I-66 Multimodal Study Final Report - Virginia Department of ...

Multimodal PackagesModel Process for Testing Multimodal PackagesAs described in Section 2.2, the earlier technical analysis conducted for the mobility optionsutilized an abbreviated model approach that did not include a feedback loop in the modelingprocess. For the multimodal package testing, the full model process was used. Figure 3.1shows an overview of the full modeling process, including a feedback loop to trip distributionand trip generation. The feedback loop allows for congestion on the transportation network tobe incorporated into travel decisions. Congestion on the network can impact the distance a triptravels, the mode of travel, and the path taken. Incorporating the feedback loop impacts theorigin and destination, mode choice, and, ultimately, the travel path selected as part of theassignment model.The full model included running a “pump prime” iteration which is completed to develop basecongested speeds. The “pump prime” iteration is followed by four full iterations of the model.For the package assessment phase, full model runs of the regional travel demand forecastingmodel were conducted, including all of the feedback loops resulting in the final fourth iterationtrip tables and loaded transportation networks. Lead Agency and PARC input was reflected inthe modeling details and each package was coded into the TPB Version 2.3 travel demand forecastingmodel and a forecast was generated. As with the mobility option analysis inSection 2.0, the results focus on comparisons between the CLRP+ Baseline scenario and eachpackage.Limitations of the regional travel demand forecasting model necessitated the adoption of offmodeltechniques to evaluate the Integrated Corridor Management, Transportation DemandManagement, and bicycle/pedestrian system components of each multimodal package.I-66 Multimodal Study 3-5