Initial support for rail custom bridge heads

docs/landscape.html

@@ -1473,10 +1473,76 @@
        </tr>
       </table>
      </li>
+     <li style="color: blue">m2 bits 2..0: rail bridge heads track reserved for pbs
+       <table style="color: blue">
+        <tr>
+          <td><tt>0</tt>&nbsp; </td>
+          <td>not reserved</td>
+        </tr>
+        <tr>
+          <td><tt>1</tt>&nbsp; </td>
+          <td>X direction</td>
+        </tr>
+        <tr>
+          <td><tt>2</tt>&nbsp; </td>
+          <td>Y direction</td>
+        </tr>
+        <tr>
+          <td><tt>3</tt>&nbsp; </td>
+          <td>north corner (W-E)</td>
+        </tr>
+        <tr>
+          <td><tt>4</tt>&nbsp; </td>
+          <td>south corner (W-E)</td>
+        </tr>
+        <tr>
+          <td><tt>5</tt>&nbsp; </td>
+          <td>west corner (N-S)</td>
+        </tr>
+        <tr>
+          <td><tt>6</tt>&nbsp; </td>
+          <td>east corner (N-S)</td>
+        </tr>
+       </table>
+     </li>
+     <li style="color: blue">m2 bit 3: rail bridge heads opposite track is reserved, too</li>
      <li>m3 bits 7..4: <a href="#OwnershipInfo">owner</a> of tram</li>
      <li>m3 bits 3..0: <a href="#TrackType">track type</a> for railway</li>
-     <li>m5 bit 4: pbs reservation state for railway</li>
+     <li style="color: blue">m4 bits 5..0: rail bridge heads track layout: bit set = track present:
-     <li>m5 bits 7 clear: tunnel entrance/exit</li>
+      <table style="color: blue">
+       <tr>
+        <td nowrap valign=top>bit 0: </td>
+        <td align=left>in the X direction</td>
+       </tr>
+
+       <tr>
+        <td nowrap valign=top>bit 1: </td>
+        <td align=left>in the Y direction</td>
+       </tr>
+
+       <tr>
+        <td nowrap valign=top>bit 2: </td>
+        <td align=left>in the north corner (direction W-E)</td>
+       </tr>
+
+       <tr>
+        <td nowrap valign=top>bit 3: </td>
+        <td align=left>in the south corner (direction W-E)</td>
+       </tr>
+
+       <tr>
+        <td nowrap valign=top>bit 4: </td>
+        <td align=left>in the west corner (direction N-S)</td>
+       </tr>
+
+       <tr>
+        <td nowrap valign=top>bit 5: </td>
+        <td align=left>in the east corner (direction N-S)</td>
+       </tr>
+      </table>
+     </li>
+     <li>m5 bit 4: pbs reservation state for railway (tunnel only)</li>
+     <li>m5 bit 7 clear: tunnel entrance/exit</li>
      <li>m5 bit 7 set: bridge ramp
       <ul>
        <li>m6 bits 5..2: <a name="BridgeType">bridge type</a>:

docs/landscape_grid.html

@@ -347,7 +347,7 @@ the array so you can quickly see what is used and what is not.
       <td class="bits">-inherit-</td>
       <td class="bits"><span class="free">OOOO OOOO</span> <span class="used_p">PPPP PPPP</span></td>
       <td class="bits">-inherit-</td>
-      <td class="bits">-inherit-</td>
+      <td class="bits"><span class="free">OO</span><span class="used_p">PP PPPP</span></td>
       <td class="bits">-inherit-</td>
       <td class="bits"><span class="free">OO</span>XX XX<span class="free">OO</span></td>
       <td class="bits">-inherit-</td>

src/bridge_map.h

@@ -171,9 +171,22 @@ static inline void MakeRoadBridgeRamp(TileIndex t, Owner o, Owner owner_road, Ow
  * @param d          the direction this ramp must be facing
  * @param r          the rail type of the bridge
  */
-static inline void MakeRailBridgeRamp(TileIndex t, Owner o, BridgeType bridgetype, DiagDirection d, RailType r)
+static inline void MakeRailBridgeRamp(TileIndex t, Owner o, BridgeType bridgetype, DiagDirection d, RailType r, bool upgrade)
 {
+	// Backup custom bridgehead data.
+	uint custom_bridge_head_reservation_backup = GB(_m[t].m2, 0, 4);
+	uint custom_bridge_head_tracks_backup = GB(_m[t].m4, 0, 6);
+
 	MakeBridgeRamp(t, o, bridgetype, d, TRANSPORT_RAIL, r);
+
+	if (upgrade) {
+		// Restore custom bridgehead data if we're upgrading an existing bridge.
+		SB(_m[t].m2, 0, 4, custom_bridge_head_reservation_backup);
+		SB(_m[t].m4, 0, 6, custom_bridge_head_tracks_backup);
+	} else {
+		// Set bridge head tracks to axial track only.
+		SB(_m[t].m4, 0, 6, DiagDirToDiagTrackBits(d));
+	}
 }
 
 /**
@@ -255,4 +268,195 @@ static inline void SetCustomBridgeHeadRoadBits(TileIndex t, RoadType rt, RoadBit
 	}
 }
 
+/**
+ * Checks if this tile is a rail bridge head
+ * @param t The tile to analyze
+ * @return true if it is a rail bridge head
+ */
+static inline bool IsRailBridgeHeadTile(TileIndex t)
+{
+	return IsBridgeTile(t) && (TransportType)GB(_m[t].m5, 2, 2) == TRANSPORT_RAIL;
+}
+
+/**
+ * Checks if this tile is a flat rail bridge head
+ * @param t The tile to analyze
+ * @return true if it is a flat rail bridge head
+ */
+static inline bool IsFlatRailBridgeHeadTile(TileIndex t)
+{
+	return IsRailBridgeHeadTile(t) && HasBridgeFlatRamp(GetTileSlope(t), DiagDirToAxis((DiagDirection)GB(_m[t].m5, 0, 2)));
+}
+
+/**
+ * Returns the track bits for a (possibly custom) rail bridge head
+ * @param tile the tile to get the track bits from
+ * @pre IsRailBridgeHeadTile(t)
+ * @return road bits for the bridge head
+ */
+static inline TrackBits GetCustomBridgeHeadTrackBits(TileIndex t)
+{
+	assert(IsRailBridgeHeadTile(t));
+	return (TrackBits)GB(_m[t].m4, 0, 6);
+}
+
+/**
+ * Sets the road track for a (possibly custom) rail bridge head
+ * @param t the tile to set the track bits of
+ * @param b the new track bits for the tile
+ * @pre IsRailBridgeHeadTile(t)
+ */
+static inline void SetCustomBridgeHeadTrackBits(TileIndex t, TrackBits b)
+{
+	assert(IsRailBridgeHeadTile(t));
+	SB(_m[t].m4, 0, 6, b);
+}
+
+/**
+ * Checks if this rail bridge head is a custom bridge head
+ * @param t The tile to analyze
+ * @pre IsRailBridgeHeadTile(t)
+ * @return true if it is a custom bridge head
+ */
+static inline bool IsRailCustomBridgeHead(TileIndex t)
+{
+	assert(IsRailBridgeHeadTile(t));
+	return GetCustomBridgeHeadTrackBits(t) != DiagDirToDiagTrackBits((DiagDirection)GB(_m[t].m5, 0, 2));
+}
+
+/**
+ * Checks if this tile is a rail bridge head with a custom bridge head
+ * @param t The tile to analyze
+ * @return true if it is a rail bridge head with a custom bridge head
+ */
+static inline bool IsRailCustomBridgeHeadTile(TileIndex t)
+{
+	return IsRailBridgeHeadTile(t) && IsRailCustomBridgeHead(t);
+}
+
+/**
+ * Checks if this tile is a bridge head with a custom bridge head
+ * @param t The tile to analyze
+ * @return true if it is a bridge head with a custom bridge head
+ */
+static inline bool IsCustomBridgeHeadTile(TileIndex t)
+{
+	return IsRailCustomBridgeHeadTile(t) || IsRoadCustomBridgeHeadTile(t);
+}
+
+/**
+ * Get the reserved track bits for a rail bridge head
+ * @pre IsRailBridgeHeadTile(t)
+ * @param t the tile
+ * @return reserved track bits
+ */
+static inline TrackBits GetBridgeReservationTrackBits(TileIndex t)
+{
+	assert(IsRailBridgeHeadTile(t));
+	byte track_b = GB(_m[t].m2, 0, 3);
+	Track track = (Track)(track_b - 1);    // map array saves Track+1
+	if (track_b == 0) return TRACK_BIT_NONE;
+	return (TrackBits)(TrackToTrackBits(track) | (HasBit(_m[t].m2, 3) ? TrackToTrackBits(TrackToOppositeTrack(track)) : 0));
+}
+
+/**
+ * Sets the reserved track bits of the rail bridge head
+ * @pre IsRailBridgeHeadTile(t)
+ * @param t the tile to change
+ * @param b the track bits
+ */
+static inline void SetBridgeReservationTrackBits(TileIndex t, TrackBits b)
+{
+	assert(IsRailBridgeHeadTile(t));
+	assert(!TracksOverlap(b));
+	Track track = RemoveFirstTrack(&b);
+	SB(_m[t].m2, 0, 3, track == INVALID_TRACK ? 0 : track + 1);
+	SB(_m[t].m2, 3, 1, (byte)(b != TRACK_BIT_NONE));
+}
+
+
+/**
+ * Try to reserve a specific track on a rail bridge head tile
+ * @pre IsRailBridgeHeadTile(t) && HasBit(GetCustomBridgeHeadTrackBits(tile), t)
+ * @param tile the tile
+ * @param t the rack to reserve
+ * @return true if successful
+ */
+static inline bool TryReserveRailBridgeHead(TileIndex tile, Track t)
+{
+	assert(IsRailBridgeHeadTile(tile));
+	assert(HasBit(GetCustomBridgeHeadTrackBits(tile), t));
+	TrackBits bits = TrackToTrackBits(t);
+	TrackBits res = GetBridgeReservationTrackBits(tile);
+	if ((res & bits) != TRACK_BIT_NONE) return false;  // already reserved
+	res |= bits;
+	if (TracksOverlap(res)) return false;  // crossing reservation present
+	SetBridgeReservationTrackBits(tile, res);
+	return true;
+}
+
+
+/**
+ * Lift the reservation of a specific track on a rail bridge head tile
+ * @pre IsRailBridgeHeadTile(t) && HasBit(GetCustomBridgeHeadTrackBits(tile), t)
+ * @param tile the tile
+ * @param t the track to free
+ */
+static inline void UnreserveRailBridgeHeadTrack(TileIndex tile, Track t)
+{
+	assert(IsRailBridgeHeadTile(tile));
+	assert(HasBit(GetCustomBridgeHeadTrackBits(tile), t));
+	TrackBits res = GetBridgeReservationTrackBits(tile);
+	res &= ~TrackToTrackBits(t);
+	SetBridgeReservationTrackBits(tile, res);
+}
+
+/**
+ * Get the possible track bits of the bridge head tile onto/across the bridge
+ * @pre IsRailBridgeHeadTile(t)
+ * @param t the tile
+ * @return reservation state
+ */
+static inline TrackBits GetAcrossBridgePossibleTrackBits(TileIndex t)
+{
+	assert(IsRailBridgeHeadTile(t));
+	return DiagdirReachesTracks(ReverseDiagDir((DiagDirection)GB(_m[t].m5, 0, 2)));
+}
+
+/**
+ * Get the reserved track bits of the bridge head tile onto/across the bridge
+ * @pre IsBridgeTile(t) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
+ * @param t the tile
+ * @return reservation state
+ */
+static inline TrackBits GetAcrossBridgeReservationTrackBits(TileIndex t)
+{
+	return GetBridgeReservationTrackBits(t) & GetAcrossBridgePossibleTrackBits(t);
+}
+
+/**
+ * Get the reservation state of the bridge head tile onto/across the bridge
+ * @pre IsBridgeTile(t) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
+ * @param t the tile
+ * @return reservation state
+ */
+static inline bool HasAcrossBridgeReservation(TileIndex t)
+{
+	return GetAcrossBridgeReservationTrackBits(t) != TRACK_BIT_NONE;
+}
+
+/**
+ * Lift the reservation of a specific track on a rail bridge head tile
+ * @pre IsRailBridgeHeadTile(t)
+ * @param tile the tile
+ */
+static inline void UnreserveAcrossRailBridgeHead(TileIndex tile)
+{
+	assert(IsRailBridgeHeadTile(tile));
+	TrackBits res = GetAcrossBridgeReservationTrackBits(tile);
+	if (res != TRACK_BIT_NONE) {
+		SetBridgeReservationTrackBits(tile, GetBridgeReservationTrackBits(tile) & ~res);
+	}
+}
+
 #endif /* BRIDGE_MAP_H */

src/elrail.cpp

@@ -103,7 +103,7 @@ static TrackBits GetRailTrackBitsUniversal(TileIndex t, byte *override)
 			if (override != NULL && (IsTunnel(t) || GetTunnelBridgeLength(t, GetOtherBridgeEnd(t)) > 0)) {
 				*override = 1 << GetTunnelBridgeDirection(t);
 			}
-			return DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t));
+			return GetTunnelBridgeTrackBits(t);
 
 		case MP_ROAD:
 			if (!IsLevelCrossing(t)) return TRACK_BIT_NONE;
@@ -199,6 +199,8 @@ static void AdjustTileh(TileIndex tile, Slope *tileh)
 	if (IsTileType(tile, MP_TUNNELBRIDGE)) {
 		if (IsTunnel(tile)) {
 			*tileh = SLOPE_STEEP; // XXX - Hack to make tunnel entrances to always have a pylon
+		} else if (IsRailCustomBridgeHeadTile(tile)) {
+			/* no change */
 		} else if (*tileh != SLOPE_FLAT) {
 			*tileh = SLOPE_FLAT;
 		} else {

src/landscape.cpp

@@ -352,7 +352,7 @@ Slope GetFoundationSlope(TileIndex tile, int *z)
 
 bool HasFoundationNW(TileIndex tile, Slope slope_here, uint z_here)
 {
-	if (IsRoadCustomBridgeHeadTile(tile) && GetTunnelBridgeDirection(tile) == DIAGDIR_NW) return false;
+	if (IsCustomBridgeHeadTile(tile) && GetTunnelBridgeDirection(tile) == DIAGDIR_NW) return false;
 
 	int z;
 
