(p1);
			if (!HasExactlyOneBit(rts) || !HasRoadTypesAvail(company, rts)) return CMD_ERROR;
			break;
		default: return CMD_ERROR;
	}
	if (company == OWNER_DEITY) {
		if (transport_type != TRANSPORT_ROAD) return CMD_ERROR;
		const Town *town = CalcClosestTownFromTile(start_tile);
		company = OWNER_TOWN;
		/* If we are not within a town, we are not owned by the town */
		if (town == NULL || DistanceSquare(start_tile, town->xy) > town->cache.squared_town_zone_radius[HZB_TOWN_EDGE]) {
			company = OWNER_NONE;
		}
	}
	int start_z;
	int end_z;
	Slope start_tileh = GetTileSlope(start_tile, &start_z);
	DiagDirection direction = GetInclinedSlopeDirection(start_tileh);
	if (direction == INVALID_DIAGDIR) return_cmd_error(STR_ERROR_SITE_UNSUITABLE_FOR_TUNNEL);
	if (HasTileWaterGround(start_tile)) return_cmd_error(STR_ERROR_CAN_T_BUILD_ON_WATER);
	CommandCost ret = DoCommand(start_tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
	if (ret.Failed()) return ret;
	/* XXX - do NOT change 'ret' in the loop, as it is used as the price
	 * for the clearing of the entrance of the tunnel. Assigning it to
	 * cost before the loop will yield different costs depending on start-
	 * position, because of increased-cost-by-length: 'cost += cost >> 3' */
	TileIndexDiff delta = TileOffsByDiagDir(direction);
	DiagDirection tunnel_in_way_dir;
	if (DiagDirToAxis(direction) == AXIS_Y) {
		tunnel_in_way_dir = (TileX(start_tile) < (MapMaxX() / 2)) ? DIAGDIR_SW : DIAGDIR_NE;
	} else {
		tunnel_in_way_dir = (TileY(start_tile) < (MapMaxX() / 2)) ? DIAGDIR_SE : DIAGDIR_NW;
	}
	TileIndex end_tile = start_tile;
	/* Tile shift coeficient. Will decrease for very long tunnels to avoid exponential growth of price*/
	int tiles_coef = 3;
	/* Number of tiles from start of tunnel */
	int tiles = 0;
	/* Number of tiles at which the cost increase coefficient per tile is halved */
	int tiles_bump = 25;
	CommandCost cost(EXPENSES_CONSTRUCTION);
	Slope end_tileh;
	for (;;) {
		end_tile += delta;
		if (!IsValidTile(end_tile)) return_cmd_error(STR_ERROR_TUNNEL_THROUGH_MAP_BORDER);
		end_tileh = GetTileSlope(end_tile, &end_z);
		if (start_z == end_z) break;
		if (!_cheats.crossing_tunnels.value && IsTunnelInWayDir(end_tile, start_z, tunnel_in_way_dir)) {
			return_cmd_error(STR_ERROR_ANOTHER_TUNNEL_IN_THE_WAY);
		}
		tiles++;
		if (tiles == tiles_bump) {
			tiles_coef++;
			tiles_bump *= 2;
		}
		cost.AddCost(_price[PR_BUILD_TUNNEL]);
		cost.AddCost(cost.GetCost() >> tiles_coef); // add a multiplier for longer tunnels
	}
	/* Add the cost of the entrance */
	cost.AddCost(_price[PR_BUILD_TUNNEL]);
	cost.AddCost(ret);
	/* if the command fails from here on we want the end tile to be highlighted */
	_build_tunnel_endtile = end_tile;
	if (tiles > _settings_game.construction.max_tunnel_length) return_cmd_error(STR_ERROR_TUNNEL_TOO_LONG);
	if (HasTileWaterGround(end_tile)) return_cmd_error(STR_ERROR_CAN_T_BUILD_ON_WATER);
	/* Clear the tile in any case */
	ret = DoCommand(end_tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
	if (ret.Failed()) return_cmd_error(STR_ERROR_UNABLE_TO_EXCAVATE_LAND);
	cost.AddCost(ret);
	/* slope of end tile must be complementary to the slope of the start tile */
	if (end_tileh != ComplementSlope(start_tileh)) {
		/* Mark the tile as already cleared for the terraform command.
		 * Do this for all tiles (like trees), not only objects. */
		ClearedObjectArea *coa = FindClearedObject(end_tile);
		if (coa == NULL) {
			coa = _cleared_object_areas.Append();
			coa->first_tile = end_tile;
			coa->area = TileArea(end_tile, 1, 1);
		}
		/* Hide the tile from the terraforming command */
		TileIndex old_first_tile = coa->first_tile;
		coa->first_tile = INVALID_TILE;
		ret = DoCommand(end_tile, end_tileh & start_tileh, 0, flags, CMD_TERRAFORM_LAND);
		coa->first_tile = old_first_tile;
		if (ret.Failed()) return_cmd_error(STR_ERROR_UNABLE_TO_EXCAVATE_LAND);
		cost.AddCost(ret);
	}
	cost.AddCost(_price[PR_BUILD_TUNNEL]);
	/* Pay for the rail/road in the tunnel including entrances */
	switch (transport_type) {
		case TRANSPORT_ROAD: cost.AddCost((tiles + 2) * _price[PR_BUILD_ROAD] * 2); break;
		case TRANSPORT_RAIL: cost.AddCost((tiles + 2) * RailBuildCost(railtype)); break;
		default: break;
	}
	if (flags & DC_EXEC) {
		Company *c = Company::GetIfValid(company);
		uint num_pieces = (tiles + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR;
		if (transport_type == TRANSPORT_RAIL) {
			if (!IsTunnelTile(start_tile) && c != NULL) c->infrastructure.rail[railtype] += num_pieces;
			MakeRailTunnel(start_tile, company, direction,                 railtype);
			MakeRailTunnel(end_tile,   company, ReverseDiagDir(direction), railtype);
			AddSideToSignalBuffer(start_tile, INVALID_DIAGDIR, company);
			YapfNotifyTrackLayoutChange(start_tile, DiagDirToDiagTrack(direction));
		} else {
			if (c != NULL) {
				RoadType rt;
				FOR_EACH_SET_ROADTYPE(rt, rts ^ (IsTunnelTile(start_tile) ? GetRoadTypes(start_tile) : ROADTYPES_NONE)) {
					c->infrastructure.road[rt] += num_pieces * 2; // A full diagonal road has two road bits.
				}
			}
			MakeRoadTunnel(start_tile, company, direction,                 rts);
			MakeRoadTunnel(end_tile,   company, ReverseDiagDir(direction), rts);
		}
		DirtyCompanyInfrastructureWindows(company);
	}
	return cost;
}
/**
 * Are we allowed to remove the tunnel or bridge at \a tile?
