Transportation

Model Documentation

COG staff develops, maintains, and improves, with some consultant assistance, a series of regional travel demand models that are used for the regional transportation planning process in the metropolitan Washington region. These regional travel demand models are developed under the guidance of the Travel Forecasting Subcommittee (TFS), which is a subcommittee of TPB's Technical Committee. At any given time, staff maintains at least two regional travel demand models: one or more production-use models and one or more developmental models. The production-use model is the one that is used for planning studies conducted by COG/TPB and is made available to outside parties for their use. If a production-use model has been used in an official COG/TPB study (such as an air quality conformity study of the Long-Range Transportation Plan), then it is designated as “adopted.” Developmental models are considered "works in progress," and are, consequently, not generally made available to outside parties. See our Data Request page for more details.

The TPB regional travel demand models are divided into two major groups or families:

  • Generation 2 (Gen2): Aggregate, trip-based travel demand models, often known as “four-step" models.
  • Generation 3 (Gen3): The TPB’s next-generation travel demand model, which is that is currently under development, and is designed to be a disaggregate, activity-based model (ABM).

The Gen2 family of models includes both production-use models (such as Ver. 2.3.78, Ver. 2.4, and Ver. 2.4.6) and developmental models (such as Ver. 2.4_PT). Only a subset of developmental models will eventually be deemed fit for production use. The Gen3 Model is currently a developmental model, being developed with consultant assistance between FY 20 and FY 24. The planned model form for the Gen3 Model is a simplified activity-based travel model (ABM).

Version naming convention: The TPB Regional Travel Demand Model is generally given a version number, which may have three parts: X.Y.Z. The first number represents major changes to the model. The second number represents more modest updates to the model. And the third number, sometimes called “build” is used to indicate smaller changes to the model, including bug fixes.

Current Production-Use Travel Models

TPB staff currently offers two production-use versions of the TPB regional travel demand forecasting model: Gen2/Ver. 2.4 Model and Gen2/Ver. 2.4.6 Model. The Gen2/Ver. 2.4 Model became the TPB’s adopted, production-use regional travel demand model for the metropolitan Washington region in June 2022 since it was used for Air Quality Conformity (AQC) analysis of the 2022 update of the Long-Range Transportation Plan (LRTP), known as Visualize 2045. By contrast, the Gen2/Ver. 2.4.6 Model is deemed ready for production-use, but it has not yet been used in an AQC analysis, which means that it has not been implicitly adopted by the TPB.  Staff plan to use the Ver. 2.4.6 Model, or its derivative, in the upcoming AQC analysis, known as Visualize 2050, which the TPB will review and possibly adopt in June 2025.

The Gen2/Ver. 2.4.6 Model was derived from the Gen2/Ver.2.4 Model. Both models are members of the Generation 2 (Gen2) family of travel models. The Gen2/Ver. 2.4.6 Model was released [FX1] [RN2] for production use on July 21, 2023. The Gen2/Ver. 2.4.6 Model transmittal package available to stakeholders includes the input data from the 2022 update of Visualize 2045, i.e., both the network inputs and Round 9.2 Cooperative Forecasts of land use.

Compared to its predecessor (Ver. 2.4 Model), the Ver. 2.4.6 Model has the following updates:

  • Migration of the transit walkshed process from ArcPy to GeoPandas.
  • Migration of the mode choice process from AEMS to TRANSIMS ModeChoice.
  • Updated the local bus speed/runtime degradation process. The updated process looks up the bus factors for both the current CPI year and modeled year (relative to 2015) and calculates the new bus degradation factors based on the original factors for both years.
  • Developed a process that would ensure that no row in the transit line files exceeds 144 columns.
  • Cleaned up the transit skimming/assignment report files.
  • Added an optional function to shut down the computer automatically after completing a model run, which can be useful when running the model on an on-demand cloud server, where cost is incurred based on time used.

The first three updates result in only small changes in modeled results (Ver. 2.4.6 Model compared to Ver. 2.4 Model) at the regional level. The last three updates result in no changes in modeled results.

See the Ver. 2.4.6 Travel Model user’s guide and the transmittal package memo below for more details:

The highway and transit networks report can be found in the following link:

In 2021, the Ver. 2.4 Model was validated to year-2018 conditions. The work was documented in the following memo:

Due to the small differences in model outputs between the Ver. 2.4 Model and Ver. 2.4.6 Model, it was decided by COG/TPB staff that there is no need to re-validate the Ver. 2.4.6 Model to the year-2018 conditions.

COG/TPB currently maintains two developmental lines of models: Generation 2 (Gen2) and Generation 3 (Gen3). The Gen2 developmental model is used to continuously improve the COG/TPB’s existing trip-based travel demand modeling processes. The Gen3 developmental model is expected to be an advanced travel model, currently under development with consultant assistance. Documentation for the interim Gen3, Phase 1, Model can be found on this webpage.