@@ -371,7 +371,7 @@ bool HasFoundationNW(TileIndex tile, Slope slope_here, uint z_here)
 
 bool HasFoundationNE(TileIndex tile, Slope slope_here, uint z_here)
 {
-	if (IsRoadCustomBridgeHeadTile(tile) && GetTunnelBridgeDirection(tile) == DIAGDIR_NE) return false;
+	if (IsCustomBridgeHeadTile(tile) && GetTunnelBridgeDirection(tile) == DIAGDIR_NE) return false;
 
 	int z;
 

src/lang/english.txt

@@ -1703,6 +1703,8 @@ STR_CONFIG_SETTING_REVERSE_AT_SIGNALS_HELPTEXT                  :Allow trains to
 
 STR_CONFIG_SETTING_ENABLE_ROAD_CUSTOM_BRIDGE_HEADS              :Enable road custom bridge heads: {STRING2}
 STR_CONFIG_SETTING_ENABLE_ROAD_CUSTOM_BRIDGE_HEADS_HELPTEXT     :Allow road bridges to have custom, non-straight flat entry/exit tiles
+STR_CONFIG_SETTING_ENABLE_RAIL_CUSTOM_BRIDGE_HEADS              :Enable rail custom bridge heads: {STRING2}
+STR_CONFIG_SETTING_ENABLE_RAIL_CUSTOM_BRIDGE_HEADS_HELPTEXT     :Allow rail bridges to have custom, non-straight flat entry/exit tiles
 
 STR_CONFIG_SETTING_QUERY_CAPTION                                :{WHITE}Change setting value
 

src/newgrf_station.cpp

@@ -209,7 +209,7 @@ static uint32 GetRailContinuationInfo(TileIndex tile)
 
 			/* With tunnels and bridges the tile has tracks, but they are not necessarily connected
 			 * with the next tile because the ramp is not going in the right direction. */
-			if (IsTileType(neighbour_tile, MP_TUNNELBRIDGE) && GetTunnelBridgeDirection(neighbour_tile) != *diagdir) {
+			if (IsTileType(neighbour_tile, MP_TUNNELBRIDGE) && GetTunnelBridgeDirection(neighbour_tile) == ReverseDiagDir(*diagdir)) {
 				continue;
 			}
 

src/pathfinder/follow_track.hpp

@@ -125,7 +125,7 @@ struct CFollowTrackT
 		m_old_td = old_td;
 		m_err = EC_NONE;
 		assert(((TrackStatusToTrackdirBits(GetTileTrackStatus(m_old_tile, TT(), IsRoadTT() ? RoadVehicle::From(m_veh)->compatible_roadtypes : 0)) & TrackdirToTrackdirBits(m_old_td)) != 0) ||
-		       (IsTram() && GetSingleTramBit(m_old_tile) != INVALID_DIAGDIR)); // Disable the assertion for single tram bits
+		       (IsTram() && GetSingleTramBit(m_old_tile) != INVALID_DIAGDIR) || (IsRailTT() && IsRailCustomBridgeHeadTile(m_old_tile))); // Disable the assertion for single tram bits
 		m_exitdir = TrackdirToExitdir(m_old_td);
 		if (ForcedReverse()) return true;
 		if (!CanExitOldTile()) return false;
@@ -153,7 +153,7 @@ struct CFollowTrackT
 
 			return false;
 		}
-		if (!Allow90degTurns()) {
+		if (!Allow90degTurns() && m_tiles_skipped == 0) {
 			m_new_td_bits &= (TrackdirBits)~(int)TrackdirCrossesTrackdirs(m_old_td);
 			if (m_new_td_bits == TRACKDIR_BIT_NONE) {
 				m_err = EC_90DEG;
@@ -216,7 +216,7 @@ protected:
 				m_tiles_skipped = GetTunnelBridgeLength(m_new_tile, m_old_tile);
 				return;
 			}
-			if (!IsRoadCustomBridgeHeadTile(m_old_tile)) assert(ReverseDiagDir(enterdir) == m_exitdir);
+			if (!IsRoadCustomBridgeHeadTile(m_old_tile) && !IsRailCustomBridgeHeadTile(m_old_tile)) assert(ReverseDiagDir(enterdir) == m_exitdir);
 		}
 
 		/* normal or station tile, do one step */
@@ -365,13 +365,22 @@ protected:
 					}
 				}
 			} else { // IsBridge(m_new_tile)
+				DiagDirection ramp_enderdir = GetTunnelBridgeDirection(m_new_tile);
+				if (!m_is_bridge && ramp_enderdir == ReverseDiagDir(m_exitdir)) {
+					m_err = EC_NO_WAY;
+					return false;
+				}
 				if (!m_is_bridge && IsRoadTT() && IsRoadCustomBridgeHeadTile(m_new_tile)) {
 					if (!(DiagDirToRoadBits(ReverseDiagDir(m_exitdir)) & GetCustomBridgeHeadRoadBits(m_new_tile, IsTram() ? ROADTYPE_TRAM : ROADTYPE_ROAD))) {
 						m_err = EC_NO_WAY;
 						return false;
 					}
+				} else if (!m_is_bridge && IsRailTT() && IsRailCustomBridgeHeadTile(m_new_tile)) {
+					if (!(DiagdirReachesTracks(m_exitdir) & GetCustomBridgeHeadTrackBits(m_new_tile))) {
+						m_err = EC_NO_WAY;
+						return false;
+					}
 				} else if (!m_is_bridge) {
-					DiagDirection ramp_enderdir = GetTunnelBridgeDirection(m_new_tile);
 					if (ramp_enderdir != m_exitdir) {
 						m_err = EC_NO_WAY;
 						return false;

src/pathfinder/yapf/yapf_rail.cpp

@@ -564,7 +564,7 @@ bool YapfTrainCheckReverse(const Train *v)
 
 	int reverse_penalty = 0;
 
-	if (v->track == TRACK_BIT_WORMHOLE) {
+	if (v->track & TRACK_BIT_WORMHOLE) {
 		/* front in tunnel / on bridge */
 		DiagDirection dir_into_wormhole = GetTunnelBridgeDirection(tile);
 
@@ -579,7 +579,7 @@ bool YapfTrainCheckReverse(const Train *v)
 		reverse_penalty -= DistanceManhattan(cur_tile, tile) * YAPF_TILE_LENGTH;
 	}
 
-	if (last_veh->track == TRACK_BIT_WORMHOLE) {
+	if (last_veh->track & TRACK_BIT_WORMHOLE) {
 		/* back in tunnel / on bridge */
 		DiagDirection dir_into_wormhole = GetTunnelBridgeDirection(tile_rev);
 

src/pbs.cpp

@@ -81,7 +81,8 @@ void SetRailStationPlatformReservation(TileIndex start, DiagDirection dir, bool
  */
 bool TryReserveRailTrack(TileIndex tile, Track t, bool trigger_stations)
 {
-	assert((GetTileTrackStatus(tile, TRANSPORT_RAIL, 0) & TrackToTrackBits(t)) != 0);
+	assert_msg((TrackStatusToTrackBits(GetTileTrackStatus(tile, TRANSPORT_RAIL, 0)) & TrackToTrackBits(t)) != 0,
+			"%X, %X, %X, %X", TrackStatusToTrackBits(GetTileTrackStatus(tile, TRANSPORT_RAIL, 0)), tile, t, TrackToTrackBits(t));
 
 	if (_settings_client.gui.show_track_reservation) {
 		/* show the reserved rail if needed */
@@ -123,10 +124,15 @@ bool TryReserveRailTrack(TileIndex tile, Track t, bool trigger_stations)
 			break;
 
 		case MP_TUNNELBRIDGE:
-			if (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL && !GetTunnelBridgeReservationTrackBits(tile)) {
+			if (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL) {
-				SetTunnelBridgeReservation(tile, true);
+				if (IsTunnel(tile) && !HasTunnelReservation(tile)) {
+					SetTunnelReservation(tile, true);
 					return true;
 				}
+				if (IsBridge(tile)) {
+					return TryReserveRailBridgeHead(tile, t);
+				}
+			}
 			break;
 
 		default:
@@ -177,7 +183,13 @@ void UnreserveRailTrack(TileIndex tile, Track t)
 			break;
 
 		case MP_TUNNELBRIDGE:
-			if (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL) SetTunnelBridgeReservation(tile, false);
+			if (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL) {
+				if (IsTunnel(tile)) {
+					SetTunnelReservation(tile, false);
+				} else {
+					UnreserveRailBridgeHeadTrack(tile, t);
+				}
+			}
 			break;
 
 		default:
@@ -270,7 +282,7 @@ static Vehicle *FindTrainOnTrackEnum(Vehicle *v, void *data)
 	if (v->type != VEH_TRAIN || (v->vehstatus & VS_CRASHED)) return NULL;
 
 	Train *t = Train::From(v);
-	if (t->track == TRACK_BIT_WORMHOLE || HasBit((TrackBits)t->track, TrackdirToTrack(info->res.trackdir))) {
+	if (t->track & TRACK_BIT_WORMHOLE || HasBit((TrackBits)t->track, TrackdirToTrack(info->res.trackdir))) {
 		t = t->First();
 
 		/* ALWAYS return the lowest ID (anti-desync!) */

src/rail_cmd.cpp

@@ -424,6 +424,25 @@ static CommandCost CheckRailSlope(Slope tileh, TrackBits rail_bits, TrackBits ex
 	return CommandCost(EXPENSES_CONSTRUCTION, f_new != f_old ? _price[PR_BUILD_FOUNDATION] : (Money)0);
 }
 
+bool IsValidFlatRailBridgeHeadTrackBits(Slope normalised_slope, DiagDirection bridge_direction, TrackBits tracks)
+{
+	/* bridge_direction  c1  c2
+	 *                0   0   1
+	 *                1   0   3
+	 *                2   2   3
+	 *                3   2   1
+	 */
+	const Corner c1 = (Corner) (bridge_direction & 2);
+	const Corner c2 = (Corner) (((bridge_direction + 1) & 2) + 1);
+	auto test_corner = [&](Corner c) -> bool {
+		if (normalised_slope & SlopeWithOneCornerRaised(c)) return true;
+		Slope effective_slope = normalised_slope | SlopeWithOneCornerRaised(OppositeCorner(c));
+		assert(effective_slope < lengthof(_valid_tracks_on_leveled_foundation));
+		return (_valid_tracks_on_leveled_foundation[effective_slope] & tracks) == tracks;
+	};
+	return test_corner(c1) && test_corner(c2);
+}
+
 /* Validate functions for rail building */
 static inline bool ValParamTrackOrientation(Track track)
 {
@@ -443,6 +462,7 @@ CommandCost CmdBuildSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 {
 	RailType railtype = Extract<RailType, 0, 4>(p1);
 	Track track = Extract<Track, 0, 3>(p2);
+	bool disable_custom_bridge_heads = HasBit(p2, 4);
 	CommandCost cost(EXPENSES_CONSTRUCTION);
 
 	if (!ValParamRailtype(railtype) || !ValParamTrackOrientation(track)) return CMD_ERROR;
@@ -497,6 +517,52 @@ CommandCost CmdBuildSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 			break;
 		}
 
+		case MP_TUNNELBRIDGE: {
+			CommandCost ret = CheckTileOwnership(tile);
+			if (ret.Failed()) return ret;
+
+			if (disable_custom_bridge_heads || !_settings_game.construction.rail_custom_bridge_heads || !IsFlatRailBridgeHeadTile(tile)) return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR); // just get appropriate error message
+
+			if (!IsCompatibleRail(GetRailType(tile), railtype)) return_cmd_error(STR_ERROR_IMPOSSIBLE_TRACK_COMBINATION);
+			if (GetRailType(tile) != railtype && !HasPowerOnRail(railtype, GetRailType(tile))) return_cmd_error(STR_ERROR_CAN_T_CONVERT_RAIL);
+
+			const DiagDirection entrance_dir = GetTunnelBridgeDirection(tile);
+			const TrackBits axial_track = DiagDirToDiagTrackBits(entrance_dir);
+			const TrackBits existing = GetCustomBridgeHeadTrackBits(tile);
+			const TrackBits future = existing | trackbit;
+
+			if (existing == future) return_cmd_error(STR_ERROR_ALREADY_BUILT);
+
+			if (flags & DC_NO_RAIL_OVERLAP) {
+				if (future != TRACK_BIT_HORZ && future != TRACK_BIT_VERT) {
+					return_cmd_error(STR_ERROR_IMPOSSIBLE_TRACK_COMBINATION);
+				}
+			}
+
+			if ((trackbit & ~axial_track) && !_settings_game.construction.build_on_slopes) {
+				return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
+			}
+
+			/* Steep slopes behave the same as slopes with one corner raised. */
+			const Slope normalised_tileh = IsSteepSlope(tileh) ? SlopeWithOneCornerRaised(GetHighestSlopeCorner(tileh)) : tileh;
+
+			if (!IsValidFlatRailBridgeHeadTrackBits(normalised_tileh, GetTunnelBridgeDirection(tile), future)) {
+				return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
+			}
+
+			const TileIndex other_end = GetOtherTunnelBridgeEnd(tile);
+			ret = TunnelBridgeIsFree(tile, other_end);
+			if (ret.Failed()) return ret;
+
+			if (flags & DC_EXEC) {
+				SetCustomBridgeHeadTrackBits(tile, future);
+				Company::Get(GetTileOwner(tile))->infrastructure.rail[GetRailType(tile)] += GetTunnelBridgeHeadOnlyRailInfrastructureCountFromTrackBits(future) - GetTunnelBridgeHeadOnlyRailInfrastructureCountFromTrackBits(existing);
+				DirtyCompanyInfrastructureWindows(_current_company);
+			}
+
+			break;
+		}
+
 		case MP_ROAD: {
 			/* Level crossings may only be built on these slopes */
 			if (!HasBit(VALID_LEVEL_CROSSING_SLOPES, tileh)) return_cmd_error(STR_ERROR_LAND_SLOPED_IN_WRONG_DIRECTION);
@@ -710,6 +776,44 @@ CommandCost CmdRemoveSingleRail(TileIndex tile, DoCommandFlag flags, uint32 p1,
 			break;
 		}
 