 * @param tile End point of the tunnel or bridge.
 * @return A succeeded command if the tunnel or bridge may be removed, a failed command otherwise.
 */
static inline CommandCost CheckAllowRemoveTunnelBridge(TileIndex tile)
{
	/* Floods can remove anything as well as the scenario editor */
	if (_current_company == OWNER_WATER || _game_mode == GM_EDITOR) return CommandCost();
	switch (GetTunnelBridgeTransportType(tile)) {
		case TRANSPORT_ROAD: {
			RoadTypes rts = GetRoadTypes(tile);
			Owner road_owner = _current_company;
			Owner tram_owner = _current_company;
			if (HasBit(rts, ROADTYPE_ROAD)) road_owner = GetRoadOwner(tile, ROADTYPE_ROAD);
			if (HasBit(rts, ROADTYPE_TRAM)) tram_owner = GetRoadOwner(tile, ROADTYPE_TRAM);
			/* We can remove unowned road and if the town allows it */
			if (road_owner == OWNER_TOWN && !(_settings_game.construction.extra_dynamite || _cheats.magic_bulldozer.value)) {
				return CheckTileOwnership(tile);
			}
			if (road_owner == OWNER_NONE || road_owner == OWNER_TOWN) road_owner = _current_company;
			if (tram_owner == OWNER_NONE) tram_owner = _current_company;
			CommandCost ret = CheckOwnership(road_owner, tile);
			if (ret.Succeeded()) ret = CheckOwnership(tram_owner, tile);
			return ret;
		}
		case TRANSPORT_RAIL:
			return CheckOwnership(GetTileOwner(tile));
		case TRANSPORT_WATER: {
			/* Always allow to remove aqueducts without owner. */
			Owner aqueduct_owner = GetTileOwner(tile);
			if (aqueduct_owner == OWNER_NONE) aqueduct_owner = _current_company;
			return CheckOwnership(aqueduct_owner);
		}
		default: NOT_REACHED();
	}
}
/**
 * Remove a tunnel from the game, update town rating, etc.
 * @param tile Tile containing one of the endpoints of the tunnel.
 * @param flags Command flags.
 * @return Succeeded or failed command.
 */
static CommandCost DoClearTunnel(TileIndex tile, DoCommandFlag flags)
{
	CommandCost ret = CheckAllowRemoveTunnelBridge(tile);
	if (ret.Failed()) return ret;
	TileIndex endtile = GetOtherTunnelEnd(tile);
	ret = TunnelBridgeIsFree(tile, endtile);
	if (ret.Failed()) return ret;
	_build_tunnel_endtile = endtile;
	Town *t = NULL;
	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
		t = ClosestTownFromTile(tile, UINT_MAX); // town penalty rating
		/* Check if you are allowed to remove the tunnel owned by a town
		 * Removal depends on difficulty settings */
		CommandCost ret = CheckforTownRating(flags, t, TUNNELBRIDGE_REMOVE);
		if (ret.Failed()) return ret;
	}
	/* checks if the owner is town then decrease town rating by RATING_TUNNEL_BRIDGE_DOWN_STEP until
	 * you have a "Poor" (0) town rating */
	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
		ChangeTownRating(t, RATING_TUNNEL_BRIDGE_DOWN_STEP, RATING_TUNNEL_BRIDGE_MINIMUM, flags);
	}
	uint len = GetTunnelBridgeLength(tile, endtile) + 2; // Don't forget the end tiles.
	if (flags & DC_EXEC) {
		if (GetTunnelBridgeTransportType(tile) == TRANSPORT_RAIL) {
			/* We first need to request values before calling DoClearSquare */
			DiagDirection dir = GetTunnelBridgeDirection(tile);
			Track track = DiagDirToDiagTrack(dir);
			Owner owner = GetTileOwner(tile);
			Train *v = NULL;
			if (HasTunnelBridgeReservation(tile)) {
				v = GetTrainForReservation(tile, track);
				if (v != NULL) FreeTrainTrackReservation(v);
			}
			if (Company::IsValidID(owner)) {
				Company::Get(owner)->infrastructure.rail[GetRailType(tile)] -= len * TUNNELBRIDGE_TRACKBIT_FACTOR;
				DirtyCompanyInfrastructureWindows(owner);
			}
			DoClearSquare(tile);
			DoClearSquare(endtile);
			/* cannot use INVALID_DIAGDIR for signal update because the tunnel doesn't exist anymore */
			AddSideToSignalBuffer(tile,    ReverseDiagDir(dir), owner);
			AddSideToSignalBuffer(endtile, dir,                 owner);
			YapfNotifyTrackLayoutChange(tile,    track);
			YapfNotifyTrackLayoutChange(endtile, track);
			if (v != NULL) TryPathReserve(v);
		} else {
			RoadType rt;
			FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
				/* A full diagonal road tile has two road bits. */
				Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
				if (c != NULL) {
					c->infrastructure.road[rt] -= len * 2 * TUNNELBRIDGE_TRACKBIT_FACTOR;
					DirtyCompanyInfrastructureWindows(c->index);
				}
			}
			DoClearSquare(tile);
			DoClearSquare(endtile);
		}
	}
	return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_CLEAR_TUNNEL] * len);
}
/**
 * Remove a bridge from the game, update town rating, etc.
 * @param tile Tile containing one of the endpoints of the bridge.
 * @param flags Command flags.
 * @return Succeeded or failed command.
 */
static CommandCost DoClearBridge(TileIndex tile, DoCommandFlag flags)
{
	CommandCost ret = CheckAllowRemoveTunnelBridge(tile);
	if (ret.Failed()) return ret;
	TileIndex endtile = GetOtherBridgeEnd(tile);
	ret = TunnelBridgeIsFree(tile, endtile);
	if (ret.Failed()) return ret;
	DiagDirection direction = GetTunnelBridgeDirection(tile);
	TileIndexDiff delta = TileOffsByDiagDir(direction);
	Town *t = NULL;
	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
		t = ClosestTownFromTile(tile, UINT_MAX); // town penalty rating
		/* Check if you are allowed to remove the bridge owned by a town
		 * Removal depends on difficulty settings */
		CommandCost ret = CheckforTownRating(flags, t, TUNNELBRIDGE_REMOVE);
		if (ret.Failed()) return ret;
	}
	/* checks if the owner is town then decrease town rating by RATING_TUNNEL_BRIDGE_DOWN_STEP until
	 * you have a "Poor" (0) town rating */
	if (IsTileOwner(tile, OWNER_TOWN) && _game_mode != GM_EDITOR) {
		ChangeTownRating(t, RATING_TUNNEL_BRIDGE_DOWN_STEP, RATING_TUNNEL_BRIDGE_MINIMUM, flags);
	}
	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.
