From 814f9f7e0f9bdbc506e2fc2a75ee9ecc22c85f49 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Sun, 17 Jun 2018 04:27:03 +0100
Subject: [PATCH] Implement bidirectional mode for signals on bridges/tunnels

---
 docs/landscape.html                   |  5 ++
 src/lang/english.txt                  |  3 ++
 src/pathfinder/npf/npf.cpp            |  2 +-
 src/pathfinder/yapf/yapf_costrail.hpp |  2 +-
 src/pbs.cpp                           | 17 +++++--
 src/rail_cmd.cpp                      | 48 ++++++++++++++++--
 src/rail_gui.cpp                      |  1 +
 src/rail_map.h                        |  2 +-
 src/settings_gui.cpp                  |  1 +
 src/settings_type.h                   |  1 +
 src/table/settings.ini                |  8 +++
 src/train_cmd.cpp                     | 42 ++++++++++------
 src/tunnelbridge.h                    | 13 +----
 src/tunnelbridge_cmd.cpp              | 70 ++++++++++++++-------------
 src/tunnelbridge_map.h                | 26 +++++++++-
 15 files changed, 170 insertions(+), 71 deletions(-)

diff --git a/docs/landscape.html b/docs/landscape.html
index 86a6943fdd..ededf0a3f0 100644
--- a/docs/landscape.html
+++ b/docs/landscape.html
@@ -1554,6 +1554,11 @@
         <td><tt>2</tt>&nbsp;</td>
         <td>signal simulation exit (bit 6 set)</td>
        </tr>
+
+       <tr>
+        <td><tt>3</tt>&nbsp;</td>
+        <td>signal simulation bidirectional entrance and exit (bits 5 and 6 set)</td>
+       </tr>
       </table>
       If signal simulation entrance or exit:
       <ul>
diff --git a/src/lang/english.txt b/src/lang/english.txt
index e3f18abcbb..90e8ee6919 100644
--- a/src/lang/english.txt
+++ b/src/lang/english.txt
@@ -1288,6 +1288,9 @@ STR_CONFIG_SETTING_POPULATION_IN_LABEL_HELPTEXT                 :Display the pop
 STR_CONFIG_SETTING_GRAPH_LINE_THICKNESS                         :Thickness of lines in graphs: {STRING2}
 STR_CONFIG_SETTING_GRAPH_LINE_THICKNESS_HELPTEXT                :Width of the line in the graphs. A thin line is more precisely readable, a thicker line is easier to see and colours are easier to distinguish
 
