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Vermont Agency of Transportation (VTrans) Statewide Travel Model Peer Review Report

5.0 Technical Questions Provided by the Vermont Agency of Transportation

The first peer review meeting was held virtually on June 5, 2013. At this meeting, VTrans and the TRC provided background information on the Vermont statewide model, further articulated their ideas for potential model improvement components from the initial vision described in Section 4.1, and presented questions to the panelists regarding the following areas of interest to lead the initial peer review meeting's discussion:

VTrans also noted their desire for the panelists to identify additional areas for improvement or specific areas for attention regarding the model's structure and functionality that would be beneficial to the agency in the development of an enhanced model. This section outlines each of VTrans's technical topics for discussion, as they were presented in the peer review.

5.1 Response to FHWA Identified Issues

In a review conducted by FHWA staff, various issues regarding the structure and operations of the current model were identified as priority areas for VTrans to address in their model enhancement efforts. FHWA's comments included the following:

VTrans provided FHWA's detailed comments to the peer review panelists for review prior to Session #2 so they could assess the recommendations and elaborate on specific topics as appropriate.

5.2 Resiliency Planning

As a response to Hurricane Irene and its significant damage to the state's transportation infrastructure, resiliency planning has become a major focus at VTrans, with an emphasis on infrastructure design. VTrans would like to utilize the statewide model as a means for resiliency planning and requested more information from the panelists as to potential related performance measures that can be estimated by the model for this purpose.

5.3 Evaluation of Energy/Emission Goals

In their long-term planning effort, Vermont established statewide energy use and emission reduction goals, which include the following:

VTrans would like advice from the expert panel as to how the statewide model can be applied as a tool for the monitoring and evaluation of the state's progress towards these energy and emissions targets from now until 2030.

5.4 System Preservation and Disinvestment

Highway system preservation is becoming an increasingly dominant force driving operations and studies at VTrans. Highway capacity projects will remain critical to the agency's workload, but this large shift to maintenance projects calls for new methods of highway facility assessment. Through the peer review sessions, VTrans would like to obtain insight regarding the potential for the statewide model to measure system preservation performance and possible disinvestment strategies.

5.5 Performance Measurements and Asset Management

Performance-based planning and programming are a core component of the MAP-21 requirements signed into law in July of 2012. In response to this legislation, VTrans would like to know how application of the statewide model can aid in the development and monitoring of performance measures for future year planning. Specifically, VTrans was interested in determining the model's ability to play a role in the development of an asset management system.

5.6 Fair-Share Methodology

VTrans is in the process of developing a fair-share methodology aimed at ensuring that developers pay for the proportional impact triggered by their development. VTrans would like to learn more regarding the potential of the statewide model to contribute to the development and implementation of a fair-share methodology.

5.7 Corridor Prioritization: Transit, Biking, and Walking

Bicycling, walking, transit, and rail are important components of Vermont's transportation system. However, some of these modes, particularly bicycling and walking, are inherently local modes of travel. VTrans requested that the panel identify the appropriate modeling scale for corridor improvement prioritization for each of these modes.

5.8 Model Areas for Improvement

Through the discussion of the model's structure and the analysis of the topics provided above, VTrans anticipated additional identification of potential improvements for the statewide model, both on a general level as well as from a more detail-oriented view. These topics were highlighted in the initial peer review meeting and then used at points for discussion in Session #2. These areas for improvement included the following:

Non-Home Based Travel: VTrans suggested further examination and assessment of the assumptions regarding non-home based travel.

Land Use Forecasting: VTrans currently does not have a standard source for growth forecasts and requested further information with regard to information sources for both population and household growth. VTrans also requested feedback regarding the practice of capping minimum household growth rate at 0.0% rather than allowing for negative growth.

Transit Inclusion Feasibility: The current statewide model does not support transit modes. Therefore, VTrans would like to assess the feasibility of including transit fully in the statewide model. The agency would like to determine the reasonability of including only certain types of regional transit or recognize if it would be more logical to exclude transit. VTrans also questioned the possibility of reflecting hourly variations in transit ridership using the statewide model, which only includes daily temporal resolution in its existing form.

Short-Distance and Long-Distance Travel: The current statewide model does not have the ability to effectively disaggregate the short and long distance trips. VTrans indicated a need for more information and resources regarding which trip purposes and modes are critical in the separation of distance categories and the best methodologies for this distinction.

Vehicle-Ownership Models: VTrans asked the panelists about the effects of vehicle-ownership models on VMT estimation and household-level travel forecasting. VTrans cited that the Travel Model Validation and Reasonableness Checking Manual provides guidelines for using vehicle ownership/availability as a validation process. The agency asked the panel if these guidelines would be a logical starting point for the development of a vehicle-ownership model, as well as the quality of household level income data required for application in the vehicle-ownership model.

Economic Modeling: VTrans noted that the incorporation of an economic model would help the model to yield more effective assessments of economic impacts. The agency questioned the variation in aptitude between an economic model with a travel component versus a travel model with an economic component. VTrans also cited NCHRP 735, which states that small samples and economic models are unable to provide significant statistical representation to prioritize capital investments or gain a deeper understanding of travel decision price breakpoints.

Long-Distance and Rural Trip Generation: VTrans identified several issues regarding best practice for generating long-distance and rural trips in a statewide model. These issues included the following:

VTrans expressed interest in identifying short-term needs that could be addressed in the near term given existing resources. VTrans also expressed a desire to develop subsequent recommendations for mid- and long-term modeling needs in order to maintain a continuous and on-going model improvement effort.

Updated: 03/28/2014
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