	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;
		if (rail && HasTunnelBridgeReservation(tile)) {
			v = GetTrainForReservation(tile, DiagDirToDiagTrack(direction));
			if (v != NULL) FreeTrainTrackReservation(v);
		}
		/* Update company infrastructure counts. */
		if (rail) {
			if (Company::IsValidID(owner)) Company::Get(owner)->infrastructure.rail[GetRailType(tile)] -= len * TUNNELBRIDGE_TRACKBIT_FACTOR;
		} else if (GetTunnelBridgeTransportType(tile) == TRANSPORT_ROAD) {
			RoadType rt;
			FOR_EACH_SET_ROADTYPE(rt, GetRoadTypes(tile)) {
				Company *c = Company::GetIfValid(GetRoadOwner(tile, rt));
				if (c != NULL) {
					/* A full diagonal road tile has two road bits. */
					c->infrastructure.road[rt] -= len * 2 * TUNNELBRIDGE_TRACKBIT_FACTOR;
					DirtyCompanyInfrastructureWindows(c->index);
				}
			}
		} else { // Aqueduct
			if (Company::IsValidID(owner)) Company::Get(owner)->infrastructure.water -= len * TUNNELBRIDGE_TRACKBIT_FACTOR;
		}
		DirtyCompanyInfrastructureWindows(owner);
		DoClearSquare(tile);
		DoClearSquare(endtile);
		for (TileIndex c = tile + delta; c != endtile; c += delta) {
			/* do not let trees appear from 'nowhere' after removing bridge */
			if (IsNormalRoadTile(c) && GetRoadside(c) == ROADSIDE_TREES) {
				int minz = GetTileMaxZ(c) + 3;
				if (height < minz) SetRoadside(c, ROADSIDE_PAVED);
			}
			ClearBridgeMiddle(c);
			MarkTileDirtyByTile(c);
		}
		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);
			YapfNotifyTrackLayoutChange(tile,    track);
			YapfNotifyTrackLayoutChange(endtile, track);
			if (v != NULL) TryPathReserve(v, true);
		}
	}
	return CommandCost(EXPENSES_CONSTRUCTION, len * base_cost);
}
/**
 * Remove a tunnel or a bridge from the game.
 * @param tile Tile containing one of the endpoints.
 * @param flags Command flags.
 * @return Succeeded or failed command.
 */
static CommandCost ClearTile_TunnelBridge(TileIndex tile, DoCommandFlag flags)
{
	if (IsTunnel(tile)) {
		if (flags & DC_AUTO) return_cmd_error(STR_ERROR_MUST_DEMOLISH_TUNNEL_FIRST);
		return DoClearTunnel(tile, flags);
	} else { // IsBridge(tile)
		if (flags & DC_AUTO) return_cmd_error(STR_ERROR_MUST_DEMOLISH_BRIDGE_FIRST);
		return DoClearBridge(tile, flags);
	}
}
/**
 * Draw a single pillar sprite.
 * @param psid      Pillarsprite
 * @param x         Pillar X
 * @param y         Pillar Y
 * @param z         Pillar Z
 * @param w         Bounding box size in X direction
 * @param h         Bounding box size in Y direction
 * @param subsprite Optional subsprite for drawing halfpillars
 */
static inline void DrawPillar(const PalSpriteID *psid, int x, int y, int z, int w, int h, const SubSprite *subsprite)
{
	static const int PILLAR_Z_OFFSET = TILE_HEIGHT - BRIDGE_Z_START; ///< Start offset of pillar wrt. bridge (downwards)
	AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, w, h, BB_HEIGHT_UNDER_BRIDGE - PILLAR_Z_OFFSET, z, IsTransparencySet(TO_BRIDGES), 0, 0, -PILLAR_Z_OFFSET, subsprite);
}
/**
 * Draw two bridge pillars (north and south).
 * @param z_bottom Bottom Z
 * @param z_top    Top Z
 * @param psid     Pillarsprite
 * @param x        Pillar X
 * @param y        Pillar Y
 * @param w        Bounding box size in X direction
 * @param h        Bounding box size in Y direction
 * @return Reached Z at the bottom
 */
static int DrawPillarColumn(int z_bottom, int z_top, const PalSpriteID *psid, int x, int y, int w, int h)
{
	int cur_z;
	for (cur_z = z_top; cur_z >= z_bottom; cur_z -= TILE_HEIGHT) {
		DrawPillar(psid, x, y, cur_z, w, h, NULL);
	}
	return cur_z;
}
/**
 * Draws the pillars under high bridges.
 *
 * @param psid Image and palette of a bridge pillar.
 * @param ti #TileInfo of current bridge-middle-tile.
 * @param axis Orientation of bridge.
 * @param drawfarpillar Whether to draw the pillar at the back
 * @param x Sprite X position of front pillar.
 * @param y Sprite Y position of front pillar.
 * @param z_bridge Absolute height of bridge bottom.
 */
static void DrawBridgePillars(const PalSpriteID *psid, const TileInfo *ti, Axis axis, bool drawfarpillar, int x, int y, int z_bridge)
{
	static const int bounding_box_size[2]  = {16, 2}; ///< bounding box size of pillars along bridge direction
	static const int back_pillar_offset[2] = { 0, 9}; ///< sprite position offset of back facing pillar
	static const int INF = 1000; ///< big number compared to sprite size
	static const SubSprite half_pillar_sub_sprite[2][2] = {
		{ {  -14, -INF, INF, INF }, { -INF, -INF, -15, INF } }, // X axis, north and south
		{ { -INF, -INF,  15, INF }, {   16, -INF, INF, INF } }, // Y axis, north and south
	};
	if (psid->sprite == 0) return;
	/* Determine ground height under pillars */
	DiagDirection south_dir = AxisToDiagDir(axis);
	int z_front_north = ti->z;
	int z_back_north = ti->z;
	int z_front_south = ti->z;
	int z_back_south = ti->z;
	GetSlopePixelZOnEdge(ti->tileh, south_dir, &z_front_south, &z_back_south);
	GetSlopePixelZOnEdge(ti->tileh, ReverseDiagDir(south_dir), &z_front_north, &z_back_north);
	/* Shared height of pillars */
	int z_front = max(z_front_north, z_front_south);
	int z_back = max(z_back_north, z_back_south);
	/* x and y size of bounding-box of pillars */
	int w = bounding_box_size[axis];
	int h = bounding_box_size[OtherAxis(axis)];
	/* sprite position of back facing pillar */
	int x_back = x - back_pillar_offset[axis];
	int y_back = y - back_pillar_offset[OtherAxis(axis)];
	/* Draw front pillars */
	int bottom_z = DrawPillarColumn(z_front, z_bridge, psid, x, y, w, h);
	if (z_front_north < z_front) DrawPillar(psid, x, y, bottom_z, w, h, &half_pillar_sub_sprite[axis][0]);
	if (z_front_south < z_front) DrawPillar(psid, x, y, bottom_z, w, h, &half_pillar_sub_sprite[axis][1]);
	/* Draw back pillars, skip top two parts, which are hidden by the bridge */
	int z_bridge_back = z_bridge - 2 * (int)TILE_HEIGHT;
	if (drawfarpillar && (z_back_north <= z_bridge_back || z_back_south <= z_bridge_back)) {
		bottom_z = DrawPillarColumn(z_back, z_bridge_back, psid, x_back, y_back, w, h);
		if (z_back_north < z_back) DrawPillar(psid, x_back, y_back, bottom_z, w, h, &half_pillar_sub_sprite[axis][0]);
		if (z_back_south < z_back) DrawPillar(psid, x_back, y_back, bottom_z, w, h, &half_pillar_sub_sprite[axis][1]);
	}
}
/**
 * Draws the trambits over an already drawn (lower end) of a bridge.