+		case MP_TUNNELBRIDGE: {
+			CommandCost ret = CheckTileOwnership(tile);
+			if (ret.Failed()) return ret;
+
+			if (!IsFlatRailBridgeHeadTile(tile) || GetCustomBridgeHeadTrackBits(tile) == DiagDirToDiagTrackBits(GetTunnelBridgeDirection(tile))) {
+				return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR); // just get appropriate error message
+			}
+
+			const TrackBits present = GetCustomBridgeHeadTrackBits(tile);
+			if ((present & trackbit) == 0) return_cmd_error(STR_ERROR_THERE_IS_NO_RAILROAD_TRACK);
+			if (present == (TRACK_BIT_X | TRACK_BIT_Y)) crossing = true;
+
+			const TrackBits future = present ^ trackbit;
+
+			if ((GetAcrossBridgePossibleTrackBits(tile) & future) == 0) return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR); // just get appropriate error message
+
+			const TileIndex other_end = GetOtherTunnelBridgeEnd(tile);
+			ret = TunnelBridgeIsFree(tile, other_end);
+			if (ret.Failed()) return ret;
+
+			cost.AddCost(RailClearCost(GetRailType(tile)));
+
+			if (flags & DC_EXEC) {
+				owner = GetTileOwner(tile);
+
+				if (HasReservedTracks(tile, trackbit)) {
+					v = GetTrainForReservation(tile, track);
+					if (v != NULL) FreeTrainTrackReservation(v);
+				}
+
+				SetCustomBridgeHeadTrackBits(tile, future);
+				Company::Get(GetTileOwner(tile))->infrastructure.rail[GetRailType(tile)] -= GetTunnelBridgeHeadOnlyRailInfrastructureCountFromTrackBits(present) - GetTunnelBridgeHeadOnlyRailInfrastructureCountFromTrackBits(future);
+				DirtyCompanyInfrastructureWindows(_current_company);
+			}
+
+			break;
+		}
+
 		default: return_cmd_error(STR_ERROR_THERE_IS_NO_RAILROAD_TRACK);
 	}
 
@@ -1224,13 +1328,27 @@ static bool CheckSignalAutoFill(TileIndex &tile, Trackdir &trackdir, int &signal
 			TileIndex orig_tile = tile; // backup old value
 
 			if (GetTunnelBridgeTransportType(tile) != TRANSPORT_RAIL) return false;
-			if (GetTunnelBridgeDirection(tile) != TrackdirToExitdir(trackdir)) return false;
+			signal_ctr += IsDiagonalTrackdir(trackdir) ? 2 : 1;
-
+			if (GetTunnelBridgeDirection(tile) == TrackdirToExitdir(trackdir)) {
 				/* Skip to end of tunnel or bridge
 				 * note that tile is a parameter by reference, so it must be updated */
 				tile = GetOtherTunnelBridgeEnd(tile);
+				signal_ctr += GetTunnelBridgeLength(orig_tile, tile) * 2;
 
-			signal_ctr += (GetTunnelBridgeLength(orig_tile, tile) + 2) * 2;
+				/* Check for track bits on the new tile */
+				trackdirbits = TrackStatusToTrackdirBits(GetTileTrackStatus(tile, TRANSPORT_RAIL, 0));
+
+				if (TracksOverlap(TrackdirBitsToTrackBits(trackdirbits))) return false;
+				trackdirbits &= TrackdirReachesTrackdirs(trackdir);
+
+				/* Get the first track dir */
+				trackdir = RemoveFirstTrackdir(&trackdirbits);
+
+				/* Any left? It's a junction so we stop */
+				if (trackdirbits != TRACKDIR_BIT_NONE) return false;
+
+				signal_ctr += IsDiagonalTrackdir(trackdir) ? 2 : 1;
+			}
 			return true;
 		}
 
@@ -1599,6 +1717,24 @@ CommandCost CmdConvertRail(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 
 		SmallVector<Train *, 2> vehicles_affected;
 
+		auto find_train_reservations = [&vehicles_affected, &totype](TileIndex tile, TrackBits reserved) {
+			Track track;
+			while ((track = RemoveFirstTrack(&reserved)) != INVALID_TRACK) {
+				Train *v = GetTrainForReservation(tile, track);
+				if (v != NULL && !HasPowerOnRail(v->railtype, totype)) {
+					/* No power on new rail type, reroute. */
+					FreeTrainTrackReservation(v);
+					*vehicles_affected.Append() = v;
+				}
+			}
+		};
+
+		auto yapf_notify_track_change = [](TileIndex tile, TrackBits tracks) {
+			while (tracks != TRACK_BIT_NONE) {
+				YapfNotifyTrackLayoutChange(tile, RemoveFirstTrack(&tracks));
+			}
+		};
+
 		/* Vehicle on the tile when not converting Rail <-> ElRail
 		 * Tunnels and bridges have special check later */
 		if (tt != MP_TUNNELBRIDGE) {
@@ -1610,16 +1746,7 @@ CommandCost CmdConvertRail(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 				}
 			}
 			if (flags & DC_EXEC) { // we can safely convert, too
-				TrackBits reserved = GetReservedTrackbits(tile);
+				find_train_reservations(tile, GetReservedTrackbits(tile));
-				Track     track;
-				while ((track = RemoveFirstTrack(&reserved)) != INVALID_TRACK) {
-					Train *v = GetTrainForReservation(tile, track);
-					if (v != NULL && !HasPowerOnRail(v->railtype, totype)) {
-						/* No power on new rail type, reroute. */
-						FreeTrainTrackReservation(v);
-						*vehicles_affected.Append() = v;
-					}
-				}
 
 				/* Update the company infrastructure counters. */
 				if (!IsRailStationTile(tile) || !IsStationTileBlocked(tile)) {
@@ -1660,10 +1787,7 @@ CommandCost CmdConvertRail(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 					default: // RAIL_TILE_NORMAL, RAIL_TILE_SIGNALS
 						if (flags & DC_EXEC) {
 							/* notify YAPF about the track layout change */
-							TrackBits tracks = GetTrackBits(tile);
+							yapf_notify_track_change(tile, GetTrackBits(tile));
-							while (tracks != TRACK_BIT_NONE) {
-								YapfNotifyTrackLayoutChange(tile, RemoveFirstTrack(&tracks));
-							}
 						}
 						cost.AddCost(RailConvertCost(type, totype) * CountBits(GetTrackBits(tile)));
 						break;
@@ -1692,22 +1816,18 @@ CommandCost CmdConvertRail(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 					}
 				}
 
+				uint middle_len = GetTunnelBridgeLength(tile, endtile);
+				uint num_raw_pieces = middle_len + CountBits(GetTunnelBridgeTrackBits(tile)) + CountBits(GetTunnelBridgeTrackBits(endtile));
+
 				if (flags & DC_EXEC) {
-					Track track = DiagDirToDiagTrack(GetTunnelBridgeDirection(tile));
+					find_train_reservations(tile, GetTunnelBridgeReservationTrackBits(tile));
-					if (HasTunnelBridgeReservation(tile)) {
+					find_train_reservations(endtile, GetTunnelBridgeReservationTrackBits(endtile));
-						Train *v = GetTrainForReservation(tile, track);
-						if (v != NULL && !HasPowerOnRail(v->railtype, totype)) {
-							/* No power on new rail type, reroute. */
-							FreeTrainTrackReservation(v);
-							*vehicles_affected.Append() = v;
-						}
-					}
 
 					/* Update the company infrastructure counters. */
-					uint num_pieces = (GetTunnelBridgeLength(tile, endtile) + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
+					uint num_infra_pieces = (middle_len* TUNNELBRIDGE_TRACKBIT_FACTOR) + GetTunnelBridgeHeadOnlyRailInfrastructureCount(tile) + GetTunnelBridgeHeadOnlyRailInfrastructureCount(endtile);
 					Company *c = Company::Get(GetTileOwner(tile));
-					c->infrastructure.rail[GetRailType(tile)] -= num_pieces;
+					c->infrastructure.rail[GetRailType(tile)] -= num_infra_pieces;
-					c->infrastructure.rail[totype] += num_pieces;
+					c->infrastructure.rail[totype] += num_infra_pieces;
 					DirtyCompanyInfrastructureWindows(c->index);
 
 					SetRailType(tile, totype);
@@ -1716,8 +1836,9 @@ CommandCost CmdConvertRail(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 					FindVehicleOnPos(tile, &affected_trains, &UpdateTrainPowerProc);
 					FindVehicleOnPos(endtile, &affected_trains, &UpdateTrainPowerProc);
 
-					YapfNotifyTrackLayoutChange(tile, track);
+					/* notify YAPF about the track layout change */
-					YapfNotifyTrackLayoutChange(endtile, track);
+					yapf_notify_track_change(tile, GetTunnelBridgeTrackBits(tile));
+					yapf_notify_track_change(endtile, GetTunnelBridgeTrackBits(endtile));
 
 					if (IsBridge(tile)) {
 						MarkBridgeDirty(tile);
@@ -1727,7 +1848,7 @@ CommandCost CmdConvertRail(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 					}
 				}
 
-				cost.AddCost((GetTunnelBridgeLength(tile, endtile) + 2) * RailConvertCost(type, totype));
+				cost.AddCost(num_raw_pieces * RailConvertCost(type, totype));
 				break;
 			}
 
@@ -2061,10 +2182,19 @@ static inline void DrawTrackSprite(SpriteID sprite, PaletteID pal, const TileInf
 	DrawGroundSprite(sprite, pal, NULL, 0, (ti->tileh & s) ? -8 : 0);
 }
 
+static RailGroundType GetRailOrBridgeGroundType(TileInfo *ti) {
+	if (IsTileType(ti->tile, MP_TUNNELBRIDGE)) {
+		return HasTunnelBridgeSnowOrDesert(ti->tile) ? RAIL_GROUND_ICE_DESERT : RAIL_GROUND_GRASS;
+	} else {
+		return GetRailGroundType(ti->tile);
+	}
+}
+
 static void DrawTrackBitsOverlay(TileInfo *ti, TrackBits track, const RailtypeInfo *rti)
 {
-	RailGroundType rgt = GetRailGroundType(ti->tile);
+	const bool is_bridge = IsTileType(ti->tile, MP_TUNNELBRIDGE);
-	Foundation f = GetRailFoundation(ti->tileh, track);
+	RailGroundType rgt = GetRailOrBridgeGroundType(ti);
+	Foundation f = is_bridge ? FOUNDATION_LEVELED : GetRailFoundation(ti->tileh, track);
 	Corner halftile_corner = CORNER_INVALID;
 
 	if (IsNonContinuousFoundation(f)) {
@@ -2103,7 +2233,10 @@ static void DrawTrackBitsOverlay(TileInfo *ti, TrackBits track, const RailtypeIn
 
 	SpriteID overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY);
 	SpriteID ground = GetCustomRailSprite(rti, ti->tile, RTSG_GROUND);
-	TrackBits pbs = _settings_client.gui.show_track_reservation ? GetRailReservationTrackBits(ti->tile) : TRACK_BIT_NONE;
+	TrackBits pbs = TRACK_BIT_NONE;
+	if (_settings_client.gui.show_track_reservation) {
+		pbs = is_bridge ? GetTunnelBridgeReservationTrackBits(ti->tile) : GetRailReservationTrackBits(ti->tile);
+	}
 
 	if (track == TRACK_BIT_NONE) {
 		/* Half-tile foundation, no track here? */
@@ -2213,7 +2346,7 @@ static void DrawTrackBitsOverlay(TileInfo *ti, TrackBits track, const RailtypeIn
  * @param ti TileInfo
  * @param track TrackBits to draw
  */
-static void DrawTrackBits(TileInfo *ti, TrackBits track)
+void DrawTrackBits(TileInfo *ti, TrackBits track)
 {
 	const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
 
@@ -2222,8 +2355,9 @@ static void DrawTrackBits(TileInfo *ti, TrackBits track)
 		return;
 	}
 
-	RailGroundType rgt = GetRailGroundType(ti->tile);
+	const bool is_bridge = IsTileType(ti->tile, MP_TUNNELBRIDGE);
-	Foundation f = GetRailFoundation(ti->tileh, track);
+	RailGroundType rgt = GetRailOrBridgeGroundType(ti);
+	Foundation f = is_bridge ? FOUNDATION_LEVELED : GetRailFoundation(ti->tileh, track);
 	Corner halftile_corner = CORNER_INVALID;
 
 	if (IsNonContinuousFoundation(f)) {
@@ -2314,7 +2448,7 @@ static void DrawTrackBits(TileInfo *ti, TrackBits track)
 	/* PBS debugging, draw reserved tracks darker */
 	if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation) {
 		/* Get reservation, but mask track on halftile slope */
-		TrackBits pbs = GetRailReservationTrackBits(ti->tile) & track;
+		TrackBits pbs = (is_bridge ? GetTunnelBridgeReservationTrackBits(ti->tile) : GetRailReservationTrackBits(ti->tile)) & track;
 		if (pbs & TRACK_BIT_X) {
 			if (ti->tileh == SLOPE_FLAT || ti->tileh == SLOPE_ELEVATED) {
 				DrawGroundSprite(rti->base_sprites.single_x, PALETTE_CRASH);

src/saveload/afterload.cpp

@@ -1212,6 +1212,17 @@ bool AfterLoadGame()
 		}
 	}
 
+	if (!SlXvIsFeaturePresent(XSLFI_CUSTOM_BRIDGE_HEADS, 2)) {
+		/* change map bits for rail bridge heads */
+		for (TileIndex t = 0; t < map_size; t++) {
+			if (IsBridgeTile(t) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL) {
+				SetCustomBridgeHeadTrackBits(t, DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t)));
+				SetBridgeReservationTrackBits(t, HasBit(_m[t].m5, 4) ? DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t)) : TRACK_BIT_NONE);
+				ClrBit(_m[t].m5, 4);
+			}
+		}
+	}
+
 	/* Elrails got added in rev 24 */
 	if (IsSavegameVersionBefore(24)) {
 		RailType min_rail = RAILTYPE_ELECTRIC;
@@ -1924,7 +1935,7 @@ bool AfterLoadGame()
 					break;
 
 				case MP_TUNNELBRIDGE: // Clear PBS reservation on tunnels/bridges
-					if (GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL) SetTunnelBridgeReservation(t, false);
+					if (GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL) UnreserveAcrossRailTunnelBridge(t);
 					break;
 
 				default: break;

src/saveload/company_sl.cpp

@@ -201,12 +201,11 @@ void AfterLoadCompanyStats()
 					/* Count each tunnel/bridge TUNNELBRIDGE_TRACKBIT_FACTOR times to simulate
 					 * the higher structural maintenance needs, and don't forget the end tiles. */
 					const uint middle_len = GetTunnelBridgeLength(tile, other_end) * TUNNELBRIDGE_TRACKBIT_FACTOR;
-					const uint len = middle_len + (2 * TUNNELBRIDGE_TRACKBIT_FACTOR);
 
 					switch (GetTunnelBridgeTransportType(tile)) {
 						case TRANSPORT_RAIL:
 							c = Company::GetIfValid(GetTileOwner(tile));
-							if (c != NULL) c->infrastructure.rail[GetRailType(tile)] += len;
+							if (c != NULL) c->infrastructure.rail[GetRailType(tile)] += middle_len + GetTunnelBridgeHeadOnlyRailInfrastructureCount(tile) + GetTunnelBridgeHeadOnlyRailInfrastructureCount(other_end);
 							break;
 
 						case TRANSPORT_ROAD: {
@@ -216,7 +215,7 @@ void AfterLoadCompanyStats()
 
 						case TRANSPORT_WATER:
 							c = Company::GetIfValid(GetTileOwner(tile));
-							if (c != NULL) c->infrastructure.water += len;
+							if (c != NULL) c->infrastructure.water += middle_len + (2 * TUNNELBRIDGE_TRACKBIT_FACTOR);
 							break;
 
 						default:

src/saveload/extended_ver_sl.cpp

@@ -45,7 +45,7 @@ std::vector<uint32> _sl_xv_discardable_chunk_ids;           ///< list of chunks
 static const uint32 _sl_xv_slxi_chunk_version = 0;          ///< current version os SLXI chunk
 
 const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
-	{ XSLFI_CUSTOM_BRIDGE_HEADS,    XSCF_NULL,                1,   1, "custom_bridge_heads",       NULL, NULL, NULL        },
+	{ XSLFI_CUSTOM_BRIDGE_HEADS,    XSCF_NULL,                2,   2, "custom_bridge_heads",       NULL, NULL, NULL        },
 	{ XSLFI_NULL, XSCF_NULL, 0, 0, NULL, NULL, NULL, NULL },// This is the end marker
 };
 

src/settings_type.h

@@ -312,6 +312,7 @@ struct ConstructionSettings {
 	uint8  extra_tree_placement;             ///< (dis)allow building extra trees in-game
 	uint8  command_pause_level;              ///< level/amount of commands that can't be executed while paused
 	uint8  road_custom_bridge_heads;         ///< allow construction of road custom bridge heads
+	uint8  rail_custom_bridge_heads;         ///< allow construction of rail custom bridge heads
 
 	uint32 terraform_per_64k_frames;         ///< how many tile heights may, over a long period, be terraformed per 65536 frames?
 	uint16 terraform_frame_burst;            ///< how many tile heights may, over a short period, be terraformed?

