Vermont Agency of Transportation (VTrans) Statewide Travel Model Peer Review Report
4.0 Model Improvement Plan
VTrans is in the process of planning and prioritizing updates for statewide model enhancement. This section summarizes the preliminary stages including identification of agency needs and subsequent model development needs.
4.1 Vermont Agency of Transportation Visioning for Model Improvements
Priorities for implementation are particularly sought by VTrans, as well as a path and process for continued improvement over the next several years. Some of the specific improvements that VTrans and the TRC are considering, as defined in their peer review application and initial model background presentations, include:
- Investigating the potential use of the results of the 2010 Vermont Trip Generation Manual for calibrating or updating the trip-generation sub-module;
- Investigating the need for calibrating or updating the traffic assignment sub-module with speed/density curves derived from speed data logged by weigh-in-motion (WIM) stations and road-weather information system (RWIS) stations;
- Exploring the need for a seasonal component including, at a minimum, an average winter day, an average summer day, and an annual average day;
- Developing a freight module based on the method and guidance provided by Sorrantini and Smith (2000) consisting of commodity flows between counties, out of the state, and into the state, with a coordination of these flows and the truck volumes which are currently in the model at the TAZ level;
- Improving road-network level of detail to get more refined estimates of travel speeds, vehicle-miles of travel, and emissions;
- Refining in the temporal resolution of the model to include a peak hour along with the current daily travel estimates;
- Incorporating of a tourist-travel component to the model to better estimate the trends in visitor travel to Vermont;
- Development and tracking of parking supply in the state for improved estimation of travel on major corridors;
- Improvements in the multi-modal aspects of the model to include passenger rail, bus transit, and airline travel, as is typical for a statewide model;
- Feedback between modeling steps, specifically traffic assignment and trip distribution;
- Roadway grade and pavement type for the model's highway network links to help in speed and emissions modeling;
- Applying a square-footage base for trip-generation; and
- Disaggregating NHB trips into 'Non-Home Based Business' and 'Non-Home Based Personal.'
In addition to the modeling visions described in the section above, VTrans is interested in how the model can be advanced to inform specific desired planning outcomes, particularly in areas where obstacles exist with respect to desired outcomes. The strategic challenges described in the agency's considerations in model development include:
- Aging and damaged infrastructure;
- Changing demographics and economy;
- Land use;
- Stagnant and declining transportation fund revenues;
- Energy constraints;
- Climate change, extreme weather events and associated impacts to infrastructure and the environment;
- Freight movement and trade globalization;
- Security needs and issues; and
- Resiliency to a changing world.
