PTM Assignment

PTM includes two types of network models: a frequency network model and a timetable network model. The frequency network model uses defined service headways within specified time periods, while the timetable network model uses a rooftop transit assignment based on a provided timetable.

PTM Model Types

The key model steps involved in the PTM network assignment model include:

  1. MODEL SETUP: Initial Setup:
    • Import necessary standard and PTM-specific modules.
    • Define the NetworkModel class, which initialises with model parameters and paths.
    • Set the preferred EMME version and establish logging mechanisms.
  2. MODEL SETUP: Project Setup:
    • Create necessary directories for matrices and outputs.
    • Build or use an existing EMME project.
    • Connect to the EMME application and set up the modeller.
  3. MODEL SETUP: Import Time Periods and User Groups:
    • Retrieve and filter relevant time periods for the network model type.
    • Load user groups and assignment modes from CSV files.
    • Generate transit assignments to be performed by combining time periods, user groups, and assignment modes.
  4. MODEL SETUP: Internal Run Validation:
    • Validate the transit assignments to ensure modes match user groups and day period codes.
    • PTM will automatically check for any unmatched modes or elastic parameters and raise errors if necessary.
  5. MODEL BUILD: Network, Demand and Fare Import:
    • Iterate over each time period to build base networks and transit networks.
    • Import or build demand for each time period.
    • Build and store fare matrices in the EMME database, ensuring this is done only once.
  6. MODEL ASSIGNMENT: Initial Transit Assignments:
    • Perform initial transit assignments for each time period to generate the initial generalised cost results and assignment volumes.
  7. MODEL ASSIGNMENT: Perform Elastic Demand Process (Optional):
    • Import base case impedance from the base PTM model run.
    • Compare changes in generalised cost and using the imported elasticities generate new demand.
  8. MODEL ASSIGNMENT: Perform Final Transit Assignment (Optional):
    • Using the demand generated in the above elastic process, run the final Transit Assignment.

More information on each of these steps is included in the following sections.