within or close to TDOT’s targets for percent of VMT by facility type. In addition, the overall ratio of VMT to Highway Performance Monitoring System (HPMS) VMT is 1.06 (excluding external centroid connectors).

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Table 11. Vehicle Miles Traveled by Model Facility Type

Facility Type Chattanooga 2007 Model VMT TDOT Target

Interstate 4,228,041 (31.4%)

Expressway 1,496,818 (11.1%) 33-38%

Principal Arterial Divided 2,067,224 (15.4%)

Principal Arterial Undivided 835,239 (6.2%) 27-33%

Minor Arterial 1,384,961 (10.3%) 18-22%

Collector 1,465,718 (10.9%) 8-12%

Ramp 215,118 n/a

One-Way 16,672 n/a

External Connectors 921,730 n/a

Centroid Connectors 827,412 n/a

Total 13,458,933

2.6 Comparison to Observed Speeds

During November 2008, the RPA conducted travel time runs during the AM and PM peak periods along all routes in their Congestion Management Plan (CMP). The results of these travel time runs were used to calculate average peak period congested speeds. These observed speeds were then compared to the daily congested speeds in the model during the 2007 model validation process. Appendix E includes a map of the observed 2008 AM peak period congested speeds, as well as a map of the daily congested speeds from the 2007 model. As expected, the model speeds compared to the observed speeds are slightly different in some instances since the model speeds are daily and the observed speeds are peak period. However, there was a significant improvement in congested speeds along interstates in the 2007 model as they were too low in the 2000 model.

3.0 Summary of 2007 Model Validation Observations

• The overall 2007 model is validating at 34.6 percent, within acceptable federal limits;

• The 2007 model is validating at a systemwide volume-to-count ratio of 0.96, within acceptable limits and improved since the 2000 model;

• The correlation coefficient of observed counts to model volumes (R2) is performing well at 0.95, exceeding TDOT’s target of 0.88;

• Eight of ten screenlines are validating within acceptable limits;

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• The overall ratio of model VMT to HPMS VMT is 1.06;

• Average trip lengths increased for some trip purposes and decreased for others, although Home-based Work (HBW) trip lengths did improve;

• The percent of intrazonal trips attributed to Home-based Work (HBW) trips are now within a more reasonable range;

• Congested speeds along the interstate and other higher facilities are improved compared to the 2000 model and observed congested speeds;

• Overall, higher facilities are generally comparable to the 2000 model, however, minor facilities got worse in the 2007 model due to additional traffic count availability and network detail;

• Overall, the 2007 model has more counts with almost 10 percent of the network having counts. As a result, the 2007 model includes improved accuracy and reliability of the model statistics;

• Employment in the 2007 model is lower than in the 2000 model, resulting in lower commercial trips; and

• As with all models, there is always room for improvement. However, this model should be sufficient for updating the 2030 LRTP to 2035.

4.0 Future Model Enhancements

Several enhancements are planned for the next generation of the Chattanooga travel demand model to be used for the next LRTP update scheduled for adoption in 2014. These enhancements, as well as the planned data collection efforts necessary to support these enhancements, are detailed below.

4.1 Data Collection

In preparation for the next LRTP Update due for adoption in 2014, the RPA is planning for multiple data collection and compilation efforts over the next two years. Below are some of the data collection efforts planned:

• Socioeconomic Data – Once the Census 2010 population and household data is released, likely in 2012, the RPA will use the data to develop the base year 2010 model socioeconomic data. In the meantime, the RPA will be providing guidelines to the counties and municipalities in the TPO region stating what socioeconomic data is required to assist with compiling the data. Additionally, proprietary employment datasets for the year 2010 may be evaluated for accuracy to determine the most appropriate data source for the

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Chattanooga region. In addition to year 2010, the RPA will be forecasting socioeconomic data to the horizon year for the next LRTP Update, likely year 2040.

• Traffic Counts – During calendar year 2010, the RPA will be identifying and collecting traffic counts at key locations throughout the TPO to assist with validating the 2010 base year model as part of the next LRTP update. The traffic counts will be collected by vehicle class and 15-minute intervals in order to validate trips at the truck level and to include a new time-of-day component in the model.

• External Origin and Destination Survey – In 2002, a roadside origin-destination intercept survey designed to obtain characteristics of travelers entering, exiting, and passing through the region from locations outside the CHCNGA study area was conducted. During the last 2030 LRTP Update, it was determined that the results from the 2002 external origin and destination survey were biased. As a result, during the last 2030 LRTP Update, as well as this current 2035 LRTP Update, the 2002 roadside origin-destination intercept survey was not used within the TransCAD model. Therefore, the RPA intends to conduct a new external origin and destination survey during the fall of 2010. In the meantime, the RPA will be designing the sampling plan and survey instrument. The results of the 2010 external origin and destination survey will be used to validate the external model for the 2010 base year validation as part of the next LRTP update.

• On-Board Transit Survey – As mentioned earlier, the RPA intends to conduct an on-board transit survey in order to validate a new mode choice/transit component in the TransCAD travel demand model. The RPA will be designing the sampling plan and survey instrument in the spring/summer of 2010 with the survey being conducted in the fall of 2010.

• Household Travel Diary Survey – In 2002, a household travel diary survey was conducted to determine trip generation rates, average trip lengths, auto occupancy factors, and other characteristics used in model development and validation. Typically, household travel diary surveys are conducted every 10 years to accurately reflect travel characteristics of the region. Pending funding availability, the RPA intends to conduct a new household travel diary survey in calendar year 2011. The results of the 2011 travel diary survey will be incorporated into the new 2010 base year model for the next LRTP update.