 * @param x       the x of the bridge
 * @param y       the y of the bridge
 * @param z       the z of the bridge
 * @param offset  number representing whether to level or sloped and the direction
 * @param overlay do we want to still see the road?
 * @param head    are we drawing bridge head?
 */
static void DrawBridgeTramBits(int x, int y, int z, int offset, bool overlay, bool head)
{
	static const SpriteID tram_offsets[2][6] = { { 107, 108, 109, 110, 111, 112 }, { 4, 5, 15, 16, 17, 18 } };
	static const SpriteID back_offsets[6]    =   {  95,  96,  99, 102, 100, 101 };
	static const SpriteID front_offsets[6]   =   {  97,  98, 103, 106, 104, 105 };
	static const uint size_x[6] = {  1, 16, 16,  1, 16,  1 };
	static const uint size_y[6] = { 16,  1,  1, 16,  1, 16 };
	static const uint front_bb_offset_x[6] = { 15,  0,  0, 15,  0, 15 };
	static const uint front_bb_offset_y[6] = {  0, 15, 15,  0, 15,  0 };
	/* The sprites under the vehicles are drawn as SpriteCombine. StartSpriteCombine() has already been called
	 * The bounding boxes here are the same as for bridge front/roof */
	if (head || !IsInvisibilitySet(TO_BRIDGES)) {
		AddSortableSpriteToDraw(SPR_TRAMWAY_BASE + tram_offsets[overlay][offset], PAL_NONE,
			x, y, size_x[offset], size_y[offset], 0x28, z,
			!head && IsTransparencySet(TO_BRIDGES));
	}
	/* Do not draw catenary if it is set invisible */
	if (!IsInvisibilitySet(TO_CATENARY)) {
		AddSortableSpriteToDraw(SPR_TRAMWAY_BASE + back_offsets[offset], PAL_NONE,
			x, y, size_x[offset], size_y[offset], 0x28, z,
			IsTransparencySet(TO_CATENARY));
	}
	/* Start a new SpriteCombine for the front part */
	EndSpriteCombine();
	StartSpriteCombine();
	/* For sloped sprites the bounding box needs to be higher, as the pylons stop on a higher point */
	if (!IsInvisibilitySet(TO_CATENARY)) {
		AddSortableSpriteToDraw(SPR_TRAMWAY_BASE + front_offsets[offset], PAL_NONE,
			x, y, size_x[offset] + front_bb_offset_x[offset], size_y[offset] + front_bb_offset_y[offset], 0x28, z,
			IsTransparencySet(TO_CATENARY), front_bb_offset_x[offset], front_bb_offset_y[offset]);
	}
}
/**
 * Draws a tunnel of bridge tile.
 * For tunnels, this is rather simple, as you only needa draw the entrance.
 * Bridges are a bit more complex. base_offset is where the sprite selection comes into play
 * and it works a bit like a bitmask. For bridge heads:
 * @param ti TileInfo of the structure to draw
 * 
- Bit 0: direction*
- Bit 1: northern or southern heads*
- Bit 2: Set if the bridge head is sloped*
- Bit 3 and more: Railtype Specific subset*
* Please note that in this code, "roads" are treated as railtype 1, whilst the real railtypes are 0, 2 and 3
 */
static void DrawTile_TunnelBridge(TileInfo *ti)
{
	TransportType transport_type = GetTunnelBridgeTransportType(ti->tile);
	DiagDirection tunnelbridge_direction = GetTunnelBridgeDirection(ti->tile);
	if (IsTunnel(ti->tile)) {
		/* Front view of tunnel bounding boxes:
		 *
		 *   122223  <- BB_Z_SEPARATOR
		 *   1    3
		 *   1    3                1,3 = empty helper BB
		 *   1    3                  2 = SpriteCombine of tunnel-roof and catenary (tram & elrail)
		 *
		 */
		static const int _tunnel_BB[4][12] = {
			/*  tunnnel-roof  |  Z-separator  | tram-catenary
			 * w  h  bb_x bb_y| x   y   w   h |bb_x bb_y w h */
			{  1,  0, -15, -14,  0, 15, 16,  1, 0, 1, 16, 15 }, // NE
			{  0,  1, -14, -15, 15,  0,  1, 16, 1, 0, 15, 16 }, // SE
			{  1,  0, -15, -14,  0, 15, 16,  1, 0, 1, 16, 15 }, // SW
			{  0,  1, -14, -15, 15,  0,  1, 16, 1, 0, 15, 16 }, // NW
		};
		const int *BB_data = _tunnel_BB[tunnelbridge_direction];
		bool catenary = false;
		SpriteID image;
		SpriteID railtype_overlay = 0;
		if (transport_type == TRANSPORT_RAIL) {
			const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
			image = rti->base_sprites.tunnel;
			if (rti->UsesOverlay()) {
				/* Check if the railtype has custom tunnel portals. */
				railtype_overlay = GetCustomRailSprite(rti, ti->tile, RTSG_TUNNEL_PORTAL);
				if (railtype_overlay != 0) image = SPR_RAILTYPE_TUNNEL_BASE; // Draw blank grass tunnel base.
