urban transportation planning task e develop standardized modal

Urban Transportation Planning Model Update - Phase II

TASK E

DEVELOP STANDARDIZED MODAL SPLIT MODELS

Prepared for:

The Florida Department of Transportation

Prepared by:

COMSIS Corporation Killearn Village Square

3644 Shamrock West Tallahassee, Florida 32308

(904) 893-3125

October 1981

FOREWORD

This report is the third in a series of four reports

documenting Phase II of the urban Transportation Planning

Model Update Study. This report documents Task E. Task E

has developed standardized modal split models for use in the

urbanized areas of Florida.

Phase I of the Urban Transportation Planning Model Up-

date has been completed. Phase I consisted of Tasks A and B.

Task A included the initial review of operating experience

within the Urban Transportation Section (now the Bureau of

Urbanized Area Systems Planning) of the Florida Department of

Transportation and the identification of individual programs

and procedures that would best serve all or groups of Flor-

ida's urbanized areas in the application mode. In Task B, a

trip generation model set was developed for potential use in

the urbanized areas of Florida.

Phase II is divided into four tasks. Task E, which is

documented herein, has developed standardized modal split

models; Task C has developed standardized distribution and

assignment models; Task D will develop a systems evaluation

model; and in Task F, corridor analysis procedures were de-

veloped.

This report is divided into four chapters which parallel

the study progress in Task E. The first chapter presents a

review of operational experience. In Chapter Two, alterna-

tive modal split procedures were recommended for further con-

sideration. In Chapter Three, an evaluation of the alterna-

i

tive modal split procedures was accomplished and specific

recommendations were advanced as to which areas should use

the recommended procedures. In Chapter Four, refinements of

this recommendation are documented based upon Florida DOT and

Model Task Force review. In addition, a procedure to stand-

ardize the application of the modal split models is pre-

sented.

ii

TABLE OF CONTENTS

FOREWORD .............................................

LIST OF FIGURES ......................................

LIST OF TABLES .......................................

CHAPTER ONE - REVIEW OF OPERATIONAL EXPERIENCE .......

Mode Choice Models - Background ................. Review of Florida Mode Choice Models ............ Auto Occupancy ..................................

CHAPTER TWO - FORMULATION OF ALTERNATIVE PROCEDURES . .

Categorization of Existing Florida Models ....... Alternatives to be Considered ................... Recommendation for Modal Choice Models .......... Accuracy Evaluations ............................

CHAPTER THREE - EVALUATION OF ALTERNATIVE MODAL SPLIT PROCEDURES ..........................

Review of Modal Split Model Categorization ...... Review of Recommended Modal Split Alternatives . . Area Sensitive Evaluation of Recommended Procedures .....................................

Recommendations ................................. Summary .........................................

CHAPTER FOUR - SELECTION AND REFINEMENT OF RECOMMENDED PROCEDURES ...............

Sensitivity Tests of Logit Formulation .......... Specific Model Recommendations .................. Procedures for Applying Standardized Modal Split Model ....................................

APPENDIX I - TRIP TABLE DEVELOPMENT CODE CONTAINING POLK COUNTY MODAL SPLIT MODEL ..........

APPENDIX II - TRIP TABLE DEVELOPMENT CODE CONTAINING GAINESVILLE MODAL SPLIT MODEL .........

Page

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: 14

17

.I7 19 20 24

29

29 30

3; 41

43

43 47

51

I-l

II-1 APPENDIX III - STANDARDIZED MODAL SPLIT PROCEDURES... III-1

iii

LIST OF FIGURES

Figure

1 Mode Choice Model Alternatives

2 Mode Choice Model for Polk Study

3 Example of Transit Trip-Making Indices for Sarasota-Manatee

4 Summary of Mode Choice Models

Page

3

9

10

12

iv

LIST OF TABLES

Table Page

1 Choice Models and Other Characteristics for Florida Study Areas 20

Chapter One

REVIEW OF OPERATIONAL EXPERIENCE

The purpose of this chapter is to accomplish a general-

ized review of the existing modal split models in use within

the State of Florida as well as to review current Urban Mass

Transportation Administration (UMTA) policy with regard to

modal split modeling. Also, a review of the current state-

of-the-art in disaggregate, behavioral modal split modeling

techniques currently being researched is made. The findings

of this task will be utilized to formulate alternative proce-

dures in Chapter Two.

Mode choice analysis is accomplished to determine the

number of transit trips and auto person trips. Auto occu-

pancy relationships are utilized to convert the auto person

trips to auto drivers and auto passengers. Although auto

occupancy relationships will be reviewed herein and alter-

nates presented in Chapter Two, Task E will not evaluate and

validate alternate relationships since this is beyond the

scope of this project.

MODE CHOICE MODELS - BACKGROUND

There are numerous methods utilized for mode choice

analysis. The four basic approaches have been:

1. Direct Generation:

Trip generation rates are developed for auto driver trips, thereby eliminating any mode choice model procedure, as such. Rates can also be developed to generate transit trips directly. This procedure is most appropriate for smaller urban areas where transit use is very low.

1

2. Pre-Distribution

A mode choice model that is applied after person trips are generated but before trip distribution. This technique results in trip distribution model applications for auto and for transit trips. Also, most approaches of this type do not consider system attributes directly. Basically, trip end characteristics such as auto ownership and population density, may be considered at the production end and employment density at the attraction end. Sys tern characteristics such as whether service is provided or not may be considered. Interchange characteristics related to specific production and attraction areas cannot be considered here. This type of approach is most appropriate in smaller to moderate size urban areas with a small bus system.

3. Post-Distribution:

A mode choice model that is applied after trip distribution of person trips. Here the model is applied to the person trip table resulting in transit passenger trips and auto passenger trips. The ad- vantage .of this technique is that it can reflect system operation between pairs of production and attraction zones based upon operating characteristics and cost of travel. This allows the ability to assess: competing highway and transit levels of service; auto operation cost; parking fees; and transit fares. This approach is most suitable for larger urban areas with a transit system large enough to support system level alternatives analysis.

4. Simultaneous:

A simultaneous trip distribution and mode choice model which in one operation determines the interchange by mode between production and attraction zone pairs. The mode choice analysis element can reflect the same system parameters as the post-distribution mode choice model. At best what is saved is a computer step. What is lost is the ability to separately evaluate the two steps of distribution and mode choice.

A pictorial representation of the place of each of the

above approaches to mode choice analysis is shown in Figure

1.

TRIP I

GENERATION

Direct Generation •--_-_-~----_.o--~

of Trips by Mode 7

I

I

I

Pte-Dlstributlon I *--- --__ -----___-

1

TRlP ti DISTRIBUTION

Simultaneous --mm--- --

i

MODE CHOICE MODEL

4-a _-

I I TRAFFIC ASSIGNMENT

Post-Distribution I

MSw--w --w-B-- J

FIGURE 1

MIDI CIiOICE MODEL ALTERNATIVES

3

REVIEW OF FLORIDA MODE CHOICE MODELS

The Logit Model - Post-Distribution

Basically, all of the above generic types of models have

been used by Florida's urbanized areas - except for the

simultaneous approach.

The most utilized model is the post-distribution LOGIT

formulation of the form:

MSt=A+l-A-B

1 + eC(Au +D)

Where: MSt = Modal Split to Transit Mode

A= Transit Captives Fraction

B= Highway Captives Fraction

c= Slope parameter which determines elasti- city of the LOGIT curve

D= Point of Symmetry of the LOCIT curve

The calibration consists of determining the values for terms

A, B, C and D. In most cases the Au, or disutility term, is

expressed as:

nu = Transit Impedance - Auto Impedance

The values forming the transit and auto impedance are both

expressed in terms of time in minutes. Impedances considered

are line haul travel time, excess time and out-of-pocket cost

converted to time.

For the automobile, the line haul time is defined to be

the time spent in the auto during travel. The excess time is

composed of access, parking and egress time. The out-of-

pocket costs consist of parking costs, tolls and a perceived

automobile operating cost per mile.