src/signal.cpp

@@ -374,22 +374,45 @@ static SigFlags ExploreSegment(Owner owner)
 			case MP_TUNNELBRIDGE: {
 				if (GetTileOwner(tile) != owner) continue;
 				if (GetTunnelBridgeTransportType(tile) != TRANSPORT_RAIL) continue;
-				DiagDirection dir = GetTunnelBridgeDirection(tile);
+				DiagDirection tunnel_bridge_dir = GetTunnelBridgeDirection(tile);
+				TrackBits tracks = GetTunnelBridgeTrackBits(tile);
+				TrackBits across_tracks = GetAcrossTunnelBridgeTrackBits(tile);
+
+				auto check_train_present = [tile, tracks, across_tracks](DiagDirection enterdir) -> bool {
+					if (tracks == TRACK_BIT_HORZ || tracks == TRACK_BIT_VERT) {
+						if (_enterdir_to_trackbits[enterdir] & across_tracks) {
+							return EnsureNoTrainOnTrackBits(tile, TRACK_BIT_WORMHOLE | across_tracks).Failed();
+						} else {
+							return EnsureNoTrainOnTrackBits(tile, tracks & (~across_tracks)).Failed();
+						}
+					} else {
+						return HasVehicleOnPos(tile, NULL, &TrainOnTileEnum);
+					}
+				};
+
+				TrackBits tracks_masked = (TrackBits)(tracks & _enterdir_to_trackbits[enterdir == INVALID_DIAGDIR ? tunnel_bridge_dir : enterdir]); // only incidating trackbits
+				if (tracks == TRACK_BIT_HORZ || tracks == TRACK_BIT_VERT) tracks = tracks_masked;
 
 				if (enterdir == INVALID_DIAGDIR) { // incoming from the wormhole
-					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;
+					if (!(flags & SF_TRAIN) && check_train_present(tunnel_bridge_dir)) flags |= SF_TRAIN;
-					enterdir = dir;
+					enterdir = tunnel_bridge_dir;
-					exitdir = ReverseDiagDir(dir);
+				} else if (enterdir != tunnel_bridge_dir) { // NOT incoming from the wormhole!
-					tile += TileOffsByDiagDir(exitdir); // just skip to next tile
+					if (tracks_masked == TRACK_BIT_NONE) continue; // no incidating track
-				} else { // NOT incoming from the wormhole!
+					if (!(flags & SF_TRAIN) && check_train_present(enterdir)) flags |= SF_TRAIN;
-					if (ReverseDiagDir(enterdir) != dir) continue;
+				}
-					if (!(flags & SF_TRAIN) && HasVehicleOnPos(tile, NULL, &TrainOnTileEnum)) flags |= SF_TRAIN;
+				for (DiagDirection dir = DIAGDIR_BEGIN; dir < DIAGDIR_END; dir++) { // test all possible exit directions
-					tile = GetOtherTunnelBridgeEnd(tile); // just skip to exit tile
+					if (dir != enterdir && (tracks & _enterdir_to_trackbits[dir])) { // any track incidating?
-					enterdir = INVALID_DIAGDIR;
+						if (dir == tunnel_bridge_dir) {
-					exitdir = INVALID_DIAGDIR;
+							if (!MaybeAddToTodoSet(GetOtherTunnelBridgeEnd(tile), INVALID_DIAGDIR, tile, INVALID_DIAGDIR)) return flags | SF_FULL;
+						} else {
+							TileIndex newtile = tile + TileOffsByDiagDir(dir);  // new tile to check
+							DiagDirection newdir = ReverseDiagDir(dir); // direction we are entering from
+							if (!MaybeAddToTodoSet(newtile, newdir, tile, dir)) return flags | SF_FULL;
 						}
 					}
-				break;
+				}
+				continue; // continue the while() loop
+				}
 
 			default:
 				continue; // continue the while() loop
@@ -489,16 +512,20 @@ static SigSegState UpdateSignalsInBuffer(Owner owner)
 		 * train entering/leaving block, train leaving depot...
 		 */
 		switch (GetTileType(tile)) {
-			case MP_TUNNELBRIDGE:
+			case MP_TUNNELBRIDGE: {
 				/* 'optimization assert' - do not try to update signals when it is not needed */
 				assert(GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL);
-				assert(dir == INVALID_DIAGDIR || dir == ReverseDiagDir(GetTunnelBridgeDirection(tile)));
+				if (IsTunnel(tile)) assert(dir == INVALID_DIAGDIR || dir == ReverseDiagDir(GetTunnelBridgeDirection(tile)));
+				TrackBits across = GetAcrossTunnelBridgeTrackBits(tile);
+				if (dir == INVALID_DIAGDIR || _enterdir_to_trackbits[dir] & across) {
 					_tbdset.Add(tile, INVALID_DIAGDIR);  // we can safely start from wormhole centre
 					_tbdset.Add(GetOtherTunnelBridgeEnd(tile), INVALID_DIAGDIR);
 					break;
-
+				}
+			}
+				/* FALL THROUGH */
 			case MP_RAILWAY:
-				if (IsRailDepot(tile)) {
+				if (IsRailDepotTile(tile)) {
 					/* 'optimization assert' do not try to update signals in other cases */
 					assert(dir == INVALID_DIAGDIR || dir == GetRailDepotDirection(tile));
 					_tbdset.Add(tile, INVALID_DIAGDIR); // start from depot inside
@@ -591,8 +618,13 @@ void AddTrackToSignalBuffer(TileIndex tile, Track track, Owner owner)
 
 	_last_owner = owner;
 
-	_globset.Add(tile, _search_dir_1[track]);
+	DiagDirection wormhole_dir = IsTileType(tile, MP_TUNNELBRIDGE) ? GetTunnelBridgeDirection(tile) : INVALID_DIAGDIR;
-	_globset.Add(tile, _search_dir_2[track]);
+
+	auto add_dir = [&](DiagDirection dir) {
+		_globset.Add(tile, dir == wormhole_dir ? INVALID_DIAGDIR : dir);
+	};
+	add_dir(_search_dir_1[track]);
+	add_dir(_search_dir_2[track]);
 
 	if (_globset.Items() >= SIG_GLOB_UPDATE) {
 		/* too many items, force update */

src/table/settings.ini

@@ -1238,6 +1238,15 @@ str      = STR_CONFIG_SETTING_ENABLE_ROAD_CUSTOM_BRIDGE_HEADS
 strhelp  = STR_CONFIG_SETTING_ENABLE_ROAD_CUSTOM_BRIDGE_HEADS_HELPTEXT
 patxname = ""custom_bridge_heads.construction.road_custom_bridge_heads""
 
+[SDT_BOOL]
+base     = GameSettings
+var      = construction.rail_custom_bridge_heads
+def      = true
+cat      = SC_BASIC
+str      = STR_CONFIG_SETTING_ENABLE_RAIL_CUSTOM_BRIDGE_HEADS
+strhelp  = STR_CONFIG_SETTING_ENABLE_RAIL_CUSTOM_BRIDGE_HEADS_HELPTEXT
+patxname = ""custom_bridge_heads.construction.rail_custom_bridge_heads""
+
 [SDT_BOOL]
 base     = GameSettings
 var      = station.adjacent_stations

src/train.h

@@ -246,7 +246,7 @@ protected: // These functions should not be called outside acceleration code.
 	inline byte GetAirDragArea() const
 	{
 		/* Air drag is higher in tunnels due to the limited cross-section. */
-		return (this->track == TRACK_BIT_WORMHOLE && this->vehstatus & VS_HIDDEN) ? 28 : 14;
+		return (this->track & TRACK_BIT_WORMHOLE && this->vehstatus & VS_HIDDEN) ? 28 : 14;
 	}
 
 	/**

src/train_cmd.cpp

@@ -427,7 +427,7 @@ int Train::GetCurrentMaxSpeed() const
 		}
 
 		/* Vehicle is on the middle part of a bridge. */
-		if (u->track == TRACK_BIT_WORMHOLE && !(u->vehstatus & VS_HIDDEN)) {
+		if (u->track & TRACK_BIT_WORMHOLE && !(u->vehstatus & VS_HIDDEN)) {
 			max_speed = min(max_speed, GetBridgeSpec(GetBridgeType(u->tile))->speed);
 		}
 	}
@@ -1568,17 +1568,17 @@ static void UpdateStatusAfterSwap(Train *v)
 	if (v->track != TRACK_BIT_DEPOT) v->direction = ReverseDir(v->direction);
 
 	/* Call the proper EnterTile function unless we are in a wormhole. */
-	if (v->track != TRACK_BIT_WORMHOLE) {
+	if (!(v->track & TRACK_BIT_WORMHOLE)) {
 		VehicleEnterTile(v, v->tile, v->x_pos, v->y_pos);
 	} else {
-		/* VehicleEnter_TunnelBridge() sets TRACK_BIT_WORMHOLE when the vehicle
+		/* VehicleEnter_TunnelBridge() may set TRACK_BIT_WORMHOLE when the vehicle
 		 * is on the last bit of the bridge head (frame == TILE_SIZE - 1).
 		 * If we were swapped with such a vehicle, we have set TRACK_BIT_WORMHOLE,
 		 * when we shouldn't have. Check if this is the case. */
 		TileIndex vt = TileVirtXY(v->x_pos, v->y_pos);
 		if (IsTileType(vt, MP_TUNNELBRIDGE)) {
 			VehicleEnterTile(v, vt, v->x_pos, v->y_pos);
-			if (v->track != TRACK_BIT_WORMHOLE && IsBridgeTile(v->tile)) {
+			if (!(v->track & TRACK_BIT_WORMHOLE) && IsBridgeTile(v->tile)) {
 				/* We have just left the wormhole, possibly set the
 				 * "goingdown" bit. UpdateInclination() can be used
 				 * because we are at the border of the tile. */
@@ -1875,7 +1875,7 @@ void ReverseTrainDirection(Train *v)
 	/* TrainExitDir does not always produce the desired dir for depots and
 	 * tunnels/bridges that is needed for UpdateSignalsOnSegment. */
 	DiagDirection dir = TrainExitDir(v->direction, v->track);
-	if (IsRailDepotTile(v->tile) || IsTileType(v->tile, MP_TUNNELBRIDGE)) dir = INVALID_DIAGDIR;
+	if (IsRailDepotTile(v->tile) || (IsTileType(v->tile, MP_TUNNELBRIDGE) && (v->track & TRACK_BIT_WORMHOLE || dir == GetTunnelBridgeDirection(v->tile)))) dir = INVALID_DIAGDIR;
 
 	if (UpdateSignalsOnSegment(v->tile, dir, v->owner) == SIGSEG_PBS || _settings_game.pf.reserve_paths) {
 		/* If we are currently on a tile with conventional signals, we can't treat the
@@ -2216,17 +2216,15 @@ static bool CheckTrainStayInDepot(Train *v)
  */
 static void ClearPathReservation(const Train *v, TileIndex tile, Trackdir track_dir)
 {
-	DiagDirection dir = TrackdirToExitdir(track_dir);
-
 	if (IsTileType(tile, MP_TUNNELBRIDGE)) {
 		/* Are we just leaving a tunnel/bridge? */
-		if (GetTunnelBridgeDirection(tile) == ReverseDiagDir(dir)) {
+		if (TrackdirExitsTunnelBridge(tile, track_dir)) {
 			TileIndex end = GetOtherTunnelBridgeEnd(tile);
 
