Move dual-use of load_unload_ticks for bridge/tun signals to new field

src/saveload/afterload.cpp

@@ -2994,6 +2994,17 @@ bool AfterLoadGame()
 			}
 		}
 	}
+	if (SlXvIsFeaturePresent(XSLFI_SIG_TUNNEL_BRIDGE, 1, 4)) {
+		/* load_unload_ticks --> tunnel_bridge_signal_num */
+		Train *t;
+		FOR_ALL_TRAINS(t) {
+			TileIndex tile = t->tile;
+			if (IsTileType(tile, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL && IsTunnelBridgeWithSignalSimulation(tile)) {
+				t->tunnel_bridge_signal_num = t->load_unload_ticks;
+				t->load_unload_ticks = 0;
+			}
+		}
+	}
 
 	/* Station acceptance is some kind of cache */
 	if (IsSavegameVersionBefore(127)) {