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traffic forecasting capabilities at the workshop. These capabilities can be used to provide workshop partici- pants with immediate feedback on the traffic impacts of different plans and projects, as well as changes in specific elements of a proposed development or land use plan. This approach allows participants to see the conse- quences of different alternatives. ⢠Traffic models used in workshops must be able to provide realistic results within approximately 15 min- utes. Participants will lose interest if the process takes longer and most workshop schedules could not accom- modate more time. The 15-minute estimate includes all aspects of running the model, including data input, pro- cessing, and printing out or displaying the results. The model must be reliable and easy to use. The outputs should focus on a few key performance measures. Thus, simplified models are most appropriate for use in workshops. ⢠A traffic forecasting model was used to examine the impacts of land use changes in visioning workshops sponsored by the San Luis Obispo Council of Govern- ments (SLOCOG) in California. San Luis Obispo, located in the central coastal region, is a very environ- mentally sensitive area. The workshops were held as part of the 2050 visioning process. The main purpose of the workshops was to build awareness and consensus, not policy analysis. The general public was invited to the workshops, and numerous elected officials and planning commission members also attended. The discussions focused on alternative land use patterns to accommodate 180,000 new residents in the county. ⢠The goal of the traffic modeling portion of the workshops was to provide immediate feedback on the relationship between land use choices and traffic impacts. The traffic forecasting was conducted using a combination of geographic information system (GIS), Excel, TransCAD, Word, and PowerPoint software pro- grams. The output was presented in flow maps that showed traffic volumes and the volumeâcapacity ratio. The results were also presented in table format so partic- ipants could see the differences from the base condition. The whole modeling process took approximately 15 minutes. Changes made to the model to accommodate use in the workshops included using only daily forecasts and reducing the number of traffic assignment zones. ⢠Participants discussed the traffic forecasting results for different land use scenarios. Many participants were surprised to learn that land use location has a big impact on traffic conditions. Previous discussions had focused primarily on how much development would occur and how close it would be to specific individuals. The loca- tion of the development in the larger sense had not been addressed. The same number of jobs and households produced different traffic impacts depending on where they were located. Most of the scenarios proposed by participants focused on locating new dwelling units in the northern portion of the county and new jobs in the southern portion of the county. After participants under- stood the negative traffic impacts of these options, smart growth alternatives, with mixed- use developments and balanced land uses, became the preferred alternative. ⢠The use of the traffic forecasting model made the workshops more effective and enjoyable. It also strength- ened SLOCOGâs credentials in addressing land use issues. Feedback from participants, including the public and policy makers, was very positive. ⢠The Sacramento Area Council of Governments (SACOG) included traffic forecasting in workshops examining roadway and transit projects for the 25-year Metropolitan Transportation Plan. A consensus had already been reached on future land uses through the SACOG Blueprint Project. Workshop participants included the public, elected officials, and planning com- missioners. The goal of the traffic forecasting component of the workshops was to provide immediate feedback on the effectiveness of different transportation elements. ⢠In the SACOG workshop, the inputs were road and transit projects, which are more difficult to enter into the model. The model results are also more subtle, making it difficult to identify appropriate indicators. Participants were provided with a maximum funding level and a list of projects and roadway types. SACOG uses an older, more complicated travel model. For use in the workshop, the PLACE3s land use program was modified to display and manipulate the Cube/Voyager networks and to pre- pare the files for Cube/Voyager runs. Cube/Voyager was run with the PLACE3s shell and the outputs were dis- played using the GIS function. ⢠Use of the model added a great deal to the work- shops. Participants quickly learned that the available budget did not result in significant improvements to the transportation system. The elected officials learned that the public participating in the workshop supported new toll projects and additional river crossings. ⢠These two case studies highlight that traffic model- ing can be incorporated successfully into workshops. This approach requires a different type of model, however. Attempting to perform complex modeling quickly in front of an audience is inherently risky. It is important to prac- tice before using a model in a workshop and to have back- ups for hardware and software. Using travel forecasting models in the SLOCOG and SACOG workshops helped reveal a disconnect between public preferences and proj - ects that agencies felt the public wanted. It also provided the public and policy makers with a more realistic picture of the importance of different land use options. Susan Handy, University of California, Davis, moder- ated this session. 44 INNOVATIONS IN TRAVEL DEMAND MODELING, VOLUME 1
