Development

PSRC's implementation of ActivitySim is structurally based on MTC's Travel Model One, while also borrowing components from SANDAG's ABM3. The following sections describe the changes made to the base MTC example from the ActivitySim repository.

Simplification of drive-to-transit modes

MTC separates all transit sub-modes as distinct alternatives in tour and trip mode choice models. To reduce skim complexity we collapsed drive-to-transit into a single skim (rather than having drive to commuter rail, drive to local bus, etc. as options). The primary reason for this is that in the current Daysim-based version of Soundcast we don't have separate sub-mode skims available, since Daysim uses a path-type model.

In order to produce the drive-to-transit skims, we added a script to the Soundcast repository that performs a mixed-mode assignment for park-and-ride trips. Specific changes made to config files include:

• removing the following mode columns and rows from trip/tour_mode_choice.csv, and trip/tour_mode_choice.yml:
  • DRIVE_LOC
  • DRIVE_EXP
  • DRIVE_HVY
  • DRIVE_COM
  • DRIVE_LRF
• adding a generic mode DRIVE_TRN (TRN for general transit)
• replacing any instance of submode-specific skims with the generic skim
  • e.g. DRV_EXP_WLK_IWAIT -> DRV_TRN_WLK_IWAIT
  • these changes needed to be made in:
    • trip_mode_choice.csv
    • trip_mode_choice_annotate_trips_preprocessor.csv
    • tour_mode_choice.csv
    • tour_mode_choice_annotate_choosers_preprocessor.csv

Auto-Ownership Model

• For now, we have borrowed SEMCOG's specification and estimated with our 2018 survey.
• We added a residential density variable (number of units/area), which has been significant. The idea is that the number of cars a household can own may be limited by parking availability (on-street, driveways, garages). Areas with higher densities may have less space to park more cars.

School-Location Model

• We added a column to the landuse file called 'GSENROLL', which has enrollment for elementary/middle school.
• 'GSENROLL' has been added to destination_choice_size_terms and used for the gradeschool alternative in school location.