2026-09-22 Australia Team

[joecastiglione]

Agenda

• v1.6.0 Release
• MoMo ActivitySim Workshop Proposal
  • Scope
  • Roles / Responsibilities
• Consultant SOQs
  • Status update
  • Review coordination (reviewers, discussion meeting scheduling)

Notes

ActivitySim Consortium meeting notes (Australia session)

ActivitySim 1.6.0 release

Jan presented the first release since November 2025, requested by TfNSW ahead of Phase 11 closeout (still 5–6 weeks away).

• Installer issue: Conda dropped Python 3.10 (end of life in October), breaking the Windows installer build. Users of pip, uv or conda/mamba are unaffected. A fix is expected within 2–3 days. Long gaps between releases make such issues more likely.
• Breaking and behavior changes:
  • Three-zone (transit virtual path builder) support removed
  • Core dependencies updated (NumPy 2.x, Sharrow)
  • Failed choices are now skipped and reported rather than crashing runs; this is configurable. Users who rely on failures for debugging should take note.
  • Sharrow fast math now defaults to off because of hard-to-diagnose problems. It can be re-enabled; expect a slight slowdown.
  • Chooser-column lists removed; unused columns are dropped automatically, saving memory
  • Sample rates no longer rounded, which may slightly change expanded results
• Highlights:
  • EET and new sampling methods, turned on with one setting
  • Park-and-ride modeling (TransLink/RSG, adopted by the consortium; being tested at PSRC)
  • Parquet skims (TfNSW request)
  • Explicit chunking for trip scheduling (Matt Richards) and mode choice (Vincent Gong, TU Delft)
  • Options to exclude unused skims and clear the Sharrow cache
• Fixes:
  • Shadow pricing
  • Trip scheduling and school escorting now reproducible (Will Alexander, RSG)
  • CDAP estimation interaction terms for larger households now correct

EET experience and testing

• TfNSW (Shaun):
  • Ran public transport fare tests (±10%, ±20%) in the ABM and the legacy tour-based model.
  • The legacy model responds sensibly, with gains concentrated in the CBD. The ABM shows noisy region-to-region changes and inconsistent mode responses (e.g., bus patronage rising with a fare increase at +10%).
  • TfNSW is ruling out bugs before sharing, expects EET to reduce the noise, and will compare runs with and without EET.
• DTP (Paris):
  • Without EET, consultant fare tests were hard to interpret beyond high-level results. With EET, they support sensible economic evaluation. Paris would recommend EET in almost all cases.
  • The consultant report is being finalized; DTP will seek permission to share it.
• Jan agreed that EET is theoretically sound with no practical downside.
• Paris said the consortium has greatly mitigated two early concerns, compute requirements (through chunking and Sharrow) and simulation noise. Validation remains the main challenge.
• DTP runs the ABM as a "shadow model" alongside the legacy trip model on real projects to prioritize re-estimation.
• Paris's ABM value propositions:
  • more realistic behavioral response
  • more policy levers (pricing, opening hours)
  • finer-grained impact analysis
• Real-world testing of major features: Joe urged testing beyond CI and unit tests. Examples: a SANDAG work location error that was only later flagged after strange results in other implementations, and the PNR feature, which is not yet widely tested.
• Agency updates: Joe invited DTP and TfNSW to present at an upcoming meeting, since their recent TPA conference presentations would interest members.
• Land use: Paris raised future PopulationSim and land use integration. Joe welcomed Rathish to the UrbanSim group, will follow up with DTP on the UrbanSim open land use model, and will share an ETC paper on land-use accessibility benefits.

Release cadence

• Joe proposed agendizing a more frequent release policy.
• Shaun suggested tying releases to task orders, with each task order stating how its work is released.
• Jan favored rolling semantic-versioned releases. These depend on automating the currently manual, time-intensive release checks.
• Joe suggested a Phase 12 task to define a release policy and build the infrastructure it needs.

MoMo 2027

Joe noted the planned ActivitySim workshop abstract (link in agenda) and welcomed comments or participation.

Action items

Action	Owner
Fix Windows installer	Jan Zill
Share fare-test findings with/without EET	Shaun Tabone
Seek permission to share DTP EET report	Paris Brunton, Kate Johns
Schedule DTP/TfNSW agency update	Joe
Agendize release policy; scope Phase 12 release automation	Joe, Jan
Share ETC paper; follow up on UrbanSim with DTP	Joe