-			if (TunnelBridgeIsFree(tile, end, v).Succeeded()) {
+			if (TunnelBridgeIsFree(tile, end, v, true).Succeeded()) {
 				/* Free the reservation only if no other train is on the tiles. */
-				SetTunnelBridgeReservation(tile, false);
+				UnreserveAcrossRailTunnelBridge(tile);
-				SetTunnelBridgeReservation(end, false);
+				UnreserveAcrossRailTunnelBridge(end);
 
 				if (_settings_client.gui.show_track_reservation) {
 					if (IsBridge(tile)) {
@@ -2237,8 +2235,11 @@ static void ClearPathReservation(const Train *v, TileIndex tile, Trackdir track_
 					}
 				}
 			}
+		} else if (TrackdirToExitdir(track_dir) != GetTunnelBridgeDirection(tile)) {
+			UnreserveRailTrack(tile, TrackdirToTrack(track_dir));
 		}
 	} else if (IsRailStationTile(tile)) {
+		DiagDirection dir = TrackdirToExitdir(track_dir);
 		TileIndex new_tile = TileAddByDiagDir(tile, dir);
 		/* If the new tile is not a further tile of the same station, we
 		 * clear the reservation for the whole platform. */
@@ -2764,7 +2765,7 @@ bool TryPathReserve(Train *v, bool mark_as_stuck, bool first_tile_okay)
 static bool CheckReverseTrain(const Train *v)
 {
 	if (_settings_game.difficulty.line_reverse_mode != 0 ||
-			v->track == TRACK_BIT_DEPOT || v->track == TRACK_BIT_WORMHOLE ||
+			v->track == TRACK_BIT_DEPOT || v->track & TRACK_BIT_WORMHOLE ||
 			!(v->direction & 1)) {
 		return false;
 	}
@@ -2924,15 +2925,18 @@ static bool TrainMovedChangeSignals(TileIndex tile, DiagDirection dir)
 void Train::ReserveTrackUnderConsist() const
 {
 	for (const Train *u = this; u != NULL; u = u->Next()) {
-		switch (u->track) {
+		if (u->track & TRACK_BIT_WORMHOLE) {
-			case TRACK_BIT_WORMHOLE:
+			if (IsRailCustomBridgeHeadTile(u->tile)) {
+				/* reserve the first available track */
+				TrackBits bits = GetAcrossBridgePossibleTrackBits(u->tile) & GetCustomBridgeHeadTrackBits(u->tile);
+				Track first_track = RemoveFirstTrack(&bits);
+				assert(IsValidTrack(first_track));
+				TryReserveRailTrack(u->tile, first_track);
+			} else {
 				TryReserveRailTrack(u->tile, DiagDirToDiagTrack(GetTunnelBridgeDirection(u->tile)));
-				break;
+			}
-			case TRACK_BIT_DEPOT:
+		} else if (u->track != TRACK_BIT_DEPOT) {
-				break;
-			default:
 			TryReserveRailTrack(u->tile, TrackBitsToTrack(u->track));
-				break;
 		}
 	}
 }
@@ -2957,7 +2961,7 @@ uint Train::Crash(bool flooded)
 			if (IsTileType(v->tile, MP_TUNNELBRIDGE)) {
 				/* ClearPathReservation will not free the wormhole exit
 				 * if the train has just entered the wormhole. */
-				SetTunnelBridgeReservation(GetOtherTunnelBridgeEnd(v->tile), false);
+				UnreserveAcrossRailTunnelBridge(GetOtherTunnelBridgeEnd(v->tile));
 			}
 		}
 
@@ -3064,14 +3068,14 @@ static bool CheckTrainCollision(Train *v)
 	/* can't collide in depot */
 	if (v->track == TRACK_BIT_DEPOT) return false;
 
-	assert(v->track == TRACK_BIT_WORMHOLE || TileVirtXY(v->x_pos, v->y_pos) == v->tile);
+	assert(v->track & TRACK_BIT_WORMHOLE || TileVirtXY(v->x_pos, v->y_pos) == v->tile);
 
 	TrainCollideChecker tcc;
 	tcc.v = v;
 	tcc.num = 0;
 
 	/* find colliding vehicles */
-	if (v->track == TRACK_BIT_WORMHOLE) {
+	if (v->track & TRACK_BIT_WORMHOLE) {
 		FindVehicleOnPos(v->tile, &tcc, FindTrainCollideEnum);
 		FindVehicleOnPos(GetOtherTunnelBridgeEnd(v->tile), &tcc, FindTrainCollideEnum);
 	} else {
@@ -3116,14 +3120,37 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 	Train *first = v->First();
 	Train *prev;
 	bool direction_changed = false; // has direction of any part changed?
+	Direction old_direction = INVALID_DIR;
+	TrackBits old_trackbits = INVALID_TRACK_BIT;
+
+	auto notify_direction_changed = [&](Direction old_direction, Direction new_direction) {
+		if (prev == NULL && _settings_game.vehicle.train_acceleration_model == AM_ORIGINAL) {
+			const AccelerationSlowdownParams *asp = &_accel_slowdown[GetRailTypeInfo(v->railtype)->acceleration_type];
+			DirDiff diff = DirDifference(old_direction, new_direction);
+			v->cur_speed -= (diff == DIRDIFF_45RIGHT || diff == DIRDIFF_45LEFT ? asp->small_turn : asp->large_turn) * v->cur_speed >> 8;
+		}
+		direction_changed = true;
+	};
 
 	/* For every vehicle after and including the given vehicle */
 	for (prev = v->Previous(); v != nomove; prev = v, v = v->Next()) {
+		old_direction = v->direction;
+		old_trackbits = v->track;
 		DiagDirection enterdir = DIAGDIR_BEGIN;
 		bool update_signals_crossing = false; // will we update signals or crossing state?
 
 		GetNewVehiclePosResult gp = GetNewVehiclePos(v);
-		if (v->track != TRACK_BIT_WORMHOLE) {
+		if (!(v->track & TRACK_BIT_WORMHOLE) && gp.old_tile != gp.new_tile &&
+				IsRailBridgeHeadTile(gp.old_tile) && DiagdirBetweenTiles(gp.old_tile, gp.new_tile) == GetTunnelBridgeDirection(gp.old_tile)) {
+			/* left a bridge headtile into a wormhole */
+			Direction old_direction = v->direction;
+			uint32 r = VehicleEnterTile(v, gp.old_tile, gp.x, gp.y); // NB: old tile, the bridge head which the train just left
+			if (HasBit(r, VETS_CANNOT_ENTER)) {
+				goto invalid_rail;
+			}
+			if (old_direction != v->direction) notify_direction_changed(old_direction, v->direction);
+		}
+		if (!(v->track & TRACK_BIT_WORMHOLE)) {
 			/* Not inside tunnel */
 			if (gp.old_tile == gp.new_tile) {
 				/* Staying in the old tile */
@@ -3145,6 +3172,7 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 						/* The new position is the end of the platform */
 						TrainEnterStation(v, r >> VETS_STATION_ID_OFFSET);
 					}
+					if (old_direction != v->direction) notify_direction_changed(old_direction, v->direction);
 				}
 			} else {
 				/* A new tile is about to be entered. */
@@ -3153,9 +3181,11 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 				enterdir = DiagdirBetweenTiles(gp.old_tile, gp.new_tile);
 				assert(IsValidDiagDirection(enterdir));
 
+				enter_new_tile:
+
 				/* Get the status of the tracks in the new tile and mask
 				 * away the bits that aren't reachable. */
-				TrackStatus ts = GetTileTrackStatus(gp.new_tile, TRANSPORT_RAIL, 0, ReverseDiagDir(enterdir));
+				TrackStatus ts = GetTileTrackStatus(gp.new_tile, TRANSPORT_RAIL, 0, (v->track & TRACK_BIT_WORMHOLE) ? INVALID_DIAGDIR : ReverseDiagDir(enterdir));
 				TrackdirBits reachable_trackdirs = DiagdirReachesTrackdirs(enterdir);
 
 				TrackdirBits trackdirbits = TrackStatusToTrackdirBits(ts) & reachable_trackdirs;
@@ -3165,7 +3195,11 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 				if (_settings_game.pf.forbid_90_deg && prev == NULL) {
 					/* We allow wagons to make 90 deg turns, because forbid_90_deg
 					 * can be switched on halfway a turn */
+					if (!(v->track & TRACK_BIT_WORMHOLE)) {
 						bits &= ~TrackCrossesTracks(FindFirstTrack(v->track));
+					} else if (v->track & TRACK_BIT_MASK) {
+						bits &= ~TrackCrossesTracks(FindFirstTrack(v->track & TRACK_BIT_MASK));
+					}
 				}
 
 				if (bits == TRACK_BIT_NONE) goto invalid_rail;
@@ -3240,9 +3274,9 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 					}
 				} else {
 					/* The wagon is active, simply follow the prev vehicle. */
-					if (prev->tile == gp.new_tile) {
+					if (TileVirtXY(prev->x_pos, prev->y_pos) == gp.new_tile) {
 						/* Choose the same track as prev */
-						if (prev->track == TRACK_BIT_WORMHOLE) {
+						if (prev->track & TRACK_BIT_WORMHOLE) {
 							/* Vehicles entering tunnels enter the wormhole earlier than for bridges.
 							 * However, just choose the track into the wormhole. */
 							assert(IsTunnel(prev->tile));
@@ -3264,7 +3298,7 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 							{TRACK_BIT_NONE,  TRACK_BIT_RIGHT, TRACK_BIT_X,     TRACK_BIT_UPPER},
 							{TRACK_BIT_RIGHT, TRACK_BIT_NONE,  TRACK_BIT_LOWER, TRACK_BIT_Y    }
 						};
-						DiagDirection exitdir = DiagdirBetweenTiles(gp.new_tile, prev->tile);
+						DiagDirection exitdir = DiagdirBetweenTiles(gp.new_tile, TileVirtXY(prev->x_pos, prev->y_pos));
 						assert(IsValidDiagDirection(exitdir));
 						chosen_track = _connecting_track[enterdir][exitdir];
 					}
@@ -3284,7 +3318,7 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 				Direction chosen_dir = (Direction)b[2];
 
 				/* Call the landscape function and tell it that the vehicle entered the tile */
-				uint32 r = VehicleEnterTile(v, gp.new_tile, gp.x, gp.y);
+				uint32 r = (v->track & TRACK_BIT_WORMHOLE) ? 0 : VehicleEnterTile(v, gp.new_tile, gp.x, gp.y);
 				if (HasBit(r, VETS_CANNOT_ENTER)) {
 					goto invalid_rail;
 				}
@@ -3315,12 +3349,7 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 				update_signals_crossing = true;
 
 				if (chosen_dir != v->direction) {
-					if (prev == NULL && _settings_game.vehicle.train_acceleration_model == AM_ORIGINAL) {
+					notify_direction_changed(v->direction, chosen_dir);
-						const AccelerationSlowdownParams *asp = &_accel_slowdown[GetRailTypeInfo(v->railtype)->acceleration_type];
-						DirDiff diff = DirDifference(v->direction, chosen_dir);
-						v->cur_speed -= (diff == DIRDIFF_45RIGHT || diff == DIRDIFF_45LEFT ? asp->small_turn : asp->large_turn) * v->cur_speed >> 8;
-					}
-					direction_changed = true;
 					v->direction = chosen_dir;
 				}
 
@@ -3343,6 +3372,10 @@ bool TrainController(Train *v, Vehicle *nomove, bool reverse)
 		} else {
 			if (IsTileType(gp.new_tile, MP_TUNNELBRIDGE) && HasBit(VehicleEnterTile(v, gp.new_tile, gp.x, gp.y), VETS_ENTERED_WORMHOLE)) {
 				/* Perform look-ahead on tunnel exit. */
+				if (IsRailCustomBridgeHeadTile(gp.new_tile)) {
+					enterdir = ReverseDiagDir(GetTunnelBridgeDirection(gp.new_tile));
+					goto enter_new_tile;
+				}
 				if (v->IsFrontEngine()) {
 					TryReserveRailTrack(gp.new_tile, DiagDirToDiagTrack(GetTunnelBridgeDirection(gp.new_tile)));
 					CheckNextTrainTile(v);
@@ -3416,6 +3449,11 @@ invalid_rail:
 	if (prev != NULL) error("Disconnecting train");
 
 reverse_train_direction:
+	if ((v->track ^ old_trackbits) & TRACK_BIT_WORMHOLE) {
+		/* Entering/exiting wormhole failed/aborted, back out changes to vehicle direction and track */
+		v->track = old_trackbits;
+		v->direction = old_direction;
+	}
 	if (reverse) {
 		v->wait_counter = 0;
 		v->cur_speed = 0;
@@ -3426,6 +3464,21 @@ reverse_train_direction:
 	return false;
 }
 
+static TrackBits GetTrackbitsFromCrashedVehicle(Train *t)
+{
+	TrackBits train_tbits = t->track;
+	if (train_tbits & TRACK_BIT_WORMHOLE) {
+		/* Vehicle is inside a wormhole, v->track contains no useful value then. */
+		train_tbits = GetAcrossTunnelBridgeReservationTrackBits(t->tile);
+		if (train_tbits != TRACK_BIT_NONE) return train_tbits;
+		/* Pick the first available tunnel/bridge head track which could be reserved */
+		train_tbits = GetAcrossTunnelBridgeTrackBits(t->tile);
+		return train_tbits ^ KillFirstBit(train_tbits);
+	} else {
+		return train_tbits;
+	}
+}
+
 /**
  * Collect trackbits of all crashed train vehicles on a tile
  * @param v Vehicle passed from Find/HasVehicleOnPos()
@@ -3437,12 +3490,8 @@ static Vehicle *CollectTrackbitsFromCrashedVehiclesEnum(Vehicle *v, void *data)
 	TrackBits *trackbits = (TrackBits *)data;
 
 	if (v->type == VEH_TRAIN && (v->vehstatus & VS_CRASHED) != 0) {
-		TrackBits train_tbits = Train::From(v)->track;
+		if (Train::From(v)->track != TRACK_BIT_DEPOT) {
-		if (train_tbits == TRACK_BIT_WORMHOLE) {
+			*trackbits |= GetTrackbitsFromCrashedVehicle(Train::From(v));
-			/* Vehicle is inside a wormhole, v->track contains no useful value then. */
-			*trackbits |= DiagDirToDiagTrackBits(GetTunnelBridgeDirection(v->tile));
-		} else if (train_tbits != TRACK_BIT_DEPOT) {
-			*trackbits |= train_tbits;
 		}
 	}
 
@@ -3479,18 +3528,14 @@ static void DeleteLastWagon(Train *v)
 	}
 
 	/* 'v' shouldn't be accessed after it has been deleted */
-	TrackBits trackbits = v->track;
+	const TrackBits orig_trackbits = v->track;
-	TileIndex tile = v->tile;
+	TrackBits trackbits = GetTrackbitsFromCrashedVehicle(v);
-	Owner owner = v->owner;
+	const TileIndex tile = v->tile;
+	const Owner owner = v->owner;
 
 	delete v;
 	v = NULL; // make sure nobody will try to read 'v' anymore
 
-	if (trackbits == TRACK_BIT_WORMHOLE) {
-		/* Vehicle is inside a wormhole, v->track contains no useful value then. */
-		trackbits = DiagDirToDiagTrackBits(GetTunnelBridgeDirection(tile));
-	}
-
 	Track track = TrackBitsToTrack(trackbits);
 	if (HasReservedTracks(tile, trackbits)) {
 		UnreserveRailTrack(tile, track);
@@ -3509,7 +3554,7 @@ static void DeleteLastWagon(Train *v)
 	if (IsLevelCrossingTile(tile)) UpdateLevelCrossing(tile);
 
