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Innovations in Travel Demand Modeling, Volume 2: Papers (2008)

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Suggested Citation:"T57054 txt_024.pdf." National Academies of Sciences, Engineering, and Medicine. 2008. Innovations in Travel Demand Modeling, Volume 2: Papers. Washington, DC: The National Academies Press. doi: 10.17226/13678.
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24 The San Francisco Model in Practice Validation, Testing, and Application Maren L. Outwater, Cambridge Systematics Billy Charlton, San Francisco County Transportation Authority The San Francisco County Chained Activity Model-ing Process (SF- CHAMP) was developed for the SanFrancisco County Transportation Authority (SFCTA) to provide detailed forecasts of travel demand for various planning applications (1). These applications included developing countywide plans, providing input to microsimulation modeling for corridor and project- level evaluations, transit planning, and neighborhood planning. The objective was to represent accurately the complexity of the destination and the temporal and modal options and to provide detailed information on travelers making discrete choices. These objectives led to the development of a tour- based model that uses synthe- sized population as the basis for decision making rather than zonal- level aggregate data sources. Most of the tour- based model’s nine components were estimated by means of household survey data for San Francisco, California, residents only that were collected by the Metropolitan Transportation Commission (MTC). Each model component was calibrated by using various observed data sources, and then the full model was validated with traffic count and transit ridership data for each of five periods. The model is applied as a focused model that combines trip making from the entire Bay Area (derived from the MTC’s BAYCAST trip tables) with the travel demand from San Francisco residents produced by the tour- based model. ORIGINAL APPROACH AND LIMITATIONS Modeling Process The main feature of the full- day pattern approach is that it simultaneously predicts the main components of all of a person’s travel across the day. This approach includes the frequency of five types of tours: • Home- based work primary tours, • Home- based education primary tours, • Home- based other primary tours, • Home- based secondary tours, and • Work- based subtours. A home- based tour includes the entire chain of trips made between leaving home and arriving back at home. The primary home- based tour is defined as the main home- based tour made during the day. If a worker makes a work tour or a student makes an education tour, then that is always the primary tour. If there are no work or education tours, the primary tour is the tour with the highest- priority activity at the destination (shop- ping–personal business followed by social–recreation followed by serve passenger). If there are two or more tours with the same activity priority, then the one with the longest duration of stay at the destination is the pri- mary tour. All other home- based tours are designated as secondary tours. A special type of tour is a work- based subtour, defined as the entire chain of trips made between leaving the primary workplace and returning to that workplace in the same day. By using tours as a key unit of travel, the interdependence of different activities in a trip chain is captured. This method provides a better understanding of non- home- based trips, especially in the case of the work- based subtours that represent a signifi- cant proportion of non- home- based travel. The study area for the model is the nine- county San Francisco Bay Area, which is represented by the MTC’s regional travel demand forecasting model, BAYCAST. The study area is divided into two parts, so the San Fran-

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TRB Conference Proceedings 42, Innovations in Travel Demand Modeling, Volume 2: Papers includes the papers that were presented at a May 21-23, 2006, conference that examined advances in travel demand modeling, explored the opportunities and the challenges associated with the implementation of advanced travel models, and reviewed the skills and training necessary to apply new modeling techniques. TRB Conference Proceedings 42, Innovations in Travel Demand Modeling, Volume 1: Session Summaries is available online.

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