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

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

TRAVEL DEMAND ANALYSIS; MODELLING AND FORECASTING

The Four Stage TDM

The fours step process

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

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

Comprehensive Transportation Planning Dimensions Economic Social Environmental

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

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

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

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

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

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

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?

Productions and Attractions

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

Cross Classification Model Number of trips by household classifications or grouping

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

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

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

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

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

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

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

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

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

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.

Trip-interchange models (cont) Let’s see how service and trip makers characteristics can affect the trip maker’s decision using Fig. 11-11. 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…

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)

Nested Mode Choice Model

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?

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

Road Sections with more than 100,000 Vehicles/Day

Top 20 Road Sections in terms of Traffic Volume

Demographic Data Autos per household Income level Household size

Network Data Highway network Transit network Graph

Representing a Network

Explanations and working

Transit Access Coding

Drive Access Path Building Parameters

AM Peak Period Bus Travel Time Factor

Midday Period Bus Travel Time Factor

Carbon Monoxide Concentrations Projected for December 1995

Thanks