			}
		} else {
			image = SPR_TUNNEL_ENTRY_REAR_ROAD;
		}
		if (HasTunnelBridgeSnowOrDesert(ti->tile)) image += railtype_overlay != 0 ? 8 : 32;
		image += tunnelbridge_direction * 2;
		DrawGroundSprite(image, PAL_NONE);
		if (transport_type == TRANSPORT_ROAD) {
			RoadTypes rts = GetRoadTypes(ti->tile);
			if (HasBit(rts, ROADTYPE_TRAM)) {
				static const SpriteID tunnel_sprites[2][4] = { { 28, 78, 79, 27 }, {  5, 76, 77,  4 } };
				DrawGroundSprite(SPR_TRAMWAY_BASE + tunnel_sprites[rts - ROADTYPES_TRAM][tunnelbridge_direction], PAL_NONE);
				/* Do not draw wires if they are invisible */
				if (!IsInvisibilitySet(TO_CATENARY)) {
					catenary = true;
					StartSpriteCombine();
					AddSortableSpriteToDraw(SPR_TRAMWAY_TUNNEL_WIRES + tunnelbridge_direction, PAL_NONE, ti->x, ti->y, BB_data[10], BB_data[11], TILE_HEIGHT, ti->z, IsTransparencySet(TO_CATENARY), BB_data[8], BB_data[9], BB_Z_SEPARATOR);
				}
			}
		} else {
			const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
			if (rti->UsesOverlay()) {
				SpriteID surface = GetCustomRailSprite(rti, ti->tile, RTSG_TUNNEL);
				if (surface != 0) DrawGroundSprite(surface + tunnelbridge_direction, PAL_NONE);
			}
			/* PBS debugging, draw reserved tracks darker */
			if (_game_mode != GM_MENU && _settings_client.gui.show_track_reservation && HasTunnelBridgeReservation(ti->tile)) {
				DrawGroundSprite(DiagDirToAxis(tunnelbridge_direction) == AXIS_X ? rti->base_sprites.single_x : rti->base_sprites.single_y, PALETTE_CRASH);
			}
			if (HasCatenaryDrawn(GetRailType(ti->tile))) {
				/* Maybe draw pylons on the entry side */
				DrawCatenary(ti);
				catenary = true;
				StartSpriteCombine();
				/* Draw wire above the ramp */
				DrawCatenaryOnTunnel(ti);
			}
		}
		if (railtype_overlay != 0 && !catenary) StartSpriteCombine();
		AddSortableSpriteToDraw(image + 1, PAL_NONE, ti->x + TILE_SIZE - 1, ti->y + TILE_SIZE - 1, BB_data[0], BB_data[1], TILE_HEIGHT, ti->z, false, BB_data[2], BB_data[3], BB_Z_SEPARATOR);
		/* Draw railtype tunnel portal overlay if defined. */
		if (railtype_overlay != 0) AddSortableSpriteToDraw(railtype_overlay + tunnelbridge_direction, PAL_NONE, ti->x + TILE_SIZE - 1, ti->y + TILE_SIZE - 1, BB_data[0], BB_data[1], TILE_HEIGHT, ti->z, false, BB_data[2], BB_data[3], BB_Z_SEPARATOR);
		if (catenary || railtype_overlay != 0) EndSpriteCombine();
		/* Add helper BB for sprite sorting that separates the tunnel from things beside of it. */
		AddSortableSpriteToDraw(SPR_EMPTY_BOUNDING_BOX, PAL_NONE, ti->x,              ti->y,              BB_data[6], BB_data[7], TILE_HEIGHT, ti->z);
		AddSortableSpriteToDraw(SPR_EMPTY_BOUNDING_BOX, PAL_NONE, ti->x + BB_data[4], ti->y + BB_data[5], BB_data[6], BB_data[7], TILE_HEIGHT, ti->z);
		DrawBridgeMiddle(ti);
	} else { // IsBridge(ti->tile)
		const PalSpriteID *psid;
		int base_offset;
		bool ice = HasTunnelBridgeSnowOrDesert(ti->tile);
		if (transport_type == TRANSPORT_RAIL) {
			base_offset = GetRailTypeInfo(GetRailType(ti->tile))->bridge_offset;
			assert(base_offset != 8); // This one is used for roads
		} else {
			base_offset = 8;
		}
		/* as the lower 3 bits are used for other stuff, make sure they are clear */
		assert( (base_offset & 0x07) == 0x00);
		DrawFoundation(ti, GetBridgeFoundation(ti->tileh, DiagDirToAxis(tunnelbridge_direction)));
		/* HACK Wizardry to convert the bridge ramp direction into a sprite offset */
		base_offset += (6 - tunnelbridge_direction) % 4;
		if (ti->tileh == SLOPE_FLAT) base_offset += 4; // sloped bridge head
		/* Table number BRIDGE_PIECE_HEAD always refers to the bridge heads for any bridge type */
		if (transport_type != TRANSPORT_WATER) {
			psid = &GetBridgeSpriteTable(GetBridgeType(ti->tile), BRIDGE_PIECE_HEAD)[base_offset];
		} else {
			psid = _aqueduct_sprites + base_offset;
		}
		if (!ice) {
			TileIndex next = ti->tile + TileOffsByDiagDir(tunnelbridge_direction);
			if (ti->tileh != SLOPE_FLAT && ti->z == 0 && HasTileWaterClass(next) && GetWaterClass(next) == WATER_CLASS_SEA) {
				DrawShoreTile(ti->tileh);
			} else {
				DrawClearLandTile(ti, 3);
			}
		} else {
			DrawGroundSprite(SPR_FLAT_SNOW_DESERT_TILE + SlopeToSpriteOffset(ti->tileh), PAL_NONE);
		}
		/* draw ramp */
		/* Draw Trambits and PBS Reservation as SpriteCombine */
		if (transport_type == TRANSPORT_ROAD || transport_type == TRANSPORT_RAIL) StartSpriteCombine();
		/* HACK set the height of the BB of a sloped ramp to 1 so a vehicle on
		 * it doesn't disappear behind it
		 */
		/* Bridge heads are drawn solid no matter how invisibility/transparency is set */
		AddSortableSpriteToDraw(psid->sprite, psid->pal, ti->x, ti->y, 16, 16, ti->tileh == SLOPE_FLAT ? 0 : 8, ti->z);
		if (transport_type == TRANSPORT_ROAD) {
			RoadTypes rts = GetRoadTypes(ti->tile);
			if (HasBit(rts, ROADTYPE_TRAM)) {
				uint offset = tunnelbridge_direction;
				int z = ti->z;
				if (ti->tileh != SLOPE_FLAT) {
					offset = (offset + 1) & 1;
					z += TILE_HEIGHT;
				} else {
					offset += 2;
				}
				/* DrawBridgeTramBits() calls EndSpriteCombine() and StartSpriteCombine() */
				DrawBridgeTramBits(ti->x, ti->y, z, offset, HasBit(rts, ROADTYPE_ROAD), true);
			}
			EndSpriteCombine();
		} else if (transport_type == TRANSPORT_RAIL) {
			const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
			if (rti->UsesOverlay()) {
				SpriteID surface = GetCustomRailSprite(rti, ti->tile, RTSG_BRIDGE);
				if (surface != 0) {
					if (HasBridgeFlatRamp(ti->tileh, DiagDirToAxis(tunnelbridge_direction))) {
						AddSortableSpriteToDraw(surface + ((DiagDirToAxis(tunnelbridge_direction) == AXIS_X) ? RTBO_X : RTBO_Y), PAL_NONE, ti->x, ti->y, 16, 16, 0, ti->z + 8);
					} else {
						AddSortableSpriteToDraw(surface + RTBO_SLOPE + tunnelbridge_direction, PAL_NONE, ti->x, ti->y, 16, 16, 8, ti->z);
					}
				}
				/* Don't fallback to non-overlay sprite -- the spec states that
				 * if an overlay is present then the bridge surface must be
				 * present. */
			}
			/* PBS debugging, draw reserved tracks darker */
			if (_game_mode != GM_MENU &&_settings_client.gui.show_track_reservation && HasTunnelBridgeReservation(ti->tile)) {
				if (HasBridgeFlatRamp(ti->tileh, DiagDirToAxis(tunnelbridge_direction))) {
					AddSortableSpriteToDraw(DiagDirToAxis(tunnelbridge_direction) == AXIS_X ? rti->base_sprites.single_x : rti->base_sprites.single_y, PALETTE_CRASH, ti->x, ti->y, 16, 16, 0, ti->z + 8);
				} else {
					AddSortableSpriteToDraw(rti->base_sprites.single_sloped + tunnelbridge_direction, PALETTE_CRASH, ti->x, ti->y, 16, 16, 8, ti->z);
				}
			}
			EndSpriteCombine();
			if (HasCatenaryDrawn(GetRailType(ti->tile))) {
				DrawCatenary(ti);
			}
		}
		DrawBridgeMiddle(ti);
	}
}
/**
 * Compute bridge piece. Computes the bridge piece to display depending on the position inside the bridge.
