From d26da461e1888089802f5400ca2d6faad2458ed6 Mon Sep 17 00:00:00 2001
From: Matt Richards <matt.richards@veitchlister.com.au>
Date: Tue, 10 Mar 2026 20:52:55 +1100
Subject: [PATCH] ENH: add trip scheduling choice explicit chunking

---
 .../abm/models/trip_scheduling_choice.py      | 10 +++++++--
 .../test_misc/test_trip_scheduling_choice.py  | 22 +++++++++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/activitysim/abm/models/trip_scheduling_choice.py b/activitysim/abm/models/trip_scheduling_choice.py
index 81d908ef1..0b73cd6cc 100644
--- a/activitysim/abm/models/trip_scheduling_choice.py
+++ b/activitysim/abm/models/trip_scheduling_choice.py
@@ -276,7 +276,9 @@ def run_trip_scheduling_choice(
             choosers,
             chunk_trace_label,
             chunk_sizer,
-        ) in chunk.adaptive_chunked_choosers(state, indirect_tours, trace_label):
+        ) in chunk.adaptive_chunked_choosers(
+            state, indirect_tours, trace_label, explicit_chunk_size=model_settings.explicit_chunk
+        ):
             # Sort the choosers and get the schedule alternatives
             choosers = choosers.sort_index()
             schedules = generate_schedule_alternatives(choosers).sort_index()
@@ -350,7 +352,11 @@ class TripSchedulingChoiceSettings(LogitComponentSettings, extra="forbid"):
     Settings for the `trip_scheduling_choice` component.
     """
 
-    pass
+    explicit_chunk: float = 0
+    """
+    If > 0, use this chunk size instead of adaptive chunking.
+    If less than 1, use this fraction of the total number of rows.
+    """
 
 
 @workflow.step
diff --git a/activitysim/abm/test/test_misc/test_trip_scheduling_choice.py b/activitysim/abm/test/test_misc/test_trip_scheduling_choice.py
index 6823a5b12..6db004b43 100644
--- a/activitysim/abm/test/test_misc/test_trip_scheduling_choice.py
+++ b/activitysim/abm/test/test_misc/test_trip_scheduling_choice.py
@@ -4,6 +4,7 @@
 import os
 from pathlib import Path
 
+from pandas.testing import assert_frame_equal
 
 from activitysim.abm.models import trip_scheduling_choice as tsc
 from activitysim.abm.tables.skims import skim_dict
@@ -285,3 +286,24 @@ def test_run_trip_scheduling_choice(model_spec, tours, skims, locals_dict):
 
     # check that tours with no inbound stops have zero inbound duration
     assert out_tours[tsc.IB_DURATION].mask(in_tours[tsc.HAS_IB_STOPS], 0).sum() == 0
+
+    # confirm explicit chunking is supported and doesn't affect results
+    model_settings_explicit_chunk = tsc.TripSchedulingChoiceSettings(
+        **{
+            "SPEC": "placeholder.csv",
+            "compute_settings": {
+                "protect_columns": ["origin", "destination", "schedule_id"]
+            },
+        }
+    )
+    out_tours_chunked = tsc.run_trip_scheduling_choice(
+        state,
+        model_spec,
+        tours,
+        skims,
+        locals_dict,
+        trace_label="PyTest Trip Scheduling",
+        model_settings=model_settings_explicit_chunk,
+    )
+    assert_frame_equal(out_tours, out_tours_chunked)
+