diff --git a/lib/signs/realtime.ex b/lib/signs/realtime.ex
index 0a526414..bb59c80d 100644
--- a/lib/signs/realtime.ex
+++ b/lib/signs/realtime.ex
@@ -213,8 +213,7 @@ defmodule Signs.Realtime do
       SourceConfig.sign_stop_ids(source)
       |> Stream.flat_map(&sign.last_trip_engine.get_recent_departures(&1))
       |> Enum.count(fn {trip_id, departure_time} ->
-        # Use a 3 second buffer to make sure trips have fully departed
-        DateTime.to_unix(current_time) - DateTime.to_unix(departure_time) > 3 and
+        trip_departed?(departure_time, current_time) and
           sign.last_trip_engine.is_last_trip?(trip_id)
       end)
 
@@ -223,6 +222,11 @@ defmodule Signs.Realtime do
     num_last_trips >= threshold
   end
 
+  defp trip_departed?(departure_time, current_time) do
+    # Use a 3 second buffer to make sure trips have fully departed
+    DateTime.to_unix(current_time) - DateTime.to_unix(departure_time) > 3
+  end
+
   defp prediction_key(prediction) do
     Map.take(prediction, [:stop_id, :route_id, :vehicle_id, :direction_id, :trip_id])
   end