4

For transit, the line haul time is the actual time spent

on the transit mode. The excess time consists of access time

(auto or walk), transfer time, waiting time and egress time.

Cost consists of transit fare and station parking fees.

The costs mentioned above are converted to equivalent

minutes through the function:

ACostmin = ACOStcnts X 60 X 2000 X 1 Income

Where: 2000 hrs./year is assumed number of working hours to convert annual income to hourly income.

60 min./HR is used to convert hourly cost to costs in minutes.

Annual income in cents/year.

The function thereby allows income to be an input parameter.

In most Florida applications, a single income value was used

for an entire urbanized area. To allow for proper sensi-

tivity this value should be estimated by zone.

The total disutility Au is then the sum of the (tran-

sit - auto) value differences for line haul time, excess time

and cost, or:

Au = (Line Haul Time A ) + 2.5fExcess Time A) + 3.0 (Cost A)

The coefficients of 2.5 and 3.0 are a result of research on

the value of time. Indications are that these parameters are

reasonably stable for urban areas.

The model coefficients A, B, C and D are calibrated by

urban area by trip purpose. This usually considers the trip

purposes of Home-Based Work (HBW), Home-Based Non-Work (HBNW)

and Non-Home-Based (NHB), but can be derived for other

5

purposes. For example, in Jacksonville, Home-Based School

was an "other" purpose.

Input data requirements for the LOGIT model used in

several Florida urbanized areas include:

Transit Network Highway Network Person Trip Table by Purpose Cost Functions: Operating Cost/Mile - Auto Parking Cost by Purpose Transit Fares Income

The LOGIT formulation has been calibrated for the fol-

lowing Florida areas:

Miami Broward Pinellas Tampa Jacksonville Orlando Pensacola Tallahassee

Basically, all the model forms are the same but values for

the parameters A,. B, C and D vary. There is a very slight

difference in weighting of parameters for the disutility

function in Orlando. Other differences include use of dif-

fering numbers of purposes and special situations such as

differing model parameters for Miami's beach and non-beach

areas.

West Palm Beach utilizes a modal share model of the mul-

tinomial logit formulation, which considers parameters simi-

lar to that described above. The form of the model and vari-

ables used are shown below for non-work trips:

6

MSP = 1 l+e(A*APA+B) + e(C*DTT+D*DIFC+E)

e(A*APA+B) MSD =

l+e(A+APA+B) + e(C*DTT+D*DIFC+E)

e(C*DTT+D*DIFC+E) MST =

l+e(A+APA+B) + e(C*DTT+D*DIFC+E)

Where:

MSP = Probability of Making an Auto Passenger Trip;

MSD = Probability of Making an Auto Driver Trip:

MST = Probability of Making a Transit Passenger Trip;

APA = Autos Per Adult;

A = Coefficient of APA;

B = Constant;

DTT = Difference in Total Time;

C = Coefficient of DTT;

DIFC = Difference in Cost;

D = Coefficient of DIFC; and

E = Constant.

7

Other Post-Distribution Model

The Polk study utilizes a cross-classification post-dis-

tribution model. Three purposes are considered: HBW, HBNW,

and NHB. A transit coverage variable is used considering:

trip interchanges not covered by transit service; trip inter-

changes covered by transit service where one end is in a ma-

jor transportation attraction zone; trip interchanges covered

by transit service where neither end is in a major transpor-

tation attraction zone. A third variable considers the num-

ber of autos per dwelling unit (D.U.) at the production end

of resident D.U.'S. Transient D.U.*s are also considered.

An example cross-classification matrix is shown in Figure 2.

Cross-Clasification Pre-Distribution

The Sarasota-Manatee area utilizes a mode choice model

based upon use of a cross-classification of transit trips per

household based on auto ownership and income range by zone at

the production end. Rates are developed and controlled based

on an areawide rate of transit system users. The general

indices are shown in Figure 3. These are multiplied by an

areawide transit trip rate to obtain the final rate table.

For example, if 25,000 users are to be served per day, and

there are 100,000 dwelling units in the transit service area,

the areawide factor for the rate table would be 0.25

(25,000 t 100,000).

Trip attractions are handled based on a rate equation

consisting of a coefficient to be multiplied by zonal (total)

employment used to calculate an index for zone-to-zone

8

TRANSIT TRIP FACTORS2

PURPOSE

YAfWU

TRIP INTERCHANGE PRODUCTION ZONE VARIABLE

TRIP RESIOENT 0. U.

PURPOSE TRANSIT SERVICE COVERAGE . TRANSIENT

NO-AUTO D.U. l-AUTO 0.U. 2.AUTO D.U. i!S(J%JE DJJ.

Trip Interchanges Not Covered By Transit Service

.ooq .ooo .ooo .ooo ,000

H&WORK Trip ht. Covered

One End in a Maj.

By Trnn* Service Trans, Att. zone

.45&t .096 .016 .ootl .059

Neither End in I Maj. Trans. Att. Zn.

.461 .040 ,091 .ooo ,059

Trip Interchanges Not Covered By Transit Service .a00 .ooo .OOO .ooo .ooo

HB=NONWORK One End in a MaL Trans. Att. fn. .1233 .018 .016 .014 ,000

Tr!p Covered by Neither End in e Tran. Service Maj. Tranr Att. fn. .1233 .018 .016 .014 .ooo

Trip Interchanges Not Covered By Transit Service .oob .OOO ,000 .ooo .a00

NON-He

Trip Interchanges Covered .007 BV Transit Service1 I

.007 .007 .007 .007

Note: (1) Factors for Non.HB interchanges cennot be related to D.U. characteristics of the production zone, hence factors do not vary by no.‘of autos in the zone of production.

(2) The above factors were input into UMOOEL modal split program along with trip production rates for each D.U. category which in effect weighted the factors by the share of trips produced by each D.U. category.

(3) H8 Nonwork factors were the same for both categories of trip interchanges covered by transit service.

FIGURE 2 : MODE CHOICE MODEL FOR POLK STUDY

INCOME LEVEL

LOW

MIDDLE

HIGH

AUTO OWNERSH IF’

0 1 ‘Zor rr0re k-.

2.33 0.90 0.66

3.32 0.73 0.43

3.83 0.65 0.32

*To be multiplied by the areawide transit trip rate.

FIGURE 3

Em@LE OF TRANSIT TRIP-MAKING INDICES

FCR SABASOTA-MANATEE

10

transit trip attractions. The coefficient is determined by

setting total transit trip attractions equal to total transit

trip productions and thereby dividing transit trip produc-

tions from the cross-classification model by total employment

from the transit service area.

Direct Generation of Auto Travel

Gainesville, Lee and Brevard generate auto trips direct-

ly, so that no modal choice model is used.

Summary of Florida Models

Figure 4 presents a summary of the mode choice model

types that have been calibrated in Florida.

Urban Mass Transportation Administration (UMTA) Input

Basically, UMTA does not recommend a specific mode

choice model to be used. UMODEL has been developed to allow

user coded subroutines to be developed for mode choice mo-

dels. The "Default" model included within UMODEL is a simul-

taneous mode choice/trip distribution model of the form:

Tijm -_ Pi . Aj - e_BIi'm

SE Aj l e-ekjrn

Where: Tijm = trips from i to j by mode m;

Pi = productions at i (home end);

Aj = attractions at j (destination end);

e = 2.71828;

0 = a calibrated constant that varies by trip purpose;

Iijm = a measure of impedance by mode m equal to: (1.0 x in-vehicle time) + (2.5 x excess time) + (trip cost)/ (.035 x. income per minute).

