The Washington State Department of Transportation (WSDOT) peer review was supported by the Travel Model Improvement Program (TMIP) sponsored by the Federal Highway Administration (FHWA). The objective of the WSDOT peer review was to seek background information and recommendations on how WSDOT should approach developing a statewide Washington travel demand forecast model. The information sought by WSDOT included:
The peer review panel was convened on July 1, 2014, at which seven expert panelists convened along with an amalgamation of WSDOT, both state and federal transportation representatives, and agency stakeholders. The peer review panel members included: Alan Horowitz, of the University of Wisconsin-Milwaukee, Keith Killough of the Arizona Department of Transportation, Becky Knudson of the Oregon Department of Transportation, Doug MacIvor of the California Department of Transportation; Subrat Mahapatra of the Maryland State Highway Administration, Ken Cervenka of the Federal Transit Administration, and Vidya Mysore of FHWA. Greg Giaimo of the Ohio Department of Transportation also provided commentary in written format.
At the beginning of the Peer Review session, each panelist provided a brief ten-minute presentation of their statewide or large-scale modeling experience at the request of WSDOT. The purpose of these presentations was to inform WSDOT of the state of the practice in statewide modeling, including information on data, model structure, and model applications, as well as the identification of the challenges to anticipate in large-scale model development.
WSDOT explicitly identified the following potential applications for a Washington statewide travel demand model:
Throughout the remainder of the one-day session, panelists provided responses to a list of questions crafted by WSDOT to further gather information on model development and possible applications. In the response to these questions and through additional discussion, the expert panelists provided an array of suggestions and recommendations for WSDOT to consider as they move forward with the development of their statewide model.
The panelists agreed that the first step WSDOT should take in the model development process is the creation of a list of statewide needs from the model and to prioritize this list based on which needs are immediate versus those that can be incorporated further down the line. Secondly, the panelists recommended that WSDOT identify a specific budget, schedule, and staff for the model development effort. The panelists recommended that WSDOT carefully consider schedule length and management's expectations when developing the budget. Panelists also underscored the importance of coordination with Metropolitan Planning Organizations (MPOs) in the model development process, as maintaining communication with regional agencies will be critical in this process.
One panelist recommended an initial model development timeline from 12 to 18 months, including staff time. The panelists collectively identified $1 million as a good starting figure for a more planning-level model that meets substantive validation requirements. It was also noted that this $1 million estimate did not include data acquisition and also that an additional $1 million would be needed for the incorporation of a full truck component.
The panelists suggested that WSDOT conduct a complete data inventory to identify all available data for application in the model and then to cross reference the available data to the identified analysis needs. After reviewing what data is available in relation to potential modeling needs, WSDOT can scope model development in phases relating to existing data and secondary data.
The panelists agreed that properly phasing the model development process would be imperative to building a successful and logical statewide model, and WSDOT should focus on the basic components of the model first. Panelists emphasized that simplicity is key in large-scale models, as is maintaining realistic expectations and managing uncertainty when developing a new model. Panelists stressed the importance of testing the model's sensitivity, particularly for extreme scenarios, in the model development process to assess how and which critical assumptions drive forecast results. The following bullets summarize the panelist recommendations for various statewide model components.
Moving forward with the information and recommendation accrued at the peer review, WSDOT will identify and prioritize their agency needs for the statewide model to create a model development plan that collaborates with MPOs, regional transportation planning organizations, state force, consultants, and academic professionals.
