GEOG 111/211A
Transportation Planning
UTPS (Review from last time)
• Urban Transportation Planning System
– Also known as the Four - Step Process
– A methodology to model traffic on a network
– Developed in 1962 (Chicago)
• Four Steps:
–
–
–
–
Trip Generation
Trip Distribution
Mode Choice
Traffic Assignment
Estimate Person Trips for each TAZ
Distribute Person Trips from TAZ to TAZ
Convert Person Trips to Vehicle Trips
Assign Vehicles to the Network
Oct/Nov 2004
GEOG 111/211A
Survey Data – interviews
of persons about their
behavior
Models of behavior –
extract key aspects to
capture most variation
Use models –
incorporate models into
a computerized map
Transportation Planning
If no survey available?
Discuss options in class!
GEOG 111/211A
Transportation Planning
The Four Steps:
• Trip Generation = Estimate Person Trips for each TAZ
• Trip Distribution = Distribute Person Trips from TAZ to
TAZ
• Mode Choice = Convert Person Trips to Vehicle Trips
• Traffic Assignment = Assign Vehicles to the Network
• Pre 4-step = Land Use and Demographics?
• Post 4-step = Emissions, Traffic Simulation, Link by Link
Evaluation
GEOG 111/211A
Transportation Planning
Key Concepts of UTPS
• TAZ: Traffic Analysis Zone
– A TAZ is an arbitrary subdivision of the study area
– TAZs are used in trip generation and trip distribution
– TAZs may be any shape or size, but US Census Blocks,
Block Groups, and Tracts are often used
Block
i.e., a
city block
Block Group
Tract
GEOG 111/211A
Transportation Planning
Key Concepts of UTPS
• Centroid
– Every TAZ (Gate and Internal Zone) has a centroid,
usually placed roughly at the geographic center of the
TAZ
– All trips to or from a TAZ are assumed to start or end at
the centroid
• Discussion
– Why do we use TAZs and centroids to model trips?
GEOG 111/211A
Transportation Planning
Key Concepts of UTPS
• Gate TAZs
– TAZs placed outside the Study Area where major roads
cross the boundaries of the study area
– Used to model External Trips (i.e., trips with an origin or
destination or both outside the study area)
– Gate TAZs represent all areas outside of the study area
Network
Gate TAZ
(Study Area)
GEOG 111/211A
Transportation Planning
Centroid
Gate TAZ
GEOG 111/211A
Transportation Planning
Every zone is a node (the centroid) with an identifier and type
GEOG 111/211A
Transportation Planning
Trip Generation
Additional suggested reading material:
Ortuzar & Willumsen, third edition,
Chapter 4.
GEOG 111/211A
Transportation Planning
Trip Generation Objectives
• Estimate amount of trip making going out of a TAZ
• Estimate amount of trip making going into a TAZ
• Account for differences among TAZs due to person
and household characteristics
• Account for differences among TAZs due to
business (establishments) characteristics
• Develop functions to predict future amount of trip
making
GEOG 111/211A
Transportation Planning
Trip Generation Usual Process
• Collect Data, usually by Surveys and Census
– Sociodemographic Data and Travel Behavior Data
• Create Trip Generation Models
• Estimate the number of Productions and Attractions
for each TAZ, by Trip Purpose
• Balance Productions and Attractions for each Trip
Purpose
– Total number of Productions and Attractions must be
equal for each Trip Purpose
GEOG 111/211A
Transportation Planning
Trip Generation Models
• Regression Models
– Explanatory Variables are used to predict trip generation
rates, usually by Multiple Regression
• Trip Rate Analysis
– Average trip generation rates are associated with different
trip generators or land uses
• Cross - Classification / Category Analysis
– Average trip generation rates are associated with different
trip generators or land uses as a function of generator or
land use attributes
• Models may be TAZ, Household, or Person - Based
GEOG 111/211A
Transportation Planning
Usual Unit of Analysis
• TAZ - zonal rates (Number of trips as a function of a
zone’s population characteristics)
• Household rates (Number of trips as a function of
household characteristics)
• Person rates (Number of trips as a function of person
characteristics)
• NEW (PennState Research)! Multilevel rates
(Number of trips as a function of person &
household & TAZ characteristics)
GEOG 111/211A
Transportation Planning