11

MIAMI

BROWARD

PINELLAS

TAMPA

JACKSONVILLE

WEST PALM BEACH

ORLANDO

POLK

BREVARD

PENSACOLA

VOLUSIA

SARASOTA-MANATEE

LEE

TALLAHASSEE

GAINESVILLE

POST DISTRIBUTION

LOGIT

LOGIT

LOGIT

LOGIT

LOGIT

PROPORTIONAL

LOGIT

CROSS CLASS

LOGIT

LOGIT

LOGIT

PRE- DISTRIBUTION OTHER

GENERATE AUTOS

CROSS CLASS

GENERATE AUTOS

GENERATE AUTOS

FIGURE 4

SUMMARY OF MODE CHOICE MODELS

12

The mode choice model can be extracted from the above and is

of the form: MSt = _@I!$q&ja x 100

Where: MSt = fractional share of trips estimated to use the transit mode

t = mode of transit

a = mode of auto

Other terms as explained previously.

This is a logit formulation where impedances for auto

and transit are treated individually by the n-ode choice model

rather than as difference values.

Some of the considerations expressed in discussions with

UMTA and FHWA relate to the use of captive riders in the lo-

git formulation and in the use of income in the impedance

calculations. It would appear that better representation of

conditions would be reflected if these two characteristics

were zonal input rather than regional parameters.

Also, with regard to disaggregate behavioral models, the

current thinking appears to be that logit-type formulations

are the most appropriate type formulations for current appli-

cations and that they do reflect the behavioral characteris-

tics of the traveler. Logit type models reflect system char-

acteristics such as headway and speed, cost factors such as

parking cost and transit fare and user variables such as

income. All these factors are related to the traveler's

decision making regarding choice of mode for any particular

trip purpose.

13

Some other thoughts from Federal personnel include:

Perhaps only work trips should be considered in mode choice analysis using a logit model formulation. For non-work trips a trip end model may be most appropriate. This is based on the thought that non-work trips often involve family travel of 2, 3, and 4 people traveling together. The logit formulation considers individuals, whereas households or groups of individuals should be considered for non-work trips. One possible solution is the use of an auto occupancy division of the cost function in the disutility portion of auto costs.

There is perhaps some reason to stratify work travelers by some economic factor(s) and calibrate separate models by classification. For example, auto ownership or auto ownership combined with workers per household could be utilized to stratify households for the development of separate models. Other possible stratifiers might include population within walking distance to transit ver- sus those not within walking distance.

The logit model will not give reasonable results if walk and auto access times are not dealt with carefully (i.e. as zones get larger, average walk time cannot be used for the entire zone).

The discussion relative to thoughts from Federal personnel

indicate there are differences in approach to mode choice

between individuals. There is no consensus relative to

approach.

AUTO OCCUPANCY

There are two basic approaches to auto occupancy estima-

tion that have been used in Florida. The one used most fre-

quently is the development of a factor by trip purpose to be

applied to auto person trips. This considers one factor for

all trip movements of a particular purpose. For example,

auto occupancy factors might look like:

HB Work 0.86 HB Shop 0.57 HBSoc-Ret 0.50 HBMisc 0.58 NHB 0.61 All Purposes 0.63

14

The second approach uses the "default" model in the pro-

gram UMODEL. This model is based on a model used by the

Metropolitan Washington Council of Governments. This app-

roach considers a cross-classification of occupancy rates

considering: three classes of trip purpose; income (1st

Quartile, 2nd and 3rd Quartile; 4th Quartile), five classes

of destination parking cost; and five classes of trip inter-

change density. Trip interchange density is equal to highway

person trips between two zones divided by the product of the

residence zone area and the non-residence zone area.

15

Chapter Two

FORMULATION OF ALTERNATIVE

The purpose of this chapter is to

Florida Modal Choice Models to assist

PROCEDURES

categorize the current

in determining appro-

priate modal choice models for application. Using the find-

ings of Chapter One and a categorization of Florida models, a

determination will be made of the alternative modal choice

models to be developed. Additionally, specifications will be

developed to allow accuracy evaluations to be made in compar-

ison of model results with ridership counts made by corridor,

cutline, trip end areas and other measures.

CATEGORIZATION OF EXISTING FLORIDA MODELS

An evaluation of modal choice model application as util-

ized in general throughout the United States indicates that

large urbanized areas utilize post distribution models that

consider system characteristics as well as rider characteris-

tics. The logit formulation is currently the model form that

is most useful for such analysis. A description of the logit

formulation has been previously presented in Chapter One.

Variations in the usage of the logit formulation were

also noted in Chapter One. In addition to the proportional

logit formulation calibrated in West Palm Beach, Orlando uses

a model that is sensitive to some zonal variables. A Summary

of the models used in the state is shown in Table 1.

17

TABLE 1

CHOICE MODELS AND OTHER CHARACTERISTICS FOR FLORIDA STUDY AREAS

Urban Area

Est. 1979 % Growth Population 1970-1980

(000'S) Per Year Number Buses Model Used1

Miami 1503

Broward 921

Pinellas 710

Tampa 615

Jacksonville 583

West Palm Beach 536

Orlando 624

Folk 285

Brevard 261

Pensacola 231

volusia 190

Sarasota-Manatee 185

Lee 181

Tallahassee 139

Gainesville 137

< 2%

> 4%

2-4%

> 4%

< 2%

> 4%

2-4%

2-4%

< 2%

2-4%

2-4%

> 4%

> 4%

2-4%

2-4%

810 Logit

101 Logit

120 Logit

80 Logit

200 Logit

47 prop. Logit

54 Logit

3 Cross-Class2

* Gen. Auto

27 Logit

* Logit

36 Cross-Class3

* Gen. Auto

35 Logit

31 Gen. Auto

FOOTNOTES:

IAll Logit models shown are post distribution models.

2This is a post distribution model.

3This is a pre-distribution model,

4Tallahassee calibrated a logit model but used a procedure based on policy determinations.

*Data not available.

18

In addition to the logit formulation, which is presently

used in most of the larger urbanized areas in Florida, the

table indicates that a variety of other techniques have been

used in Florida. A few areas have not developed modal split

models. These areas for the most part generate auto or

auto-person trips. In Gainesville, a procedure has been

adopted which permits policy decision to provide a "modal

split" technique. This technique identifies subareas within

the urbanized area that should attract high transit usage.

Transit usage for these areas is estimated and then sub-

tracted from the input trip tables. Tallahassee also adopted

a similar policy sensitive modal

a target split percentage for

lished, and the model determined

ted to result in this target.

split model. In this

the entire area was

which trips would be

ALTERNATIVES TO BE CONSIDERED

An evaluation of the models utilized in Florida

ized areas, consideration of UMTA and FHWA comments,

evaluation of logical need for systemwide modal choice

sis has resulted in a determination of alternatives

considered.

model,

estab-

selec-

urban-

and an

analy-

to be

Also among the issues considered in the determination of

the recommended modal choice alternatives was Florida's

experience with the logit formulation. The fact that this

expression has been used in several urban areas provides

strong impetus to utilizing it as an alternative. Also, con-

sidering the data variables used for highway and transit

19

networks, and the trip purposes and cross-class variables

used for trip generation leads to a selection of a modal

choice alternatives which would not put additional burdens on

local study staffs if possible in data forecasting. This

means that some consideration must be given to expressions

which do not require forecasting income.

Bus transit studies or the long range planning of sys-

tems where fixed capital investments are not required usually

do not warrant ultra-sophistication in the choice of mode

share modeling techniques. The modal choice modeling, where

non-fixed rolling stock is the alternative to be considered

in systems planning is basically a mechanism to determine

fleet size and physical facilities and the impact on highway

needs. In systems such as this, modal split modeling tech-

niques that are not system sensitive can be used. These

techniques are most appropriate for use in the smaller urban-

ized areas.

RECOMMENDATION FOf! MODAL CHOICE MODELS

The standard trip generation model will produce internal

person trips by five purposes. It is possible using the

standard generation model set to utilize a modal choice model

of either the post distribution or pre-distribution type. It

is recommended that three modal choice models alternatives be

tested. One model would be a logit model of the form cur-

rently in use in Florida, but with some recommended changes.

