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D E S I G N F E AT U R E S O F A C T I V I T Y- B A S E D M I C R O S I M U L AT I O N M O D E L S 17 been recommended for the Bay Area. However, in a wider of infrequent cases of walk escort. Furthermore, chil- sense, the final decision has not been made on the extent dren's school locations can easily be included as special to which the additional accuracy of explicitly modeling alternatives in the parents' escort tour destination choice household interactions will merit additional complexity. sets, so that at least the location is accurate, even if the For that reason, such models will not be included in the exact trip timing and car occupancy are not matched. Denver system, at least in the initial version. ALLOCATED ACTIVITIES DIVIDED EXPLICITLY ESCORT TRIPS LINKED EXPLICITLY ACROSS AMONG HOUSEHOLD MEMBERS HOUSEHOLD MEMBERS Certain types of activities, such as grocery shopping, Another type of joint travel, known as an escort trip, escorting, and some other maintenance chores, are likely occurs when two or more household members travel to be allocated across individuals in a household, show- together to or from (or both to and from) an activity ing a negative correlation across frequencies within a location but do not participate in the same activity there. household day. The Columbus and Atlanta model sys- The most common example is a parent driving a child to tems include explicit models of the generation of these school and then either returning home (an escort tour) or activities at the household level and then allocation to else driving on to work (an escort stop on a work tour). particular individuals. In the Atlanta case, this model Because these types of tours are partly joint and partly was estimated jointly with the model for household joint independent, it can be very complex to link them explic- travel generation. Compared with explicitly linking peo- itly across persons. For that reason, explicit modeling of ple who make joint tours together, predicting which peo- escort linkages has not been done in any of the applied ple within a household perform allocated activities models or recommended for the models under design. appears less important to the model results: nothing fun- Most of the models, however, do include a separate damental about the tours is being changed, only which escort purpose, so that the most important special char- person makes them. So, in relation to the tradeoff acteristics can be captured--particularly the fact that the between accuracy and complexity, these models seem mode is nearly always by automobile, with the exception less crucial than the joint travel models, and thus they Brief Note on FAMOS Florida Activity Mobility Simulator Ram Pendyala, University of South Florida T he Florida Activity Mobility Simulator (FAMOS) was completed in 2004 with a full-fledged devel- opment and application in southeast Florida. Since that in Florida. Final Report, Volume II: FAMOS Users Guide. Research Center, Florida Department of Trans- portation, Tallahassee, 2004. www.eng.usf.edu/~pen time, work has progressed to reengineer FAMOS and dyala/publications/report/FAMOS%20Users%20Guide integrate it with the land use model UrbanSim in con- .pdf. junction with an ongoing 3-year EPA project. Table 1 Pendyala, R. M., R. Kitamura, A. Kikuchi, T. Yamamoto, (page 12) compares model features of FAMOS and var- and S. Fujii. FAMOS: The Florida Activity Mobility Sim- ious models from other locations throughout the ulator. In Transportation Research Record: Journal of United States. the Transportation Research Board, No. 1921, Trans- portation Research Board of the National Academies, Washington, D.C., 2005, pp. 123130. REFERENCES Pendyala, R.M. Phased Implementation of a Multi- modal Activity-Based Travel Demand Modeling System