For Model Users GroupJune 10, 2011
Kyeil Kim, Ph.D., PTP
Atlanta Regional Commission
Today’s MenuOverall features of ARC’s Activity-Based Model
(ABM)ABM Visualization Software, ABMVIZQuality Assurance/Quality Control of ABM
Daily Travel
• Trip-Based Model - Home-Work: 2 trips - Work-Eat: 2 trips - Home-Gym: 2 trips
• Activity-Based Model - Follows daily activity patterns (departure time, duration, location, frequency, mode)
What is Activity-Based Model?ABM aims at predicting which activities are
conducted where, when, for how long, with whom, the transportation mode involved and ideally also the implied route decisions
Disaggregate, Micro-simulation, Behavioral, Tour-based
ABM reflects the scheduling of activities in time and space
Structure of ARC Models: TBM vs. ABM
Trip GenerationTrip
DistributionMode Choice
Route Choice
Long-Term
Choices
Daily Activity Patterns
Tour Mode
Choice/Stop
Trip Mode Choice
Synthetic Populatio
n
Trip-Based Model
Activity-Based Model
Demand
Supply
Population SynthesizerGenerates synthetic population to represent
actual households and populationBase year
Input: Census data (marginal distributions of various household control variables), PUMS
Control variables: householder age, HH size, HH income, presence of children in HH, number of workers in HH
Joint distribution through Frata PUMS 5% sample as seed matrix, control totals from Census
Draws from PUMS households from the joint distribution 1 record/hh and 1 record/person
Population Synthesizer (cont’d)Forecast year
Input: ARC lane-use forecast, PUMSControl variables: HH size, HH income, householder’
age, number of workers in HHJoint distribution through Frata
Base year distribution as seed matrix, control totals from land-use forecasts
Draws from PUMS households from the joint distribution 1 record/hh and 1 record/person
Structure of ARC Models: TBM vs. ABM
Trip GenerationTrip
DistributionMode Choice
Route Choice
Long-Term
Choices
Daily Activity Patterns
Tour Mode
Choice/Stop
Trip Mode Choice
Synthetic Populatio
n
Trip-Based Model
Activity-Based Model
Demand
Supply
Long-Term ChoicesMandatory activity location choice
Work/school/university locations for the synthesized population Work location choice for workers Grade school for persons age 5-12 University for university students
Multinomial logit: [subzones]=[person characteristics, size terms, mc logsums, distance, etc.]
Car ownership modelNumber of vehicles owned by each householdMultinomial logit: [# cars]=[hh size, income, parking
cost, mc logsums, etc.]
Structure of ARC Models: TBM vs. ABM
Trip GenerationTrip
DistributionMode Choice
Route Choice
Long-Term
Choices
Daily Activity Patterns
Tour Mode
Choice/Stop
Trip Mode Choice
Synthetic Populatio
n
Trip-Based Model
Activity-Based Model
Demand
Supply
Coordinated Daily Activity PatternGenerates personal DAPs and individual tours by
purpose for all synthesized populationDAPs
Mandatory, Non-mandatory & At-home patternsDecision-making unit: HouseholdsMultinomial logit: [# DAPs]=[person/hh characteristics,
accessibility measures, intra-household interaction terms, etc.]
363 alternatives: 3 (1-p hh), 9 (2-p hh), 27 (3-p hh), 81 (4-p hh), 243 (5-p hh)
Tour ModelsPredicts the number and purpose of tours for
each person, destinations, and time-of-day choices
Four different toursIndividual Mandatory
Joint Non-Mandatory
Individual Non-Mandatory
At-Work Sub-Tours
Residual Time
Individual Mandatory TourTour Frequency
Number and purpose of tours for each personMultinomial logit: [# of work/school tour]=[hh
composition, income, car ownership, location of work/school activities, accessibility, etc.]
Tour Time-of-DaySelect the combinations of tour departure/arrival timeMultinomial logit: [combination of tour departure/arrival
hours]=[household and personal characteristics, network LOS variables, etc.]
Alternatives: 190 combinations of tour departure hour and arrival hour back at home
Joint Non-Mandatory TourJoint tours by household members after mandatory
tours have been generated and scheduledJoint Tour Frequency
Generates the number/purposes of joint toursMultinomial logit: [0, 1 or 2 tours by purpose]=[household
variables, accessibility, overlapping time windows, etc.]