+STR_CONFIG_SETTING_ADV_SIG_BRIDGE_TUN_MODES                     :Enable signals on bridges/tunnels advanced modes: {STRING2}
+STR_CONFIG_SETTING_ADV_SIG_BRIDGE_TUN_MODES_HELPTEXT            :Enables use of advanced modes of signal simulation on bridges and tunnels. When disabled, bridges/tunnels which are not already in an advanced mode cannot be changed to an advanced mode, however other players may choose to enable this setting and use an advanced mode.
+
 STR_CONFIG_SETTING_LANDSCAPE                                    :Landscape: {STRING2}
 STR_CONFIG_SETTING_LANDSCAPE_HELPTEXT                           :Landscapes define basic gameplay scenarios with different cargos and town growth requirements. NewGRF and Game Scripts allow finer control though
 STR_CONFIG_SETTING_LAND_GENERATOR                               :Land generator: {STRING2}
diff --git a/src/pathfinder/npf/npf.cpp b/src/pathfinder/npf/npf.cpp
index 41ec4b53f3..880f14cfc0 100644
--- a/src/pathfinder/npf/npf.cpp
+++ b/src/pathfinder/npf/npf.cpp
@@ -936,7 +936,7 @@ static void NPFFollowTrack(AyStar *aystar, OpenListNode *current)
 				break;
 			}
 		}
-		if (IsTileType(dst_tile, MP_TUNNELBRIDGE) && IsTunnelBridgeSignalSimulationExit(dst_tile) && DiagDirToDiagTrackdir(GetTunnelBridgeDirection(dst_tile)) == dst_trackdir) {
+		if (IsTileType(dst_tile, MP_TUNNELBRIDGE) && IsTunnelBridgeSignalSimulationExitOnly(dst_tile) && DiagDirToDiagTrackdir(GetTunnelBridgeDirection(dst_tile)) == dst_trackdir) {
 			/* Entering a signalled bridge/tunnel from the wrong side, equivalent to encountering a one-way signal from the wrong side */
 			break;
 		}
diff --git a/src/pathfinder/yapf/yapf_costrail.hpp b/src/pathfinder/yapf/yapf_costrail.hpp
index 5b90f0b82e..08abcb7aaf 100644
--- a/src/pathfinder/yapf/yapf_costrail.hpp
+++ b/src/pathfinder/yapf/yapf_costrail.hpp
@@ -244,7 +244,7 @@ public:
 				}
 			}
 		}
-		if (IsTileType(tile, MP_TUNNELBRIDGE) && IsTunnelBridgeSignalSimulationExit(tile) && DiagDirToDiagTrackdir(GetTunnelBridgeDirection(tile)) == trackdir) {
+		if (IsTileType(tile, MP_TUNNELBRIDGE) && IsTunnelBridgeSignalSimulationExitOnly(tile) && DiagDirToDiagTrackdir(GetTunnelBridgeDirection(tile)) == trackdir) {
 			/* Entering a signalled bridge/tunnel from the wrong side, equivalent to encountering a one-way signal from the wrong side */
 			n.m_segment->m_end_segment_reason |= ESRB_DEAD_END;
 		}
diff --git a/src/pbs.cpp b/src/pbs.cpp
index 8e9edb8e55..29e987c7e7 100644
--- a/src/pbs.cpp
+++ b/src/pbs.cpp
@@ -125,7 +125,6 @@ bool TryReserveRailTrack(TileIndex tile, Track t, bool trigger_stations)
 		case MP_TUNNELBRIDGE:
 			if (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL && !GetTunnelBridgeReservationTrackBits(tile)) {
 				SetTunnelBridgeReservation(tile, true);
-				if (IsTunnelBridgeSignalSimulationExit(tile) && IsTunnelBridgePBS(tile)) SetTunnelBridgeExitSignalState(tile, SIGNAL_STATE_GREEN);
 				MarkTileDirtyByTile(tile);
 				return true;
 			}
@@ -434,7 +433,7 @@ bool IsSafeWaitingPosition(const Train *v, TileIndex tile, Trackdir trackdir, bo
 			return include_line_end;
 		}
 		if (IsTileType(ft.m_new_tile, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(ft.m_new_tile) == TRANSPORT_RAIL &&
-				IsTunnelBridgeSignalSimulationExit(ft.m_new_tile) && IsTunnelBridgePBS(ft.m_new_tile)) {
+				IsTunnelBridgeSignalSimulationExitOnly(ft.m_new_tile) && IsTunnelBridgePBS(ft.m_new_tile)) {
 			return include_line_end;
 		}
 	}
@@ -462,7 +461,19 @@ bool IsWaitingPositionFree(const Train *v, TileIndex tile, Trackdir trackdir, bo
 	/* Not reserved and depot or not a pbs signal -> free. */
 	if (IsRailDepotTile(tile)) return true;
 	if (IsTileType(tile, MP_RAILWAY) && HasSignalOnTrackdir(tile, trackdir) && !IsPbsSignal(GetSignalType(tile, track))) return true;
-	if (IsTileType(tile, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL && IsTunnelBridgeSignalSimulationEntrance(tile)) return true;
+	if (IsTileType(tile, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL && IsTunnelBridgeSignalSimulationEntrance(tile)) {
+		if (IsTunnelBridgeSignalSimulationBidirectional(tile)) {
+			TileIndex other_end = GetOtherTunnelBridgeEnd(tile);
+			if (HasTunnelBridgeReservation(other_end) && GetTunnelBridgeExitSignalState(other_end) == SIGNAL_STATE_RED) return false;
+			Direction dir = DiagDirToDir(GetTunnelBridgeDirection(other_end));
+			if (HasVehicleOnPos(other_end, &dir, [](Vehicle *v, void *data) -> Vehicle * {
+				if (v->type != VEH_TRAIN) return nullptr;
+				if (v->direction != *((Direction *) data)) return nullptr;
+				return v;
+			})) return false;
+		}
+		return true;
+	}
 
