Development of a Transit Model
Incorporating the Effects of
Accessibility and Connectivity
9th Conference on the
Application of Transportation Planning Methods
Baton Rouge, Louisiana
April 6-10, 2003
Research Team
 Ram M. Pendyala
Dept of Civil & Environmental Engineering, Univ of South Florida, Tampa
 Steve Polzin & Xuehao Chu
Center for Urban Trans Research (CUTR), Univ of South Florida, Tampa
 Seongsoon Yun
Gannett Fleming, Inc., Tampa
 Fadi Nassar
Keith & Schnars PA, Fort Lauderdale
 Project Manager: Ike Ubaka
Public Transit Office, Florida Dept of Transportation, Tallahassee
 Programming Services: Gannett Fleming, Inc.
Outline
 Background
 History of transit model development in Florida
 BEST 3.0: Third generation transit model system
 Role of accessibility and connectivity
 BEST 3.0 methodology
 Accessibility/connectivity methodology
 Model development
 Data
 Estimation
 Application
Background
 Transit systems planning and analysis
 Accessibility
 Availability
 Quality of Service
 Ridership
 Temporal Characteristics
 Transfers
 Route/Network Design
 Fare Policies and Structure
 Alternative Modal Options/Technologies/Route Types
 Disaggregate Stop-Level Analysis
History of Transit Model Development
 FDOT Public Transit Office very proactive in transit
planning tool development
 TLOS, FTIS, and INTDAS examples of transit
planning and information tools
 Transit ridership modeling tools
 ITSUP:
Integrated Transit Demand & Supply Model
 RTFAST: Regional Transit Feasibility Analysis & Simulation
Tool
 Powerful stop-level ridership forecasting models
Stop-Level Ridership Forecasting
 First generation ITSUP sensitive to demographic
variables and frequency and fare of service
 Second generation RTFAST accounted also for
network connectivity (destination possibilities)
 Desire transit ridership forecasting model that
accurately accounts for accessibility/connectivity
 Third generation model called BEST 3.0
 Boardings
Estimation and Simulation Tool
BEST 3.0
 Model estimates number of boardings at stop by:
 Route
 Direction
 Time period
 Model estimates two types of boardings:
 Direct Boardings: Walk and Bike Access
 Transfer Boardings: Transit Access
Separating Direct and Transfer Boardings
 Consider two types of stops, i.e., stops with no
transfer possibility and transfer stops
 Estimate direct boardings model using data from
non-transfer stops
 Apply direct boardings model to transfer stops to
estimate direct boardings at transfer stops
 Subtract estimated direct boardings from total
boardings to estimate transfer boardings
 Then estimate transfer boardings model
Role of Accessibility and Connectivity
 Transit ridership strongly affected b y:
 Destination accessibility
 Temporal availability
 Network connectivity
 Desire to have BEST 3.0 sensitive to all three
aspects of transit accessibility
 Ability to test effects of alternative route and
network design configurations on transit boardings
 Sophisticated methodology incorporated into BEST
3.0
BEST 3.0 Methodology


Dns  f Rns , B s , O2sn , O3sn , O4sn , O5sn , X ns ,
s
n  1, ... , N
refers to stop on a route in a given direction and
n refers to time period
 D = direct boardings
 R = number of bus runs
 B = vector of buffer characteristics
 Oi = vector of accessibility to characteristics of buffer
areas for Hi stops, i = 2, 3, 4, 5
 X = vector of other route and stop characteristics
BEST 3.0 Methodology


Tns  g Rns , O1sn , O2sn , O3sn , O4sn, O5sn , Yns ,
n  1,..., N
T
= transfer boardings
 O1 = vector of accessibility of boarding at H1 stops
during period n toward stop s
Y
= vector of other route and stop characteristics
 Methodology thus includes both direct and transfer
boardings equations
 Accessibility vectors play major role
Definition of Stops
 Stops are defined with three pieces of information:
 Physical location
 Route
1 1
 Direction
41 41
4 4
 Example 1:
 2 routes intersect
 Example 2:
 4 routes serve one location in the same direction
Neighboring Stops
 N1 = Neighboring stops along the same route
 N2 = Stops along the same route but in the
opposite direction that lead to different destinations
providing the same opportunities.
 N3 = Neighboring stops along other routes that lead
to different destinations providing access to
opportunities for the same activities.
 N4 = Neighboring stops along other routes that lead
to the same destinations. These routes may or may
not share the same roads with the particular route
in question
Neighboring Stops (N1)
 N1 = Neighboring stops along the same route
Stop in
Question
Neighboring Stops (N2)
 N2 = Stops along the same route but in the
opposite direction that lead to different destinations
providing the same opportunities
Stop in
Question
Neighboring Stops (N3)
 N3 = Neighboring stops along other routes that lead
to different destinations providing access to
opportunities for the same activities
1
1
41
41
4 4
Stop in
Question
1
4
Neighboring Stops (N4)
 N4 = Neighboring stops along other routes that lead to the
same destinations; these routes may or may not share the
same roads with the particular route in question
Stop in
Question
Competing Routes/Stops
 Notion of neighboring stops effectively captures
effects of competing routes/stops
 Riders may choose alternative stops, routes,
destinations for pursuing activities
 Need to identify and define upstream and
downstream stops that can be reached using
neighboring stops
 Define series of stops, H1 through H5, identified by
network connectivity
Accessible Stops: Illustration Network
1
2
3
4
5
6
7
8
11
12
9
111
14
44
4
10
13
14
15
16
Route 6
Route 7
Route 8
Route 5
Route 1
Route 2
Route 3
Route 4
Neighboring Stops: Illustration Network
 Network
 8 routes (each two way)
 16 nodes (n=1, …, 16)
 64 stops (nX, n=1,…, 16; X=N,S,E,W)
 Neighboring Stops
 N1 = {2S}
 N2 = {6N}
 N3 = {6W, 6E}
 N4 = {6W, 6E}
Accessible Stops: Illustration Network
 H1 = {1S, 1E, 2E, 2W, 3E, 3W, 3S, 4W, 4S, 5E, 7W, 8W, 9N,