 	/* Update signals */
-	if (IsTileType(tile, MP_TUNNELBRIDGE) || IsRailDepotTile(tile)) {
+	if ((orig_trackbits & TRACK_BIT_WORMHOLE) || IsRailDepotTile(tile)) {
 		UpdateSignalsOnSegment(tile, INVALID_DIAGDIR, owner);
 	} else {
 		SetSignalsOnBothDir(tile, track, owner);
@@ -3533,7 +3578,7 @@ static void ChangeTrainDirRandomly(Train *v)
 			/* Refrain from updating the z position of the vehicle when on
 			 * a bridge, because UpdateInclination() will put the vehicle under
 			 * the bridge in that case */
-			if (v->track != TRACK_BIT_WORMHOLE) {
+			if (!(v->track & TRACK_BIT_WORMHOLE)) {
 				v->UpdatePosition();
 				v->UpdateInclination(false, true);
 			} else {
@@ -3648,7 +3693,7 @@ static bool TrainApproachingLineEnd(Train *v, bool signal, bool reverse)
 static bool TrainCanLeaveTile(const Train *v)
 {
 	/* Exit if inside a tunnel/bridge or a depot */
-	if (v->track == TRACK_BIT_WORMHOLE || v->track == TRACK_BIT_DEPOT) return false;
+	if (v->track & TRACK_BIT_WORMHOLE || v->track == TRACK_BIT_DEPOT) return false;
 
 	TileIndex tile = v->tile;
 
@@ -3656,6 +3701,13 @@ static bool TrainCanLeaveTile(const Train *v)
 	if (IsTileType(tile, MP_TUNNELBRIDGE)) {
 		DiagDirection dir = GetTunnelBridgeDirection(tile);
 		if (DiagDirToDir(dir) == v->direction) return false;
+		if (IsRailCustomBridgeHeadTile(tile) && TrainExitDir(v->direction, v->track) == dir) {
+			if (_settings_game.pf.forbid_90_deg && v->Previous() == NULL && GetTunnelBridgeLength(tile, GetOtherTunnelBridgeEnd(tile)) == 0) {
+				/* Check for 90 degree turn on zero-length bridge span */
+				if (!(GetCustomBridgeHeadTrackBits(tile) & ~TrackCrossesTracks(FindFirstTrack(v->track)))) return true;
+			}
+			return false;
+		}
 	}
 
 	/* entering a depot? */
@@ -4042,6 +4094,8 @@ Trackdir Train::GetVehicleTrackdir() const
 	if (this->track == TRACK_BIT_WORMHOLE) {
 		/* train in tunnel or on bridge, so just use his direction and assume a diagonal track */
 		return DiagDirToDiagTrackdir(DirToDiagDir(this->direction));
+	} else if (this->track & TRACK_BIT_WORMHOLE) {
+		return TrackDirectionToTrackdir(FindFirstTrack(this->track & TRACK_BIT_MASK), this->direction);
 	}
 
 	return TrackDirectionToTrackdir(FindFirstTrack(this->track), this->direction);

src/tunnel_map.h

@@ -37,6 +37,40 @@ static inline bool IsTunnelTile(TileIndex t)
 	return IsTileType(t, MP_TUNNELBRIDGE) && IsTunnel(t);
 }
 
+/**
+ * Checks if this tile is a rail tunnel
+ * @param t the tile that might be a rail tunnel
+ * @return true if it is a rail tunnel
+ */
+static inline bool IsRailTunnelTile(TileIndex t)
+{
+	return IsTunnelTile(t) && (TransportType)GB(_m[t].m5, 2, 2) == TRANSPORT_RAIL;
+}
+
+/**
+ * Get the reservation state of the rail tunnel
+ * @pre IsRailTunnelTile(t)
+ * @param t the tile
+ * @return reservation state
+ */
+static inline bool HasTunnelReservation(TileIndex t)
+{
+	assert(IsRailTunnelTile(t));
+	return HasBit(_m[t].m5, 4);
+}
+
+/**
+ * Set the reservation state of the rail tunnel
+ * @pre IsRailTunnelTile(t)
+ * @param t the tile
+ * @param b the reservation state
+ */
+static inline void SetTunnelReservation(TileIndex t, bool b)
+{
+	assert(IsRailTunnelTile(t));
+	SB(_m[t].m5, 4, 1, b ? 1 : 0);
+}
+
 TileIndex GetOtherTunnelEnd(TileIndex);
 bool IsTunnelInWay(TileIndex, int z);
 bool IsTunnelInWayDir(TileIndex tile, int z, DiagDirection dir);

src/tunnelbridge_cmd.cpp

@@ -52,6 +52,7 @@ TileIndex _build_tunnel_endtile; ///< The end of a tunnel; as hidden return from
 /** Z position of the bridge sprites relative to bridge height (downwards) */
 static const int BRIDGE_Z_START = 3;
 
+extern void DrawTrackBits(TileInfo *ti, TrackBits track);
 extern void DrawRoadBits(TileInfo *ti);
 extern const RoadBits _invalid_tileh_slopes_road[2][15];
 
@@ -315,7 +316,6 @@ CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, u
 	int z_end;
 	Slope tileh_start = GetTileSlope(tile_start, &z_start);
 	Slope tileh_end = GetTileSlope(tile_end, &z_end);
-	bool pbs_reservation = false;
 
 	CommandCost terraform_cost_north = CheckBridgeSlopeNorth(direction, &tileh_start, &z_start);
 	CommandCost terraform_cost_south = CheckBridgeSlopeSouth(direction, &tileh_end,   &z_end);
@@ -369,15 +369,6 @@ CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, u
 		is_new_owner = (owner == OWNER_NONE);
 		if (is_new_owner) owner = company;
 
-		switch (transport_type) {
-			case TRANSPORT_RAIL:
-				/* Keep the reservation, the path stays valid. */
-				pbs_reservation = HasTunnelBridgeReservation(tile_start);
-				break;
-
-			default: break;
-		}
-
 		is_upgrade = true;
 	} else {
 		/* Build a new bridge. */
@@ -491,11 +482,9 @@ CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, u
 		switch (transport_type) {
 			case TRANSPORT_RAIL:
 				/* Add to company infrastructure count if required. */
-				if (is_new_owner && c != NULL) c->infrastructure.rail[railtype] += (bridge_len + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
+				MakeRailBridgeRamp(tile_start, owner, bridge_type, dir,                 railtype, is_upgrade);
-				MakeRailBridgeRamp(tile_start, owner, bridge_type, dir,                 railtype);
+				MakeRailBridgeRamp(tile_end,   owner, bridge_type, ReverseDiagDir(dir), railtype, is_upgrade);
-				MakeRailBridgeRamp(tile_end,   owner, bridge_type, ReverseDiagDir(dir), railtype);
+				if (is_new_owner && c != NULL) c->infrastructure.rail[railtype] += (bridge_len * TUNNELBRIDGE_TRACKBIT_FACTOR) + GetTunnelBridgeHeadOnlyRailInfrastructureCount(tile_start) + GetTunnelBridgeHeadOnlyRailInfrastructureCount(tile_end);
-				SetTunnelBridgeReservation(tile_start, pbs_reservation);
-				SetTunnelBridgeReservation(tile_end,   pbs_reservation);
 				break;
 
 			case TRANSPORT_ROAD: {
@@ -834,7 +823,7 @@ static CommandCost DoClearTunnel(TileIndex tile, DoCommandFlag flags)
 			Owner owner = GetTileOwner(tile);
 
 			Train *v = NULL;
-			if (HasTunnelBridgeReservation(tile)) {
+			if (HasTunnelReservation(tile)) {
 				v = GetTrainForReservation(tile, track);
 				if (v != NULL) FreeTrainTrackReservation(v);
 			}
@@ -909,24 +898,48 @@ static CommandCost DoClearBridge(TileIndex tile, DoCommandFlag flags)
 		ChangeTownRating(t, RATING_TUNNEL_BRIDGE_DOWN_STEP, RATING_TUNNEL_BRIDGE_MINIMUM, flags);
 	}
 
+	CommandCost cost(EXPENSES_CONSTRUCTION);
+
+	const bool rail = GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL;
+	TrackBits tile_tracks = TRACK_BIT_NONE;
+	TrackBits endtile_tracks = TRACK_BIT_NONE;
+	if (rail) {
+		tile_tracks = GetCustomBridgeHeadTrackBits(tile);
+		endtile_tracks = GetCustomBridgeHeadTrackBits(endtile);
+		cost.AddCost(RailClearCost(GetRailType(tile)) * (CountBits(tile_tracks) + CountBits(endtile_tracks) - 2));
+	}
+
 	Money base_cost = (GetTunnelBridgeTransportType(tile) != TRANSPORT_WATER) ? _price[PR_CLEAR_BRIDGE] : _price[PR_CLEAR_AQUEDUCT];
-	uint len = GetTunnelBridgeLength(tile, endtile) + 2; // Don't forget the end tiles.
+	uint middle_len = GetTunnelBridgeLength(tile, endtile);
+	uint len = middle_len + 2; // Don't forget the end tiles.
+
+	cost.AddCost(len * base_cost);
 
 	if (flags & DC_EXEC) {
 		/* read this value before actual removal of bridge */
-		bool rail = GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL;
 		Owner owner = GetTileOwner(tile);
 		int height = GetBridgeHeight(tile);
-		Train *v = NULL;
+		SmallVector<Train *, 2> vehicles_affected;
 
-		if (rail && HasTunnelBridgeReservation(tile)) {
+		if (rail) {
-			v = GetTrainForReservation(tile, DiagDirToDiagTrack(direction));
+			auto find_train_reservations = [&vehicles_affected](TileIndex tile) {
-			if (v != NULL) FreeTrainTrackReservation(v);
+				TrackBits reserved = GetBridgeReservationTrackBits(tile);
+				Track track;
+				while ((track = RemoveFirstTrack(&reserved)) != INVALID_TRACK) {
+					Train *v = GetTrainForReservation(tile, track);
+					if (v != NULL) {
+						FreeTrainTrackReservation(v);
+						*vehicles_affected.Append() = v;
+					}
+				}
+			};
+			find_train_reservations(tile);
+			find_train_reservations(endtile);
 		}
 
 		/* Update company infrastructure counts. */
 		if (rail) {
-			if (Company::IsValidID(owner)) Company::Get(owner)->infrastructure.rail[GetRailType(tile)] -= len * TUNNELBRIDGE_TRACKBIT_FACTOR;
+			if (Company::IsValidID(owner)) Company::Get(owner)->infrastructure.rail[GetRailType(tile)] -= (middle_len * TUNNELBRIDGE_TRACKBIT_FACTOR) + GetTunnelBridgeHeadOnlyRailInfrastructureCount(tile) + GetTunnelBridgeHeadOnlyRailInfrastructureCount(endtile);
 		} else if (GetTunnelBridgeTransportType(tile) == TRANSPORT_ROAD) {
 			SubtractRoadTunnelBridgeInfrastructure(tile, endtile);
 		} else { // Aqueduct
@@ -948,18 +961,28 @@ static CommandCost DoClearBridge(TileIndex tile, DoCommandFlag flags)
 
 		if (rail) {
 			/* cannot use INVALID_DIAGDIR for signal update because the bridge doesn't exist anymore */
-			AddSideToSignalBuffer(tile,    ReverseDiagDir(direction), owner);
-			AddSideToSignalBuffer(endtile, direction,                 owner);
 
-			Track track = DiagDirToDiagTrack(direction);
+			auto notify_track_change = [owner](TileIndex tile, DiagDirection direction, TrackBits tracks) {
-			YapfNotifyTrackLayoutChange(tile,    track);
+				auto check_dir = [&](DiagDirection d) {
-			YapfNotifyTrackLayoutChange(endtile, track);
+					if (DiagdirReachesTracks(d) & tracks) AddSideToSignalBuffer(tile, d, owner);
+				};
+				check_dir(ChangeDiagDir(direction, DIAGDIRDIFF_90RIGHT));
+				check_dir(ChangeDiagDir(direction, DIAGDIRDIFF_REVERSE));
+				check_dir(ChangeDiagDir(direction, DIAGDIRDIFF_90LEFT));
+				while (tracks != TRACK_BIT_NONE) {
+					YapfNotifyTrackLayoutChange(tile, RemoveFirstTrack(&tracks));
+				}
+			};
+			notify_track_change(tile, direction, tile_tracks);
+			notify_track_change(endtile, ReverseDiagDir(direction), endtile_tracks);
 
-			if (v != NULL) TryPathReserve(v, true);
+			for (uint i = 0; i < vehicles_affected.Length(); ++i) {
+				TryPathReserve(vehicles_affected[i], true);
+			}
 		}
 	}
 
-	return CommandCost(EXPENSES_CONSTRUCTION, len * base_cost);
+	return cost;
 }
 
 /**
@@ -1202,7 +1225,7 @@ static void DrawTile_TunnelBridge(TileInfo *ti)
 			}
 
 			/* PBS debugging, draw reserved tracks darker */
-			if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasTunnelBridgeReservation(ti->tile)) {
+			if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasTunnelReservation(ti->tile)) {
 				if (rti->UsesOverlay()) {
 					SpriteID overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY);
 					DrawGroundSprite(overlay + RTO_X + DiagDirToAxis(tunnelbridge_direction), PALETTE_CRASH);
@@ -1241,6 +1264,14 @@ static void DrawTile_TunnelBridge(TileInfo *ti)
 			DrawBridgeMiddle(ti);
 			return;
 		}
+		if (transport_type == TRANSPORT_RAIL && IsRailCustomBridgeHead(ti->tile)) {
+			DrawTrackBits(ti, GetCustomBridgeHeadTrackBits(ti->tile));
+			if (HasRailCatenaryDrawn(GetRailType(ti->tile))) {
+				DrawRailCatenary(ti);
+			}
+			DrawBridgeMiddle(ti);
+			return;
+		}
 
 		const PalSpriteID *psid;
 		int base_offset;
@@ -1324,7 +1355,7 @@ static void DrawTile_TunnelBridge(TileInfo *ti)
 			}
 
 			/* PBS debugging, draw reserved tracks darker */
-			if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasTunnelBridgeReservation(ti->tile)) {
+			if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && GetBridgeReservationTrackBits(ti->tile) != TRACK_BIT_NONE) {
 				if (rti->UsesOverlay()) {
 					SpriteID overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY);
 					if (HasBridgeFlatRamp(ti->tileh, DiagDirToAxis(tunnelbridge_direction))) {
@@ -1489,7 +1520,7 @@ void DrawBridgeMiddle(const TileInfo *ti)
 			}
 		}
 