 	/* Check the next tile, if it's a PBS signal, it has to be free as well. */
 	CFollowTrackRail ft(v, GetRailTypeInfo(v->railtype)->compatible_railtypes);
diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
index bfc1f7c78e..6e97ad513c 100644
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -1042,6 +1042,7 @@ static void SetupBridgeTunnelSignalSimulation(TileIndex entrance, TileIndex exit
  * - p1 = (bit 12-14)-wrap around after this signal type
  * - p1 = (bit 15-16)-cycle the signal direction this many times
  * - p1 = (bit 17)  - 1 = don't modify an existing signal but don't fail either, 0 = always set new signal type
+ * - p1 = (bit 18)  - permit creation of/conversion to bidirectionally signalled bridges/tunnels
  * @param p2 used for CmdBuildManySignals() to copy direction of first signal
  * @param text unused
  * @return the cost of this operation or an error
@@ -1080,22 +1081,47 @@ CommandCost CmdBuildSingleSignal(TileIndex tile, DoCommandFlag flags, uint32 p1,
 	CommandCost cost;
 	/* handle signals simulation on tunnel/bridge. */
 	if (IsTileType(tile, MP_TUNNELBRIDGE)) {
+		bool bidirectional = HasBit(p1, 18) && (sigtype == SIGTYPE_PBS);
 		TileIndex tile_exit = GetOtherTunnelBridgeEnd(tile);
 		cost = CommandCost();
 		bool flip_variant = false;
 		bool is_pbs = (sigtype == SIGTYPE_PBS) || (sigtype == SIGTYPE_PBS_ONEWAY);
 		if (!IsTunnelBridgeWithSignalSimulation(tile)) { // toggle signal zero costs.
 			if (convert_signal) return_cmd_error(STR_ERROR_THERE_ARE_NO_SIGNALS);
-			if (p2 != 12) cost = CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_SIGNALS] * ((GetTunnelBridgeLength(tile, tile_exit) + 4) >> 2)); // minimal 1
+			if (p2 != 12) cost = CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_SIGNALS] * ((GetTunnelBridgeLength(tile, tile_exit) + 4) >> 2) * (bidirectional ? 2 : 1)); // minimal 1
 		} else {
 			if (HasBit(p1, 17)) return CommandCost();
+			bool is_bidi = IsTunnelBridgeSignalSimulationBidirectional(tile);
+			bool will_be_bidi = is_bidi;
+			if (p2 == 0) {
+				if (convert_signal) {
+					will_be_bidi = bidirectional && !ctrl_pressed;
+				} else if (ctrl_pressed) {
+					will_be_bidi = false;
+				}
+			} else if (!is_pbs) {
+				will_be_bidi = false;
+			}
 			if ((p2 != 0 && (sigvar == SIG_SEMAPHORE) != IsTunnelBridgeSemaphore(tile)) ||
 					(convert_signal && (ctrl_pressed || (sigvar == SIG_SEMAPHORE) != IsTunnelBridgeSemaphore(tile)))) {
 				flip_variant = true;
-				cost = CommandCost(EXPENSES_CONSTRUCTION, (_price[PR_BUILD_SIGNALS] + _price[PR_CLEAR_SIGNALS]) *
+				cost = CommandCost(EXPENSES_CONSTRUCTION, ((_price[PR_BUILD_SIGNALS] * (will_be_bidi ? 2 : 1)) + (_price[PR_CLEAR_SIGNALS] * (is_bidi ? 2 : 1))) *
 						((GetTunnelBridgeLength(tile, tile_exit) + 4) >> 2)); // minimal 1
+			} else if (is_bidi != will_be_bidi) {
+				cost = CommandCost(EXPENSES_CONSTRUCTION, _price[will_be_bidi ? PR_BUILD_SIGNALS : PR_CLEAR_SIGNALS] * ((GetTunnelBridgeLength(tile, tile_exit) + 4) >> 2)); // minimal 1
 			}
 		}
+		auto remove_pbs_bidi = [&]() {
+			if (IsTunnelBridgeSignalSimulationBidirectional(tile)) {
+				ClrTunnelBridgeSignalSimulationExit(tile);
+				ClrTunnelBridgeSignalSimulationEntrance(tile_exit);
+			}
+		};
+		auto set_bidi = [&](TileIndex t) {
+			SetTunnelBridgeSignalSimulationEntrance(t);
+			SetTunnelBridgeEntranceSignalState(t, SIGNAL_STATE_GREEN);
+			SetTunnelBridgeSignalSimulationExit(t);
+		};
 		if (flags & DC_EXEC) {
 			Company * const c = Company::Get(GetTileOwner(tile));
 			if (IsTunnelBridgeWithSignalSimulation(tile)) c->infrastructure.signal -= GetTunnelBridgeSignalSimulationSignalCount(tile, tile_exit);
@@ -1108,11 +1134,18 @@ CommandCost CmdBuildSingleSignal(TileIndex tile, DoCommandFlag flags, uint32 p1,
 					if (!ctrl_pressed) {
 						SetTunnelBridgePBS(tile, is_pbs);
 						SetTunnelBridgePBS(tile_exit, is_pbs);
+						if (bidirectional) {
+							set_bidi(tile);
+							set_bidi(tile_exit);
+						} else {
+							remove_pbs_bidi();
+						}
 					}
 				} else if (ctrl_pressed) {
 					SetTunnelBridgePBS(tile, !IsTunnelBridgePBS(tile));
 					SetTunnelBridgePBS(tile_exit, IsTunnelBridgePBS(tile));
-				} else {
+					if (!IsTunnelBridgePBS(tile)) remove_pbs_bidi();
+				} else if (!IsTunnelBridgeSignalSimulationBidirectional(tile)) {
 					if (IsTunnelBridgeSignalSimulationEntrance(tile)) {
 						ClearBridgeTunnelSignalSimulation(tile, tile_exit);
 						SetupBridgeTunnelSignalSimulation(tile_exit, tile);
@@ -1124,7 +1157,12 @@ CommandCost CmdBuildSingleSignal(TileIndex tile, DoCommandFlag flags, uint32 p1,
 			} else {
 				/* Create one direction tunnel/bridge if required. */
 				if (p2 == 0) {
-					SetupBridgeTunnelSignalSimulation(tile, tile_exit);
+					if (bidirectional) {
+						set_bidi(tile);
+						set_bidi(tile_exit);
+					} else {
+						SetupBridgeTunnelSignalSimulation(tile, tile_exit);
+					}
 				} else if (p2 == 4 || p2 == 8) {
 					DiagDirection tbdir = GetTunnelBridgeDirection(tile);
 					/* If signal only on one side build accoringly one-way tunnel/bridge. */
@@ -1142,6 +1180,7 @@ CommandCost CmdBuildSingleSignal(TileIndex tile, DoCommandFlag flags, uint32 p1,
 					SetTunnelBridgeSemaphore(tile_exit, sigvar == SIG_SEMAPHORE);
 					SetTunnelBridgePBS(tile, is_pbs);
 					SetTunnelBridgePBS(tile_exit, is_pbs);
+					if (!IsTunnelBridgePBS(tile)) remove_pbs_bidi();
 				}
 			}
 			if (IsTunnelBridgeSignalSimulationExit(tile) && IsTunnelBridgePBS(tile) && !HasTunnelBridgeReservation(tile)) SetTunnelBridgeExitSignalState(tile, SIGNAL_STATE_RED);
@@ -1577,6 +1616,7 @@ CommandCost CmdRemoveSingleSignal(TileIndex tile, DoCommandFlag flags, uint32 p1
 		if (!IsTunnelBridgeWithSignalSimulation(tile)) return_cmd_error(STR_ERROR_THERE_ARE_NO_SIGNALS);
 