• Bicycle and Pedestrian Counts – If a nonmotorized component is added to the travel demand model prior to validating the 2010 base year model for the next LRTP Update, the RPA will collect bicycle and pedestrian counts. Currently, the RPA owns three bicycle and pedestrian counters and has begun collecting counts in key locations.

4.2 Travel Demand Model Enhancements

The above mentioned data collection efforts will be used to incorporate several enhancements to the current CHCNGA TPO TransCAD model. These enhancements could potentially include the following additions to the TransCAD model prior to the next LRTP Update:

• Updated external model based on 2010 external data;

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• Updated trip generation structure based on 2011 household travel diary survey data;

• New mode choice/transit component not previously included in the model to be used to forecast transit ridership;

• New nonmotorized component not previously included in the model to be used to forecast bicycle and pedestrian trips;

• New time-of-day component used to disaggregate daily trips into three to four time periods. This will improve the accuracy in calculating air quality emissions and is typically necessary for transit models; and

• Validate truck trips in addition to total trips, whereas in the past, only total trips were validated.

5.0 Next Steps

Below is a list of the remaining information to be provided to TDOT and GDOT for review and approval, once the draft LRTP has been documented:

• Full model documentation report and user’s guide; and

• All TransCAD files (future years).

The 2007 model files are being provided to TDOT and GDOT as part of this technical submittal.

As discussed during the modeling workshop held on August 20, 2008, please provide any comments back to the RPA within 10 days, if not sooner. We thank you in advance for understanding our time constraints and look forward to coordinating with you throughout the development of our model and LRTP. If you have any questions about the model, please do not hesitate to contact Melissa Taylor at the RPA via e-mail at [email protected] or phone at (423) 757-0077.

Appendices:

Appendix A: Table and Maps of 2007 Network Projects

Appendix B: Maps of 2007 Model Network Area Type, Facility Type, and Number of Lanes

Appendix C: Map of Screenline Locations

Appendix D: Maps of 2007 Volume-to-Count Ratios

Appendix E: Maps of Congested Speeds (Daily Model and Observed Peak-Period)

Appendix F: Year 2007 Validation Worksheets

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2007

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ttano

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a


Appendix E: 2007 Volume-to-Count Ratios


Appendix F: User’s Guide

Installing the Chattanooga TransCAD Model for the First Time

Upon opening the TransCAD 5.0 environment the following quick start dialog box will appear. Click on the Cancel button. You may also want to check the “Use startup action without Quick Start “ checkbox as well to prevent future displays of this box.

Proceed to Tools then GIS Developer’s Kit on the Menu.

With the GISDK Toolbox open , compile the Chattanooga.lst batch file that calls three .rsc script files to a User Interface file.

- 2 -

Wherever the model directory was copied on your computer or network, change the directories referred to on the .lst file to ensure the correct files are being used. For example, if the Inputs folder was placed on the C: then the .lst file should refer to C:\Inputs\New Attributes List File as the directory for the three .rsc files. This is also the directory location for the .lst file.

You will be asked for a location in which to save the User Interface file. Navigate to the C:\Program Files\TransCAD directory and save the file as Chattanooga_ui.dbd

- 3 -

Once the User interface file has been created, proceed to Tools then Setup Add-Ins to bring up the respective dialog box. Select Add and proceed to enter a description for the Chattanooga Model. Any meaningful description will suffice. A name like “Chattanooga Model Interface” will do. Select the Dialog Box radio button. Enter the value “Chattanooga” under the Name list box. This name must match exactly the described dialog box name in the script file. Browse to the stored location of the compiled User Interface file (C:\Program Files\TransCAD) and open the Chattanooga_ui.dbd. Click OK.

- 4 -

The model has now been set up to run on the User’s machine. Subsequent model runs will not require the setup of the Chattanooga User Interface Add-In.

To run the model, go to Tools then click on “Chattanooga Model Interface” and click OK. The model interface dialog box will now be displayed.

- 5 -

Click on Reset Directories to see the input files for the Chattanooga model. The inputs are now ready to be selected.

- 6 -

To run the 2007 Base Year for example, enter the values as illustrated, remembering to use the base model directory to which you copied all the model files.

The LRTP_Master_Network.dbd file is a master network that includes all model network years. It is the only file that should be selected within the Network Database window.

The TAZ.dbd file is a master socioeconomic data file that includes all socioeconomic data years and should be the only file selected within the TAZ Geography window.

The SPGEN.bin file is a master special generators file that includes special generators for each model year. It is the only file that should be selected within the Special Generators window.

Select the desired socioeconomic data year from the SocEc Year window. Note that socioeconomic data has been developed for 2002, 2007, 2009, 2015, 2025, and 2035. Any interim years are automatically interpolated using the interface.

The Chatt_Turn_Penalty.bin files is a master turn penalty file that includes turn penalties for all model network years. It is the only file that should be selected within the Turn Penalty window.

Select the desired transportation network from the Network Scenario window. The following network scenarios are available:

o 2002 AQ – Used for air quality baseline emissions.

o 2007 Base – Base year validated model.