-		if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && !IsInvisibilitySet(TO_BRIDGES) && HasTunnelBridgeReservation(rampnorth)) {
+		if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && !IsInvisibilitySet(TO_BRIDGES) && (HasAcrossBridgeReservation(rampnorth) || HasAcrossBridgeReservation(rampsouth))) {
 			if (rti->UsesOverlay()) {
 				SpriteID overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY);
 				AddSortableSpriteToDraw(overlay + RTO_X + axis, PALETTE_CRASH, ti->x, ti->y, 16, 16, 0, bridge_z, IsTransparencySet(TO_BRIDGES));
@@ -1556,7 +1587,7 @@ static int GetSlopePixelZ_TunnelBridge(TileIndex tile, uint x, uint y)
 		/* In the tunnel entrance? */
 		if (5 <= pos && pos <= 10) return z;
 	} else { // IsBridge(tile)
-		if (IsRoadCustomBridgeHeadTile(tile)) {
+		if (IsCustomBridgeHeadTile(tile)) {
 			return z + TILE_HEIGHT + (IsSteepSlope(tileh) ? TILE_HEIGHT : 0);
 		}
 
@@ -1587,7 +1618,7 @@ static int GetSlopePixelZ_TunnelBridge(TileIndex tile, uint x, uint y)
 
 static Foundation GetFoundation_TunnelBridge(TileIndex tile, Slope tileh)
 {
-	if (IsRoadCustomBridgeHeadTile(tile)) return FOUNDATION_LEVELED;
+	if (IsCustomBridgeHeadTile(tile)) return FOUNDATION_LEVELED;
 	return IsTunnel(tile) ? FOUNDATION_NONE : GetBridgeFoundation(tileh, DiagDirToAxis(GetTunnelBridgeDirection(tile)));
 }
 
@@ -1677,15 +1708,14 @@ static TrackStatus GetTileTrackStatus_TunnelBridge(TileIndex tile, TransportType
 
 	DiagDirection dir = GetTunnelBridgeDirection(tile);
 
-	if (mode == TRANSPORT_ROAD && IsRoadCustomBridgeHeadTile(tile)) {
 	if (side != INVALID_DIAGDIR && side == dir) return 0;
+	if (mode == TRANSPORT_ROAD && IsRoadCustomBridgeHeadTile(tile)) {
 		TrackBits bits = TRACK_BIT_NONE;
 		if (sub_mode & ROADTYPES_TRAM) bits |= _road_trackbits[GetCustomBridgeHeadRoadBits(tile, ROADTYPE_TRAM)];
 		if (sub_mode & ROADTYPES_ROAD) bits |= _road_trackbits[GetCustomBridgeHeadRoadBits(tile, ROADTYPE_ROAD)];
 		return CombineTrackStatus(TrackBitsToTrackdirBits(bits), TRACKDIR_BIT_NONE);
 	}
-	if (side != INVALID_DIAGDIR && side != ReverseDiagDir(dir)) return 0;
+	return CombineTrackStatus(TrackBitsToTrackdirBits(mode == TRANSPORT_RAIL ? GetTunnelBridgeTrackBits(tile) : DiagDirToDiagTrackBits(dir)), TRACKDIR_BIT_NONE);
-	return CombineTrackStatus(TrackBitsToTrackdirBits(DiagDirToDiagTrackBits(dir)), TRACKDIR_BIT_NONE);
 }
 
 static void UpdateRoadTunnelBridgeInfrastructure(TileIndex begin, TileIndex end, bool add) {
@@ -1743,9 +1773,6 @@ void SubtractRoadTunnelBridgeInfrastructure(TileIndex begin, TileIndex end) {
 static void ChangeTileOwner_TunnelBridge(TileIndex tile, Owner old_owner, Owner new_owner)
 {
 	const TileIndex other_end = GetOtherTunnelBridgeEnd(tile);
-	/* Set number of pieces to zero if it's the southern tile as we
-	 * don't want to update the infrastructure counts twice. */
-	const uint num_pieces = tile < other_end ? (GetTunnelBridgeLength(tile, other_end) + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR : 0;
 	const TransportType tt = GetTunnelBridgeTransportType(tile);
 
 	if (tt == TRANSPORT_ROAD && tile < other_end) {
@@ -1772,9 +1799,15 @@ static void ChangeTileOwner_TunnelBridge(TileIndex tile, Owner old_owner, Owner
 
 	Company *old = Company::Get(old_owner);
 	if (tt == TRANSPORT_RAIL) {
+		/* Set number of middle pieces to zero if it's the southern tile as we
+		 * don't want to update the infrastructure counts twice. */
+		const uint num_pieces = GetTunnelBridgeHeadOnlyRailInfrastructureCount(tile) + (tile < other_end ? GetTunnelBridgeLength(tile, other_end) * TUNNELBRIDGE_TRACKBIT_FACTOR : 0);
 		old->infrastructure.rail[GetRailType(tile)] -= num_pieces;
 		if (new_owner != INVALID_OWNER) Company::Get(new_owner)->infrastructure.rail[GetRailType(tile)] += num_pieces;
 	} else if (tt == TRANSPORT_WATER) {
+		/* Set number of pieces to zero if it's the southern tile as we
+		 * don't want to update the infrastructure counts twice. */
+		const uint num_pieces = tile < other_end ? (GetTunnelBridgeLength(tile, other_end) + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR : 0;
 		old->infrastructure.water -= num_pieces;
 		if (new_owner != INVALID_OWNER) Company::Get(new_owner)->infrastructure.water += num_pieces;
 	}
@@ -1813,23 +1846,31 @@ extern const byte _tunnel_visibility_frame[DIAGDIR_END] = {12, 8, 8, 12};
 
 static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex tile, int x, int y)
 {
+	/* Direction into the wormhole */
+	const DiagDirection dir = GetTunnelBridgeDirection(tile);
+	/* New position of the vehicle on the tile */
+	int pos = (DiagDirToAxis(dir) == AXIS_X ? x - (TileX(tile) * TILE_SIZE) : y - (TileY(tile) * TILE_SIZE));
+	/* Number of units moved by the vehicle since entering the tile */
+	int frame = (dir == DIAGDIR_NE || dir == DIAGDIR_NW) ? TILE_SIZE - 1 - pos : pos;
+
+	if (frame > (int) TILE_SIZE || frame < 0) return VETSB_CANNOT_ENTER;
+	if (frame == TILE_SIZE) {
+		TileIndexDiffC offset = TileIndexDiffCByDiagDir(ReverseDiagDir(dir));
+		x += offset.x;
+		y += offset.y;
+	}
+
 	int z = GetSlopePixelZ(x, y) - v->z_pos;
 
 	if (abs(z) > 2) return VETSB_CANNOT_ENTER;
-	/* Direction into the wormhole */
-	const DiagDirection dir = GetTunnelBridgeDirection(tile);
-	/* Direction of the vehicle */
-	const DiagDirection vdir = DirToDiagDir(v->direction);
-	/* New position of the vehicle on the tile */
-	byte pos = (DiagDirToAxis(vdir) == AXIS_X ? x : y) & TILE_UNIT_MASK;
-	/* Number of units moved by the vehicle since entering the tile */
-	byte frame = (vdir == DIAGDIR_NE || vdir == DIAGDIR_NW) ? TILE_SIZE - 1 - pos : pos;
 
 	if (IsTunnel(tile)) {
+		/* Direction of the vehicle */
+		const DiagDirection vdir = DirToDiagDir(v->direction);
 		if (v->type == VEH_TRAIN) {
 			Train *t = Train::From(v);
 
-			if (t->track != TRACK_BIT_WORMHOLE && dir == vdir) {
+			if (!(t->track & TRACK_BIT_WORMHOLE) && dir == vdir) {
 				if (t->IsFrontEngine() && frame == TUNNEL_SOUND_FRAME) {
 					if (!PlayVehicleSound(t, VSE_TUNNEL) && RailVehInfo(t->engine_type)->engclass == 0) {
 						SndPlayVehicleFx(SND_05_TRAIN_THROUGH_TUNNEL, v);
@@ -1844,7 +1885,7 @@ static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex ti
 				}
 			}
 
-			if (dir == ReverseDiagDir(vdir) && frame == TILE_SIZE - _tunnel_visibility_frame[dir] && z == 0) {
+			if (dir == ReverseDiagDir(vdir) && frame == (int) (_tunnel_visibility_frame[dir] - 1) && z == 0) {
 				/* We're at the tunnel exit ?? */
 				t->tile = tile;
 				t->track = DiagDirToDiagTrackBits(vdir);
@@ -1870,7 +1911,7 @@ static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex ti
 			}
 
 			/* We're at the tunnel exit ?? */
-			if (dir == ReverseDiagDir(vdir) && frame == TILE_SIZE - _tunnel_visibility_frame[dir] && z == 0) {
+			if (dir == ReverseDiagDir(vdir) && frame == (int) (_tunnel_visibility_frame[dir] - 1) && z == 0) {
 				rv->tile = tile;
 				rv->state = DiagDirToDiagTrackdir(vdir);
 				rv->frame = frame;
@@ -1888,11 +1929,12 @@ static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex ti
 			first->cur_speed = min(first->cur_speed, spd);
 		}
 
-		if (vdir == dir) {
+		const Direction bridge_dir = DiagDirToDir(dir);
-			/* Vehicle enters bridge at the last frame inside this tile. */
+		if (v->direction == bridge_dir) {
-			if (frame != TILE_SIZE - 1) return VETSB_CONTINUE;
 			switch (v->type) {
 				case VEH_TRAIN: {
+					/* Trains enter bridge at the first frame beyond this tile. */
+					if (frame != TILE_SIZE) return VETSB_CONTINUE;
 					Train *t = Train::From(v);
 					t->track = TRACK_BIT_WORMHOLE;
 					ClrBit(t->gv_flags, GVF_GOINGUP_BIT);
@@ -1901,6 +1943,8 @@ static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex ti
 				}
 
 				case VEH_ROAD: {
+					/* Non-train vehicles enter bridge at the last frame inside this tile. */
+					if (frame != TILE_SIZE - 1) return VETSB_CONTINUE;
 					RoadVehicle *rv = RoadVehicle::From(v);
 					if (IsRoadCustomBridgeHeadTile(tile)) {
 						RoadBits bits = ROAD_NONE;
@@ -1916,28 +1960,35 @@ static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex ti
 				}
 
 				case VEH_SHIP:
+					/* Non-train vehicles enter bridge at the last frame inside this tile. */
+					if (frame != TILE_SIZE - 1) return VETSB_CONTINUE;
 					Ship::From(v)->state = TRACK_BIT_WORMHOLE;
 					break;
 
 				default: NOT_REACHED();
 			}
 			return VETSB_ENTERED_WORMHOLE;
-		} else if (vdir == ReverseDiagDir(dir)) {
+		} else if (v->direction == ReverseDir(bridge_dir)) {
-			v->tile = tile;
 			switch (v->type) {
 				case VEH_TRAIN: {
 					Train *t = Train::From(v);
-					if (t->track == TRACK_BIT_WORMHOLE) {
+					if (t->track & TRACK_BIT_WORMHOLE) {
-						t->track = DiagDirToDiagTrackBits(vdir);
+						if (IsRailCustomBridgeHeadTile(tile)) {
+							return VETSB_ENTERED_WORMHOLE;
+						} else {
+							v->tile = tile;
+							t->track = DiagDirToDiagTrackBits(DirToDiagDir(v->direction));
+						}
 						return VETSB_ENTERED_WORMHOLE;
 					}
 					break;
 				}
 
 				case VEH_ROAD: {
+					v->tile = tile;
 					RoadVehicle *rv = RoadVehicle::From(v);
 					if (rv->state == RVSB_WORMHOLE) {
-						rv->state = DiagDirToDiagTrackdir(vdir);
+						rv->state = DiagDirToDiagTrackdir(DirToDiagDir(v->direction));
 						rv->frame = 0;
 						return VETSB_ENTERED_WORMHOLE;
 					}
@@ -1945,9 +1996,10 @@ static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex ti
 				}
 
 				case VEH_SHIP: {
+					v->tile = tile;
 					Ship *ship = Ship::From(v);
 					if (ship->state == TRACK_BIT_WORMHOLE) {
-						ship->state = DiagDirToDiagTrackBits(vdir);
+						ship->state = DiagDirToDiagTrackBits(DirToDiagDir(v->direction));
 						return VETSB_ENTERED_WORMHOLE;
 					}
 					break;
@@ -1955,6 +2007,29 @@ static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex ti
 
 				default: NOT_REACHED();
 			}
+		} else if (v->type == VEH_TRAIN && IsRailCustomBridgeHeadTile(tile)) {
+			DirDiff dir_diff = DirDifference(v->direction, bridge_dir);
+			DirDiff reverse_dir_diff = DirDifference(v->direction, ReverseDir(bridge_dir));
+
+			if (dir_diff == DIRDIFF_45RIGHT || dir_diff == DIRDIFF_45LEFT) {
+				if (frame != TILE_SIZE) return VETSB_CONTINUE;
+
+				Train *t = Train::From(v);
+				TileIndex other = GetOtherTunnelBridgeEnd(tile);
+				if (GetTunnelBridgeLength(tile, other) == 0 && IsRailCustomBridgeHead(other))  {
+					t->track |= TRACK_BIT_WORMHOLE;
+				} else {
+					t->direction = bridge_dir;
+					t->track = TRACK_BIT_WORMHOLE;
+				}
+				ClrBit(t->gv_flags, GVF_GOINGUP_BIT);
+				ClrBit(t->gv_flags, GVF_GOINGDOWN_BIT);
+				return VETSB_ENTERED_WORMHOLE;
+			}
+			if (reverse_dir_diff == DIRDIFF_45RIGHT || reverse_dir_diff == DIRDIFF_45LEFT) {
+				Train *t = Train::From(v);
+				if (t->track & TRACK_BIT_WORMHOLE) return VETSB_ENTERED_WORMHOLE;
+			}
 		}
 	}
 	return VETSB_CONTINUE;
@@ -1980,6 +2055,16 @@ static CommandCost TerraformTile_TunnelBridge(TileIndex tile, DoCommandFlag flag
 				return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
 			}
 		}
+		if (IsRailCustomBridgeHeadTile(tile)) {
+			extern bool IsValidFlatRailBridgeHeadTrackBits(Slope normalised_slope, DiagDirection bridge_direction, TrackBits tracks);
+
+			/* Steep slopes behave the same as slopes with one corner raised. */
+			const Slope normalised_tileh_new = IsSteepSlope(tileh_new) ? SlopeWithOneCornerRaised(GetHighestSlopeCorner(tileh_new)) : tileh_new;
+
+			if (!IsValidFlatRailBridgeHeadTrackBits(normalised_tileh_new, direction, GetCustomBridgeHeadTrackBits(tile))) {
+				return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
+			}
+		}
 
