diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index 4976412f9d..490f3e9f42 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -44,6 +44,7 @@
 #include "scope.h"
 #include "core/checksum_func.hpp"
 #include "debug_settings.h"
+#include "train_speed_adaptation.h"
 
 #include "table/strings.h"
 #include "table/train_cmd.h"
@@ -76,39 +77,7 @@ enum ChooseTrainTrackFlags {
 };
 DECLARE_ENUM_AS_BIT_SET(ChooseTrainTrackFlags)
 
-struct SignalSpeedKey
-{
-	TileIndex signal_tile;
-	Track signal_track;
-	Trackdir last_passing_train_dir;
-
-	bool operator==(const SignalSpeedKey& other) const
-	{
-		return signal_tile == other.signal_tile &&
-			signal_track == other.signal_track &&
-			last_passing_train_dir == other.last_passing_train_dir;
-	}
-};
-
-struct SignalSpeedValue
-{
-	uint16 train_speed;
-	DateTicksScaled time_stamp;
-};
-
-struct SignalSpeedKeyHashFunc
-{
-	std::size_t operator() (const SignalSpeedKey &key) const
-	{
-		const std::size_t h1 = std::hash<TileIndex>()(key.signal_tile);
-		const std::size_t h2 = std::hash<Trackdir>()(key.last_passing_train_dir);
-		const std::size_t h3 = std::hash<Track>()(key.signal_track);
-
-		return (h1 ^ h2) ^ h3;
-	}
-};
-
-static std::unordered_map<SignalSpeedKey, SignalSpeedValue, SignalSpeedKeyHashFunc> _signal_speeds(1 << 16);
+std::unordered_map<SignalSpeedKey, SignalSpeedValue, SignalSpeedKeyHashFunc> _signal_speeds(1 << 16);
 
 static void TryLongReserveChooseTrainTrackFromReservationEnd(Train *v, bool no_reserve_vehicle_tile = false);
 static Track ChooseTrainTrack(Train *v, TileIndex tile, DiagDirection enterdir, TrackBits tracks, ChooseTrainTrackFlags flags, bool *p_got_reservation, ChooseTrainTrackLookAheadState lookahead_state = {});
diff --git a/src/train_speed_adaptation.h b/src/train_speed_adaptation.h
new file mode 100644
index 0000000000..4f4c3e20b2
--- /dev/null
+++ b/src/train_speed_adaptation.h
@@ -0,0 +1,53 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file train_speed_adaptation.h Train speed adaptation data structures. */
+
+#ifndef TRAIN_SPEED_ADAPTATION_H
+#define TRAIN_SPEED_ADAPTATION_H
+
+#include "date_type.h"
+#include "track_type.h"
+#include "tile_type.h"
+
+#include <unordered_map>
+
+struct SignalSpeedKey
+{
+	TileIndex signal_tile;
+	Track signal_track;
+	Trackdir last_passing_train_dir;
+
+	bool operator==(const SignalSpeedKey& other) const
+	{
+		return signal_tile == other.signal_tile &&
+			signal_track == other.signal_track &&
+			last_passing_train_dir == other.last_passing_train_dir;
+	}
+};
+
+struct SignalSpeedValue
+{
+	uint16 train_speed;
+	DateTicksScaled time_stamp;
+};
+
+struct SignalSpeedKeyHashFunc
+{
+	std::size_t operator() (const SignalSpeedKey &key) const
+	{
+		const std::size_t h1 = std::hash<TileIndex>()(key.signal_tile);
+		const std::size_t h2 = std::hash<Trackdir>()(key.last_passing_train_dir);
+		const std::size_t h3 = std::hash<Track>()(key.signal_track);
+
+		return (h1 ^ h2) ^ h3;
+	}
+};
+
+extern std::unordered_map<SignalSpeedKey, SignalSpeedValue, SignalSpeedKeyHashFunc> _signal_speeds;
+
+#endif /* TRAIN_SPEED_ADAPTATION_H */