 		cost *= ((GetTunnelBridgeLength(tile, end) + 4) >> 2);
+		if (IsTunnelBridgeSignalSimulationBidirectional(tile)) cost *= 2;
 
 		CommandCost ret = EnsureNoTrainOnTrack(GetOtherTunnelBridgeEnd(tile), track);
 		if (ret.Failed()) return ret;
diff --git a/src/rail_gui.cpp b/src/rail_gui.cpp
index 73fe29da0d..68797ff389 100644
--- a/src/rail_gui.cpp
+++ b/src/rail_gui.cpp
@@ -248,6 +248,7 @@ static void GenericPlaceSignals(TileIndex tile)
 			SB(p1, 8, 1, 0);
 			SB(p1, 9, 6, cycle_bounds[_settings_client.gui.cycle_signal_types]);
 		}
+		SB(p1, 18, 1, _settings_client.gui.adv_sig_bridge_tun_modes);
 
 		DoCommandP(tile, p1, 0, CMD_BUILD_SIGNALS |
 				CMD_MSG((w != NULL && _convert_signal_button) ? STR_ERROR_SIGNAL_CAN_T_CONVERT_SIGNALS_HERE : STR_ERROR_CAN_T_BUILD_SIGNALS_HERE),
diff --git a/src/rail_map.h b/src/rail_map.h
index 05faec9018..91310e6e2c 100644
--- a/src/rail_map.h
+++ b/src/rail_map.h
@@ -480,7 +480,7 @@ static inline bool HasOnewaySignalBlockingTrackdir(TileIndex tile, Trackdir td)
 			!HasSignalOnTrackdir(tile, td) && IsOnewaySignal(tile, TrackdirToTrack(td))) {
 		return true;
 	}
-	if (IsTileType(tile, MP_TUNNELBRIDGE) && IsTunnelBridgeSignalSimulationExit(tile) &&
+	if (IsTileType(tile, MP_TUNNELBRIDGE) && IsTunnelBridgeSignalSimulationExitOnly(tile) &&
 			DiagDirToDiagTrackdir(GetTunnelBridgeDirection(tile)) == td) {
 		return true;
 	}
diff --git a/src/settings_gui.cpp b/src/settings_gui.cpp
index ec415952fb..1e63016f34 100644
--- a/src/settings_gui.cpp
+++ b/src/settings_gui.cpp
@@ -1545,6 +1545,7 @@ static SettingsContainer &GetSettingsTree()
 			interface->Add(new SettingEntry("gui.timetable_in_ticks"));
 			interface->Add(new SettingEntry("gui.timetable_arrival_departure"));
 			interface->Add(new SettingEntry("gui.expenses_layout"));
+			interface->Add(new SettingEntry("gui.adv_sig_bridge_tun_modes"));
 		}
 