Units and Models
• TAZ-based models = productions and attractions
converted to origins and destinations
• Household and/or person - based models = origins
and destinations
• Establishment - based = attractions need to convert
to destinations
GEOG 111/211A
Transportation Planning
Common Trip Definitions in CE422
• Trip: a one - way movement from one place to another
• HB = Home Based: a trip where the home of the traveler is
either the origin or the destination of the trip
• HBW = Home Based Work: trips between home and work
• HBNW = Home Based Non-Work: trips between home and
shopping, also called HBS (Home Based Shopping)
• HBO = Home Based Other: trips between home and a non
- work / shopping location
• NHB = Non Home Based: trips where neither end of the
trip is the home of the traveler
GEOG 111/211A
Transportation Planning
Related Definitions
1.Home-based school trip
Home
1+2+3=Tour or Trip
Chain (home-based)
School
2.NonHome-based
work trip
3. Home-based
work trip
Work
GEOG 111/211A
Transportation Planning
Productions - Attractions
All Home - Based Trips
Residential
Area
Production
Attraction
Production
Attraction
Non-Residential
Area
Non - Home - Based Trips
Non-Residential
Area
Production
Attraction
Attraction
Production
= Origin
= Destination
See also OW-p. 124
Non-Residential
Area
GEOG 111/211A
Transportation Planning
Trip Balancing Methods
• Hold Productions Constant
– Attractions are multiplied by the ratio of the sum of nongate productions to the sum of non - gate attractions
– Most common form of trip balancing
• Hold Attractions Constant
– Productions are multiplied by the ratio of the sum of nongate productions to the sum of non - gate attractions
• Hold Neither Productions or Attractions Constant
– Not used very often
Note: Gate Productions and Attractions are not
included in this balancing process
GEOG 111/211A
Transportation Planning
Examples
• http://tmip.fhwa.dot.gov/clearinghouse/docs/TimeDay/ - discussion of time-of-day issues
• http://www.psrc.org/datapubs/index.htm (this is the
metropolitan plan where models are used)
• http://tmip.fhwa.dot.gov/clearinghouse/ <the
ultimate web site for GEOG 111/211A>
All sites verified October 2004
GEOG 111/211A
Transportation Planning
Gate Trip Estimation
• Gate Trips Must be Modeled Separately
– Gates have specific traffic volumes associated with them
– Gates do not have sociodemographic data
– Gates may represent trips with extremely variable trip
lengths
• Gate Trip Modeling
– Correlate percentages of traffic volumes to different trip
purposes (e.g., X% * Total daily volume observed = trips
for commuting)
GEOG 111/211A
Transportation Planning
ITE Trip Generation Manual
• Trip Rate Analysis Model
– Univariate regression for trip generation
– Primarily for businesses (attraction rates)
– Explanatory variables are usually number of employees or
square footage
– Models developed using data from national averages and
numerous studies from around the US
Copies of the ITE Trip Generation Manual may be
Found in the Hammond and PTI Libraries
GEOG 111/211A
Transportation Planning
GEOG 111/211A
Transportation Planning
TAZ Issues
TAZ Scale
Modeling Accuracy
Data Availability
Block
Good
Poor
Block Group
Not Good
Excellent
Tract
Poor
Good
• Data availability limited by privacy issues
• Larger TAZs, with complete data, are no longer
necessarily homogeneous
• Model accuracy decreases with larger TAZs
GEOG 111/211A
Transportation Planning
Model Formulation and Surveys
• Privacy
– May limit data collection efforts
– Private information must remain secure
• Response Rate
– Good survey should have at least 85% response rate
• Representative Sample Size
– Pop. representation most important
• Model Stability and Transferability
– Over time, behavior may change
– Behavior is not necessarily the same from place to place
GEOG 111/211A
Transportation Planning
Trip Generation Example
•
•
•
•
Similar to the lab exercise
From the Puget Sound Region in 1989
Subsistence (work + school trips)
These are one way trips (origins) instead of
productions
GEOG 111/211A
Transportation Planning
Sample Descriptives
e
t
N
e
i
i
m
a
m
H
0
0
8
1
T
0
0
9
3
T
0
0
5
1
N
0
0
6
6
A
0
0
2
4
E
0
0
9
9
S
0
0
1
0
V
Class: What do you observe?
