Thurston Regional Planning Council (TRPC) Travel Model Peer Review Report
5.0 Topics of Interest to Thurston Regional Planning Council
Prior to the peer review, TRPC issued two Requests for Qualifications (RFQs) for modeling support, one for a model developer and one for a model consultant. TRPC intends for the model developer to co-locate with TRPC staff to carry out a comprehensive update to the region's travel model under the direct management of the TRPC project manager and with the support and advice of the model consultant. The RFQs specify a draft scope for the model update work. That draft work scope, the TRPC application for a TMIP peer review, and materials prepared and presented by TRPC staff to the peers together identify the issues driving the model update and its potential work tasks.
This section of the report blends the materials listed above to set a detailed context for the specific TRPC questions and panel responses following in Sections 6 and 7. The intent here is to organize stated TRPC modeling interests in a framework easily recognizable to a modeler for quick identification of the model and data features on which TRPC planned to focus the most attention. Each subtopic within this section describes the stated TRPC interest and indicates the scope of the peers' response. Actual peer responses follow in Section 6. This section also includes topics about which TRPC did not originally express interest but which the panel concluded deserved attention.
5.1 Overall Modeling Framework
Geographic Extent and External Travel
The highest TRPC model update priority is to appropriately treat travel to and from the PSRC region to the north, especially in the I-5 corridor and for travel to and from Joint Base Lewis-McChord (JBLM). Prior to requesting this peer review TRPC had already concluded that this would entail expanding the geographic coverage internal to its travel demand model with both additional TAZs and additional network details. The question of geographic coverage creates implications for almost every other model update task; the panel spent considerable time discussing and making recommendations on this topic.
TRPC's original draft scope of work includes coefficient re-calibration "in all stages of the model"
plus appropriate general re-calibration and re-validation. The geographic expansion of the model already mentioned will create additional demands upon the trip generation components, their update, and the necessary supporting data. The panel discussion touched in several ways upon these needs.
- Trip Distribution/Destination Choice
- Similar to the update of trip generation, TRPC intends to re-calibrate trip distribution (currently a multinomial logit destination choice model). Similarly to trip generation, the necessary geographic expansion of the model will impinge upon the updates needed in destination choice and its supporting data. The panel made several suggestions on this topic.
- Mode Choice Model
- The TRPC region needs to analyze vanpoolers/carpoolers who rendezvous at Park and Rides to access their shared-ride vehicles.The agency would also like to improve its capabilities for modeling fixed-route transit and to ensure that walk and bike access to transit are treated appropriately to avoid distorting the model's overall transit response. The panel offered some observations on how these needs create potential additional update considerations beyond a general coefficient recalibration in mode choice.
- Network Characteristics and Assignment
- TRPC has several interests in updating the network component of its travel model. First, modeling travel flows well in all modes along the I-5 corridor and to/from JBLM is a high priority, even in areas outside the official TRPC planning area. Second, the region has policies in place that focus transportation investments--especially on arterials--on system and demand management techniques rather than capacity expansion. Third, the region is contemplating geometry-specific strategies including hard shoulder running, managed lanes, priced managed lanes, and congestion pricing as potential components of an overall system management approach. Fourth, the geographic expansion of the model will create a need simply for more network links and coverage. Finally, TRPC perceives that this update is an opportunity to ensure that the model representation of network characteristics (lanes, capacities, speed limits, etc.) is as up-to-date as possible for its new base year. The panel's recommendations touch on these interests in a variety of ways.
- Temporal Detail
- TRPC expressed an interest in expanding its model's current three peak-hour assignments (AM, midday, and PM) to period assignments (multiple hours each) with the goal of being able to model congestion effects such as peak spreading. While by itself this objective is sufficient to justify examining the model's time-of-day capabilities, other agency priorities including pricing analysis, demand management analysis, and system management analysis add impetus to updating time-of-day estimation. The panel offered several suggestions on this topic.
- While TRPC's explicitly-stated interests did not include feedback aspects of the model, several of its priority analysis needs (e.g. pricing, time-of-day response) justify examining the opportunities for updating feedback mechanisms to enhance the model's sensitivity. Some of the panel's remarks identify such opportunities.
5.2 Modeling Framework Specific To Transit
- Special Modes
- The Thurston region has a significant number of vanpool and carpool travelers who use Park and Ride lots as rendezvous points. The panel made a suggestion on how these could be treated in the updated model.
- Access to Transit
- TRPC, especially given a policy commitment to treating all transportation modes, wants to ensure that its model is representing access modes to transit appropriately. The panel offered several recommendations on this topic.