 		SettingsPage *advisors = main->Add(new SettingsPage(STR_CONFIG_SETTING_ADVISORS));
diff --git a/src/settings_type.h b/src/settings_type.h
index 4c8f695723..d954509b65 100644
--- a/src/settings_type.h
+++ b/src/settings_type.h
@@ -136,6 +136,7 @@ struct GUISettings {
 	byte   missing_strings_threshold;        ///< the number of missing strings before showing the warning
 	uint8  graph_line_thickness;             ///< the thickness of the lines in the various graph guis
 	uint8  osk_activation;                   ///< Mouse gesture to trigger the OSK.
+	bool   adv_sig_bridge_tun_modes;         ///< Enable advanced modes for signals on bridges/tunnels.
 
 	uint16 console_backlog_timeout;          ///< the minimum amount of time items should be in the console backlog before they will be removed in ~3 seconds granularity.
 	uint16 console_backlog_length;           ///< the minimum amount of items in the console backlog before items will be removed.
diff --git a/src/table/settings.ini b/src/table/settings.ini
index 1529cabaac..9070aa6818 100644
--- a/src/table/settings.ini
+++ b/src/table/settings.ini
@@ -3151,6 +3151,14 @@ strhelp  = STR_CONFIG_SETTING_GRAPH_LINE_THICKNESS_HELPTEXT
 strval   = STR_JUST_COMMA
 proc     = RedrawScreen
 
+[SDTC_BOOL]
+var      = gui.adv_sig_bridge_tun_modes
+flags    = SLF_NOT_IN_SAVE | SLF_NO_NETWORK_SYNC
+def      = false
+str      = STR_CONFIG_SETTING_ADV_SIG_BRIDGE_TUN_MODES
+strhelp  = STR_CONFIG_SETTING_ADV_SIG_BRIDGE_TUN_MODES_HELPTEXT
+cat      = SC_EXPERT
+
 ; For the dedicated build we'll enable dates in logs by default.
 [SDTC_BOOL]
 ifdef    = DEDICATED
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index fbcdf65bb5..64da7da717 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -2263,13 +2263,15 @@ static void HandleLastTunnelBridgeSignals(TileIndex tile, TileIndex end, DiagDir
 	if (free) {
 	/* Open up the wormhole and clear m2. */
 		if (IsBridge(end)) {
-			SetAllBridgeEntranceSimulatedSignalsGreen(end);
+			if (IsTunnelBridgeSignalSimulationEntrance(tile)) SetAllBridgeEntranceSimulatedSignalsGreen(tile);
+			if (IsTunnelBridgeSignalSimulationEntrance(end)) SetAllBridgeEntranceSimulatedSignalsGreen(end);
 		}
 
 		if (IsTunnelBridgeSignalSimulationEntrance(end) && GetTunnelBridgeEntranceSignalState(end) == SIGNAL_STATE_RED) {
 			SetTunnelBridgeEntranceSignalState(end, SIGNAL_STATE_GREEN);
 			MarkTileDirtyByTile(end);
-		} else if (IsTunnelBridgeSignalSimulationEntrance(tile) && GetTunnelBridgeEntranceSignalState(tile) == SIGNAL_STATE_RED) {
+		}
+		if (IsTunnelBridgeSignalSimulationEntrance(tile) && GetTunnelBridgeEntranceSignalState(tile) == SIGNAL_STATE_RED) {
 			SetTunnelBridgeEntranceSignalState(tile, SIGNAL_STATE_GREEN);
 			MarkTileDirtyByTile(tile);
 		}
@@ -2790,7 +2792,7 @@ bool TryPathReserve(Train *v, bool mark_as_stuck, bool first_tile_okay)
 		}
 	}
 