9E, 10W, 10E, 11W, 11E, 12N, 12W, 13N, 13E, 14W, 14E, 15W,
15E, 16W, 16N}
H2 = {1W, 2N, 3E, 4E, 5S, 7S, 8S, 9S, 11S, 12S, 13S, 15S,
16S}
H3 = {1N, 3N, 4N, 5N, 7N, 8N, 9W, 9N, 10S, 11E, 11N, 12E,
12N, 13S, 13W, 14S, 15E, 15S, 16E, 16S}
H4 = {1N, 1W, 2E, 2W, 3N, 3E, 3W, 4E, 4N, 5W, 5N, 7E, 8E,
9S, 10E, 10W, 11E, 11W, 12S, 12E, 13S, 13W, 14E, 14W, 15E,
15S, 15W, 16S, 16E}
H5 = {1N, 1W, 3N, 3E, 3W, 4E, 4N, 5W, 5N, 7E, 8E, 9S, 10E,
10W, 11E, 11W, 12S, 12E, 13S, 13W, 14E, 14W, 15E, 15S,
15W, 16S, 16E}
Defining Accessible Stops
 H1 includes stops that can reach the N3 and N4 neighboring




stops (Interest: boardings)
H2 includes upstream stops that can be reached from the N2
stops (Interest: buffer area)
H3 includes stops downstream that can be reached from stop
in question through route serving the stop in question via the
transit network (Interest: buffer area)
H4 includes stops that can be reached from the N3 and N4
neighboring stops (Interest: buffer area)
H5 includes stops in H4 that overlap with stops in H3 (Interest:
overlapped area)
Computing Transit Accessibility
 Two components of transit accessibility
 Access/egress at stop in question
 Accessibility from stop to all other stops in network
 Access/egress at stop in question measured through
simple air-distance buffer distance
 Accessibility from one stop to all other stops in
network uses gravity-type measure:
 
O  Q G
sij
s
jn
sij
sij
n

Computing Transit Accessibility
 Oi is the measure(s) of accessibility included in the
boarding equations
 Q represents buffer characteristics of stops in H2
through H5 and boardings at stops in H1
 G represents impedance from stops in H1 and
impedance to stops in H2 through H5
  is gravity model parameter
 Impedance measured by generalized cost of traveling
from one stop to another
Computing Impedance, G
 Components of impedance
 First wait time
 First boarding fare
 In-vehicle time
 Transfer wait time
 Number of transfers
 Transfer walking time
 Transfer fare
 Model sensitive to host of service characteristics
Components of Impedance, G
Components
Unit
Value/Source
First-wait time
Minutes
Half of first headway with a cap
of 30
First-boarding
fare
Dollars
In-vehicle-time
Symbol
Weight
Symbol
Value
FWT
WFWT
3.0
Base cash fare
FBF
WFBF
1/v
Minutes
Cumulative scheduled travel time
IVL
WIVL
1.0
Transfer-wait
time
Minutes
TWT
WTWT
3.0
Number of
transfers
Headway of transfer stop if no
coordination and deviation if
coordinated for up to two transfers
Number
Up to two
NTF
WNTF
5.0
Transferwalking time
Minutes
Time to transfer stops at 3 mph
TWK
WTWK
1.5
Transferboarding fare
Dollars
Base cash fare for transfers
TBF
WTBF
1/v
v = half of average hourly wage rate in service area
Model Functionality
 BEST 3.0 will retain user functionality from
first two generations
 GIS
interface for database setup and displays
 Sets of default equations by time period
 Automated buffering
 Automated accessibility and impedance
computations
 Report generation including performance measures
Model Development
 BEST 3.0 software development underway
 Model estimation using APC data from
Jacksonville, Florida
 Using Census 2000 data for socio-economic
variables
 Programming accessibility and impedance
computation capability at this time
 Anticipated release of software in late summer
or early fall
Conclusions
 BEST 3.0 will provide a powerful framework for
modeling transit ridership at stop level
 Incorporates effects of accessibility and connectivity
on ridership
 Accessibility and impedance computations very
sophisticated and accurate
 More precisely accommodates effects of service span
and frequency (temporal aspects)
 Focus on ease of use and quick response capability