Fix train reverse inside signalled tunnel/bridge entrance clearing reservation of incoming train

src/train_cmd.cpp

@@ -2725,6 +2725,9 @@ void FreeTrainTrackReservation(const Train *v, TileIndex origin, Trackdir orig_t
 	/* Don't free reservation if it's not ours. */
 	if (TracksOverlap(GetReservedTrackbits(tile) | TrackToTrackBits(TrackdirToTrack(td)))) return;
 
+	/* Do not attempt to unreserve out of a signalled tunnel/bridge entrance, as this would unreserve the reservations of another train coming in */
+	if (IsTunnelBridgeWithSignalSimulation(tile) && TrackdirExitsTunnelBridge(tile, td) && IsTunnelBridgeSignalSimulationEntranceOnly(tile)) return;
+
 	CFollowTrackRail ft(v, GetRailTypeInfo(v->railtype)->compatible_railtypes);
 	while (ft.Follow(tile, td)) {
 		tile = ft.m_new_tile;

src/tunnelbridge_map.h

@@ -372,6 +372,18 @@ static inline bool IsTunnelBridgeSignalSimulationEntrance(TileIndex t)
 	return HasBit(_m[t].m5, 5);
 }
 
+/**
+ * Is this a tunnel/bridge entrance tile with signal only?
+ * @param t the tile that might be a tunnel/bridge.
+ * @pre IsTileType(t, MP_TUNNELBRIDGE)
+ * @return true if and only if this tile is a tunnel/bridge entrance only.
+ */
+static inline bool IsTunnelBridgeSignalSimulationEntranceOnly(TileIndex t)
+{
+	assert_tile(IsTileType(t, MP_TUNNELBRIDGE), t);
+	return HasBit(_m[t].m5, 5) && !HasBit(_m[t].m5, 6);
+}
+
 /**
  * Is this a tunnel/bridge exit?
  * @param t the tile that might be a tunnel/bridge.