 * bridges pieces sequence (middle parts).
 * Note that it is not covering the bridge heads, which are always referenced by the same sprite table.
 * bridge len 1: BRIDGE_PIECE_NORTH
 * bridge len 2: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_SOUTH
 * bridge len 3: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_MIDDLE_ODD   BRIDGE_PIECE_SOUTH
 * bridge len 4: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_SOUTH
 * bridge len 5: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_MIDDLE_EVEN  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_SOUTH
 * bridge len 6: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_SOUTH
 * bridge len 7: BRIDGE_PIECE_NORTH  BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_MIDDLE_ODD   BRIDGE_PIECE_INNER_NORTH  BRIDGE_PIECE_INNER_SOUTH  BRIDGE_PIECE_SOUTH
 * #0 - always as first, #1 - always as last (if len>1)
 * #2,#3 are to pair in order
 * for odd bridges: #5 is going in the bridge middle if on even position, #4 on odd (counting from 0)
 * @param north Northernmost tile of bridge
 * @param south Southernmost tile of bridge
 * @return Index of bridge piece
 */
static BridgePieces CalcBridgePiece(uint north, uint south)
{
	if (north == 1) {
		return BRIDGE_PIECE_NORTH;
	} else if (south == 1) {
		return BRIDGE_PIECE_SOUTH;
	} else if (north < south) {
		return north & 1 ? BRIDGE_PIECE_INNER_SOUTH : BRIDGE_PIECE_INNER_NORTH;
	} else if (north > south) {
		return south & 1 ? BRIDGE_PIECE_INNER_NORTH : BRIDGE_PIECE_INNER_SOUTH;
	} else {
		return north & 1 ? BRIDGE_PIECE_MIDDLE_EVEN : BRIDGE_PIECE_MIDDLE_ODD;
	}
}
/**
 * Draw the middle bits of a bridge.
 * @param ti Tile information of the tile to draw it on.
 */
void DrawBridgeMiddle(const TileInfo *ti)
{
	/* Sectional view of bridge bounding boxes:
	 *
	 *  1           2                                1,2 = SpriteCombine of Bridge front/(back&floor) and TramCatenary
	 *  1           2                                  3 = empty helper BB
	 *  1     7     2                                4,5 = pillars under higher bridges
	 *  1 6 88888 6 2                                  6 = elrail-pylons
	 *  1 6 88888 6 2                                  7 = elrail-wire
	 *  1 6 88888 6 2  <- TILE_HEIGHT                  8 = rail-vehicle on bridge
	 *  3333333333333  <- BB_Z_SEPARATOR
	 *                 <- unused
	 *    4       5    <- BB_HEIGHT_UNDER_BRIDGE
	 *    4       5
	 *    4       5
	 *
	 */
	if (!IsBridgeAbove(ti->tile)) return;
	TileIndex rampnorth = GetNorthernBridgeEnd(ti->tile);
	TileIndex rampsouth = GetSouthernBridgeEnd(ti->tile);
	TransportType transport_type = GetTunnelBridgeTransportType(rampsouth);
	Axis axis = GetBridgeAxis(ti->tile);
	BridgePieces piece = CalcBridgePiece(
		GetTunnelBridgeLength(ti->tile, rampnorth) + 1,
		GetTunnelBridgeLength(ti->tile, rampsouth) + 1
	);
	const PalSpriteID *psid;
	bool drawfarpillar;
	if (transport_type != TRANSPORT_WATER) {
		BridgeType type =  GetBridgeType(rampsouth);
		drawfarpillar = !HasBit(GetBridgeSpec(type)->flags, 0);
		uint base_offset;
		if (transport_type == TRANSPORT_RAIL) {
			base_offset = GetRailTypeInfo(GetRailType(rampsouth))->bridge_offset;
		} else {
			base_offset = 8;
		}
		psid = base_offset + GetBridgeSpriteTable(type, piece);
	} else {
		drawfarpillar = true;
		psid = _aqueduct_sprites;
	}
	if (axis != AXIS_X) psid += 4;
	int x = ti->x;
	int y = ti->y;
	uint bridge_z = GetBridgePixelHeight(rampsouth);
	int z = bridge_z - BRIDGE_Z_START;
	/* Add a bounding box that separates the bridge from things below it. */
	AddSortableSpriteToDraw(SPR_EMPTY_BOUNDING_BOX, PAL_NONE, x, y, 16, 16, 1, bridge_z - TILE_HEIGHT + BB_Z_SEPARATOR);
	/* Draw Trambits as SpriteCombine */
	if (transport_type == TRANSPORT_ROAD || transport_type == TRANSPORT_RAIL) StartSpriteCombine();
	/* Draw floor and far part of bridge*/
	if (!IsInvisibilitySet(TO_BRIDGES)) {
		if (axis == AXIS_X) {
			AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 16, 1, 0x28, z, IsTransparencySet(TO_BRIDGES), 0, 0, BRIDGE_Z_START);
		} else {
			AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 1, 16, 0x28, z, IsTransparencySet(TO_BRIDGES), 0, 0, BRIDGE_Z_START);
		}
	}
	psid++;
	if (transport_type == TRANSPORT_ROAD) {
		RoadTypes rts = GetRoadTypes(rampsouth);
		if (HasBit(rts, ROADTYPE_TRAM)) {
			/* DrawBridgeTramBits() calls EndSpriteCombine() and StartSpriteCombine() */
			DrawBridgeTramBits(x, y, bridge_z, axis ^ 1, HasBit(rts, ROADTYPE_ROAD), false);
		} else {
			EndSpriteCombine();
			StartSpriteCombine();
		}
	} else if (transport_type == TRANSPORT_RAIL) {
		const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(rampsouth));