The second model would be a cross-classification model

that would consider the type of variables used in the trip

20

generation model. These include autos per dwelling unit,

persons per dwelling unit and type of unit at the production

end and employment by category at the destination end. A mo-

del of the type used in the Folk Study, where supply of tran-

sit is also a variable is a good example of a cross-classifi-

cation rate procedure utilizing the trip generation para-

meters plus some measure of transit service. This second

choice of a modeling technique would be non-system sensitive

and as such would not require a coded transit network.

This leads to the recommendation of two procedures. One

would require explicit network coding regarding the transit

system; thereby allowing the testing and analysis of policy

type variables such as level of service and fare structures.

This model is of course system sensitive. The logit model

formulation is recommended based on its previous use in the

state, the evaluation of the alternatives available, and dis-

cussions with Federal personnel. Some recommended modifica-

tions are described later. The second procedure would not

require a coded transit network and would thus be non-system

sensitive. This procedure would consider population related

characteristics such as considered for trip generation and a

measure of the availability of transit service to determine

split characteristics. The cross-classification post distri-

bution model utilized in Polk County is recommended as an

alternative to be tested.

As an additional alternative in the areas where a non-

system sensitive model can be used, the technique used in

21

Gainesville will be studied to determine if it has use in

other areas.

The logit formulation would most appropriately be

applied in areas with greater than 500,000 population and/or

with more than 50 buses in the forecast year. In the smaller

areas and/or with smaller bus fleets the non-system sensitive

model would be used.

The logit modal choice models already calibrated will

allow evaluation of the A, B, C and D parameters to determine

possible groupings and allow and evaluation of accuracies now

being achieved. It is recommended that three general im-

provements to the process should be considered for the stan-

dard model. First, zonal income rather than an areawide in-

come should be used to convert transit fares, parking costs

and other costs to time. Secondly, auto occupancy by trip

purpose should be used in the consideration of auto costs to

determine a cost per person. Thirdly, the captive riders for

auto and transit should be a zonal characteristic rather than

one value for the entire area.

This project was not intended to

research required to re-calibrate and

meters based on these considerations.

posed that an already calibrated model

support the type of

determine new

However, it is

for one study

whose areawide parameters were used, be applied with

para-

pro-

area,

esti-

mates of zone level income, auto occupancies and estimates of

captives by zone. The results will be compared with base

data and results of previous calibration runs to determine if

22

improvements in results are achieved. If so, this will be

the recommended procedure. If not, the existing modal choice

models for the larger areas will be incorporated in the stan-

dard model set. It is important to note that there is a

great need to recalibrate the model split models in all of

the areas.

TO further test the sensitivity of zonal as opposed to

areawide estimates of model inputs, the opposite test will

also be conducted. In an area, such as Orlando, where zonal

inputs are currently used, the modal split model will be

applied using areawide estimates of the model inputs. The

results of using these inputs will be compared with the

results obtained from zonal inputs.

The major effort will be to develop the procedure for

the smaller urban areas utilizing the procedures of the Folk

Study (See Figure 2 on page 9). It is recommended that

tables similar to that shown in Figure 2 be developed for

Gainesville and the results of the two areas (Polk and

Gainesville) compared for consistency and possible transfera-

bility to other areas which would not use the LOGIT model.

Polk and Gainesville provide a good population spread for

areas under 500,000 population (See Table 1). Also, data for

Gainesville were used for trip generation and should be in

good condition for this use. The effort for the smaller

areas will also attempt to determine if the policy sensitive

models developed in Gainesville and Tallahassee are usable in

other areas.

23

ACCURACY EVALUATIONS

The mode choice estimates produced by the standard model

set must be evaluated to determine their ability to reflect

reality. This will be accomplished as part of the validation

work effort. Basically, the validation involves comparisons

of model results with field observations. So mode choice

estimates would be compared with patronage information. This

patronage information is scheduled to be gathered as has been

presented in the CENVAL effort.* The validation for 1980

conditions to be accomplished as part of the CENVAL effort

will not be possible within this work effort since data will

not be available until sometime after completion of this

contract.

Calibration will be accomplished as part of this effort

in the sense of comparing model application results with some

base year conditions. The comparisons are made utilizing

travel survey and field information, if available, for the

base year. The comparison process will make use of available

data documenting current or base year transit usage and com-

pare these figures with the results obtained from the appli-

cation of the modal split model. These comparisons will be

made at the following levels:

Areawide Transit Usage Cutline Comparisons Screenline Comparisons Route Comparisons

*“Utilization of 1980 CeIlSUS Data in Urban Travel EStima- tion,l Final Report, COMSIS Corporation, September, 1980.

24

Care must be taken that the modal split model is being

evaluated and not the results of the transit assignment which

might be accomplished in a subsequent, step. Some urban areas

may not accomplish a transit assignment since they do not

necessarily require a transit network as input. Therefore,

route comparisons would actually be a check of both the modal

split and transit assignment, where this latter step is

accomplished. The areawide transit comparison is basic and

would be accomplished in both validation (against field data)

and in calibration (usually against survey data).

Screenline comparisons are again basic for validation

and calibration and would check major directional movements

across the entire study area. Cutline comparisons are most

valid as an assignment check where routes are grouped into

major corridors and comparisons made against ground counts.

However, where survey data is available, the survey data as

well as the model results may be compared across screenlines.

What must be carefully evaluated, however, is the fact that

transit use is very low in smaller urban areas and is not

accurate at this level. On-board survey results are most

appropriate for these type comparisons when available.

Route checks can be made for calibration by assigning

survey data and model data and comparing results on a route-

by-route basis. The same consideration made above for cut-

lines is even more significant here.

For the areas using the non-system sensitive approach,

there generally will not be a network for assignment purposes.

25

In these cases comparisons will be on an areawide basis and

across screenlines. For those using the logit formulation,

the four types of checks can be made, realizing, however,

that the individual route and cutline checks will also be a

check of assignment results.

There are no standards of accuracy available for modal

choice model estimates, as is the case for highway traffic

assignments. Therefore, the accuracy standards that have

been established for use in validating highway assignments

have been transferred to the application of modal split mo-

dels.

The standards established below are also based upon

experience, review of both highway and transit results and

intuition. Basically, the same types of accuracy obtained in

person trip distribution should be obtained in mode choice

estimates while keeping in mind the differences in the volume

sizes between the two types of travel. Also, the use of the

estimates is taken into account. For non-capital intensive

systems, long range planning generally is accomplished to

"size" the bus system in terms of maintenance and storage

facilities as well as number of buses. The individual route

demands except as it may help size the facility needs are not

of primary importance. Likewise, where transit assignments

are not made, the major reason for acceptable mode choice

estimation is to insure accurate highway trips and assign-

ments.

26

For calibration purposes, the range of error that should

not be exceeded for transit trips are presented below:

Total Area Transit Trips: Trips Entering the Central Area: Sectors of the Central Area Boundary:

(perhaps 4-5 corridors) Total Area Transit Average Trip Length: Cutlines and/or Routes:

(1000 Passengers/Day: 1000-2000 Passengers/Day: 2000-5000 Passengers/Day: SOOO-10,000 Passengers/Day: lO,OOO-20,000 Passengers/Day:

>20,000 Passengers/Day:

< 3% error < 5% error <20% error

< 5% error

<150% error <90% error (70% error (45% error (35% error (30% error

For validation in a year other than used for calibration

the following is recommended:

Total Area Transit Trips: < 6% error Trips Entering the Central Area: (10% error Sectors of the Central Area Boundary: (25% error Total Area Transit Average Trip Length: < 8% error Cutlines and/or Routes: Same as above

27

EVALUATION OF ALTERNATIVE MODAL SPLIT PROCEDURES

The purpose of Chapter Three is to evaluate the alterna-

tive modal split procedures advanced in Chapter Two, and to

CHAPTER THREE

determine which of these alternatives is most appropriate for

use in each of the four test areas determined in Phase I of

this effort. This evaluation will develop a recommended

modal split procedure for each of the urbanized areas in the

state. The evaluation documented in this chapter was

designed to determine the ability of the alternative modal

split procedures advanced in Chapter Two to respond to the

issue requirements of the four test areas. This evaluation

and analysis will permit the determination of a recommended

model set for each of the urbanized areas in the state.

