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Design Features of Activity-Based Microsimulation Models for U.S. Metropolitan Planning Organizations A Summary Mark Bradley, Mark Bradley Research and Consulting John L. Bowman, Bowman Research and Consulting T his paper provides a concise summary of important Tour level: main destination and mode, begin and design features of various activity-based model sys- end times, and number of stops; and tems that have been implemented or have recently Trip level: intermediate stop location and the mode been designed for planning agencies in the United States. and departure time of each trip. The models described are for Portland, Oregon; San Fran- cisco, California; New York; Columbus, Ohio; Atlanta, Within this structure, several important design fea- Georgia; Sacramento, California; the Bay Area of Califor- tures distinguish the models, and these are summarized nia; and Denver, Colorado. These models were selected in Table 1. The models are listed in the table roughly because they are in the same family of activity-based mod- chronologically, with the earliest ones on the left and the els, and one or both of the authors have been involved in later ones on the right. At the time of writing, the Bay the design of all of them except for New York. Two other Area Metropolitan Transit Commission (in California) examples have also been included in the summary table and and the Denver (Colorado) Regional Council of Govern- supplementary text of activity-based models in the United ments models are in the design stage; therefore, the States: the CEMDAP model for Dallas, Texas, and the design characteristics shown for these models are those FAMOS model for southeast Florida (see sidebars, pages currently envisioned. Each following paragraph is a 14 and 17). Not included is the TRANSIMS model or the more detailed annotation of a row in the comparison TLUMIP model for Oregon. Although those models share table. some of the features discussed here, the authors are not suf- ficiently familiar with them to compare them at the level of detail included here; that, however, could be a useful exten- CONTROLS AND CATEGORIES FOR sion of this paper. All model systems described in this paper POPULATION SYNTHESIS share a similar overall structure, with a hierarchy of levels from top to bottom, with the lower choices predicted con- All model systems simulate persons one by one and ditionally on higher-level choices. The levels are require a representative sample of households and persons for the base year and forecast years. All Population synthesis: geographic allocation of regions use zone-level data and forecasts of household households; size and income as control variables for sampling Longer-term decisions: auto ownership and (in households from the regional Public Use Microdata some cases) work and school locations; Samples households. In addition, most regions have Personhousehold day level: number of tours and used the number of workers in the household as a activities made for various purposes; third control variable, both because it is important 11