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ment of Transportation (CDOT), the FasTracks rapid transit ballot initiate, and DRCOGâs MetroVision Plan. ⢠DRCOG conducted the IRM vision phase to ensure that the new model would address the Denver Region MetroVision Plan. The vision phase included an evalua- tion of other advanced modeling projects in North Amer- ica and Europe. A panel composed of modeling experts, regional planners and engineers, and regional policy mak- ers provided guidance throughout the model develop- ment process. The vision phase identified the top 10 core planning issues that the travel demand model should sup- port. These core planning issues included (a) the effects of development patterns on travel behavior, (b) the sensitiv- ity to price and behavioral change, (c) the effects of the transportation system and system condition, (d) improved validity and reliability, (e) the ability to evalu- ate policy initiatives, (f) better analysis of freight move- ments, (g) the ability to evaluate environmental effects, (h) the ability to model low- share alternatives, (i) an enhanced ability to evaluate the effects on specific popu- lation subgroups, and (j) the ability to reflect intelligent transportations system and transportation demand man- agement and other nonsystem policy changes. ⢠The CTE, which was established by the state legis- lature within CDOT, has been analyzing corridors in the Denver area for potential toll facilities. Six possible cor- ridors have been identified to date. The need for a new activity- based model to analyze toll facilities was identi- fied as important in the IRM vision phase. Toll options are also being considered in several environmental impact statements under way in the region. ⢠The FasTracks ballot initiative, which was approved by voters in 2004, includes approximately 130 miles of rapid transit. The FasTracks projects are sched- uled to be completed by 2017. The ability for the new model to evaluate the impacts of the FasTracks system was identified as important in the IRM vision phase. ⢠The ability to analyze the effects of the MetroVi- sion Urban Growth Boundary was also identified as an important feature for the new model. Approximately 750 square miles are included inside the 2030 urban growth boundary. The need to expand the boundary to accommodate forecast growth will be examined as part of the MetroVision 2035 process. ⢠There is also a need to model the effects of the MetroVision urban centers and transit- oriented develop- ments, which are intended to foster a more balanced transportation system. The MetroVision 2030 plan includes approximately 70 centers. Other needed model capabilities include the ability to assess air quality and environmental impacts, as well as lower-density develop- ment patterns and traditional highway projects. ⢠Activity- based models would be expected to pro- duce more accurate results for policy analysis because these models are able to consider a wider range of vari- ables and interactions than conventional trip- based models. Trip- based models tend to be relatively insensi- tive to many input data changes and do not include enough detail to respond fully to these changes. Activity- based models are expected to provide improved fore- casting for various types of policy analysis. ⢠One advantage of activity- based models is that mod- eling individuals in the synthetic population allows for dis- tributed values of time rather than fixed values for a relatively small number of market segments. For example, if the value of time is $12 an hour for a specific geographic market to find using a toll road desirable, and the average value of time for that market segment is $10 an hour, the model would estimate that no one from that market seg- ment would use the facility. If value of time distribution were used with an average value of $10 an hour with a 20% probability of having a value of time greater than $12 an hour, there would be demand estimated for the market segment. Demand for toll roads with tolls varying by time of day can also be modeled more accurately. ⢠There are also benefits to modeling travel to urban centers and transit- oriented development from use of the proposed activity- based approach. Activity- based mod- els permit descriptions of individuals using a richer set of variables than traditional models. The tour- based approach also captures the effects of trip chaining. Dis- aggregate models can accommodate more demographic variables than traditional models. ⢠The proposed activity- based approach appears practical. It greatly enhances sensitivity to tripâtour interactions and provides improved demographic detail, geographic detail, and interaction between model components. There are some limits with the pro- posed approach, however. A conventional static traffic assignment process will be used. The lack of a fully dis- aggregate or at least a dynamic traffic assignment pro- cedure will limit the ability to analyze the effects of traffic queuing and variations of traffic flow within peak periods. Even with these limitations, the new model will greatly enhance travel forecasting in the Denver area. HARDWARE REQUIREMENTS AND RUNNING TIME FOR THE MID- OHIO REGIONAL PLANNING COMMISSION TRAVEL FORECASTING MODEL Rebekah Anderson, Zhuojun Jiang, and Chandra Parasa Rebekah Anderson discussed the model formulation, the hardware requirements, and the running times for the Mid- Ohio Regional Planning Commission (MORPC) disaggregate tour- based travel model. Volume 2 includes 56 INNOVATIONS IN TRAVEL DEMAND MODELING, VOLUME 1
