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

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Suggested Citation:"T57054 txt_160.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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tory dependency in time allocation and activity partici- pation, in- home versus out- of- home activity substitution and generation, induced demand, and travel efficiency (say, through chaining of trips) are but a few of the con- cepts that merit recognition. • Behavioral processes and decision rules: Recent work in activity–travel modeling has focused on the behavioral processes and decision- making rules that peo- ple employ when scheduling and executing activities and trips. Rule- based heuristics, in addition to random utility theory- based models, are being incorporated into mod- els to reflect these behavioral processes in microsimula- tion frameworks. Understanding behavioral processes is key to developing robust model structures, specifica- tions, and forms. Comparisons Between Model Systems The discussion so far has dwelled on how one might assess the performance of an activity- based travel demand model system. However, the following questions remain: 1. How does one know or determine whether the activity- based travel demand model is giving the right answer or level of sensitivity for a particular scenario? 2. In comparing the outputs (in response to a scenario analysis) between an existing four- step travel demand model and an activity- based travel demand model, how does one know or determine which one is right or more accurate (in cases in which it is not obvious)? CONCLUSIONS AND CONTENT OF PRESENTATION This white paper raises important questions regarding the potential adoption of new and innovative activity- based travel demand modeling systems in practice. The proposed presentation serves to deliver the following information with a view to stimulate discussion among conference participants on how best to validate and assess activity- based model systems vis- à- vis existing four- step models: 1. Model validation guidelines for activity- based travel demand models including information on what base- year traffic conditions activity- based travel demand models should replicate, the margins of error that are acceptable, and the extent to which adjustments of model components and parameters are acceptable; 2. Model assessment guidelines for activity- based travel demand models including the range- of- sensitivity tests, policy measures, land use scenarios, and technolo- gies to which the activity- based models should be sub- jected, the model outputs that should be examined, and the acceptable ranges of responses in model outputs; 3. Model comparison guidelines for comparing activity- based travel demand models with existing four- step travel demand models including the development and presentation of a comprehensive matrix that clearly shows how and where four- step models, tour- based models, and activity- based microsimulation models are applicable to addressing a range of issues; and 4. The design of comprehensive experiment(s) for performing controlled comparisons of activity- based travel model outputs and existing four- step travel model outputs. A variety of scenarios have played out in the real world, thus providing real- world data against which model predictions can be assessed. Both activity- based and existing four- step travel models can be applied to these situations and the outputs can be assessed against real- world observational data. The presentation will also include results of model validation and assessment exercises that have been undertaken using the Florida Activity Mobility Simula- tor and Comprehensive Econometric Microsimulator of Daily Activity Patterns to illustrate how the guidelines presented can be used to assess and validate activity- based travel demand models. 160 INNOVATIONS IN TRAVEL DEMAND MODELING, VOLUME 2

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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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