 		/* Check if new slope is valid for bridges in general (so we can safely call GetBridgeFoundation()) */
 		if ((direction == DIAGDIR_NW) || (direction == DIAGDIR_NE)) {

src/tunnelbridge_map.h

@@ -14,6 +14,8 @@
 
 #include "bridge_map.h"
 #include "tunnel_map.h"
+#include "track_func.h"
+#include "core/bitmath_func.hpp"
 
 
 /**
@@ -83,31 +85,34 @@ static inline TileIndex GetOtherTunnelBridgeEnd(TileIndex t)
 	return IsTunnel(t) ? GetOtherTunnelEnd(t) : GetOtherBridgeEnd(t);
 }
 
-
 /**
- * Get the reservation state of the rail tunnel/bridge
+ * Get the track bits for a rail tunnel/bridge
  * @pre IsTileType(t, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
  * @param t the tile
- * @return reservation state
+ * @return reserved track bits
  */
-static inline bool HasTunnelBridgeReservation(TileIndex t)
+static inline TrackBits GetTunnelBridgeTrackBits(TileIndex t)
 {
-	assert(IsTileType(t, MP_TUNNELBRIDGE));
+	if (IsTunnel(t)) {
-	assert(GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL);
+		return DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t));
-	return HasBit(_m[t].m5, 4);
+	} else {
+		return GetCustomBridgeHeadTrackBits(t);
+	}
 }
 
 /**
- * Set the reservation state of the rail tunnel/bridge
+ * Get the track bits for a rail tunnel/bridge onto/across the tunnel/bridge
  * @pre IsTileType(t, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
  * @param t the tile
- * @param b the reservation state
+ * @return reserved track bits
  */
-static inline void SetTunnelBridgeReservation(TileIndex t, bool b)
+static inline TrackBits GetAcrossTunnelBridgeTrackBits(TileIndex t)
 {
-	assert(IsTileType(t, MP_TUNNELBRIDGE));
+	if (IsTunnel(t)) {
-	assert(GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL);
+		return DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t));
-	SB(_m[t].m5, 4, 1, b ? 1 : 0);
+	} else {
+		return GetCustomBridgeHeadTrackBits(t) & GetAcrossBridgePossibleTrackBits(t);
+	}
 }
 
 /**
@@ -118,7 +123,122 @@ static inline void SetTunnelBridgeReservation(TileIndex t, bool b)
  */
 static inline TrackBits GetTunnelBridgeReservationTrackBits(TileIndex t)
 {
-	return HasTunnelBridgeReservation(t) ? DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t)) : TRACK_BIT_NONE;
+	if (IsTunnel(t)) {
+		return HasTunnelReservation(t) ? DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t)) : TRACK_BIT_NONE;
+	} else {
+		return GetBridgeReservationTrackBits(t);
+	}
+}
+
+/**
+ * Get the reserved track bits for a rail tunnel/bridge onto/across the tunnel/bridge
+ * @pre IsTileType(t, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
+ * @param t the tile
+ * @return reserved track bits
+ */
+static inline TrackBits GetAcrossTunnelBridgeReservationTrackBits(TileIndex t)
+{
+	if (IsTunnel(t)) {
+		return HasTunnelReservation(t) ? DiagDirToDiagTrackBits(GetTunnelBridgeDirection(t)) : TRACK_BIT_NONE;
+	} else {
+		return GetAcrossBridgeReservationTrackBits(t);
+	}
+}
+
+/**
+ * Get whether there are reserved track bits for a rail tunnel/bridge onto/across the tunnel/bridge
+ * @pre IsTileType(t, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
+ * @param t the tile
+ * @return whether there are reserved track bits
+ */
+static inline bool HasAcrossTunnelBridgeReservation(TileIndex t)
+{
+	if (IsTunnel(t)) {
+		return HasTunnelReservation(t);
+	} else {
+		return GetAcrossBridgeReservationTrackBits(t) != TRACK_BIT_NONE;
+	}
+}
+
+/**
+ * Get the rail infrastructure count of a rail tunnel/bridge head tile (excluding the tunnel/bridge middle)
+ * @param bits the track bits
+ * @return rail infrastructure count
+ */
+static inline uint GetTunnelBridgeHeadOnlyRailInfrastructureCountFromTrackBits(TrackBits bits)
+{
+	uint pieces = CountBits(bits);
+	if (TracksOverlap(bits)) pieces *= pieces;
+	return (TUNNELBRIDGE_TRACKBIT_FACTOR / 2) * (1 + pieces);
+}
+
+/**
+ * Get the rail infrastructure count of a rail tunnel/bridge head tile (excluding the tunnel/bridge middle)
+ * @pre IsTileType(t, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
+ * @param t the tile
+ * @return rail infrastructure count
+ */
+static inline uint GetTunnelBridgeHeadOnlyRailInfrastructureCount(TileIndex t)
+{
+	return IsBridge(t) ? GetTunnelBridgeHeadOnlyRailInfrastructureCountFromTrackBits(GetTunnelBridgeTrackBits(t)) : TUNNELBRIDGE_TRACKBIT_FACTOR;
+}
+
+/**
+ * Check if the given track direction on a rail bridge head tile enters the bridge
+ * @pre IsTileType(t, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
+ * @param t the tile
+ * @param td track direction
+ * @return reservation state
+ */
+static inline bool TrackdirEntersTunnelBridge(TileIndex t, Trackdir td)
+{
+	assert(IsTileType(t, MP_TUNNELBRIDGE));
+	assert(GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL);
+	return TrackdirToExitdir(td) == GetTunnelBridgeDirection(t);
+}
+
+/**
+ * Check if the given track direction on a rail bridge head tile exits the bridge
+ * @pre IsTileType(t, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
+ * @param t the tile
+ * @param td track direction
+ * @return reservation state
+ */
+static inline bool TrackdirExitsTunnelBridge(TileIndex t, Trackdir td)
+{
+	assert(IsTileType(t, MP_TUNNELBRIDGE));
+	assert(GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL);
+	return TrackdirToExitdir(ReverseTrackdir(td)) == GetTunnelBridgeDirection(t);
+}
+
+/**
+ * Check if the given track on a rail bridge head tile enters/exits the bridge
+ * @pre IsTileType(t, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(t) == TRANSPORT_RAIL
+ * @param tile the tile
+ * @param t track
+ * @return reservation state
+ */
+static inline bool IsTrackAcrossTunnelBridge(TileIndex tile, Track t)
+{
+	assert(IsTileType(tile, MP_TUNNELBRIDGE));
+	assert(GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL);
+	return DiagdirReachesTracks(ReverseDiagDir(GetTunnelBridgeDirection(tile))) & TrackToTrackBits(t);
+}
+
+/**
+ * Lift the reservation of a specific track on a tunnel or rail bridge head tile
+ * @pre IsTileType(tile, MP_TUNNELBRIDGE) && GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL
+ * @param tile the tile
+ */
+static inline void UnreserveAcrossRailTunnelBridge(TileIndex tile)
+{
+	assert(IsTileType(tile, MP_TUNNELBRIDGE));
+	assert(GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL);
+	if (IsTunnel(tile)) {
+		SetTunnelReservation(tile, false);
+	} else {
+		UnreserveAcrossRailBridgeHead(tile);
+	}
 }
 
 void AddRoadTunnelBridgeInfrastructure(TileIndex begin, TileIndex end);

src/vehicle.cpp

@@ -525,11 +525,23 @@ CommandCost EnsureNoVehicleOnGround(TileIndex tile)
 	return CommandCost();
 }
 
+struct GetVehicleTunnelBridgeProcData {
+	const Vehicle *v;
+	TileIndex t;
+	bool across_only;
+};
+
 /** Procedure called for every vehicle found in tunnel/bridge in the hash map */
 static Vehicle *GetVehicleTunnelBridgeProc(Vehicle *v, void *data)
 {
+	const GetVehicleTunnelBridgeProcData *info = (GetVehicleTunnelBridgeProcData*) data;
 	if (v->type != VEH_TRAIN && v->type != VEH_ROAD && v->type != VEH_SHIP) return NULL;
-	if (v == (const Vehicle *)data) return NULL;
+	if (v == info->v) return NULL;
+
+	if (v->type == VEH_TRAIN && info->across_only && IsBridge(info->t)) {
+		TrackBits vehicle_track = Train::From(v)->track;
+		if (!(vehicle_track & TRACK_BIT_WORMHOLE) && !(GetAcrossBridgePossibleTrackBits(info->t) & vehicle_track)) return NULL;
+	}
 
 	return v;
 }
@@ -539,16 +551,24 @@ static Vehicle *GetVehicleTunnelBridgeProc(Vehicle *v, void *data)
  * @param tile first end
  * @param endtile second end
  * @param ignore Ignore this vehicle when searching
+ * @param across_only Only find vehicles which are passing across the bridge/tunnel or on connecting bridge head track pieces
  * @return Succeeded command (if tunnel/bridge is free) or failed command (if a vehicle is using the tunnel/bridge).
  */
-CommandCost TunnelBridgeIsFree(TileIndex tile, TileIndex endtile, const Vehicle *ignore)
+CommandCost TunnelBridgeIsFree(TileIndex tile, TileIndex endtile, const Vehicle *ignore, bool across_only)
 {
 	/* Value v is not safe in MP games, however, it is used to generate a local
 	 * error message only (which may be different for different machines).
 	 * Such a message does not affect MP synchronisation.
 	 */
-	Vehicle *v = VehicleFromPos(tile, const_cast<Vehicle *>(ignore), &GetVehicleTunnelBridgeProc, true);
+	GetVehicleTunnelBridgeProcData data;
-	if (v == NULL) v = VehicleFromPos(endtile, const_cast<Vehicle *>(ignore), &GetVehicleTunnelBridgeProc, true);
+	data.v = ignore;
+	data.t = tile;
+	data.across_only = across_only;
+	Vehicle *v = VehicleFromPos(tile, &data, &GetVehicleTunnelBridgeProc, true);
+	if (v == NULL) {
+		data.t = endtile;
+		v = VehicleFromPos(endtile, &data, &GetVehicleTunnelBridgeProc, true);
+	}
 
 	if (v != NULL) return_cmd_error(STR_ERROR_TRAIN_IN_THE_WAY + v->type);
 	return CommandCost();
@@ -561,6 +581,12 @@ static Vehicle *EnsureNoTrainOnTrackProc(Vehicle *v, void *data)
 	if (v->type != VEH_TRAIN) return NULL;
 
 	Train *t = Train::From(v);
+	if (rail_bits & TRACK_BIT_WORMHOLE) {
+		if (t->track & TRACK_BIT_WORMHOLE) return v;
+		rail_bits &= ~TRACK_BIT_WORMHOLE;
+	} else if (t->track & TRACK_BIT_WORMHOLE) {
+		return NULL;
+	}
 	if ((t->track != rail_bits) && !TracksOverlap(t->track | rail_bits)) return NULL;
 
 	return v;

src/vehicle_func.h

@@ -60,7 +60,7 @@ byte GetBestFittingSubType(Vehicle *v_from, Vehicle *v_for, CargoID dest_cargo_t
 void ViewportAddVehicles(DrawPixelInfo *dpi);
 
 void ShowNewGrfVehicleError(EngineID engine, StringID part1, StringID part2, GRFBugs bug_type, bool critical);
-CommandCost TunnelBridgeIsFree(TileIndex tile, TileIndex endtile, const Vehicle *ignore = NULL);
+CommandCost TunnelBridgeIsFree(TileIndex tile, TileIndex endtile, const Vehicle *ignore = NULL, bool across_only = false);
 
 void DecreaseVehicleValue(Vehicle *v);
 void CheckVehicleBreakdown(Vehicle *v);

src/viewport.cpp

@@ -84,6 +84,7 @@
 #include "linkgraph/linkgraph_gui.h"
 #include "viewport_sprite_sorter.h"
 #include "bridge_map.h"
+#include "tunnelbridge_map.h"
 
 #include <map>
 
@@ -976,11 +977,23 @@ static const HighLightStyle _autorail_type[6][2] = {
  */
 static void DrawAutorailSelection(const TileInfo *ti, uint autorail_type)
 {
-	SpriteID image;
-	PaletteID pal;
-	int offset;
-
 	FoundationPart foundation_part = FOUNDATION_PART_NORMAL;
+	int offset;
+	bool bridge_head_mode = false;
+
+	if (IsFlatRailBridgeHeadTile(ti->tile)) {
+		extern bool IsValidFlatRailBridgeHeadTrackBits(Slope normalised_slope, DiagDirection bridge_direction, TrackBits tracks);
+
+		offset = _AutorailTilehSprite[SLOPE_FLAT][autorail_type];
+		const Slope real_tileh = GetTileSlope(ti->tile, nullptr);
+		const Slope normalised_tileh = IsSteepSlope(real_tileh) ? SlopeWithOneCornerRaised(GetHighestSlopeCorner(real_tileh)) : real_tileh;
+		if (!IsValidFlatRailBridgeHeadTrackBits(normalised_tileh, GetTunnelBridgeDirection(ti->tile), TrackToTrackBits((Track) autorail_type))) {
+			offset = -offset;
+		}
+		if (!IsRailCustomBridgeHead(ti->tile)) {
+			bridge_head_mode = true;
+		}
+	} else {
 		Slope autorail_tileh = RemoveHalftileSlope(ti->tileh);
 		if (IsHalftileSlope(ti->tileh)) {
 			static const uint _lower_rail[4] = { 5U, 2U, 4U, 3U };
@@ -991,8 +1004,11 @@ static void DrawAutorailSelection(const TileInfo *ti, uint autorail_type)
 				autorail_tileh = SlopeWithThreeCornersRaised(OppositeCorner(halftile_corner));
 			}
 		}
-
 		offset = _AutorailTilehSprite[autorail_tileh][autorail_type];
+	}
+
+	SpriteID image;
+	PaletteID pal;
 	if (offset >= 0) {
 		image = SPR_AUTORAIL_BASE + offset;
 		pal = PAL_NONE;
@@ -1001,7 +1017,11 @@ static void DrawAutorailSelection(const TileInfo *ti, uint autorail_type)
 		pal = PALETTE_SEL_TILE_RED;
 	}
 
+	if (bridge_head_mode) {
+		AddSortableSpriteToDraw(image, _thd.make_square_red ? PALETTE_SEL_TILE_RED : pal, ti->x, ti->y, 16, 16, 0, ti->z + 15);
+	} else {
 		DrawSelectionSprite(image, _thd.make_square_red ? PALETTE_SEL_TILE_RED : pal, ti, 7, foundation_part);
+	}
 }
 
 /**