presented to

Model Task Force Model Advancement Committee

presented byThomas RossiKrishnan ViswanathanCambridge Systematics Inc.

Date

November 24, 2008

Activity Based Models Review

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Presentation Overview

Study Background and Objectives

Models Studied

Study Findings

Discussion

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Study Background and Objectives

Examine existing activity based models to determine model features, application procedures, and requirements

Determine planning analysis needs for which travel models are used

Summarize the ability of activity based models to provide accurate information for planning analysis needs

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Models Studied

Urban Models• San Francisco County, CA (2001)• New York, NY (2002)• Columbus, OH (2005)• Sacramento, CA (2007)• Lake Tahoe, NV/CA (2007)• Atlanta, GA• Portland, OR• Denver, CO• San Francisco Urban Area (MTC), CA

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Models Studied (Cont’d)

Statewide Models• Ohio Model (2007)• Oregon Model

Research Models• FAMOS (University of South Florida)• CEMDAP (University of Texas)• TASHA (University of Toronto)

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Models Studied (Cont’d)

SFCTANew York

Columbus

Sacramento

Lake Taho

e AtlantaPortlan

d Denver

San Francisco (MTC) Ohio

Oregon

Year Completed 2001 2002 2005 2007 2007 2008 (est.)

2008 (est.)

2008 (est.)

2009 (est.)

2007 2008 (est.)

Base Year 2000 1996 2000 2005 2000 2000 2005 2000Forecast Year 2020 2030 2035 2030 2035 2030,

2050Survey Data Year 1990 1998 1999 2000 2001 1994 1997 2000 2003 No

Survey

Number of Households in Survey

1,300 11,000

5,600 3,900 1,220

8,100 6,000 4,900 15,000 15,000

No Surve

yZones (approximate)

1,700(750 in

SF)

3,600 1,800 1,500 289 2,000 2,000 2,800 1,454 5,300 3,000

Area Size (square meters)

50 (SF

only)

150 (est.)

4,000 501 500 7,000

Base Year Population

750,000

(SF only)

1,500,000

2,000,000 63,448

4,700,000

1,600,000

6,783,760

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Study FindingsModel Structure

All models estimated from household activity/travel survey• Same type of survey used for four-step model

development

Individuals in region’s population are simulated• Activity patterns• Locations and times of activities• Modes used to travel between activity locations

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Study FindingsModel Structure (Cont’d)

Model structure• Generate daily activity patterns• Location, time and mode made at two levels : Tour and Trip

Five to eight activity purposes• Work, school, shop, meal, social/recreation, and personal

business

Some models consider household interactions• Implications for time of day and mode choice• Is it cost effective to include this to gain accuracy? The “jury is

still out.”

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Study FindingsModel Components

Population Synthesizer

Long Term Choice Models

• Auto ownership

• Usual workplace location

Daily Activity Pattern Models

Tour Level Models (primary activity)

• Destination choice

• Mode choice

• Time of day choice

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Study FindingsModel Components (Cont’d)

Trip Level Models (intermediate stops)• Destination choice• Mode choice• Time of day choice

Trip Assignment• Highway• Transit

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Study Findings Model Development Process

Model development between 1.5 to 8 years (typically 2-3 years)

Model development costs – typically $600,000-$800,000

Consultants nearly always used for model development

Most models used local household activity survey data along with other sources such as transit on-board, external or visitor surveys

Lake Tahoe model was transferred from Columbus

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Study Findings Model Execution

Standard transportation modeling software such as CUBE/Voyager, TransCAD used along with custom programs in C++, Java, or Python

Run times range from 10 hours to 2 days • Distributed computing preferable to reduce runtime

Models need around 7 to 10 GB of storage per run

Most models run only in-house

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Study Findings Policy Planning Analysis

Activity Based Models benefit the following types of analysis• Congestion Management Systems • Toll Feasibility Studies  • High-Occupancy Vehicle (HOV) Lane Studies  • New Starts/Small Starts Analyses • Hurricane Evacuation Modeling Support  • Air Quality Conformity Determinations  • Integrated Land Use Model  • Incorporate Ability to Test Impact of Gasoline Prices  • Freight Studies• Growth Management/Concurrency Applications

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Study Findings Data Needs

No special data needs required to develop activity based models beyond what is used for four-step models

Existing household travel surveys can be used to develop data for activity based models

Other data sources such as transit on-board surveys, external and visitor surveys are also helpful for activity based models

Census data sources such as PUMS useful for population synthesis

• ACS disclosure rules can be problematic

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ConclusionsModels use similar approaches• Main differences related to explicit modeling of household

interactions

Members of population simulated individually• Their activities, locations, times, and mode choices

Standard modeling software used along with custom programs

Typically 2-3 years, $600,000-$800,000 to develop models

Run times typically 0.5 to 2 days

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Discussion