- 7 -

o 2009 Interim – Used to compare with emissions in the State Implementation Plan (SIP) for PM2.5.

o 2011 E+C (Existing-Plus-Committed) – Used to determine what congestion would be if no further transportation improvements were funded above and beyond what currently is in the FY ‘08-‘11 Transportation Improvement Program (TIP). Nonexempt (new road or widening) projects expected to complete construction by the end of calendar year 2011 are included in the E+C transportation network.

o 2015 FFP (Financially Feasible Plan or Fiscally Constrained LRTP (Tier 1)) – Includes all nonexempt projects funded for construction prior to or during year 2015 (Tier 1) of the fiscally constrained LRTP.



If the user chooses to run the time-of-day assignment to get AM and/or PM peak hour volumes (time-of-day factors derived from 2002 Chattanooga Household Travel Survey are applied AFTER assignment), the AM Assignment and/or PM Assignment boxes should be checked.

Once all the desired inputs have been selected, the model can be run all at once by clicking on Run All (Gen Asgn). This runs the general assignment and does not account for HOV or truck-only lanes. None of the model networks in the fiscally constrained LRTP include projects for HOV or truck-only lanes and thus, General Assignment can be run on all model networks listed above. Should a model user decide to test HOV or truck-only lanes, the user should select Run All (Truck Asgn) or Run All (HOV Asgn).

If the user wants to test each individual model step, the user should click on each individual model step in the following sequence:

• Highway Skims • Trip Generation • Trip Distribution • Mode Split • General Highway Assignment (if no HOV or truck-only lanes) • Truck Only Assignment (if testing truck lanes) • HOV Only Assignment (if testing HOV lanes)

Once the model is run, the assigned volumes are stored in the master network. See the attached attribute list for a description of each network attribute.

Chattanooga Year 2007 Model

DATA DICTIONARY

Developed as Part of 2035 LRTP Update

TABLE OF CONTENTS

1.0 Introduction ............................................................................................................................................. 1 2.0 Input files ................................................................................................................................................ 2

LRTP_NETWORK.DBD ....................................................................................................................... 3 CHATT_TURN_PENALTY.BIN .......................................................................................................... 6 TAZ.DBD ............................................................................................................................................... 7 SPGEN.BIN ......................................................................................................................................... 11 F_FACTORS.DBF ............................................................................................................................... 14 K_FACTORS.MTX ............................................................................................................................. 15 YR_EXTERNAL-EXTERNAL.MTX ................................................................................................. 16 HRLY_CHATT.DBF ........................................................................................................................... 17 STATE{Year}_EMISSIONS_LOOKUP.TXT .................................................................................... 19

3.0 Output Files ........................................................................................................................................... 20 LRTP_NETWORK.DBD ..................................................................................................................... 21 HWYDIST1.MTX ................................................................................................................................ 22 HWYTIME1.MTX ............................................................................................................................... 23 TRIPGEN_REPORT.TXT ................................................................................................................... 24 GRAVITY_MODEL_REPORT.TXT .................................................................................................. 25 CGRAV.MTX ...................................................................................................................................... 26 SCREENLINE_REPORT.TXT ............................................................................................................ 28 GENERAL_ASSIGN_REPORT.TXT ................................................................................................. 29 MOBILE6_ADJ.CSV ........................................................................................................................... 30 {Year}MOBILE6_SUMMARY_REPORT.CSV ................................................................................. 31 MOBILE6_REPORT_AQ.CSV ........................................................................................................... 33

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1.0 Introduction The purpose of this document is to describe the input and output files for the Chattanooga 2007 TransCAD model updated as part of the 2035 Long Range Transportation Plan. This data dictionary defines the input network, socioeconomic data, and other files and attributes required to run the Chattanooga model. Attributes within each of the output files are also defined. The following are the file formats that are used for inputs, outputs and script compilation. • CSV – Tabular format readable in Excel (comma separated values). • DBF – Database format readable by a variety of software programs. • MTX – TransCAD format matrix file in which several sub matrix cores can be placed. • NET – TransCAD binary network database. • TXT – ASCII text file. • RSC – TransCAD GISDK text script file. • LST – TransCAD GISDK text list batch run file. • DBD – TransCAD geographic file. • BIN – TransCAD binary data file.

Files are listed in order by: • HIGHWAY SKIMS - Highway network and path building. • TRIP GENERATION – Trip generation and external-external trips. • TRIP DISTRIBUTION – Trip distribution and congested skims. • MODE SPLIT – Mode choice and auto occupancy. • HIGHWAY ASSIGNMENT – Highway assignment.

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2.0 Input files The following are the input files used to run the Chattanooga model.They represent the zone data, network data, and required files in trip distribution, such as K-factor matrices, friction factors, daily adjustment factors, and external-external matrices. Additionally, the Mobile6.2 emissions factor lookup files are necessary to calculate emissions in the air quality post processor .

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LRTP_NETWORK.DBD FILE TYPE: TransCAD Geographic File DBD MODEL STEP: HIGHWAY SKIMS PRIMARY FUNCTION: Line geographic file used to create TransCAD model network. DATA FORMAT: Abbreviations: yr = year time# = peak hour (AM or PM) VARIABLE (FIELD) NAME DESCRIPTION Inputs: * LENGTH Link Length in miles. * DIR One way or two-way link flag. * COUNTY Link County.

* STATE Link State. * AB_LNyr Number of lanes in AB direction for year and scenario if applicable (i.e. FFP =

financially feasible plan, EC = Existing-Plus-Committed).