-	if (IsTileType(v->tile, MP_TUNNELBRIDGE) && IsTunnelBridgeSignalSimulationExit(v->tile) &&
+	if (IsTileType(v->tile, MP_TUNNELBRIDGE) && IsTunnelBridgeSignalSimulationExitOnly(v->tile) &&
 			DiagDirToDiagTrackBits(GetTunnelBridgeDirection(v->tile)) == v->track) {
 		// prevent any attempt to reserve the wrong way onto a tunnel/bridge exit
 		return false;
@@ -3520,13 +3522,19 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 							v->vehstatus |= VS_TRAIN_SLOWING;
 							return false;
 						}
-						if (IsTunnelBridgeSignalSimulationExit(gp.new_tile)) {
+						if (IsTunnelBridgeSignalSimulationExitOnly(gp.new_tile)) {
 							v->cur_speed = 0;
 							goto invalid_rail;
 						}
 						/* Flip signal on tunnel entrance tile red. */
 						SetTunnelBridgeEntranceSignalState(gp.new_tile, SIGNAL_STATE_RED);
 						MarkTileDirtyByTile(gp.new_tile);
+						if (IsTunnelBridgeSignalSimulationBidirectional(gp.new_tile)) {
+							/* Set incoming signal in other direction to red as well */
+							TileIndex other_end = GetOtherTunnelBridgeEnd(gp.new_tile);
+							SetTunnelBridgeEntranceSignalState(other_end, SIGNAL_STATE_RED);
+							MarkTileDirtyByTile(other_end);
+						}
 					}
 				}
 
@@ -3586,7 +3594,7 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 			TileIndex old_tile = TileVirtXY(v->x_pos, v->y_pos);
 			if (old_tile != gp.new_tile && IsTunnelBridgeWithSignalSimulation(v->tile) && (v->IsFrontEngine() || v->Next() == NULL)) {
 				if (old_tile == v->tile) {
-					if (v->IsFrontEngine() && v->force_proceed == 0 && IsTunnelBridgeSignalSimulationExit(v->tile)) goto invalid_rail;
+					if (v->IsFrontEngine() && v->force_proceed == 0 && IsTunnelBridgeSignalSimulationExitOnly(v->tile)) goto invalid_rail;
 					/* Entered wormhole set counters. */
 					v->wait_counter = (TILE_SIZE * _settings_game.construction.simulated_wormhole_signals) - TILE_SIZE;
 					v->tunnel_bridge_signal_num = 0;
@@ -3842,17 +3850,21 @@ static void DeleteLastWagon(Train *v)
 		if (IsTunnelBridgeWithSignalSimulation(tile)) {
 			TileIndex end = GetOtherTunnelBridgeEnd(tile);
 			UpdateSignalsOnSegment(end, INVALID_DIAGDIR, owner);
-			bool is_entrance = IsTunnelBridgeSignalSimulationEntrance(tile);
-			TileIndex entrance = is_entrance ? tile : end;
 			if (TunnelBridgeIsFree(tile, end, nullptr).Succeeded()) {
-				if (IsBridge(entrance)) {
-					SetAllBridgeEntranceSimulatedSignalsGreen(entrance);
-					MarkBridgeDirty(entrance);
-				}
-				if (IsTunnelBridgeSignalSimulationEntrance(entrance) && GetTunnelBridgeEntranceSignalState(entrance) == SIGNAL_STATE_RED) {
-					SetTunnelBridgeEntranceSignalState(entrance, SIGNAL_STATE_GREEN);
-					MarkTileDirtyByTile(entrance);
-				}
+				auto process_tile = [](TileIndex t) {
+					if (IsTunnelBridgeSignalSimulationEntrance(t)) {
+						if (IsBridge(t)) {
+							SetAllBridgeEntranceSimulatedSignalsGreen(t);
+							MarkBridgeDirty(t);
+						}
+						if (IsTunnelBridgeSignalSimulationEntrance(t) && GetTunnelBridgeEntranceSignalState(t) == SIGNAL_STATE_RED) {
+							SetTunnelBridgeEntranceSignalState(t, SIGNAL_STATE_GREEN);
+							MarkTileDirtyByTile(t);
+						}
+					}
+				};
+				process_tile(tile);
+				process_tile(end);
 			}
 		}
 	} else if (IsRailDepotTile(tile)) {
diff --git a/src/tunnelbridge.h b/src/tunnelbridge.h
index 96134272c0..6dc8c73ba2 100644
--- a/src/tunnelbridge.h
+++ b/src/tunnelbridge.h
@@ -17,7 +17,7 @@
 void MarkBridgeDirty(TileIndex begin, TileIndex end, DiagDirection direction, uint bridge_height);
 void MarkBridgeDirty(TileIndex tile);
 void MarkBridgeOrTunnelDirty(TileIndex tile);
-uint GetTunnelBridgeSignalSimulationSignalCount(uint length);
+uint GetTunnelBridgeSignalSimulationSignalCount(TileIndex begin, TileIndex end);
 
 /**
  * Calculates the length of a tunnel or a bridge (without end tiles)
@@ -35,17 +35,6 @@ static inline uint GetTunnelBridgeLength(TileIndex begin, TileIndex end)
 	return abs(x2 + y2 - x1 - y1) - 1;
 }
 