REVIEW OF MODAL SPLIT MODEL CATEGORIZATION

In Chapter Two, a categorization of the modal split

models currently used in Florida was accomplished. The

results of the categorization indicates that in the fifteen

urbanized areas in the state, a large variety of modal split

models are used, This large variety of model choices has

been utilized as a source of models from which models appro-

priate for standardization can be drawn.

As can be seen from Chapter Two, a large variety of

modal split techniques are in use in the state. This indi-

cates that a large amount of effort has been applied in Flor-

ida to addressing a problem of making logical decisions as to

the future course of public transportation in the state. It

29

also indicates that available experience in Florida is not

being fully utilized as new modal split techniques are de-

vised.

REVIEW OF RECOMMENDED MODAL SPLIT ALTERNATIVES

Three general recommendations of modal split models to

be evaluated further were advanced as a part of the effort

documented in Chapter Two. These are: 1) The logit model

with some modifications to permit more standardization in its

application and use and to permit policy sensitivity; 2) A

non-system sensitive post distribution Cross Classification

modal split model similar to that used in the Polk study; and

3) A non-system sensitive Policy Modal Split Model that would

permit simulation of high transit usage scenarios.

Logit Model

Of these three alternatives, the logit model is current-

ly used in the majority of the urbanized areas in the state.

A thorough technical discussion of the logit model and its

functions has previously been presented in Chapter One.

Non-System Sensitive Non-Policy Sensitive Post Distribution Cross Classification Model

A table provided in Chapter One illustrates the concept

behind the post-distribution cross classification model cur-

rently used in Polk. This is the cross classification model

previously recommended for further evaluation in this effort.

As can be seen from the table which was presented as Figure

2, modal split ratios or transit trip factors are determined

in Polk based upon whether or not transit service is avail-

30

able to the trip interchange and also based upon certain den-

sity definitions of the attraction and production ends of the

trip and also based upon trip purpose.

The computer set-up used to apply the Polk modal split

procedure is shown in Appendix I. This set-up is labeled

PL931PO.DISCOMOD.2430.CNTL.

This set-up is used to build

form trip distribution, trip

split. There are a number

detailed below.

There is also a 2552 version.

and update highway skims, per-

purpose, combinations and modal

of steps in this procedure as

1) STEP0

2) s2

3) AGM

4) STEP1

5) STEP2

6) STEP3

7) STEP4

8) STEP5

9) STEP6

10) TESTMCON- UMCON to convert from FHWA to UTPS format.

11) USRCD - USERCODE of split procedures.

12) MODSPLT - UMODEL to apply previous step.

UROAD to build time and distance skims.

UMODEL to update time skims.

AGM to distribute person trips.

UMCON to convert tables to FHWA format.

TRPTAB to create HB work trip tables for zones covered and not covered by transit service.

TRPTAB to separate HB work trips covered into those with and without major attractions.

TRPTAB to create HB Non-work trip tables for zones covered and not covered by transit service.

TRPTAB to separate HB Non-work trips covered into those with and without major attraction.

TRPTAB to create one dataset with 6 tables - HB work - covered, not covered and covered with major attraction; HB Non-work - covered, not covered and covered with major attraction.

31

13) STEP7 -

14) STEP8 -

15) Tl

16) T2 -

TRPTAB to separate NHB trips into those covered and not covered by transit. Also mod-split percentages and auto occupancy factors are applied.

UMCON to convert NHB and IE trip tables to UTPS format.

UMATRIX to balance (P-A to O-D) and combine NHB, truck, IE and EE trips.

UMATRIX to balance (P-A to O-D) and combine HB trips.

Non-System Sensitive - Policy Sensitive Modal Split Model

The third modal split modeling scheme recqmmended for

further evaluation in Chapter Two was the policy sensitive

model currently under development in the Gainesville area.

This model functions by establishing "desired" modal split

fractions at certain trip ends. Trip interchanges involving

the targeted trip ends are modified to result in the desired

modal split or transit usage at that trip end. This process

is heavily dependent upon "hand manipulation" to achieve its

desired results. This type of modeling effort is extremely

important to the transportation planning effort in a number

of urbanized areas in the state where the populace and the

decision making bodies have become aware of the need to

increase transit ridership to alleviate several of the socio/

economic problems that will confront them in the coming de-

cades.

The computer set-up used to apply this procedure is

shown in Appendix II. This set-up is located on PL931RD.GA.

DISCOMOD.CNTL. This set-up also builds and updates highway

skims, performs trip distribution, trip purpose combination,

32

and modal split. The function of each of the program steps is

detailed below.

1) UROAD -

2) s2

3) AGM

4) UMATRIXl -

5) UMCON -

6) UMATRIXZ -

UROAD to build time and distance skims.

UMODEL to update skims

AGM to distribute trips

UMATRIX to add EE trips and balance tables (P-A to O-D).

UMCON to perform modal split. Split factors are read in from dataset of the form PL93lGA.UMCON.SPLIT-.DATA

UMATRIX to create an auto trip table and a transit passenger trip table

AREA SENSITIVE EVALUATION OF RECOMMENDED PROCEDURES

The three recommended modal split procedures must be

evaluated to determine their usefulness as a standardized mo-

dal split procedure in each of the various Florida urbanized

areas or in a selected sub-set of these urbanized areas.

Based on this evaluation, and subject to the intent to test

each of the various procedures that might be recommended, test

areas for each of the various procedures will be established.

It is important to note that the tests accomplished as a

part of this effort will in all probability not provide the

final answer as to the appropriateness of the standardized

modal split procedures to be recommended. The lack of data

available to completely evaluate the models' functions will

most likely not be alleviated until the Census Validation

Phase III activities now scheduled for 1982 are accomplished.

The tests accomplished as a part of this effort will attempt

to define the limits of the proposed modal split schemes and

33

to develop standardized procedures that can be further defined

following collection of adequate data in the Census Validation

effort.

The first step in the evaluation of each of the proposed

standardized modal split models was to determine if the pro-

posed models are able to respond to the issue requirements in

the various urbanized areas in the state. This determination

was made in each of the test areas used in Phase I of this

study. (These areas are Broward, Orlando, Tallahassee, and

Tampa Bay.) The evaluation of the various models' ability to

respond to the issues in these test areas was based upon dis-

cussions with DOT personnel and local officials in the various

test areas.

Broward County

The Broward Urban Area Transportation Study currently

uses a logit model to perform modal split modeling. The par-

ticular model calibrated in Broward County was developed from

the Miami model with some modification to simulate transit

travel in Broward County. The resultant model simulated

23,682 daily transit trips, which was 8.3 percent lower than

the 1976 daily patronage. BY purpose# the model assigned 47.3

percent of the transit trips to homebased work, 46.5 percent

to homebased other, and 6.2 percent to non-homebased.

Local officials in Broward County and officials of the

DOT agree that the logit formulation has been and in all lik-

lihood will continue to be an adequate tool for performing mo-

dal split in this area. The post-distribution cross classifi-

34

cation alternative and the policy-sensitive alternative both

have features that are attractive to planners in the Broward

area; however, the general feeling is that while these models

would not be sufficient for systems planning, they might pro-

vide a valuable tool for supplementing the systems effort in

special conditions. The concensus is that the logit formula-

tion should be used in the area, but that the other expres-

sions should be made available for use if they are needed.

Broward County is now participating in a study being con-

ducted by the Florida DOT to determine the need for a regional

transit system. The general feeling in the area is that the

logit expression is the only alternative under consideration

that could be used to perform the modal split function in this

area.