* BA_LNyr Number of lanes in BA direction for year and

scenario if applicable (i.e. FFP = financially feasible plan, EC = Existing-Plus-Committed).

* TOT_LNyr Total lanes for year and scenario if applicable (i.e. FFP = financially feasible plan, EC = Existing-Plus-Committed).

* FT_yr Facility type for year and scenario if applicable (i.e. FFP = financially feasible plan, EC = Existing-Plus-Committed).

* AT_yr Area type for year and scenario if applicable (i.e. FFP = financially feasible plan, EC = Existing-Plus-Committed).

. * Added Road Road added in 2007 model network compared to 2000. * Screenline Screenline flag.

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* AB/BA_CNT_yr Directional link counts for 2007, 2008 or 2009. * SRCE Source of count data.

* HPMS_FCyr HPMS functional class for 1990, 2000 and 2007 * HOV_Only_Lane Flag to indicate link is an exclusive HOV

lane. * Truck_Only_Lane Flag to indicate link is an exclusive truck

lane. * Exec_Area_Type Working area type field populated

depending on scenario year specified. Any edits will be overwritten when the model is executed.

* Exec_Facility_Type Working facility type field populated depending on scenario year specified. Any

edits will be overwritten when the model is executed.

* Exec_AB_Lanes Working AB direction lane field populated depending on scenario year specified. Any


* Exec_BA_Lanes Working BA direction lane field populated depending on scenario year specified. Any


* yr_AADT Annual average daily traffic (2007, 2008 or 2009). * year_Count Link count (2007, 2008 or 2009). * DOT_CNT_FLAG DOT count source flag. * CITY_CNT_FLAG City count source flag. * CSATD_CNT_FLAG TPO 2008 source count flag.

Outputs: * TerminalTime Terminal times for link. * AB/BA_FF_Time Directional free flow travel times. * AB/BA_Cong_Time Directional congested travel times. * Table_Speed Free-flow speeds from input lookup table. * Model_Speed Congested speeds following assignment. * AB/BA_Table_HrCap Directional hourly capacities from

input lookup table.

* AB/BA_Model_HrCap Directional hourly capacities for model execution.

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* AB_BA_Model_DlyCap Directional daily capacities for model. * Alpha BPR delay function alpha parameter. * Beta BPR delay function beta parameter. * AB/BA_Model_VMT Directional link vehicle miles traveled

(VMT) * AB/BA_Model_VMT_Adj Directional link VMT adjusted with HPMS factors for air quality purposes. * AB/BA_Daily_EEHT Directional external-external heavy truck

trips. * AB/BA_time#_EEHT Directional external-external heavy truck

trips (AM or PM). * AB/BA_TOTPASSVEH Directional total passenger vehicle volumes. * AB/BA_time#_PassV Directional passenger vehicle volumes (AM

or PM) * AB/BA_Daily_Allveh Directional daily vehicle volumes. * Tot_Daily_Allveh Total daily vehicle volumes. * AB/BA_time#_Allveh Directional peak hour vehicle volumes (AM

or PM) * AB/BA_SOV Directional single occupancy vehicle (SOV)

volumes. * AB/BA_HOV2 Directional 2 person high occupany vehicle

(HOV) vehicle volumes. * AB/BA_HOV3 Directional 3 person+ HOV vehicle

volumes. * AB/BA_ALLHOV Directional 2 or more person HOV vehicle volumes (all HOV). * AB/BA_LTTRK Directional light-duty truck volumes. * AB/BA_MDTRK Directional medium-duty truck volumes. * AB/BA_HDTRK Directional heavy-duty duty truck volumes. * AB/BA_TOTTRK Directional total truck volume. * AB/BA_TOTEE Directional total external-external volume. * AB/BA_VoverC Directional volume-over-capacity ratios. SPECIAL NOTES: The AM and PM values (time#) represent values collected over the peak hour rather than a 3 or 4 hour peak period. The peak hour values are based on the temporal distribution of trips from the household travel survey conducted in the Chattanooga region in 2002. These peak hour factors are applied after assignment and thus, do not account for diversion of trips as a result of congestion. In addition, the 2007 model was validated to the total trip level, not peak hour or truck trip level.

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CHATT_TURN_PENALTY.BIN FILE TYPE: TransCAD Binary (BIN) MODEL STEP: HIGHWAY SKIMS PRIMARY FUNCTION: Contains link penalty data. DATA FORMAT: VARIABLE (FIELD) NAME DESCRIPTION * FROM_ID TransCAD link ID from which trips enduring the penalty pass.

* TO_ID TransCAD link ID to which trips enduring the penalty proceed.

* PENALTY Value of the penalty in minutes. SPECIAL NOTES: If PENALTY is 0, the movement is prohibited.

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TAZ.DBD FILE TYPE: TransCAD Geographic File DBD MODEL STEP: TRIP GENERATION PRIMARY FUNCTION: Master zone data file that includes socioeconomic data for each

model year. DATA FORMAT: VARIABLE (FIELD) NAME DESCRIPTION Inputs: * ID Zone ID number. (Centroid or External Station) * Area Zone area in square miles. * COUNTY Zone County. * STATE Zone State. * DISTRICT_C RPA Planning District ID number. * DISTRICT RPA Planning District description. * Total_Households Working field for total zonal

households. Any edits will be overwritten when the model is executed.

* Total_Population Working field for total zonal population. Any edits will be overwritten when the model is executed.

