diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index 270d88df96..c954add1ab 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -114,12 +114,6 @@ static DateTicksScaled GetSpeedRestrictionTimeout(const Train *t)
 	return _scaled_date_ticks + ticks;
 }
 
-/** Checks if the timeout of the specified signal speed restriction value has passed */
-static bool IsOutOfDate(const SignalSpeedValue& value)
-{
-	return _scaled_date_ticks > value.time_stamp;
-}
-
 /** Removes all speed restrictions from all signals */
 void ClearAllSignalSpeedRestrictions()
 {
@@ -137,7 +131,7 @@ void AdjustAllSignalSpeedRestrictionTickValues(DateTicksScaled delta)
 void ClearOutOfDateSignalSpeedRestrictions()
 {
 	for (auto key_value_pair = _signal_speeds.begin(); key_value_pair != _signal_speeds.end(); ) {
-		if (IsOutOfDate(key_value_pair->second)) {
+		if (key_value_pair->second.IsOutOfDate()) {
 			key_value_pair = _signal_speeds.erase(key_value_pair);
 		} else {
 			++key_value_pair;
@@ -7582,7 +7576,7 @@ void ApplySignalTrainAdaptationSpeed(Train *v, TileIndex tile, uint16 track)
 	const auto found_speed_restriction = _signal_speeds.find(speed_key);
 
 	if (found_speed_restriction != _signal_speeds.end()) {
-		if (IsOutOfDate(found_speed_restriction->second)) {
+		if (found_speed_restriction->second.IsOutOfDate()) {
 			_signal_speeds.erase(found_speed_restriction);
 			v->signal_speed_restriction = 0;
 		} else {
diff --git a/src/train_speed_adaptation.h b/src/train_speed_adaptation.h
index 6407c7b22f..7affd34b26 100644
--- a/src/train_speed_adaptation.h
+++ b/src/train_speed_adaptation.h
@@ -11,13 +11,13 @@
 #define TRAIN_SPEED_ADAPTATION_H
 
 #include "date_type.h"
+#include "date_func.h"
 #include "track_type.h"
 #include "tile_type.h"
 
 #include <unordered_map>
 
-struct SignalSpeedKey
-{
+struct SignalSpeedKey {
 	TileIndex signal_tile;
 	uint16 signal_track;
 	Trackdir last_passing_train_dir;
@@ -30,14 +30,18 @@ struct SignalSpeedKey
 	}
 };
 
-struct SignalSpeedValue
-{
+struct SignalSpeedValue {
 	uint16 train_speed;
 	DateTicksScaled time_stamp;
+
+	/** Checks if the timeout has passed */
+	bool IsOutOfDate() const
+	{
+		return _scaled_date_ticks > this->time_stamp;
+	}
 };
 
-struct SignalSpeedKeyHashFunc
-{
+struct SignalSpeedKeyHashFunc {
 	std::size_t operator() (const SignalSpeedKey &key) const
 	{
 		const std::size_t h1 = std::hash<TileIndex>()(key.signal_tile);