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Define Scenarios

In TDM23, model runs are organized into distinct Scenarios. A scenario is a specific combination of parameters including inputs, outputs, and run configurations.

Best Practices

  • Utilizing Scenarios over Model Duplication: Instead of duplicating the entire model for different runs, create and utilize multiple scenarios. This approach enhances organization and efficiency by focusing on scenario differences.

  • Making Copies of Input Files Instead of Overwriting: Maintain data integrity by creating copies of modified input files. Rename these copies and reference them in your scenarios to avoid direct alterations to original files. This practice reduces the risk of unintended changes and simplifies version control.

Scenario Structuring

Scenarios within TDM23 are structured using the TransCAD user interface (UI) for model scenario, which utilizes a generational format with inheritance. This means each scenario can inherit parameter values from both the model defaults and its parent scenario, if applicable. Users primarily modify parameters that differ from these inherited values, and the modifications will be shown as highlighted in the UI.

For instance, scenario 2050 inherits values from model parameter defaults and serves as the parent scenario for 2050\Plan, as shown in the slides below.

Specify Model or Scenario

From the dropdownlist, specify whether you are referring to the model defaults or a particular scenario that you want to check or edit.

Specify Model or Scenario

Model Parameters

These are the default parameter values for the model.

Model Parameters

Scenario Parameters: 2050

These are the parameter values for Scenario 2050, with the highlight showing the difference to the model parameter values.

Scenario 2050 Parameters

Scenario Parameters: 2050\Plan

These are the parameter values for Scenario 2050\Plan, with the highlights showing the difference to the Scenario 2050 parameter values.

Scenario 2050\Plan Parameters

Scenarios are stored in text files, facilitating accessibility and customization for experienced users. Model parameter values are stored in the CTPS_TDM23.parameters file. Scenario parameter values are stored in the CTPS_TDM23.scenarios file. Users adjust scenario parameters here only where they differ from model defaults or the parent scenario.

Refer to the Inputs and Outputs pages for detailed descriptions of inputs and outputs. By default, the output folder for each scenario is a subfolder within the ./outputs directory. Each scenario's outputs, including those of its child scenarios, are organized accordingly. For example, the outputs for Scenario 2050 are located in ./outputs/2050 , and the outputs for Scenario 2050\Plan are in ./outputs/2050/Plan.

Default Scenarios

The TDM23 model comes with several predefined scenarios:

  1. Base: A full model run with feedback using 2019 networks and socioeconomic (SE) data.

  2. 2050: A full model run with feedback using 2050 SE data and user-defined networks (not a functional scenario on its own).

  3. 2050\Plan: Inherits settings from the "2050" scenario and includes network inputs with Long-Range Transportation Plan (LRTP) Projects.

  4. AssignOnly: Uses user-defined demand inputs and networks to run highway and transit assignment steps only (see details on the Assign Only page).

  5. AssignTransitOnly: Uses user-defined demand inputs and networks to run transit assignment steps only (see details on the Assign Only page).