APPENDIX Committee Statement of Task

This project will gather information and determine the state of the practice of metropolitan travel demand modeling by metropolitan planning organizations and state departments of transportation. The practice of interest includes such features of travel modeling as

  • The size and scope of the transportation network and how it is represented;

  • Population, employment, and land use forecasts and travel surveys and how they are generated and input into the modeling process;

  • How key model details, such as trip purposes, are represented, including how light-duty and heavy-duty commercial vehicle travel are modeled;

  • The nature, extent, and justification of model adjustments to fit unique local circumstances;

  • How congestion on networks is represented and how it is used as an input to mode choice models;

  • Techniques and measures used in model estimation, calibration, and validation;

  • Postprocessing of travel demand modeling outputs to become inputs to emissions factor modeling;

  • Feedback and model iterations;

  • Induced travel demand;

  • Staff capability and resources; and

  • Unique conditions in individual areas.

The committee will commission a consulting firm to gather and synthesize information from MPOs and state DOTs. This work will be guided by the committee’s judgment about appropriate information to collect and how the information should be presented. The committee will further guide the



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APPENDIX Committee Statement of Task T his project will gather information and determine the state of the practice of metropolitan travel demand modeling by metropolitan planning organizations and state departments of transportation. The prac- tice of interest includes such features of travel modeling as • The size and scope of the transportation network and how it is represented; • Population, employment, and land use forecasts and travel surveys and how they are generated and input into the modeling process; • How key model details, such as trip purposes, are represented, includ- ing how light-duty and heavy-duty commercial vehicle travel are modeled; • The nature, extent, and justification of model adjustments to fit unique local circumstances; • How congestion on networks is represented and how it is used as an input to mode choice models; • Techniques and measures used in model estimation, calibration, and validation; • Postprocessing of travel demand modeling outputs to become inputs to emissions factor modeling; • Feedback and model iterations; • Induced travel demand; • Staff capability and resources; and • Unique conditions in individual areas. The committee will commission a consulting firm to gather and synthe- size information from MPOs and state DOTs. This work will be guided by the committee’s judgment about appropriate information to collect and how the information should be presented. The committee will further guide the 125

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METROPOLITAN TRAVEL FORECASTING Current Practice and Future Direction 126 consultant by recommending a taxonomy of area types with similar modeling needs, considering such factors as population size, modal complexity, special needs such as recreation and through travel, and air quality attainment status. The committee may recommend a sampling plan associated with this taxon- omy for data collection. The committee’s findings will address modeling in each area type, within the limitations of the data. In addition to overseeing the collection of information about current practice, the committee will respond to the following questions: a. What models do MPOs currently use or have under development? b. Are MPOs using multiple models for multiple purposes? c. What are key similarities and differences among MPOs in the develop- ment and application of models, and what factors are associated with these differences? Factors to be considered may be from the taxonomy developed by the committee or from other sources. d. Based on evidence collected by the consultant, what, if any, are the technical shortcomings in the models for their intended uses, such as technical analysis of the Transportation Improvement Program and the Long-Range Plan, emissions analyses, FTA New Starts analyses, and NEPA analyses? e. What, if any, are the obstacles to appropriate applications of the models? f. Any other questions or issues raised by the consultant’s reporting. Finally, the committee may identify actions needed to ensure that the appro- priate technical processes are being used for travel modeling.