		if (rti->UsesOverlay() && !IsInvisibilitySet(TO_BRIDGES)) {
			SpriteID surface = GetCustomRailSprite(rti, rampsouth, RTSG_BRIDGE, TCX_ON_BRIDGE);
			if (surface != 0) {
				AddSortableSpriteToDraw(surface + axis, PAL_NONE, x, y, 16, 16, 0, bridge_z, IsTransparencySet(TO_BRIDGES));
			}
		}
		EndSpriteCombine();
		if (HasCatenaryDrawn(GetRailType(rampsouth))) {
			DrawCatenaryOnBridge(ti);
		}
	}
	/* draw roof, the component of the bridge which is logically between the vehicle and the camera */
	if (!IsInvisibilitySet(TO_BRIDGES)) {
		if (axis == AXIS_X) {
			y += 12;
			if (psid->sprite & SPRITE_MASK) AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 16, 4, 0x28, z, IsTransparencySet(TO_BRIDGES), 0, 3, BRIDGE_Z_START);
		} else {
			x += 12;
			if (psid->sprite & SPRITE_MASK) AddSortableSpriteToDraw(psid->sprite, psid->pal, x, y, 4, 16, 0x28, z, IsTransparencySet(TO_BRIDGES), 3, 0, BRIDGE_Z_START);
		}
	}
	/* Draw TramFront as SpriteCombine */
	if (transport_type == TRANSPORT_ROAD) EndSpriteCombine();
	/* Do not draw anything more if bridges are invisible */
	if (IsInvisibilitySet(TO_BRIDGES)) return;
	psid++;
	if (ti->z + 5 == z) {
		/* draw poles below for small bridges */
		if (psid->sprite != 0) {
			SpriteID image = psid->sprite;
			SpriteID pal   = psid->pal;
			if (IsTransparencySet(TO_BRIDGES)) {
				SetBit(image, PALETTE_MODIFIER_TRANSPARENT);
				pal = PALETTE_TO_TRANSPARENT;
			}
			DrawGroundSpriteAt(image, pal, x - ti->x, y - ti->y, z - ti->z);
		}
	} else {
		/* draw pillars below for high bridges */
		DrawBridgePillars(psid, ti, axis, drawfarpillar, x, y, z);
	}
}
static int GetSlopePixelZ_TunnelBridge(TileIndex tile, uint x, uint y)
{
	int z;
	Slope tileh = GetTilePixelSlope(tile, &z);
	x &= 0xF;
	y &= 0xF;
	if (IsTunnel(tile)) {
		uint pos = (DiagDirToAxis(GetTunnelBridgeDirection(tile)) == AXIS_X ? y : x);
		/* In the tunnel entrance? */
		if (5 <= pos && pos <= 10) return z;
	} else { // IsBridge(tile)
		DiagDirection dir = GetTunnelBridgeDirection(tile);
		uint pos = (DiagDirToAxis(dir) == AXIS_X ? y : x);
		z += ApplyPixelFoundationToSlope(GetBridgeFoundation(tileh, DiagDirToAxis(dir)), &tileh);
		/* On the bridge ramp? */
		if (5 <= pos && pos <= 10) {
			int delta;
			if (tileh != SLOPE_FLAT) return z + TILE_HEIGHT;
			switch (dir) {
				default: NOT_REACHED();
				case DIAGDIR_NE: delta = (TILE_SIZE - 1 - x) / 2; break;
				case DIAGDIR_SE: delta = y / 2; break;
				case DIAGDIR_SW: delta = x / 2; break;
				case DIAGDIR_NW: delta = (TILE_SIZE - 1 - y) / 2; break;
			}
			return z + 1 + delta;
		}
	}
	return z + GetPartialPixelZ(x, y, tileh);
}
static Foundation GetFoundation_TunnelBridge(TileIndex tile, Slope tileh)
{
	return IsTunnel(tile) ? FOUNDATION_NONE : GetBridgeFoundation(tileh, DiagDirToAxis(GetTunnelBridgeDirection(tile)));
}
static void GetTileDesc_TunnelBridge(TileIndex tile, TileDesc *td)
{
	TransportType tt = GetTunnelBridgeTransportType(tile);
	if (IsTunnel(tile)) {
		td->str = (tt == TRANSPORT_RAIL) ? STR_LAI_TUNNEL_DESCRIPTION_RAILROAD : STR_LAI_TUNNEL_DESCRIPTION_ROAD;
	} else { // IsBridge(tile)
		td->str = (tt == TRANSPORT_WATER) ? STR_LAI_BRIDGE_DESCRIPTION_AQUEDUCT : GetBridgeSpec(GetBridgeType(tile))->transport_name[tt];
	}
	td->owner[0] = GetTileOwner(tile);
	Owner road_owner = INVALID_OWNER;
	Owner tram_owner = INVALID_OWNER;
	RoadTypes rts = GetRoadTypes(tile);
	if (HasBit(rts, ROADTYPE_ROAD)) road_owner = GetRoadOwner(tile, ROADTYPE_ROAD);
	if (HasBit(rts, ROADTYPE_TRAM)) tram_owner = GetRoadOwner(tile, ROADTYPE_TRAM);
	/* Is there a mix of owners? */
	if ((tram_owner != INVALID_OWNER && tram_owner != td->owner[0]) ||
			(road_owner != INVALID_OWNER && road_owner != td->owner[0])) {
		uint i = 1;
		if (road_owner != INVALID_OWNER) {
			td->owner_type[i] = STR_LAND_AREA_INFORMATION_ROAD_OWNER;
			td->owner[i] = road_owner;
			i++;
		}
		if (tram_owner != INVALID_OWNER) {
			td->owner_type[i] = STR_LAND_AREA_INFORMATION_TRAM_OWNER;
			td->owner[i] = tram_owner;
		}
	}
	if (tt == TRANSPORT_RAIL) {
		const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(tile));
		td->rail_speed = rti->max_speed;
		if (!IsTunnel(tile)) {
			uint16 spd = GetBridgeSpec(GetBridgeType(tile))->speed;
			if (td->rail_speed == 0 || spd < td->rail_speed) {
				td->rail_speed = spd;
			}
		}
	}
}
static void TileLoop_TunnelBridge(TileIndex tile)
{
	bool snow_or_desert = HasTunnelBridgeSnowOrDesert(tile);
	switch (_settings_game.game_creation.landscape) {
		case LT_ARCTIC: {
			/* As long as we do not have a snow density, we want to use the density
			 * from the entry endge. For tunnels this is the lowest point for bridges the highest point.
