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

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Suggested Citation:"T57054 txt_178.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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3. Effects of transportation system and system condition; 4. Need for improved validity and reliability; 5. Ability to evaluate policy initiatives; 6. Better analysis of freight movement; 7. Ability to show environmental effects; 8. Modeling low- share alternatives; 9. Better ability to evaluate effects on specific sub- groups; and 10. Reflect nonsystem policy changes (TDM, ITS). HIGH- INTEREST POLICY ISSUES These issues were boiled down in the vision process to keep the list short. More specific, high- interest policy issues in the Denver region include: • The Colorado Tolling Enterprise (CTE): Estab- lished 2 years ago by the state legislature, the CTE has been working to identify a set of corridors with the potential for toll facility establishment. The CTE has identified about six such corridors in the Denver area and is conducting an evaluation of these corridors, which is expected to be submitted to the regional planning process for inclusion in the regional plan. These efforts also have caused planners conducting several environ- mental impact statements in the region to take a harder look at toll options in their alternatives’ analyses. • The effects of MetroVision urban centers and other transit- oriented developments: Support of such develop- ment patterns is intended to foster a more balanced transportation system, reduce the number and lengths of trips, foster additional bicycle and pedestrian use, and so forth. The MetroVision 2030 update developed in 2004 included approximately 70 such centers, and the evalua- tion of the effects of these centers is a key aspect of the regional model’s usefulness. These will be evaluated again during the MetroVision 2035 process. • Effects of the MetroVision urban growth bound- ary: The extent of the urban growth boundary or area currently is set at approximately 750 sq mi for the year 2030, and the extent to which it may need to be expanded for 2035 will be a key part of the MetroVision 2035 process. • Reexamination of lower- density development, referred to as semi- urban: Issues include defining semi- urban, estimating how much of it there is, how much should there be, and its transportation and air quality effects. • The FasTracks ballot initiative of 2004: Passage of this initiative kicked off a project to build about 130 mi of rapid transit to all parts of the region by 2017. The ability to evaluate the effects of such a system will be critical over the next decade. • Air quality: As always, evaluation of the effects on air quality of various policy and transportation initia- tives will continue to be a key issue in regional planning. • Highway project planning: This also will continue to be a core focus of the planning process in the region. ACTIVITY- BASED MODELING APPROACH In addition to providing guidance concerning the needs that a new model must address, the vision phase vali- dated DRCOG planners’ initial impression that an activity- based modeling approach would best meet those planning analysis needs for the region. While it is clear that activity- based modeling as it can be imple- mented now cannot fully address all of the issues dis- cussed above, it is superior to conventional four- step modeling in many respects. DRCOG and its consultant team have concluded detailed design of an activity- based model, considering the region’s planning needs and resource constraints, and model development is now in progress. The activity- based modeling approach chosen by DRCOG is based on that used in the model developed for the San Francisco County Transportation Authority in 2000–2001, but includes enhancements informed by the capabilities of some of the activity- based models implemented more recently in other areas. The approach includes microsimulating the daily activity patterns of individuals in a synthetic population; determination of “regular” workplaces and school locations in relation to the home location; the modeling of the times of day, des- tinations, and modes of tours and trips; and the use of conventional static highway and transit assignment pro- cedures. The model design is described more completely by Cambridge Systematics, Inc., et al. (1). In general, the activity- based modeling approach would be expected to produce more accurate results for policy testing because it can consider a wider range of variables and interactions than a conventional trip- based model. Trip- based models tend to be relatively insensitive to many input data changes (such as transit- oriented, development- related land use changes) because they usu- ally do not include enough detail (geographic location, demographic variables, trip–tour relationships, and so forth) to permit them to respond fully to such changes. Trip- based model users often resort to adjustment factors to account for behavior that cannot be analyzed by these models, with varying degrees of reliability and success; activity- and tour- based models are expected to provide considerably improved forecasting for all types of policy analyses. Of course, the level of increased accuracy may depend on how much the analysis of the specific policy depends on the factors that are considered in the activity- based approach but not in the trip- based approach. 178 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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