-/**
- * Get number of signals on bridge or tunnel with signal simulation.
- * @param begin The begin of the tunnel or bridge.
- * @param end   The end of the tunnel or bridge.
- * @pre IsTunnelBridgeWithSignalSimulation(begin)
- */
-static inline uint GetTunnelBridgeSignalSimulationSignalCount(TileIndex begin, TileIndex end)
-{
-	return GetTunnelBridgeSignalSimulationSignalCount(GetTunnelBridgeLength(begin, end));
-}
-
 extern TileIndex _build_tunnel_endtile;
 
 #endif /* TUNNELBRIDGE_H */
diff --git a/src/tunnelbridge_cmd.cpp b/src/tunnelbridge_cmd.cpp
index ccb25a315f..35b1f52bac 100644
--- a/src/tunnelbridge_cmd.cpp
+++ b/src/tunnelbridge_cmd.cpp
@@ -97,12 +97,15 @@ void MarkBridgeOrTunnelDirty(TileIndex tile)
 
 /**
  * Get number of signals on bridge or tunnel with signal simulation.
- * @param length Length of bridge/tunnel middle
- * @return Number of signals on signalled bridge/tunnel of this length
+ * @param begin The begin of the tunnel or bridge.
+ * @param end   The end of the tunnel or bridge.
+ * @pre IsTunnelBridgeWithSignalSimulation(begin)
  */
-uint GetTunnelBridgeSignalSimulationSignalCount(uint length)
+uint GetTunnelBridgeSignalSimulationSignalCount(TileIndex begin, TileIndex end)
 {
-	return 2 + (length / _settings_game.construction.simulated_wormhole_signals);
+	uint result = 2 + (GetTunnelBridgeLength(begin, end) / _settings_game.construction.simulated_wormhole_signals);
+	if (IsTunnelBridgeSignalSimulationBidirectional(begin)) result *= 2;
+	return result;
 }
 
 /** Reset the data been eventually changed by the grf loaded. */
@@ -1157,10 +1160,10 @@ static void DrawBridgeTramBits(int x, int y, int z, int offset, bool overlay, bo
 	}
 }
 
-/* Draws a signal on tunnel / bridge entrance tile. */
-static void DrawTunnelBridgeRampSignal(const TileInfo *ti)
+static void DrawTunnelBridgeRampSingleSignal(const TileInfo *ti, bool is_green, uint position, SignalType type, bool show_exit)
 {
 	bool side = (_settings_game.vehicle.road_side != 0) &&_settings_game.construction.train_signal_side;
+	DiagDirection dir = GetTunnelBridgeDirection(ti->tile);
 
 	static const Point SignalPositions[2][4] = {
 		{   /*  X         X         Y         Y     Signals on the left side */
@@ -1170,30 +1173,6 @@ static void DrawTunnelBridgeRampSignal(const TileInfo *ti)
 		}
 	};
 
-	uint position;
-	DiagDirection dir = GetTunnelBridgeDirection(ti->tile);
-
-	switch (dir) {
-		default: NOT_REACHED();
-		case DIAGDIR_NE: position = 0; break;
-		case DIAGDIR_SE: position = 2; break;
-		case DIAGDIR_SW: position = 1; break;
-		case DIAGDIR_NW: position = 3; break;
-	}
-
-	SignalType type = SIGTYPE_NORMAL;
-
-	bool is_green, show_exit;
-	if (IsTunnelBridgeSignalSimulationExit(ti->tile)) {
-		is_green = (GetTunnelBridgeExitSignalState(ti->tile) == SIGNAL_STATE_GREEN);
-		show_exit = true;
-		position ^= 1;
-		if (IsTunnelBridgePBS(ti->tile)) type = SIGTYPE_PBS_ONEWAY;
-	} else {
-		is_green = (GetTunnelBridgeEntranceSignalState(ti->tile) == SIGNAL_STATE_GREEN);
-		show_exit = false;
-	}
-
 	uint x = TileX(ti->tile) * TILE_SIZE + SignalPositions[side != show_exit][position ^ show_exit].x;
 	uint y = TileY(ti->tile) * TILE_SIZE + SignalPositions[side != show_exit][position ^ show_exit].y;
 	uint z = ti->z;
@@ -1216,6 +1195,32 @@ static void DrawTunnelBridgeRampSignal(const TileInfo *ti)
 	AddSortableSpriteToDraw(sprite, PAL_NONE, x, y, 1, 1, TILE_HEIGHT, z, false, 0, 0, BB_Z_SEPARATOR);
 }
 