* HotelMotel_Units Working field for zonal hotel/motel units. Any edits will be overwritten

when the model is executed. * School_Age_Children Working field for zonal school age children. Any edits will be

overwritten when the model is executed.

* Total_Employment Working field for total zonal employment. Any edits will be


* Agr/Min/Const Working field for zonal agricultural, mining and construction

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employment. Any edits will be overwritten when the model is executed.

* Manu/Trans Working field for zonal manufacturing and transportation employment. Any edits will be overwritten when the model is executed.

* Retail Working field for zonal retail employment. Any edits will be


* Service Working field for zonal service employment. Any edits will be


* Government Working field for zonal government employment. Any edits will be


* School_Enrollment Working field for zonal school enrollment. Any edits will be


* College_Enrollment Working field for zonal college enrollment. Any edits will be


* Total_School_Enrollment Working field for total school enrollmment. (school + college) Any


* External_Internal Working field for zonal external- internal trips. Any edits will be overwritten when the model is executed.

* yr_TOTHH Zonal households for scenario year. * yr_TOTPOP Zonal population for scenario year. * yr_HOTMOT Zonal hotel/motel units for scenario

year. * yr_TOTEMP Zonal employment for scenario year. * yr_CHILD Zonal school age children for

scenario year.

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* yr_AMC Zonal agricultural, mining and construction employment for scenario year. * yr_MANTRN Zonal manufacturing and

transportation employment for scenario year.

* yr_RETAIL Zonal retail employment for scenario year. * yr_SERV Zonal service employment for

scenario year. * yr_GOVT Zonal government employment for scenario year. * yr_GRSCH Zonal grade school enrollment for scenario year. * yr_COL Zonal college enrollment for scenario year. * yr_TOTSCH Zonal total school enrollment ( grade school + college) for scenario year. * yr_EXTINT Zonal external to internal trips for

scenario year. * PERC_#_VEH Percent (0, 1, 2 or 3+) vehicle households in zone. Outputs: * HBWork_p Home Based Work productions. * HBWork_a Home Based Work attractions. * HBSchool_p Home Based School productions. * HBSchool_a Home Based School attractions. * HBShop_p Home Based Shopping productions. * HBShop_a Home Based Shopping attractions. * HBSocRec_p Home Based Social/Recreational

Work productions. * HBSocRec_a Home Based Social/Recreational

Work attractions. * HBOther_p Home Based Other productions. * HBOther_a Home Based Other attractions. * NHB_p Non Home Based productions. * NHB_a Non Home Based attractions. * LgtTruck_p Light Truck productions. * LgtTruck_a Light Truck attractions. * MedTruck_p Medium Truck productions. * MedTruck_a Medium Truck attractions. * HvyTruck_p Heavy Truck productions.

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* HvyTruck_a Heavy Truck attractions. * LATITUDE Latitude in decimal degrees. * LONGITUDE Longitude in decimal degrees.

SPECIAL NOTES: The working field variables are populated initially upon running the trip generation scenario and the values are obtained from the scenario year fields for whichever year is selected.

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SPGEN.BIN FILE TYPE: TransCAD Binary (BIN) MODEL STEP: TRIP GENERATION PRIMARY FUNCTION: Special generator data for trip generation DATA FORMAT: VARIABLE (FIELD) NAME DESCRIPTION * ID Zone Number. * yr_HBWork_p Home Based Work special generator productions for scenario year. * yr_HBWork_a Home Based Work special generator attractions. * yr_HBSchool_p Home Based School special generator productions. * yr_HBSchool_a Home Based School special generator attractions. * yr_HBShop_p Home Based Shopping special

generator productions. * yr_HBShop_a Home Based Shopping special

generator attractions. * yr_HBSocRec_p Home Based Social Recreational

special generator productions. * yr_HBSocRec_a Home Based Social Recreational

special generator attractions. * yr_OTher_p Home Based Other special generator productions. * yr_OTher_a Home Based Other special generator attractions. * yr_NHB_p Non Home Based special generator productions. * yr_NHB_a Non Home Based special generator attractions. * yr_LightTruck_p Light Truck special generator productions. * yr_LightTruck_a Light Truck special generator attractions. * yr_MedTruck_p Medium Truck special generator productions.

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* yr_MedTruck_a Medium Truck special generator attractions. * yr_HeavTruck_p Heavy Truck special generator productions. * yr_HeavTruck_a Heavy Truck special generator attractions.

* HBWork_p Working variable for Home Based Work special generator productions. Any edits will be overwritten when the model is executed.

* HBWork_a Working variable for Home Based Work special generator attractions. Any edits will be overwritten when the model is executed.

* HBSchool_p Working variable for Home Based School special generator productions. Any edits will be overwritten when the model is executed.

* HBSchool_a Working variable for Home Based School special generator attractions. Any edits will be overwritten when the model is executed.

* HBShop_p Working variable for Home Based Shopping special generator productions. Any edits will be overwritten when the model is executed.

* HBShop_a Working variable for Home Based Shopping special generator attractions. Any edits will be overwritten when the model is executed.

* HBSocRec_p Working variable for Home Based Social Recreational special generator

productions. Any edits will be overwritten when the model is executed.

* HBSocRec_a Working variable for Home Based Social Recreational special generator

attractions. Any edits will be overwritten when the model is executed.

* OTher_p Working variable for Home Based

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Other. Any edits will be overwritten when the model is executed.

special generator productions. * OTher_a Working variable for Home Based

Other special generator attractions. Any edits will be overwritten when the model is executed.