Orlando

The Orlando Urbanized Area Transportation Study (OUATS)

utilizes a modal split model of the logit formula that was

originally calibrated in 1973. This model was updated

and minor changes to the model's functions were made

adequately model certain conditions. The logit model

Orlando is different than those used in other areas

in 1978

to more

used in

in the

state in that internal calculations in the model which calcu-

late the disutility functions utilize zonal income data, and

also because the highway and transit captive portions for a

particular trip interchange are related to the income at the

production end of the trip. Information on transit and auto

captives were based on attitudinal surveys conducted in 1973

and repeated in 1978.

35

In Orlando, it appears that the logit model is adequate

to respond to the systems planning issues. Some questions

have been raised in the past as to the Orlando model's

results, particularly in specific corridors, but generally,

the reaction to the modal split results has been favorable.

Orlando has a series of future alternative transit networks

which have already been developed. These networks will reduce

the transit network coding requirements in future updates of

the study.

Although Orlando has a number of "special attractors", it

is felt that the existing logit model has adequately modeled

modal split for these attractions. The area is in the process

of studying at least one major future transit corridor to de-

termine if fixed guideway rail service should be provided a-

long this corridor. The last update of the OUATS did not show

the level of transit service on this corridor that many

thought it should have. The general feeling is that the

determination of the need for more sophisticated service in

this corridor should be made a part of a corridor analysis

procedure and not as a direct result of a systems planning

effort.

The review in Orlando has led to the conclusions that a

standardized expression of the logit formulation would be

adequate to handle the systems planning requirements. The

ability to make modifications to this process should not be

eliminated and some desire to see a process similar to the

Gainesville model available in unique areas was expressed.

36

Tallahassee

The Tallahassee Urbanized Area Transportation Study has

developed both a logit formulation and a policy-sensitive

modal split process. Dissatisfaction with the results of the

calibration of the logit model, a consultant's recommendation

that the model should not be used for long-range planning, and

local policy makers' desire to see what would happen if large

modal split percentages could be obtained led to the develop-

ment of a policy-sensitive model for the area.

The policy-sensitive modal split model was designed to

produce a target split percentage for the entire area. Speci-

fic trips were dependent upon trip purpose, zonal income, and

the magnitude of the areawide split. The model was not sys-

tem-sensitive, however transit trips were not allowed in zones

which did not have transit service. Modal splits as high as

25 percent were tested in the study. In general, satisfaction

was expressed with the results of this model and the plan

adopted had a target modal split percentage of 5 percent.

General feeling now in the area is that sophisticated

system-sensitive modal split procedures such as the proposed

logit formulation should not be used in Tallahassee. The

ability to maintain policy maker participation in the process

is thought to be important, and thus the area seems to favor

an approach like the one previously used in the area or like

the one now being developed in Gainesville. These models

would adequately meet the technical needs of the area and

would also permit policy participation in the effort.

37

Tampa Bay

The Tampa Bay study effort has calibrated a logit model

to perform the modal split function. This model is used in

the regional study effort but different values of the elasti-

city and bias coefficients are used in the three transit ser-

vice areas in the region.

As with the other large study areas evaluated, local

users of the logit formulation in the Tampa Bay area appear

satisfied with its results and are hesitant to substitute

other models, particularly a model that is non-system-sensi-

tive. General interest in the ability to make modifications

in the results of the logit model are expressed, usually in an

effort to obtain results in special studies, Satisfaction in

the models' ability to simulate HOV lane usage was noted in

the past experiences in using the existing logit formulation.

Some reservation in the logit formulation's ability to

produce adequate results in special study efforts was ex-

pressed. Such a special study effort is currently underway in

a Tampa Central Business District transit study. Generally,

however, it was agreed that this probably was not a function

that a standardized systems modal split model should perform.

RECOMMENDATIONS

Current use of the logit formulation to perform modal

split is pervasive in Florida, particularly in the larger

urbanized areas. The evaluation of the issues impacting modal

split decisions generally tend to indicate that in these lar-

ger areas, some sort of modal split procedure which is system-

38

sensitive should be used. In the smaller areas in the state,

the general feeling is that the more sophisticated modal split

procedures are not needed and that other procedures such as

the Polk County procedure would be adequate to perform the

modal split function. In both the larger and in the smaller

areas, some type of policy input to the modal split process

was seen as desirable and an important element to be main-

tained as a part of the standardized modal split procedure.

These considerations, the past experiences of the various

urbanized areas in the state along with an appraisal of the

possible future functions of a modal split model led to the

preliminary recommendation of two separate models for use in

the state. The first of these models would be the logit form-

ulation. To permit standardization, different formulations of

the logit expression such as that currently used in West Palm

Beach and use of non-standard variables as is currently done

in the Orlando effort would be eliminated.

Calibrated values of the A, B, C, and D parameters that

are currently used in the various areas should continue to be

used until better data becomes available as a part of the Cen-

sus Validation effort. West Palm Beach should borrow cali-

brated A, B, C, and D parameters from another area, probably

from the Broward area. In Orlando, survey results should be

used to develop area-wide parameter values.

The areas that should use the logit formulation are:

Broward, Jacksonville, Miami, Orlando, Pinellas, Tampa, and

West Palm Beach. These areas are a preliminary recommendation

39

and are based upon a number of characteristics and assumptions

about the various areas. Generally, the areas recommended are

the larger areas in the state and are the areas that now have

or are considering capital intensive involving construction of

fixed facilities transit plans. Each of these areas currently

has a coded transit network and generally, the transit plan-

ning requirements of the area require at least the sophistica-

tion of a coded transit network. The policy-sensitive func-

tion and modeling techniques available from the Gainesville

experience should also be made available to the areas using

the logit expression.

The other recommended modal split model will be a post-

distribution cross classification model of the type now used

in Polk County. Modifications will be made to this model to

permit policy-sensitive modal split procedures similar to

those currently being used in Gainesville. This will be

accomplished by an additional row added to the existing cross-

classification matrix to permit modeling policy-sensitive cor-

ridors or trip interchanges as is currently done in Gaines-

ville. Actual transit split percentages for input into the

standardized procedure will not be recommended at this time.

Values for those parameters should be determined during the

Census Validation procedure. During the next Chapter in this

analysis, the values currently used in Polk County will be

carefully evaluated for their potential input into a standar-

dized procedure.

40

The areas that should use this recommended procedure are:

Brevard, Gainesville, Lee, Pensacola, Polk, Sarasota-Manatee,

Tallahassee, Volusia, and the various new urbanized areas

designated by the 1980 Census. These areas are generally the

areas in the state that require less sophistication in modal

split modeling. These areas are currently served by small

transit systems, and current planning efforts do not include

planning for capital intensive improvements.

SUMMARY

This chapter has presented the results of evaluation that

was accomplished to determine the type of standardized modal

split model that should be used in Florida. In addition, pre-

liminary recommendations as to which areas should make the

alternative modal split procedures a part of their standard-

ized model application were advanced.. Because of the flexi-

bility of the Gainesville modal split model, this model can be

made available to both groups of areas. This will permit pol-

icy input to the process in all of the areas of the state.

41

Chapter Four

SELECTION AND REFINEMENT OF RECOMMENDED PROCEDURES

The purpose of this chapter is to refine the recommenda-

tions presented in Chapter Three and to advance specific re-

commendations as to the standardized modal split procedures to

be followed in each of the fifteen urbanized areas in Florida.

These specific recommendations build upon two general recom-

mendations presented in the earlier chapters. Chapter Four

also outlines the program steps that should be followed in

applying the two procedures and presents Division of Transpor-

tation Planning Procedures for each of the two processes.

SENSITIVITY TESTS OF LOGIT PROCEDURES

The preliminary recommendations in Chapter Three stated

that the larger areas in the state should continue to use the

logit formulation to perform modal split. In each of these

areas, this model has been calibrated and is currently used to

perform modal split modeling. Three of the areas for which

this procedure were recommended use slightly different ver-

sions of the logit formulation. The Miami model uses slightly

differing model parameters for beach and non-beach areas, the

West Palm Beach area model uses a multinomial logit formula-

tion, and the Orlando model uses a differing weighing of the

parameters and also a zonal value of income as input into the

calculation of the disutility function.