+/* Draws a signal on tunnel / bridge entrance tile. */
+static void DrawTunnelBridgeRampSignal(const TileInfo *ti)
+{
+	DiagDirection dir = GetTunnelBridgeDirection(ti->tile);
+
+	uint position;
+	switch (dir) {
+		default: NOT_REACHED();
+		case DIAGDIR_NE: position = 0; break;
+		case DIAGDIR_SE: position = 2; break;
+		case DIAGDIR_SW: position = 1; break;
+		case DIAGDIR_NW: position = 3; break;
+	}
+
+	if (IsTunnelBridgeSignalSimulationExit(ti->tile)) {
+		SignalType type = SIGTYPE_NORMAL;
+		if (IsTunnelBridgePBS(ti->tile)) {
+			type = IsTunnelBridgeSignalSimulationEntrance(ti->tile) ? SIGTYPE_PBS : SIGTYPE_PBS_ONEWAY;
+		}
+		DrawTunnelBridgeRampSingleSignal(ti, (GetTunnelBridgeExitSignalState(ti->tile) == SIGNAL_STATE_GREEN), position ^ 1, type, true);
+	}
+	if (IsTunnelBridgeSignalSimulationEntrance(ti->tile)) {
+		DrawTunnelBridgeRampSingleSignal(ti, (GetTunnelBridgeEntranceSignalState(ti->tile) == SIGNAL_STATE_GREEN), position, SIGTYPE_NORMAL, false);
+	}
+}
+
 /* Draws a signal on tunnel / bridge entrance tile. */
 static void DrawBridgeSignalOnMiddlePart(const TileInfo *ti, TileIndex bridge_start_tile, uint z)
 {
@@ -1646,9 +1651,8 @@ void DrawBridgeMiddle(const TileInfo *ti)
 		if (HasRailCatenaryDrawn(GetRailType(rampsouth))) {
 			DrawRailCatenaryOnBridge(ti);
 		}
-		if (IsTunnelBridgeWithSignalSimulation(rampsouth)) {
-			IsTunnelBridgeSignalSimulationExit(rampsouth) ? DrawBrigeSignalOnMiddlePart(ti, rampnorth, z): DrawBrigeSignalOnMiddlePart(ti, rampsouth, z);
-		}
+		if (IsTunnelBridgeSignalSimulationEntrance(rampsouth)) DrawBridgeSignalOnMiddlePart(ti, rampsouth, z);
+		if (IsTunnelBridgeSignalSimulationEntrance(rampnorth)) DrawBridgeSignalOnMiddlePart(ti, rampnorth, z);
 	}
 
 	/* draw roof, the component of the bridge which is logically between the vehicle and the camera */
diff --git a/src/tunnelbridge_map.h b/src/tunnelbridge_map.h
index f6a21e9992..e079a23269 100644
--- a/src/tunnelbridge_map.h
+++ b/src/tunnelbridge_map.h
@@ -183,7 +183,7 @@ static inline bool IsTunnelBridgeWithSignalSimulation(TileIndex t)
 static inline bool IsTunnelBridgeSignalSimulationEntrance(TileIndex t)
 {
 	assert(IsTileType(t, MP_TUNNELBRIDGE));
-	return HasBit(_m[t].m5, 5) && !HasBit(_m[t].m5, 6);
+	return HasBit(_m[t].m5, 5);
 }
 
 /**
@@ -193,11 +193,35 @@ static inline bool IsTunnelBridgeSignalSimulationEntrance(TileIndex t)
  * @return true if and only if this tile is a tunnel/bridge exit.
  */
 static inline bool IsTunnelBridgeSignalSimulationExit(TileIndex t)
+{
+	assert(IsTileType(t, MP_TUNNELBRIDGE));
+	return HasBit(_m[t].m5, 6);
+}
+
+/**
+ * Is this a tunnel/bridge exit 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 exit only.
+ */
+static inline bool IsTunnelBridgeSignalSimulationExitOnly(TileIndex t)
 {
 	assert(IsTileType(t, MP_TUNNELBRIDGE));
 	return !HasBit(_m[t].m5, 5) && HasBit(_m[t].m5, 6);
 }
 
+/**
+ * Is this a tunnel/bridge entrance and exit?
+ * @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 and exit.
+ */
+static inline bool IsTunnelBridgeSignalSimulationBidirectional(TileIndex t)
+{
+	assert(IsTileType(t, MP_TUNNELBRIDGE));
+	return HasBit(_m[t].m5, 5) && HasBit(_m[t].m5, 6);
+}
+
 /**
  * Get the signal state for a tunnel/bridge entrance with signal simulation
  * @param t the tunnel/bridge entrance or exit tile with signal simulation