* NHB_p Working variable for Non Home Based special generator productions. Any edits will be overwritten when the model is executed.

* NHB_a Working variable for Non Home Based special generator attractions. Any edits will be overwritten when the model is executed.

* LightTruck_p Working variable for Light Truck special generator productions. Any edits will be overwritten when the model is executed.

* LightTruck_a Working variable for Light Truck special generator attractions. Any edits will be overwritten when the model is executed.

* MedTruck_p Working variable for Medium Truck special generator productions. Any


* MedTruck_a Working variable for Medium Truck special generator attractions. Any


* HeavTruck_p Working variable for Heavy Truck special generator productions. Any


* HeavTruck_a Working variable for Heavy Truck special generator attractions. Any edits will be overwritten when the model is executed.

SPECIAL NOTES: The working field variables are populated initially upon running the trip generation scenario and the values are obtained from the scenario year fields for whichever year is selected. Balncing trip productions with attractions is done after the special generator values have been included.

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F_FACTORS.DBF FILE TYPE: DBF MODEL STEP: TRIP DISTRIBUTION PRIMARY FUNCTION: Friction factors by trip purpose by travel time for input to Gravity Model DATA FORMAT: VARIABLE (FIELD) NAME DESCRIPTION * TIME Skimmed network travel time.

* HBW_FF Home-based Work Friction Factors. * HBSCH_FF Home-based School Friction Factors. * HBSHOP_FF Home-based Shopping Friction Factors.

* HBSR_FF Home-based Social/Recreational Friction Factors.

* HBOTHER_FF Home-based Other Friction Factors. * NHB_FF Non Home-Based Friction Factors. * LTRUCK_FF Light Truck Friction Factors. * MTRUCK_FF Medium Truck Friction Factors. * HTRUCK_FF Heavy Truck Friction Factors. * INTEXT_FF Internal-External Friction Factors. SPECIAL NOTES: Users should not edit this file as it will impact model validation.

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K_FACTORS.MTX FILE TYPE: TransCAD Matrix File (MTX) MODEL STEP: TRIP DISTRIBUTION PRIMARY FUNCTION: K-Factor trip table used to assist with validating the trip

distribution step. DATA FORMAT: TABLE NAME DESCRIPTION * K-Factor K-factor matrix core. (#zones by #zones) SPECIAL NOTES: #Zones represent total of internal zones and external stations. Do not edit this file as it will impact validation.

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YR_EXTERNAL-EXTERNAL.MTX FILE TYPE: TransCAD Matrix File (MTX) MODEL STEP: MODE SPLIT PRIMARY FUNCTION: External-external trip table DATA FORMAT: TABLE NAME DESCRIPTION * YR EE External matrix (#zones by #zones) core for year. SPECIAL NOTES: #Zones represent total of internal zones and external stations.

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HRLY_CHATT.DBF FILE TYPE: DBF MODEL STEP: MODE SPLIT PRIMARY FUNCTION: Daily-to-hourly lookup table by occupancy level. DATA FORMAT: VARIABLE (FIELD) NAME DESCRIPTION * HOUR Hour of the day from 0 to 23 (i.e. 0 = 12-1

AM) * F_FLOW_ALL Percentage of daily origin-destination (O-D)

trips that occur during the hour. * F_FLOW_HBW Percentage of daily HBW O-D trips that

occur during the hour. * F_FLOW_HBN Percentage of daily HBNW O-D trips that occur during the hour. * F_FLOW_HBO Percentage of daily HBO O-D trips that occur during the hour. * F_FLOW_NHB Percentage of daily NHB O-D trips that occur during the hour. * DEP_ALL Percentage of daily P-A trips that depart

during the hour. * RET_ALL Percentage of daily P-A trips that return

during the hour. * DEP_HBW Percentage of daily HBW P-A trips that

depart during the hour. * RET_HBW Percentage of daily HBW P-A trips that

return during the hour. * DEP_HBSC Percentage of daily HBSC P-A trips that

depart during the hour. * RET_HBSC Percentage of daily HBSC P-A trips that

return during the hour. * DEP_HBSH Percentage of daily HBSH P-A trips that

depart during the hour. * RET_HBSH Percentage of daily HBSH P-A trips that

return during the hour. * DEP_HBSR Percentage of daily HBSR P-A trips that

depart during the hour. * RET_HBSR Percentage of daily HBSR P-A trips that

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return during the hour. * DEP_HBO Percentage of daily HBO P-A trips that

depart during the hour. * RET_HBO Percentage of daily HBO P-A trips that return during the hour. * DEP_NHB Percentage of daily NHB P-A trips that

depart during the hour. * RET_NHB Percentage of daily NHB P-A trips that return during the hour. * OCCADJ_HBW Absolute hourly vehicle adjustment factor for HBW trips. * OCCADJ_HBN Absolute hourly vehicle adjustment factor for HBNW trips. * OCCADJ_HBO Absolute hourly vehicle adjustment factor for HBO trips. * OCCADJ_NHB Absolute hourly vehicle adjustment factor for NHB trips. * OCCADJ_ALL Absolute hourly vehicle adjustment factor for all trip types. SPECIAL NOTES: • HBW – Home based work. • HBNW – Home based non-work. • HBO –Home based other. • NHB – Non home based. • HBSC - Home based school. • HBSH – Home based shopping. • HBSR – Home based social recreational.