It was desired to test the sensitivity of one of these

outlying models to determine if critical differences in model

performance would occur if more standardized procedures were

43

used. The area selected for this analysis was the Orlando

area. The specific test selected was a test to determine if

differences in model results would be observed if average in-

come values were substituted for the zonal income values cur-

rently used in the Orlando model.

The Orlando model uses the zonal income data in two ways.

First, the zonal income is divided into five groupings to es-

tablish zonal auto and transit captivity rates. These rates

are based on two surveys that have been completed in the last

several years. The rates range from a transit captive rate of

0% in high income areas for some trip purposes to 18.6% in low

income areas for Home-Based Shop trips. Auto captivity rates

vary from a low of 29.7% to a high of 77.9%. Those trips

which are neither transit captive or auto captive are the free

choice trips and it is these trips on which the Orlando modal

split model operates.

The second use of the zonal income data is in the calcu-

lation of the trip interchange disutility value. The value of

the zonal interchange modal disutility determines what percen-

tage of the free choice trips will split to which mode. The

range of split that can occur in the Orlando model is between

0.3% transit to 93.0% transit. The Orlando model translates

the various dollar costs implied in the disutility expression

to time by relating the value of time to a dollar value using

the zonal income inputs.

The modifications to the zonal income variable that were

accomplished in the test consisted of equating all zonal

44

income values to a midpoint value of income in the income

range in which the zone lies. This would equate to five in-

come values or ranges being used. In other words, the model

would then operate as if the income values forecast for the

area were five ranges from low to high. Most planners feel

more comfortable forecasting income ranges rather than actual

zonal income values. This test was designed to duplicate that

situation.

Although most areas in the state only use three values of

income (low, middle, and high), it was decided to test five

values in Orlando since the model currently duplicates the

five ranges in parts of its calculations as explained above.

Thus, for purposes of the sensitivity tests zonal income value

input to the model were equated to a midpoint value within

each range. The five values used in this subsitution were:

$1500, $4500, $7500, $12,000, and $18,000. The model thus

used the same values of auto and transit captives as would

have been obtained if the zonal income values would have been

used, but different values of income were input into the dis-

utility calculation.

The results of the runs using both zonal income values

were somewhat surprising, Notably, extremely small differ-

ences were observad in total modal split values, and no dis-

cernable differences in individual zonal interchange values

were noted. These results indicate that the modal split model

depends very heavily on the values input to the model for

transit captivity and auto captivity, and that the split

45

obtained from the disutility calculation or the split of the

free choice trips are very minor in comparison.

To further test these assumptions, an additional test was

performed to determine what results would be obtained if dif-

ferent values were input into the portion of the model which

determined the auto and transit captivity. In this test, the

model was manipulated in such a way as to duplicate the situa-

tion when only one value of income was used in the various

calculations. In this instance, the middle income value was

used.

In this case, very noticeable differences in model re-

sults were observed. The transit split values were some 20%

higher than before and differences in zonal auto and transit

trip totals were noted. These results were not particularly

surprising because zonal income figures used in the Orlando

area are generally higher than the mid range, and so the re-

sult of the model manipulation was to place most zones in a

lower income range. Of course, the location of the modal

split demand was greatly changed because in fact, what the

model projected was that greater use of transit would occur in

high income zones and less transit use in low income zones.

These results, although showing a greater use of transit,

would be very dangerous because the transit demand was obvi-

ously misplaced.

The overall results of the sensitivity tests was

lize that the modal split model in use in the Orlando

to rea-

area and

no doubt in the other areas as well, is very sensitive to the

46

definition in the model to the mode captivity and sensitive to

a much lesser degree to disutility calculations where it would

appear due to existing and historic use of transit, the calcu-

lations are very much slanted to auto use.

SPECIFIC MODEL RECOMMENDATIONS

In Chapter Three, preliminary recommendations were ad-

vanced as to the general modal split scheme each of the urban-

ized areas in Florida should use. These recommendations were

based for the most part on the area sensitive evaluation of

the various alternative model schemes and on a desire to stan-

dardize the modal split model to the maximum extent possible.

These recommendations stated that the seven larger urbanized

areas in the state should use the logit formulation with the

addition of a policy-sensitive function, and that the areas

that

made

had model expressions that varied from the norm

more standard.

should be

The preliminary recommendations for the other areas in

the state was to adopt the Polk County Cross-Classification

model with the addition of functions of the Gainesville model.

These two models are non-system sensitive and would not re-

quire the coding of a transit network, although a definition

of areas served by a potential transit system would have to be

made. This model was recommended for those areas which are

not expected to be planning for capital intensive transit

plans which would require the construction of fixed

facilities.

47

The results of the sensitivity tests reported earlier in

this chapter have changed these preliminary recommendations

somewhat. Due to the significant changes in both the total

split values and the locations of these changes, it is felt

that it would be a mistake to eliminate any outlying model

functions which would result in changes in how the model se-

lects the transit and auto captive trips. This means in fact,

that the internal calculations used in the various areas in

applying the logit formulation should not be changed. Modal

split model standardization should occur in model application

and in the fact that the Department of Transportation should

work toward being able to forecast more specific variables

that would result in a finer level of detail in the calcula-

tion or setting of the auto and transit captive rates in the

various areas.

The areas using the logit formulation should also be per-

mitted to input policy decisions to the modal split calcula-

tions. This can be accomplished by adding the Gainesville

model to the model chain following the application of the lo-

git formulation, This addition would permit further opera-

tions on the auto portions of the trips between selected zones

to increase modal split for these interchanges. Details of

how this would be accomplished are presented later. In all of

the areas for which it is recommended that the logit formula-

tion be used, standardization in model application should be

accomplished. This standardization would require placing the

various programs used to manipulate the trips and to create

48

separate transit person and auto trip tables within the

DISCOMOD module in a standard order. This order will be de-

tailed later in this chapter.

The standardization process also requires that the applf-

cation of the source codes containing the logit .formulation in

the various areas should be applied in a standardized manner.

It is recommended that the UTPS USERCODE function be used and

that the model applied with the UTPS program UMODEL. This

standardization would permit easier understanding of the var-

ious model applications in the state. The specific recommen-

dations

greater

0

for the areas using the logit formulation, until

standardization can be obtained are detailed below:

Broward - Use existing modal split model. Existing A, B, C, and D parameters as calibrated for the areas should continue to be used.

0

0

0

Jacksonville - Use existing modal split model. Existing A, B, C, and D parameters should be used.

Miami - Use existing modal split model. Existing A, B, C, and D parameters should continue to be used.

Orlando - Use existing modal split model. Existing calculations to determine auto and transit captive proportions should continue to be used.

0 Pinellas - Use existing modal split model. Existing A, B, C, and D parameters should continue to be used.

0

0

Tampa - Use existing modal split model. Existing A, B, C, and D parameters should continue to be used.

West Palm Beach - Model functions should be changed to the logit formulation as used in the other areas. Model and parameter values should be borrowed from Broward.

In each of these areas, the ability to provide policy

sensitive modal split modelling should be added to the

49

DISCOMOD module. This addition can be accomplished by inser-

ting the Gainesville model which is applied with runs of the

UTPS programs UMCON and UMATRIX. The procedures herein recom-

mended will detail how this addition will be made and how the

Gainesville model should be used.

The model recommended for the smaller areas in the state

is the model currently used in the Polk County area. This mo-

del is a non-system sensitive cross classification model that

splits trips to the transit mode based on trip purpose, number

of autos per DU, and whether the zone being served is a major

attractor. A figure showing these relationships has previ-

ously been presented. This model is applied through a series

of FBWA programs TRPTAB which are used to separate the zones

which are either served or not served by transit and those

which are defined as special attractors. These runs are fol-

lowed by the UTPS programs USERCODE and UMODEL which actually

apply the modal split procedure. The set-up used to accom-

plish this modeling is shown in Appendix I.