5.3 Modeling Framework Specific to Freight
- Trucks--Trip Generation and Distribution
- Given that the Thurston region has attracted a number of freight distribution centers and also has the Port of Olympia (to which a majority of trips are log export-related), it has an interest in a "high level"
freight model update, primarily focused on truck travel. The panel offered a series of observations on freight modeling predicated on the understanding that "high level" means less costly. Potential updates to the model's freight elements could affect both truck trip generation and truck trip distribution.
5.4 New and Existing Data Sources
- Travel Surveys
- TRPC plans to commission a new travel survey to commence in fall 2012 for support of its model update. It therefore has a keen interest in ensuring that the survey is well-designed and is coordinated with its overall model update plan. The geographic expansion of the model area, the presence of JBLM, and extensive interregional travel all create special considerations for the survey. TRPC posed many questions about the survey and the panel responded in some detail.
External Origin-Destination Surveys
- The importance of what are now treated as external trips to the TRPC region is such that TRPC conducted a new external trip origin-destination survey in 2010. This will provide valuable insights for the model updates.The panel made additional data-related recommendations on this topic.
- Transit Data
- TRPC is interested in having robust transit analysis capabilities in its model and in regular updates to the model base year. It expressed curiosity about transit data sources that it should maintain in-house for these purposes and what other data might be necessary to support appropriate representations of bike/walk access to transit. Note that the region is fortunate that its sole internal transit provider has a robust Automatic Passenger Count (APC) system. The panel addressed these topics and added a recommendation regarding a transit on-board survey.
System Characteristics and Performance Data (including Network, Traffic Counts, Speeds, and others)
- The scope of TRPC's planned model updates is such that it has a natural interest in up-to-date observed system data both in terms of system characteristics and system performance. Given partnerships with local agencies and WSDOT, TRPC will have reasonably robust roadway data available in its new base year (2012); as mentioned above it will also have useful transit ridership information. The panel did not explicitly address these specific data aspects, but its other recommendations implicitly assume a reasonably robust set of this "foundation" data.
- Aside from its general interest in high-level freight model enhancements TRPC preparatory material did not explicitly mention new freight data. Even a high-level approach to truck modeling, though, requires a certain minimum amount of data with which to work-this gives the agency a natural interest in obtaining new freight data and the panel made a suggestion in this regard.
5.5 Integration with Simulation and Dynamic Traffic Assignment (DTA) tools
With its system-management-oriented policies TRPC has a strong interest in analysis capabilities that provide more operational and temporal detail than the demand model. Indeed, the agency has already developed a DTA model for its "Smart Corridors" project involving two bisecting corridors that converge in downtown Olympia. TRPC intends to enhance its DTA capability for a number of reasons including its preference for operational/management strategies and its need to support more locally-driven studies. The panel made a series of recommendations on this topic.
5.6 Other Panel Observations/Recommendations
Section 6 below lists the explicit TRPC questions posed to the panel along with the panel's responses. As is often the case in model peer reviews, though, the draft scope of model update work and accompanying explicit questions do not necessarily cover all points necessary for the panel to make a complete and consistent set of recommendations. Section 6 therefore includes these extra topics under the heading to which they most logically apply and also lists them for quick reference under their own separate heading, 6.6, for easy identification.
5.7 Model Application Discussion
It is worth concluding this section's discussion of TRPC's modeling interests with a brief overview of the applications TRPC intends for its updated model.The panel recommendations were made with the clear understanding that the updated model will be used to:
- Evaluate and Prioritize I-5 Mobility Alternatives
- Support a Transit Alternatives Analysis
- Conduct operational analysis of key travel corridors, including the evaluation of demand management techniques, access management strategies, and land use policy/investment strategies
Conduct forecasting for Regional Transportation Plan updates
Conduct air quality conformity analyses
- Support the development and application of regional transportation performance measures
Support sustainable/livable communities analyses
Support state- and locally-sponsored studies (it is important to note that all agencies within the TRPC region use the TRPC model, or start with the TRPC model, for their studies), including:
- Traffic Impact Analyses
- Concurrency Demonstration
- Interchange Justification Reports (IJRs)
- Transit System and Park-and-Ride planning
- Local comprehensive plan updates.
REQUEST FOR QUALIFICATIONS #2 - TRAVEL DEMAND MODEL CONSULTANT Thurston Regional Planning Council (TRPC) Travel Demand Model Enhancements April, 2012. p. 3.
TRPC Application for a TMIP Peer Review. 2012. p.5.