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BREAKOUT SESSION Tour-Based Models Mark Bradley, Mark Bradley Research and Consulting John Bowman, John Bowman Research and Consulting Peter Vovsha, PB Consult, Inc. Kuo-Ann Chiao, New York Metropolitan Transportation Council Maren Outwater, Cambridge Systematics, Inc. Billy Charlton, San Francisco Transportation Authority David Schmitt, AECOM Consulting Rebekah Anderson, Ohio Department of Transportation DESIGN FEATURES OF ACTIVITY-BASED The activity-based models examined share a simi- MICROSIMULATION MODELS FOR U.S. lar overall structure, with a hierarchy of levels. They are METROPOLITAN PLANNING ORGANIZATIONS all microsimulation based, simulating people and house- holds one at a time. The models also produce trips that Mark Bradley and John Bowman go into an aggregate equilibrium assignment. The assign- ment procedure is the same as in the four-step modeling Mark Bradley discussed the design features of activity- process. The process for trips going into the model based models recently developed or implemented at assignment is different, however. At the bottom level are selected metropolitan planning organizations (MPOs) trips and stops, which are similar to trip-based models. throughout the country. The metropolitan areas exam- The second level, which includes tour-level decisions, ined included Portland, Oregon; San Francisco; Sacra- and the third level, which includes person-day decisions mento; New York; Columbus, Ohio; Atlanta; and and household-day decisions, are different. The top level Denver. Volume 2 includes a paper on this topic.1 The of longer-term household and person-level decisions is following points were covered in the presentation. also different. This level includes decisions related to work, school, and automobile ownership. There are The activity-based models in the seven areas are in important design features that distinguish the different different stages of development, implementation, and use. models. The Portland model was developed in the late 1990s and All of the model systems simulate persons one-by- has been used in a number of studies, including examining one and require a representative sample of households road pricing options. The San Francisco model and the and persons for the base year and a given forecast year. New York model were implemented after Portland. The Most of the models use a synthetic sample, which repre- Sacramento model is being implemented. The Atlanta sents every person in the population in a given forecast model is in the estimation stages. The design stages of the year. Most areas use three variables to design and con- Denver and the San Francisco Bay Area models are just struct the sample for every zone. These variables are being completed and the estimation stages are beginning. household size, number of workers in the household, and household income. Other variables used in some 1See Bradley, M., and J. Bowman. Design Features of Activity-Based models include the age of the head of the household, the Microsimulation Models for U.S. Metropolitan Planning presence of children under 18 years of age, the presence Organizations: A Summary. In Conference Proceedings 42: Innovations in Travel Demand Modeling, Volume 2: Papers, of adults over 65 years of age, and family and nonfamily Transportation Research Board of the National Academies, households. Race and ethnicity are being added to the Washington, D.C., 2008, pp. 1120. San Francisco model. 13