feat: attach schedules explicitly to added routes

apps/api_web/lib/api_web/controllers/schedule_controller.ex

@@ -18,7 +18,7 @@ defmodule ApiWeb.ScheduleController do
 
   @filters ~w(date direction_id max_time min_time route stop stop_sequence route_type trip)s
   @pagination_opts ~w(offset limit order_by)a
-  @includes ~w(stop trip prediction route)
+  @includes ~w(stop trip prediction route added_routes)
 
   def state_module, do: State.Schedule
 
@@ -368,6 +368,7 @@ defmodule ApiWeb.ScheduleController do
           relationship(:trip)
           relationship(:stop)
           relationship(:prediction)
+          relationship(:added_routes, type: :has_many)
         end,
       Schedules: page(:ScheduleResource)
     }

apps/api_web/lib/api_web/views/schedule_view.ex

@@ -1,7 +1,7 @@
 defmodule ApiWeb.ScheduleView do
   use ApiWeb.Web, :api_view
   alias ApiWeb.Plugs.Deadline
-  alias JaSerializer.Relationship.HasOne
+  alias JaSerializer.Relationship.{HasMany, HasOne}
 
   def relationships(_, _) do
     %{
@@ -15,6 +15,13 @@ defmodule ApiWeb.ScheduleView do
         serializer: ApiWeb.PredictionView,
         identifiers: :when_included,
         include: false
+      },
+      added_routes: %HasMany{
+        type: :route,
+        name: :added_routes,
+        data: :added_routes,
+        serializer: ApiWeb.RouteView,
+        include: true
       }
     }
   end
@@ -92,6 +99,10 @@ defmodule ApiWeb.ScheduleView do
     State.Prediction.prediction_for(schedule, date)
   end
 
+  def added_routes(%{added_route_ids: added_route_ids}, conn) do
+    optional_relationship("added_route", added_route_ids, &State.Route.by_ids/1, conn)
+  end
+
   defp format_time(seconds, conn) when is_integer(seconds) do
     conn.assigns
     |> case do

apps/api_web/test/api_web/views/schedule_view_test.exs

@@ -18,7 +18,8 @@ defmodule ApiWeb.ScheduleViewTest do
     pickup_type: 2,
     drop_off_type: 3,
     timepoint?: true,
-    stop_headsign: "headsign"
+    stop_headsign: "headsign",
+    added_route_ids: []
   }
 
   test "renders the dates properly", %{conn: conn} do
@@ -155,4 +156,31 @@ defmodule ApiWeb.ScheduleViewTest do
       refute prediction
     end
   end
+
+  describe "added_routes" do
+    test "empty if not present", %{conn: conn} do
+      conn = assign(conn, :date, ~D[2026-03-31])
+      rendered = render(ApiWeb.ScheduleView, "index.json-api", data: @schedule, conn: conn)
+      assert %{"added_routes" => %{"data" => []}} = rendered["data"]["relationships"]
+    end
+
+    test "populated if present", %{conn: conn} do
+      conn = assign(conn, :date, ~D[2026-03-31])
+
+      rendered =
+        render(ApiWeb.ScheduleView, "index.json-api",
+          data: %{@schedule | added_route_ids: ["route1", "route2"]},
+          conn: conn
+        )
+
+      assert %{
+               "added_routes" => %{
+                 "data" => [
+                   %{"type" => "route", "id" => "route1"},
+                   %{"type" => "route", "id" => "route2"}
+                 ]
+               }
+             } = rendered["data"]["relationships"]
+    end
+  end
 end

apps/model/lib/model/schedule.ex

@@ -23,7 +23,8 @@ defmodule Model.Schedule do
     :route_id,
     :direction_id,
     :service_id,
-    :timepoint?
+    :timepoint?,
+    added_route_ids: []
   ]
 
   @typedoc """
@@ -73,6 +74,7 @@ defmodule Model.Schedule do
       [GTFS `trips.txt` `route_id`](https://github.com/google/transit/blob/master/gtfs/spec/en/reference.md#tripstxt)
   * `:service_id` - The service that `trip_id` is following to determine when it is active.  See
       [GTFS `trips.txt` `service_id`](https://github.com/google/transit/blob/master/gtfs/spec/en/reference.md#tripstxxt)
+  * `:added_route_ids` - Routes that this trip has been added to via [`multi_route_trips.txt`](https://github.com/mbta/gtfs-documentation/blob/master/reference/gtfs.md#multi_route_tripstxt)
   * `:stop_id` - The stop being arrived at and departed from.  See
       [GTFS `stop_times.txt` `stop_id`](https://github.com/google/transit/blob/master/gtfs/spec/en/reference.md#stop_timestxt)
   * `:stop_sequence` - The sequence the `stop_id` is arrived at during the `trip_id`.  See

apps/model/lib/model/trip.ex

@@ -17,7 +17,8 @@ defmodule Model.Trip do
     :route_type,
     :bikes_allowed,
     :route_pattern_id,
-    revenue: :REVENUE
+    revenue: :REVENUE,
+    added_route_ids: []
   ]
 
   @type id :: String.t()
@@ -36,7 +37,8 @@ defmodule Model.Trip do
           alternate_route: boolean | nil,
           bikes_allowed: 0..2,
           route_pattern_id: Model.RoutePattern.id() | nil,
-          revenue: :REVENUE | :NON_REVENUE
+          revenue: :REVENUE | :NON_REVENUE,
+          added_route_ids: [Model.Route.id()]
         }
 
   @doc """

apps/parse/lib/parse/stop_times.ex

@@ -37,7 +37,8 @@ defmodule Parse.StopTimes do
       stop_headsign: optional_copy(row["stop_headsign"]),
       pickup_type: pick_drop_type(row["pickup_type"]),
       drop_off_type: pick_drop_type(row["drop_off_type"]),
-      timepoint?: row["timepoint"] != "0"
+      timepoint?: row["timepoint"] != "0",
+      added_route_ids: []
     }
   end
 
@@ -72,6 +73,7 @@ defmodule Parse.StopTimes do
           &%{
             &1
             | route_id: trip.route_id,
+              added_route_ids: trip.added_route_ids,
               direction_id: trip.direction_id,
               service_id: trip.service_id
           }

apps/state/lib/state/trip.ex

@@ -154,7 +154,7 @@ defmodule State.Trip do
         %{trip | route_id: route_id, alternate_route: true}
       end
 
-    new_trip = %{trip | alternate_route: false}
+    new_trip = %{trip | alternate_route: false, added_route_ids: alternate_routes}
     [new_trip | new_alternates]
   end
 

apps/state/test/state/schedule_test.exs

@@ -177,21 +177,18 @@ defmodule State.ScheduleTest do
       ]
 
       schedules = [
-        @schedule
+        %{@schedule | added_route_ids: [other_route_id]}
       ]
 
       State.Route.new_state(routes)
       State.Trip.new_state(trips)
       Schedule.new_state(schedules)
       State.RoutesPatternsAtStop.update!()
 
-      assert Enum.sort(Schedule.filter_by(%{stops: [@stop.id], routes: [@route.id]})) == [
-               @schedule
-             ]
+      assert Enum.sort(Schedule.filter_by(%{stops: [@stop.id], routes: [@route.id]})) == schedules
 
-      assert Enum.sort(Schedule.filter_by(%{stops: [@stop.id], routes: [other_route_id]})) == [
-               @schedule
-             ]
+      assert Enum.sort(Schedule.filter_by(%{stops: [@stop.id], routes: [other_route_id]})) ==
+               schedules
     end
 
     test "filters on :stops and :routes" do