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THE SAN FRANCISCO MODEL IN PRACTICE 25 cisco tour-based model can be used to predict travel by Limitations of Approach San Francisco County residents, while the BAYCAST model can be used to predict travel by residents from the There were a few limitations of this approach that were other eight counties. a result of the available time and resources of the project: Figure 1 presents a schematic diagram of SF- CHAMP. This diagram includes the model components Initially, there was no onboard survey data avail- and data inputs for these components. A synthesized able for validation of the mode choice model. There was population of San Francisco residents is input into each a discrepancy between the U.S. Census journey-to-work model component to estimate choices for work loca- data and the observed transit boarding data; this dis- tion; vehicle availability; and tours and trips by time of crepancy could not be resolved without the additional day, destination, and mode of travel. The synthesized onboard survey data. These onboard survey data were tours and trips are aggregated to represent flows collected in the spring of 2006 and are being used to between traffic analysis zones before traffic assignment. update the mode choice model now. A separate model of visitor travel is estimated so as to The resources for the peak-spreading model were incorporate trips made by tourists and business travel- limited in the original project, and, as a result, a peak- ers visiting San Francisco County. The model system spreading model was transferred from the MTC rather also incorporates trips made by non-San Francisco resi- than estimated for San Francisco. This transfer did not dents by merging regional trip tables into the process for produce reliable results and was not used in any plan- assignment. ning applications. Subsequently, the FHWA funded a Population Zonal Data Synthesizer Person Records All Models Workplace Vehicle Availability Location Model Model Full-Day Tour Accessibility Pattern Models Measures Time of Day Models Logsum Variables Nonwork Tour Network Destination Choice Level of Service Models Logsum Trip Diary Records Variables All Remaining Models Tour Mode Choice Models Intermediate Stop Visitor Trip and Choice Models Destination Choice Model Regional Trip Tables for NonSF Trip Mode Choice Visitor Trip Mode Trips Models Choice Model Trip Tables Transit Highway Assignment by Assignment by Time Period (5) Time Period (5) FIGURE 1 Model components.