Documentation for Past Adopted Travel Models

Version 2.4

The latest adopted, regional, production-use travel demand model was the Ver. 2.4 Model. This model became the adopted, production-use model on June 15, 2022, when the TPB adopted the following two resolutions:

  • R15-2022: Resolution approving the 2022 Update to the Visualize 2045 LRTP and the FY 2023 - 2026 TIP.
  • R16-2022: Resolution finding that the 2022 Update to the Visualize 2045 LRTP and the FY 2023-2026 TIP conform with the requirements of the Clear Air Act Amendments of 1990.

The Ver. 2.4 Model is documented in a user’s guide:

The TPB Version 2.4 Travel Model was validated to year-2014 conditions, and the work was documented in the following memo:

Version 2.3.78

The previous adopted, regional, production-use travel demand model was the Ver. 2.3.78 model. This model became the adopted, production-use model on March 18, 2020, when the TPB adopted the following two resolutions:

  • R14-2020: Resolution finding that the 2020 Amendment to the Visualize 2045 Long-Range Transportation Plan and the FY 2021-2024 Transportation Improvement Program (TIP) conform with the requirements of the Clean Air Act Amendments of 1990

  • R15-2020: Resolution approving the 2020 Amendment to the Visualize 2045 Long-Range Transportation Plan for the National Capital Region and the FY 2021-2024 TIP

The Ver. 2.3.78 Model is the last member in a series of adopted, regional, production-use travel demand models, within the Gen2/Version 2.3 model family.  As noted above, all the model versions in the Version 2.3 model family are aggregate, trip-based, four-step travel demand models.

The TPB Version 2.3 Travel Model was calibrated and validated to year-2007 conditions in 2012, and this work was documented in the following calibration report:

In 2013, the Version 2.3 Travel Model was validated to year-2010 conditions. Updates to the model resulting from this validation work were part of Ver.2.3.52. The model validation effort was documented in the following memo:

In 2019, staff conducted a re-validation of Version 2.3.75 to year-2014 conditions. The work was documented in the following memo:

The user's guide and the highway and transit networks documentation for the Ver. 2.3.78 Model were released on April 14, 2020.

COG/TPB currently maintains two developmental lines for Generation-2 (Gen2) and Generation-3 (Gen3) Travel Models. The Gen2 developmental model, a trip-based travel demand model, currently known as Ver. 2.3, will be re-branded as Ver. 2.4 Model and likely made available for production use in the fall of 2020. The Gen3 developmental model is expected to be an advanced travel model, currently under development with consultant assistance from Resource Systems Group (RSG).

Version 2.3.75

Version 2.3.70

Version 2.3.66

Version 2.3.57a

Version 2.3.57

Version 2.3.52

  • User's Guide for the MWCOG/NCRTPB Travel Forecasting Model, Version 2.3, Build 52. Draft Report. Metropolitan Washington Council of Governments, National Capital Region Transportation Planning Board, September 18, 2013.
  • User's Guide for the MWCOG/NCRTPB Travel Forecasting Model, Version 2.3, Build 52: Appendices B (Batch Files), C (Cube Voyager Scripts), and D (AEMS Fortran Control Files). Metropolitan Washington Council of Governments, National Capital Region Transportation Planning Board, September 18, 2013.
  • Highway and Transit Networks for the Version 2.3.52 Travel Model, Based on the 2013 CLRP and FY 2013-2018 TIP. Final Report. Washington, D.C.: Metropolitan Washington Council of Governments, National Capital Region Transportation Planning Board, March 18, 2014.

Version 2.3 (Builds 33 through 39)

  • Calibration Report for the TPB Travel Forecasting Model, Version 2.3, on the 3,722-Zone Area System. Final Report. National Capital Region Transportation Planning Board, January 20, 2012.
  • User's Guide for the TPB Travel Forecasting Model, Version 2.3, Build 38, on the 3,722-Zone Area System. Final Report. National Capital Region Transportation Planning Board, January 20, 2012.
  • Snead, Milone, Hamlin, Davis, Seifu, and Martchouk. FY-2010 Network Documentation: Highway and Transit Network Development. Draft. National Capital Region Transportation Planning Board, June 30, 2010.

Version 2.2

  • COG/TPB Travel Forecasting Model Version 2.2 Specification, Validation, and User's Guide - March 1, 2008
  • Two-Step Traffic Assignment for HOT Lane Modeling in 2008 CLRP - December 2, 2008
  • Transmittal of Version 2.2 travel model files as per the 2008 CLRP/2009-2014 TIP air quality determination - December 17, 2008
  • TPB Models Development Status Report - presentation to the Travel Forecasting Subcommittee on November 21, 2008. Slides 6-11 discuss updates to the Version 2.2 travel model, including the two-step assignment.
  • FY-2008 Network Documentation: Highway and Transit Network Development- September 19, 2008.
  • FY-2009 Network Documentation: Highway and Transit Network Development. Draft report. June 30, 2009.

Version 2.1D

  • Status of the TPB Version 2.1D Regional Travel Model - September 17, 2004
  • COG/TPB Travel Forecasting Model Version 2.1 D Draft #50 Calibration Report - November 17, 2004
  • COG/TPB Travel Forecasting Model Version 2.1 D Draft #50 User's Guide - November 17, 2004
  • FY-2004 Network Documentation: Highway and Transit Network Development- November 17, 2004

 

Page updated 7/21/2023.