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STATE{Year}_EMISSIONS_LOOKUP.TXT FILE TYPE: Comma delimited text file. MODEL STEP: HIGHWAY ASSIGNMENT PRIMARY FUNCTION: Emissions factor lookup table from Mobile6.2 for each state by

model scenario year. DATA FORMAT: VARIABLE (FIELD) NAME DESCRIPTION * PM2.5 Particulate matter (2.5 micron) emissions

factor for freeways in grams. * NOX Oxides of Nitrogen emissions factor for

for freeways in grams. * VOC Volatile Organic Compounds (Non-methane hydrocarbon) emissions factor for freeways

in grams. SPECIAL NOTES: Repeated for arterial, local and freeway ramps (MOBILE6.2 road types). Values delimited by a comma. For VOC, a placeholder value of 1 has been included as actual factors for VOC were not obtained from MOBILE 6.2.

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3.0 Output Files The following are the output files produced from the Chattanooga model. They primarily represent the output reporting text files, the emission factor summary and other related air quality files. Please note that the assignment outputs are stored directly in the TransCAD geographic network line input file and thus a separate output network is not created. A copy of the network file is, however, automatically copied in to the OUT directory.

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LRTP_NETWORK.DBD FILE TYPE: TransCAD Geographic File DBD MODEL STEP: HIGHWAY SKIMS PRIMARY FUNCTION: Line geographic file used to create TransCAD model network. The LRTP_NETWORK.DBD is a master transportation network that includes both the input and output network attributes. See the LRTP_NETWORK.DBD file in the Input Files section for specific data format.

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HWYDIST1.MTX FILE TYPE: TransCAD Matrix File (MTX) MODEL STEP: HIGHWAY SKIMS PRIMARY FUNCTION: Interzonal and intrazonal network skim distance (distance between

each pair of zones). DATA FORMAT: TABLE NAME DESCRIPTION * Distance Skim-Length Matrix (#zones by #zones) core. SPECIAL NOTES: #Zones represent total of internal zones and external stations.

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HWYTIME1.MTX FILE TYPE: TransCAD Matrix File (MTX) MODEL STEP: HIGHWAY SKIMS PRIMARY FUNCTION: Interzonal and intrazonal network skim travel time (time in

minutes between each pair of zones). DATA FORMAT: TABLE NAME DESCRIPTION * Distance Skim-Length Matrix (#zones by #zones) core. SPECIAL NOTES: #Zones represent total of internal zones and external stations.

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TRIPGEN_REPORT.TXT FILE TYPE: ASCII text file (TXT) MODEL STEP: TRIP GENERATION PRIMARY FUNCTION: Summary of trip generation. DATA FORMAT: SPECIAL NOTES: Text summary table of trip productions and balanced/unbalanced attractions by trip purpose. Included are the special generator trips, summary population, and household trip data.

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GRAVITY_MODEL_REPORT.TXT FILE TYPE: ASCII text file (TXT) MODEL STEP: TRIP DISTRIBUTION PRIMARY FUNCTION: Summary of trip distribution. DATA FORMAT: SPECIAL NOTES: Text summary report of average travel times/distnaces by trip purpose, as well as the number of intrazonal trips.

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CGRAV.MTX FILE TYPE: TransCAD Matrix File (MTX) MODEL STEP: MODE SPLIT PRIMARY FUNCTION: Final trip table to be used for assignment. DATA FORMAT: TABLE NAME DESCRIPTION * HBWork Home Based Work trip matrix (#zones by #zones) core. * HBSchool Home Based School trip matrix (#zones by #zones) core. * HBShop Home Baesd Shopping trip matrix (#zones by #zones) core.

* HBSocRec Home Based Social Recreational trip matrix (#zones by #zones) core.

* HBOther Home Baes Other trip matrix (#zones by #zones) core. * NHB Non Home Based trip matrix (#zones by #zones) core. * LgtTruck Light Truck trip matrix (#zones by #zones) core. * MedTruck Medium Truck trip matrix (#zones by #zones) core. * HvyTruck Heavy Truck trip matrix (#zones by #zones) core. * Ext2Int External to Internal trip matrix (#zones by #zones)

core. * I-I:SOVs Internal – Internal Single Occupancy vehicle trip matrix (#zones by #zones) core. * I-I:HOV2 Internal – Internal 2 person High Occupancy vehicle trip matrix (#zones by #zones) core. * I-I:HOV3 Internal – Internal 3 or more person High Occupancy vehicle trip matrix (#zones by #zones) core. * I-I:Light_Truck Internal – Internal Light Truck trip matrix (#zones by #zones) core. * I-I:Medium_Truck Internal – Internal Medium Truck trip matrix (#zones by #zones) core. * I-I:Heavy_Truck Internal – Internal Heavy Truck trip matrix (#zones by #zones) core.

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* I-I:Light_Truck Internal – Internal Light Truck trip matrix (#zones by #zones) core. * E-E:SOVs External – External Single Occupancy vehicle trip

matrix (#zones by #zones) core. * E-E:HOV2 External – External 2 person High Occupancy vehicle trip matrix (#zones by #zones) core. * E-E:HOV3 External – External 3 or more person High

Occupancy vehicle trip matrix (#zones by #zones) core.

