1. Transport Modelling– An overview of the four modeling stages
Prof. Dr. Mir Shabbar Ali

2. Lecture covers Travel demand modeling concepts Four stage TDM
Explanation
Data requirements
Forecasting

3. TRAVEL DEMAND ANALYSIS; MODELLING AND FORECASTING

4. The Four Stage TDM

6. The fours step process

9. Key Concepts in transportation planning Model
Long-run decrease in friction of distance
Interaction t2 t3 t1
Distance
Due to innovations in transportation methods
and improvements in media themselves
Result: Lowered average ton-mile costs of transportation
and decreased importance of transport costs as a
factor cost  AND other costs rise in importance

10. Four basic elements of the urban transportation forecasting process
Data collection (population, land use, etc.)
Economic activity (employment, sales volume, income, etc.), land use (type, intensity), travel characteristics (trip and traveler profile), and transportation facilities (capacity, travel speed, etc.), population and demography, Origin-destination trip data.
Analysis of existing conditions and calibration
Analyze the data collected in the data collection stage. You may build mathematical models describe the existing conditions and then use the relationships you have found in the existing parameters to forecast future values.
Forecast of future travel demand
4-step transportation demand forecasting process
Analysis of the results
Analyze what you get from the 4-stop demand forecasting process

11. Comprehensive Transportation Planning Dimensions
Economic
Social
Environmental

12. Why Use Travel Demand Models
A relationship between transport system and indicators
Access
Purpose
Frequency
Use T
Land use
Travel behavior
System performance
TRAVEL
DEMAND
MODEL

13. Economic, Social, and Environmental Dimensions
Where do they come in to this process?
TRAVEL
DEMAND
MODEL
Evaluate
progress to
goal
Indicators
System performance
Other data

14. …through performance indicators
For example:
Commute speed
Land use mix
Transport diversity
Transport equity
Residential
Employment
Service

15. Example Model output = travel times between all points
Indicator: Commute speed
Indicator: Land use mix
Indicator: Transport diversity
Indicator: Equity

16. Introduction to Travel Demand Modeling
What is a travel demand model
Assignment: Discuss your knowledge
Input data
Trip generation
Trip distribution
Mode choice
Traffic/trip assignment

17. Four Step Travel Demand Model (FSTDM)
Step 1: Trip Generation
Step 2: Trip Distribution
Step 3: Mode Choice
Step 4: Trip/ Traffic Assignment
Demographic Data
Transportation Network

18. Trip Generation Questions
How much do people use the transport system?
Why do people use the transport system?
Where can different types of activities be satisfied?

19. Productions and Attractions

20. Types of Urban Movements
Movement Type
Pattern
Dominant Time
Destination
Pendular
Structured
Morning and afternoon
Localized (employment)
Professional
Varied
Workdays
Localized
Personal
Evening
Varied with some foci
Touristic
Seasonal
Day
Highly localized
Distribution
Nighttime

21. Cross Classification Model
Number of trips by household classifications or grouping

22. Trip Distribution Questions
Given a location, where do people go to satisfy demand for an activity type?

23. Trip Distribution Models
You can consider this as the
probability spatial distribution
P(Tj)
Gravity Model
Tij = Ti
Tij = trips from zone i to zone j
Ti = total trips originating at zone i
Aj = attraction factor at j
Ax = attraction factor at any zone x
Cij = travel friction from i to j expressed as a generalized cost function
Cix = travel friction from i to any zone x expressed as a generalized cost function
a = friction exponent or restraining influence
Aj / Cij a
Sum (Ax / Cix) a

24. O - D Matrix Example: Destinations 1 2 3 4 5 6 Sum Origins
T11 T12 T13 T14 T15 T16 O1
T21 T22 T23 T24 T25 T26 O2
T31 T32 T33 T34 T35 T36 O3
T41 T42 T43 T44 T45 T46 O4
T51 T52 T53 T54 T55 T56 O5
T61 T62 T63 T64 T65 T66 O6
D1 D2 D3 D4 D5 D6

25. Trip-interchange models
What is modal split?
Split trips to different available transportation modes, by analyzing people’s decisions regarding mode of travel they use.
Can be done here
Trip-end models
vs.
Trip-interchange models

26. Mode choice Questions How do people use the transport system?
What modes do they choose?
How do they react to varying transport service quality?

27. What affects people’s mode choice?
Characteristics of the trip: trip distance, time of day, trip purpose
Characteristics of the trip maker: Income, # of autos available, family size, residential density, gender
Characteristics of the transportation system: riding time, waiting time, transfers, out-of-pocket cost

28. Direct-generation usage models (Trip-end models)
Generate trips for transit and highway users separately  meaning transit users use only transit (“captive” users).
Used for small communities or in developing countries where ridership is primarily a function of socioeconomic variables

29. Direct-generation usage models (Trip-end models) (cont)
Same categories but different trip rates
Or, use separate models, like:
P(T) = A + B(POP) – C(INC)
P(A) = A + B (POP) – C(AUTO)
Advantage: Simplicity
Disadvantage: Cannot reflect “change of mind” of trip makers responding to policy and service changes

30. Trip-interchange models
Influencing all three phases.
Trip-interchange models are used AFTER the trip distribution phase.

31. Trip-interchange models (cont)
Competing modes
Because trip-interchange models are used after trip distribution, they can utilize the service characteristics of the modes available for the given trip, along with any relevant socioeconomic characteristics to determine the modal splits. This is the preferred and overwhelmingly typical approach for urban areas in which significant transit service exists and in which the “competition” between auto, transit, and other modes of travel must be explicitly considered.

32. Trip-interchange models (cont)
Let’s see how service and trip makers characteristics can affect the trip maker’s decision using Fig
In-vehicle time (Auto – Transit) = -15 min
Out of pocket cost (Auto – Transit) = 25 cents
Excess time (Auto – Transit) = 3 min
If so, 37% of trips will be made by transit.
Looks like a logit curve…

33. Use of logit models for modal choice
(“Disaggregate, random utility modal choice model”)
The logit model trades off the relative utilities of various modes.
“The better a mode is, the more utility it has for the potential user”
(See Examples 11& 12)

34. Nested Mode Choice Model

35. Trip / Traffic Assignment Questions
How do people use the transport system?
Given a mode, which route do they choose?
Do they satisfy multiple activities in one tour?
Which parts of the transport system do they use?
How do they react to varying transport service quality?

37. Network Level of Service
Highway
Travel distance ij
Travel time ij
Travel Cost
Transit
Walk time ij
First wait ij
In-vehicle time ij
Transfer time ij
Fare ij
Number of transfers
Drive access areas
Walk access areas

38. Road Sections with more than 100,000 Vehicles/Day

39. Top 20 Road Sections in terms of Traffic Volume

40. Demographic Data
Autos per household
Income level
Household size

41. Network Data
Highway network
Transit network
Graph

44. Representing a Network

45. Explanations and working

46. Transit Access Coding

47. Drive Access Path Building Parameters

48. AM Peak Period Bus Travel Time Factor

49. Midday Period Bus Travel Time Factor

53. Carbon Monoxide Concentrations
Projected for December 1995

54. Thanks