Joint Tour CompositionDetermines the person types participating in the tourMultinomial logit: [combination of adults &
children]=[household characteristics, purpose of joint tour, overlapping time windows]
Joint Non-Mandatory Tour (cont’d)Joint Tour Primary Destination Choice
Location of the tour primary destinationMultinomial logit: [subzones]=[household/person
characteristics, tour purpose, size variables, mc logsum, distance, etc.]
Joint Tour Time-of-Day ChoiceTour departure time from home and arrival time back at
homeMultinomial logit: [combination of tour departure/arrival
hours]=[household and personal characteristics, network LOS variables, etc.]
Alternatives: 190 combinations of tour departure hour and arrival hour back at home
Other ToursIndividual Non-Mandatory Tour
Tour FrequencyTour Primary Destination ChoiceTour Time-of-Day Choice
At-Work Sub-TourTour FrequencyTour Primary Destination ChoiceTour Time-of-Day Choice
Structure of ARC Models: TBM vs. ABM
Trip GenerationTrip
DistributionMode Choice
Route Choice
Long-Term
Choices
Daily Activity Patterns
Tour Mode
Choice/Stop
Trip Mode Choice
Synthetic Populatio
n
Trip-Based Model
Activity-Based Model
Demand
Supply
Tour Mode ChoiceTour mode choice: main tour mode used from
origin to primary destination and backTwo-level mode choice in ARC ABM
Tour mode level (upper-level choice)Trip mode level (lower-level choice conditional on the
upper-level)
Tour Mode Choice (cont’d)Tour MC models
Work, University, K-12, Non-mandatory, At-work12 AlternativesNested logit: [tour mode]=[household and personal
characteristics, urban form variables, network LOS variables, etc.]
Use the round-trip LOS between the tour anchor location and the primary destination
Intermediate Stop ModelsStop Frequency Model
Number of intermediate stops on the way to/from the primary destination by tour purpose
Multinomial logit: [# of stops]=[household and personal characteristics, tour duration, tour distance, accessibility, etc.]
Stop Location Choice ModelLocation of stops along the tour other than the primary
destinationMultinomial logit: [Subzones]=[mc logsum, distance,
size variables, etc.]
Structure of ARC Models: TBM vs. ABM
Trip GenerationTrip
DistributionMode Choice
Route Choice
Long-Term
Choices
Daily Activity Patterns
Tour Mode
Choice/Stop
Trip Mode Choice
Synthetic Populatio
n
Trip-Based Model
Activity-Based Model
Demand
Supply
Trip Mode ChoiceDetermines the mode for each trip along the tourConstrained by the main tour modeCorrespondence rules to determine which trip
modes are available for which tour modesE.g., drive-alone pay trip is only available for drive-alone
pay tourE.g., transit tours can include auto shared-ride trips for
particular legs
Structure of ARC Models: TBM vs. ABM
Trip GenerationTrip
DistributionMode Choice
Route Choice
Long-Term
Choices
Daily Activity Patterns
Tour Mode
Choice/Stop
Trip Mode Choice
Synthetic Populatio
n
Trip-Based Model
Activity-Based Model
Demand
Supply
Route ChoiceSame routine as the trip-based modelMultimodal User Equilibrium Time-of-Day
AssignmentBi-Conjugate Frank-Wolfe for both TBM and
ABM, departing from the traditional Frank-Wolfe
Run Environment Java-PackageCube/TP+Three 64-bit Windows machinesEach machine with 32GB of RAMBase year run: approx. 30 hours2040 run:
approx. 50 hours
VisualizationModel generates huge databaseModel visualization system, ABMVIZPrimary starting point for most model
analysis questions Interactive/dynamic visualization
of model estimates/resultsSome unique visualization types
Tables, Bar Charts/Maps Time Use Tour Tracing Tree Map Radar Charts
Quality Assurance/Quality ControlQuality Assurance (QA): a systematic review process
by personnel not directly involved in model developmentQuality Control (QC): a technical routine to control
quality of the model performed in model development
Full understanding of the models’ capabilities/limits
ARC initiated internal a year-long QA/QC process for both ABM and TBM
New QA/QC guidelines
QA/QCOverall processes
Reasonableness checking for EVERY modeling stepTemporal validation between base and forecast yearsComparability between ABM and TBM
ComponentsModeling flows/ScriptsSocioeconomic dataTransportation network dataExternal tripsTrip generation, Trip distribution, Mode choice, &
Traffic assignment
QA/QC (cont’d)Tools
SQL Express Management StudioSTATAABMVIZCustom scripts
Voyager/TP+ R
Our brain
Thank You!
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