This model has been chosen for a number of reasons. The

model, despite the multiple runs of TRPTAB which are required,

is easy to run. The functions of the model are easy to under-

stand, the variables required by the model are also required

by the standard trip generation model. The model does not re-

quire the coding of a transit network and the model results

can be modified to permit policy sensitive modelling by adding

the functions of the Gainesville model. These points led to

the recommendation that this model be incorporated into the

50

modal split modelling procedures in the following areas: Bre-

vard, Gainesville, Lee, Pensacola, Polk, Sarasota-Manatee,

Tallahassee, Volusia, and the emerging areas. As will be de-

tailed in the section dealing with modal split procedures, the

functions of the Gainesville model will also be incorporated

into the standard procedure to permit the flexibility of poli-

cy sensitive modelling in these areas.

The specific rates used in the Polk model were also exam-

ined to determine if these rates were adequate for the stan-

dardized procedure or if different rates should be substitu-

ted. This analysis showed that the rates used in Polk County

are adequate, but that some areas might desire more specifici-

ty in trip purpose modelling and that rates for Home-Based

Shop trips be separated from the more general rates now ap-

plied for Home-Based Nonwork trips. It is the recommendation

of this effort that the rates as used in Polk County be made

part of the standardized procedure and that the DOT examine

more closely the need for additional trip purpose modelling

within the set-up.

PROCEDURES FOR APPLYING STANDARDIZED MODAL SPLIT MODEL

The review of the recommended modal split modelling tech-

niques has led to the recommendation of specific Division of

Planning Procedures for the application of the models. These

procedures are detailed

should be made a part of

and their application

in Appendix III. These procedures

the DISCOMOD module within each area

begins immediately following the

51

AGM run which is used

tion model in each of

The standardized

to apply the standardized trip distribu-

the areas.

model in the larger urbanized areas in

the state or those areas which elect to use the logit formula-

tion procedure should be applied using the following programs

in a standardized procedure:

UMATRIX - The first UMATRIX run is used to combine trip purposes ror splitting. The standardized trip distribution model creates six trip tables in the following order: Home-Based Work, Home-Based Shop, Home-Based Social/Recreational, Home- Based Other, Non Home-Based, and Internal-External. In addition, some areas require a separate AGM run to distribute trips for special purposes. Generally these trips are generated vehicle trips, although in some cases, person trips are generated and modal split should be acomplished with the Non Home-Based Trips.

USERCODE - The program USERCODE is used to integrate the source code containing the modal split program in each of the areas with a sketeton UTPS source code to create a new execua- ble program.

UMODEL - UMODEL is used to apply the source code created in theERc0~~ step.

UMATRIX - UMATRIX is used again to combine the trip tables as produced by UMODEL into a single auto vehicle trip table and a single transit person trip table. This step also applies the auto-occupancy model which can be accomplished by using simple rates for each purpose.

UMATRIX - This application of UMATRIX is used to balance the output trip tables or to modify these tables from the P/A ar- rangement to the O/D convention.

UMCON - This run of the program UMCON is used to apply the Gainesville modal split model. This model permits the user to select a range of trip interchanges for which special modal split rates can be applied. UMCON applys these rates to the interchange as defined and creates a new trip table containing the extra split trips. As an example, it might be desired to determine the impact if 75% (or any other percentage) of the trips currently using the automobile to travel to and from the CBD could be induced to use transit. UMCON can be used to apply a factor of 75% to all auto trips with a origin or desti-

52

nation in the CBD. This UMCON run would produce a new trip

table with just those trips.

UMATRIX - This run of UMATRIX would then be required to subtract the special split trips as created above from the auto trip table and to add these trips to the transit trip table. The output of this run would be the standard HWY.TRN trip table as used throughout the standardized procedure.

In the areas using the Polk County model, the following

steps are required to apply the model and produce the desired

HWY.TRN trip table.

UMATRIX - UMATRIX is used to combine the trip tables as created by the application of the standard trip distribution procedures into the purposes required for modal split. At the current time using the non-system sensitive model, the purposes required are Home-Based Work, Home-Based NonWork, and Non Home-Based. Other purposes (IE and Special Generators) should also be combined since generally these purposes are auto trips and modal split is not appropriate.

UMCON - UMCON is used to convert the trip tables created above fromUTPS format to FHWA format for application of the program TRPTAB.

TRPTAB - TRPTAB is used to separate the zonal interchanges into three separate groupings, namely, those not covered by transit, those covered by transit but with no special attractor, and those covered by transit with a special attractor. To accomplish this, five runs of TRPTAB are required. These runs require the user to identify the zones which are covered by transit, not covered by transit, and covered by transit and containing a special transit attractor. The first application of* TRPTAB separates Non-Work trips from Work trips and also work trips covered and not covered by transit. The second application splits the work trips into those with a special attractor and those without a special attractor. The third application carries forward the three work trip categories and separates non work trips into those covered and not covered by transit service. The fourth TRPTAB application carries forward the tables created earlier and separates the non-work covered trips into those with and without special attractors. The fifth application reorders the tables for input into the split model.

USERCODE - USERCODE is used to integrate the Polk County modal split source code into the UTPS framework.

UMODEL - UMODEL applies the modal split model and outputs 16 purpose and mode tables including totals.

53

TRPTAB - An additional application of TRPTAB is required to separate the Non Home-Based transit and auto trips and the Internal-External trips.

UMCON - UMCON is used again to convert the trip tables crea- my TRPTAB back to UMTA format. UMATRIX - UMATRIX is next used to again balance and created a single auto vehicle table and a transit trip table.

UMCON - This run of UMCON is used to apply the Gainesville modal split model. As with the procedure in the areas using the logit formulation, UMCON allows the user to select a group of zones for application of modal split percentages in re- sponse to policy decisions to test unique modal conditions. UMCON can be used to apply a factor to any groups of zonal interchanges thus permitting splitting of trips.

UMATRIX - UMATRIX is used to subtract the special transit trips from the total auto trip table and to add these trips to the transit trips.

The existing set-up used in Polk County is shown in Ap-

pendix I. This set-up is the base for these recommendations

but certain changes have been made to reflect more flexibility

in trip purpose selection. The recommended procedures for ap-

plication of the recommended standard modal split models are

provided in Appendix III.

It is important to realize that the Gainesville modal

split function recommended in these procedures must be applied

with a great amount of care and a full understanding of what

the model can do and what it cannot do. The model permits the

transportation planner to consider various "what if" scenar-

ios, but the model does not address the types of strategies

that might be required to produce the modelled transit "de-

mand". The model should not be used in the forecast mode if

strategies to support modes other than the auto cannot support

the figures obtained. This would result in unrealistic plan-

54

ning for the auto mode and the development of auto improvement

strategies based upon situations which it is known will not

happen. Thus the application of the Gainesville function in

the standardized procedure must be followed by an analysis of

what strategies are required to fulfill the desired policy.

OTHER ISSUES

Not all of the tests recommended in the earlier chapters

were completed. Data shortcomings and a reassessment of the

objectives of this effort dictated in some instances that

tests different from those recommended be performed. In Chap-

ter One, a specific test to apply the Polk County model to the

Gainesville area was suggested. This test was not completed

because the evaluation of the Polk model, as reported earlier,

showed that the more critical question in regard to the Polk

rates dealt with the trip purposes considered in the model.

It was felt that any rates used in the application of the Polk

model should be developed during the Census validation

effort.

It was also recommended that zonal income variables be

substituted for area-wide estimates in a test of the logit

formulation. This test could not be completed due to a lack

of zonal income variables to input to the test. In place of

this test, an additional test of the Orlando model was con-

ducted as reported earlier.

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urban transportation planning task e develop standardized modal

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