Section 3: Travel Demand Modeling
Anchor: #i1000350Overview
A Travel Demand Model (TDM) is a tool to support the urban transportation planning process. It is a series of analytical techniques used to predict future demand for transportation facilities and services and estimates the impacts of policies and program on behavior and travel demand. A TDM can predict how changes in size and character of the population will impact the transportation system in the future.
Federal regulations for Urban Travel Demand Modeling include 23 CFR 450 Planning Assistance and Standards; 40 CFR 51 Requirements for Preparation, Adoption, and Submittal of Implementation Plans; 49 CFR Transportation; 40 CFR 93 Determining Conformity of Federal Actions to State or Federal Implementation Plans, 122b&c; and 23 CFR 500 Management and Monitoring Systems.
Anchor: #i1000381Statewide Modeling Process
The Statewide Modeling Process includes development and implementation of travel demand modeling (TDM) as part of the Continuous, Cooperative, and Comprehensive (3C) planning process with TxDOT Districts and Metropolitan Planning Organizations (MPOs).
The state's development of urban travel demand modeling benefits 18 MPOs directly and 5 large MPOs indirectly. All MPOs receive support in data acquisition and travel surveys to support model development. All MPOs also have access to demographic support through TPP's IAC with the Texas State Data Center. And, MPOs have access to the Travel Demand Modeling Helpdesk and Travel Demand Modeling Dashboard coordination platform through TPP's TDM IAC. Five large MPOs develop travel demand models using in-house or contract staff. TxDOT participates in the 3C process with these MPOs including the review of the models developed, as appropriate.
MPOs gain the benefits from having access to standard programs, processes, and resources which TPP provides to support the development of MPO models. Model timelines are mutually agreed to by all parties. Schedule deviations are documented and schedules are adjusted within reason or additional resources are assigned to the projects. When models are updated a review of the previous models capabilities and challenges is undertaken, and the information is used to improve the process.
During the initiation of each model, TPP works with the MPO to define who is responsible for each step of the process. Typically, MPOs develop the locally specific input data, and TPP develops the models and trains staff in the use of the models. Then, the MPOs use the models for Metropolitan Transportation Plan development and project analysis. The breakdown in responsibilities for specific steps can vary between areas.
Anchor: #i1000406Statewide Analysis Model (SAM)
The Statewide Analysis Model (SAM) includes expanded coverage of its travel demand modeling to a statewide model that includes different passenger and freight modes and the interaction among those modes. SAM Version 4 (SAM-V4) has 2015 as a base year and 2050 as a horizon year.
Anchor: #i1000423Travel Survey Program
TxDOT obtains information on travel behavior from travel surveys and uses it to develop trip generation and trip attraction rates from each urban area. A typical travel survey in Texas contains a household survey, an establishment survey and external data analysis using passive data. Support is available for MPO or transit agency conducted surveys, i.e. on-board public transit surveys. In some nonattainment or near nonattainment areas, an air quality survey may be conducted.
TxDOT’s Travel Survey Program supplements internal efforts using InfoGroup data and National Household Travel Survey (NHTS) data.
The Texas Travel Survey Program complies with 23 CFR 500.
Anchor: #i1000447Demographic Assistance Interagency Contract
TPP Traffic Analysis provides information, training, and assistance to analysts and designated MPOs for the development of base and forecast year demographic data for input into TDMs or for use in transportation analysis.
Anchor: #i1000467TexPACK
TexPACK is an Integrated Travel Demand Modeling Application that includes a suite of TDM software incorporating trip generation and distribution techniques that are integrated into TransCAD travel demand modeling platform and takes advantage of inherent GIS capabilities.
The implementation of TexPACK increased the use of travel demand model applications by improving the application interface that creates a standard platform to create, apply and deploy models throughout the state. TexPACK also creates a common system for measuring and communicating results as well as permitting flexibility for enhancement.
Anchor: #i1000482Texas Travel Demand Modeling Dashboard
The Travel Demand Modeling Dashboard facilitates shared team management of the TDM development and application process and enhances communication, coordination, and collaboration. As an enhanced way of doing business, the Dashboard provides a tool for high level status and progress summary and review.
The Dashboard continues ongoing efforts to move towards statewide consistency, while providing project management and oversight as well as cultivating team-level ownership and responsibility.
Anchor: #i1000497Help Desk Assistance
Assistance can be reached at TPP-TRANSCAD-HELPDESK@txdot.gov or by calling 512-486-5177.
Anchor: #i1000507Reference Materials
TexPACK TDM Application Guidebook
TxDOT TDM Application Guidebook
Network and Zone Editing Guidebook
Demographic Development Guidebook
Pre-STARS II Count Annotation Guidebook