* E-E:Light_Truck External – External Light Truck trip matrix (#zones by #zones) core. * E-E:Medium_Truck External – External Medium Truck trip matrix (#zones by #zones) core. * E-E:Heavy_Truck External – External Heavy Truck trip matrix (#zones by #zones) core. SPECIAL NOTES: #Zones represent total of internal zones and external stations. This trip table is used in a multi-modal multi-class assignment routine to assign separate categories, such as E-E trips, truck trips, etc.

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SCREENLINE_REPORT.TXT FILE TYPE: ASCII text file (TXT) MODEL STEP: HIGHWAY ASSIGNMENT PRIMARY FUNCTION: Summary of screenline validation statistics. DATA FORMAT: SPECIAL NOTES: Text summary report of total screenline volumes/observed counts and derived volume-over-count ratios.

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GENERAL_ASSIGN_REPORT.TXT FILE TYPE: ASCII text file (TXT) MODEL STEP: HIGHWAY ASSIGNMENT PRIMARY FUNCTION: Summary of trip assignment results. DATA FORMAT: SPECIAL NOTES: Text summary report of assignment results. Included statistics are volume-over-count ratios, root mean square error (RMSE), vehicle miles traveled (VMT), and vehicle hours traveled (VHT) by various categories. Categories include facility type, area type, Highway Performance Monitoring System (HPMS) functional classification, number of lanes, and volume assignment group.

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MOBILE6_ADJ.CSV

FILE TYPE: CSV (Comma Delimited) MODEL STEP: AIR QUALITY POST PROCESSOR IN HIGHWAY ASSIGNMENT PRIMARY FUNCTION: Stores HPMS adjustment factors from base year (2007) model run. DATA FORMAT: VARIABLE (FIELD) NAME DESCRIPTION * FACTOR HPMS adjustment factor by county

and HPMS functional class code. SPECIAL NOTES: The adjustment factors are reported for each of Hamilton, Catoosa, Dade, and Walker counties by HPMS functional classification.

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{Year}MOBILE6_SUMMARY_REPORT.CSV

FILE TYPE: CSV (Comma Delimited) MODEL STEP: AIR QUALITY POST PROCESSOR IN HIGHWAY ASSIGNMENT PRIMARY FUNCTION: Reports air quality post processor summary emissions information by county and HPMS Federal Functional Classification. DATA FORMAT: VARIABLE (FIELD) NAME DESCRIPTION * YEAR Model Run Year * DESCRIPTION HPMS Functional Class description. * FUNCTIONAL CLASS(ES) HPMS Functional Class code. (0, 1, 2, 6, 7, 8, 9, 11, 12, 14, 16, 17 and 19) * DAILY MODEL VMT Daily vehicle miles traveled from model for county and fucntional class. * DAILY MODEL VHT Daily vehicle hours traveled from model for county and functional class. * DAILY MODEL PM2.5(grams) Daily 2.5 micron and greater particulate matter in grams for county and functional class. * DAILY MODEL Nox (grams) Daily Oxides of Nitrogen emissions in grams for county and functional class. * DAILY MODEL VOC (grams) Daily Volatile Organic Compound (Non-methane hydrocarbon) emissions in grams for county and functional class. * MODEL AVG SPEED Average speed by county and functional class in miles per hour. * DAILY 2007 HPMS Daily HPMS reported volumes by county and functional class * 2007 HPMS ADJ FACTOR HPMS adjustment factor to align HPMS volumes with model volumes. * DAILY ADJ. MODEL PM2.5(grams) Daily 2.5 micron and greater

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particulate matter in grams for county and functional class adjusted by HPMS factor. * DAILY ADJ. MODEL NOx (grams) Daily Oxides of Nitrogen emissions in grams for county and functional class adjusted by HPMS factor. * DAILY ADJ. MODEL VOC (grams) Daily Volatile Organic Compound (Non-methane hydrocarbon) emissions in grams for county and functional class adjusted by HPMS factor. SPECIAL NOTES: The adjustment factors are reported for each of Hamilton, Catoosa, Dade and Walker counties by HPMS functional classification in sequential order. Please note, the VOC values are a placeholder until local emission factors are obtained for VOCs through interagency consultation.

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MOBILE6_REPORT_AQ.CSV

FILE TYPE: CSV (Comma Delimited) MODEL STEP: AIR QUALITY POST PROCESSOR IN HIGHWAY

ASSIGNMENT PRIMARY FUNCTION: Reports link level emissions output from the air quality post processor. DATA FORMAT: VARIABLE (FIELD) NAME DESCRIPTION * ID TransCAD link ID number. * CNTY County ID (47-Catoosa, 65- Hamilton,83-Dade and 295-Walker) * DIR Link directionality. (1 – one way AB, 0 – two way, -1 – one way BA) * A/B TransCAD A and B node ID numbers. * MILES Link distance in miles. * FTYPE Link facility type 1 – 9. * HPMS Link HPMS functional classification code (0 – 18). * CONGTIME Link congested travel time. * AUTOLT Auto and Light Truck assigned volume. * MT Medium Truck assigned volume. * HT Heavy Truck assigned volume. * COMPVOL Total assigned volumes on link. * COMPVMT VMT for all vehicles on link. * CONGSPD Link congested speed. * PMFAC Particulate matter emission factor used for specific link. (Obtained from lookup table for speed, county and functional class) * NOXFAC Oxides of nitrogen emission factor used for specific link. (Obtained from lookup table for speed, county and functional class) * PM25 2.5 micron and greater particulate

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matter emissions on link in grams. * NOX Oxides of nitrogen emissions on link in grams.

volume 3 travel demand model documentation and user's guide

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