GEOG 111/211A
Class: Interpret the model
Transportation Planning
Trip Generation Linear Regression
Model for Subsistence Trips
i
a
c
n
d
e
e
d
f
n
i
t
c
S
B
e
M
E
i
t
g
1
(
9
0
3
1
H
3
5
3
3
8
T
2
2
3
5
2
T
6
9
5
0
7
N
3
9
1
7
2
A
3
2
1
5
7
E
6
3
6
8
0
a
D
GEOG 111/211A
Transportation Planning
Goodness of fit
b
O
m
e
d
u
F
i
a
M
a
1
R
0
6
5
6
0
R
1
2
7
T
1
8
a
P
b
D
u
E
t
t
q
R
u
m
M
u
a
1
a
P
N
GEOG 111/211A
Let’s Improve the Model
If (age < 20) Teen = 1 .
If (age >= 20 and age < 35) Young=1.
If (age >= 35 and age < 65) Midage=1.
If (age >= 65 and age < 75) Senior=1.
If (age >=75) VSenior=1.
Transportation Planning
GEOG 111/211A
Transportation Planning
Descriptives of the New Vars
e
t
N
e
i
i
m
a
m
Y
1
0
0
7
4
T
1
0
0
2
3
M
1
0
0
8
8
S
1
0
0
4
6
V
1
0
0
2
2
V
1
GEOG 111/211A
Transportation Planning
Linear Regression
i
a
c
n
d
e
e
d
f
n
i
t
c
S
B
e
M
E
i
t
g
1
(
1
4
5
9
E
7
3
5
0
0
T
9
3
8
0
0
Y
3
0
8
1
7
M
2
4
3
1
2
S
8
6
3
6
9
V
7
6
5
3
9
a
D
GEOG 111/211A
Transportation Planning
Leisure Trip Generation
i
a
c
n
d
e
e
d
f
n
i
t
c
S
B
e
M
E
i
t
g
1
(
8
1
7
0
E
2
7
2
9
9
T
2
1
4
6
4
Y
2
4
4
8
6
M
2
0
6
3
0
S
0
6
7
6
2
V
5
8
8
1
7
a
D
The same model as for subsistence did not work!!!!!
GEOG 111/211A
Transportation Planning
New model for leisure
i
a
c
n
d
e
e
d
f a
f
n
i
t
c
S
B
e
M
E
i
t
1
(
2
8
5
0
L
9
6
2
5
1
W
5
0
7
0
4
T
1
5
4
1
0
T
2
4
1
1
5
N
2
3
0
5
7
S
2
3
0
6
8
S
3
1
4
4
7
S
2
6
4
1
0
a
D
GEOG 111/211A
Transportation Planning
Goodness of fit
b
O
e
m
d
u
F
M
i
a
g
a
1
R
4
8
7
4
0
R
9
2
1
T
3
0
a
P
W
b
D
u
E
t
t
q
R
u
m
M
u
a
a
1
a
P
T
GEOG 111/211A
Transportation Planning
Compare frequencies
700
1000
600
800
500
600
400
300
400
200
200
100
Std. Dev = .87
Std. Dev = 1.45
Mean = .8
Mean = 2.2
N = 1621.00
0
0.0
SFREQ1
1.0
2.0
3.0
4.0
5.0
6.0
7.0
N = 1621.00
0
0.0
LFREQ1
Class: Which one is easier to estimate?
2.0
4.0
6.0
8.0
10.0
12.0
GEOG 111/211A
Transportation Planning
Traditional Trip Generation
• Input: social and economic characteristics
• Output: productions/attractions, origins/destinations
by zone
• Key concepts: trip generation by purpose maybe
more accurate but some purposes easier to predict
(trips to work)
• Other: Goods movement productions/attractions are
handled in a similar way (Freight Forecasting
Manual exists)
GEOG 111/211A
Transportation Planning
Post-MTC Lawsuit Models
• Level of service = “quality” of transportation system
measured in travel time from an origin to a
destination
• Trip generation also function of level of service
• New models for induced demand = new demand for
travel after improvements in level of service
• Activity-based models to reflect “scheduling” of
persons, coordination of activities
• Multilevel models to reflect within group
coordination
GEOG 111/211A
Transportation Planning
In the Lab - Check
•
•
•
•
TAZ population and productions
Businesses and attractions
What do you expect the relationship to be?
Does the relationship make sense?
GEOG 111/211A
Transportation Planning
Summary
• Collect data using surveys
• Derive a model using statistics
• Use the model to predict number of trips generated
in each zone
• Apply this at each centroid representing a zone
• Have all this ready for the next step – trip
distribution
If you cannot run a survey – use equations from ITE trip
generation manual or other studies – check for similarities/verify
results!