			 * (Independent of foundations) */
			int z = IsBridge(tile) ? GetTileMaxZ(tile) : GetTileZ(tile);
			if (snow_or_desert != (z > GetSnowLine())) {
				SetTunnelBridgeSnowOrDesert(tile, !snow_or_desert);
				MarkTileDirtyByTile(tile);
			}
			break;
		}
		case LT_TROPIC:
			if (GetTropicZone(tile) == TROPICZONE_DESERT && !snow_or_desert) {
				SetTunnelBridgeSnowOrDesert(tile, true);
				MarkTileDirtyByTile(tile);
			}
			break;
		default:
			break;
	}
}
static TrackStatus GetTileTrackStatus_TunnelBridge(TileIndex tile, TransportType mode, uint sub_mode, DiagDirection side)
{
	TransportType transport_type = GetTunnelBridgeTransportType(tile);
	if (transport_type != mode || (transport_type == TRANSPORT_ROAD && (GetRoadTypes(tile) & sub_mode) == 0)) return 0;
	DiagDirection dir = GetTunnelBridgeDirection(tile);
	if (side != INVALID_DIAGDIR && side != ReverseDiagDir(dir)) return 0;
	return CombineTrackStatus(TrackBitsToTrackdirBits(DiagDirToDiagTrackBits(dir)), TRACKDIR_BIT_NONE);
}
static void ChangeTileOwner_TunnelBridge(TileIndex tile, Owner old_owner, Owner new_owner)
{
	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. */
	uint num_pieces = tile < other_end ? (GetTunnelBridgeLength(tile, other_end) + 2) * TUNNELBRIDGE_TRACKBIT_FACTOR : 0;
	for (RoadType rt = ROADTYPE_ROAD; rt < ROADTYPE_END; rt++) {
		/* Update all roadtypes, no matter if they are present */
		if (GetRoadOwner(tile, rt) == old_owner) {
			if (HasBit(GetRoadTypes(tile), rt)) {
				/* Update company infrastructure counts. A full diagonal road tile has two road bits.
				 * No need to dirty windows here, we'll redraw the whole screen anyway. */
				Company::Get(old_owner)->infrastructure.road[rt] -= num_pieces * 2;
				if (new_owner != INVALID_OWNER) Company::Get(new_owner)->infrastructure.road[rt] += num_pieces * 2;
			}
			SetRoadOwner(tile, rt, new_owner == INVALID_OWNER ? OWNER_NONE : new_owner);
		}
	}
	if (!IsTileOwner(tile, old_owner)) return;
	/* Update company infrastructure counts for rail and water as well.
	 * No need to dirty windows here, we'll redraw the whole screen anyway. */
	TransportType tt = GetTunnelBridgeTransportType(tile);
	Company *old = Company::Get(old_owner);
	if (tt == TRANSPORT_RAIL) {
		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) {
		old->infrastructure.water -= num_pieces;
		if (new_owner != INVALID_OWNER) Company::Get(new_owner)->infrastructure.water += num_pieces;
	}
	if (new_owner != INVALID_OWNER) {
		SetTileOwner(tile, new_owner);
	} else {
		if (tt == TRANSPORT_RAIL) {
			/* Since all of our vehicles have been removed, it is safe to remove the rail
			 * bridge / tunnel. */
			CommandCost ret = DoCommand(tile, 0, 0, DC_EXEC | DC_BANKRUPT, CMD_LANDSCAPE_CLEAR);
			assert(ret.Succeeded());
		} else {
			/* In any other case, we can safely reassign the ownership to OWNER_NONE. */
			SetTileOwner(tile, OWNER_NONE);
		}
	}
}
/**
 * Frame when the 'enter tunnel' sound should be played. This is the second
 * frame on a tile, so the sound is played shortly after entering the tunnel
 * tile, while the vehicle is still visible.
 */
static const byte TUNNEL_SOUND_FRAME = 1;
/**
 * Frame when a vehicle should be hidden in a tunnel with a certain direction.
 * This differs per direction, because of visibility / bounding box issues.
 * Note that direction, in this case, is the direction leading into the tunnel.
 * When entering a tunnel, hide the vehicle when it reaches the given frame.
 * When leaving a tunnel, show the vehicle when it is one frame further
 * to the 'outside', i.e. at (TILE_SIZE-1) - (frame) + 1
 */
extern const byte _tunnel_visibility_frame[DIAGDIR_END] = {12, 8, 8, 12};
static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex tile, int x, int 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)) {
		if (v->type == VEH_TRAIN) {
			Train *t = Train::From(v);
			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);
					}
					return VETSB_CONTINUE;
				}
				if (frame == _tunnel_visibility_frame[dir]) {
					t->tile = tile;
					t->track = TRACK_BIT_WORMHOLE;
					t->vehstatus |= VS_HIDDEN;
					return VETSB_ENTERED_WORMHOLE;
				}
			}
			if (dir == ReverseDiagDir(vdir) && frame == TILE_SIZE - _tunnel_visibility_frame[dir] && z == 0) {
				/* We're at the tunnel exit ?? */
				t->tile = tile;
				t->track = DiagDirToDiagTrackBits(vdir);
				assert(t->track);
				t->vehstatus &= ~VS_HIDDEN;
				return VETSB_ENTERED_WORMHOLE;
			}
		} else if (v->type == VEH_ROAD) {
			RoadVehicle *rv = RoadVehicle::From(v);
			/* Enter tunnel? */
			if (rv->state != RVSB_WORMHOLE && dir == vdir) {
				if (frame == _tunnel_visibility_frame[dir]) {
					/* Frame should be equal to the next frame number in the RV's movement */
					assert(frame == rv->frame + 1);
					rv->tile = tile;
					rv->state = RVSB_WORMHOLE;
					rv->vehstatus |= VS_HIDDEN;
					return VETSB_ENTERED_WORMHOLE;
				} else {
					return VETSB_CONTINUE;
				}
			}
			/* We're at the tunnel exit ?? */
			if (dir == ReverseDiagDir(vdir) && frame == TILE_SIZE - _tunnel_visibility_frame[dir] && z == 0) {
				rv->tile = tile;
				rv->state = DiagDirToDiagTrackdir(vdir);
				rv->frame = frame;
				rv->vehstatus &= ~VS_HIDDEN;
				return VETSB_ENTERED_WORMHOLE;
			}
		}
	} else { // IsBridge(tile)
		if (v->type != VEH_SHIP) {
			/* modify speed of vehicle */
			uint16 spd = GetBridgeSpec(GetBridgeType(tile))->speed;
			if (v->type == VEH_ROAD) spd *= 2;
			Vehicle *first = v->First();
			first->cur_speed = min(first->cur_speed, spd);
		}
		if (vdir == dir) {
			/* Vehicle enters bridge at the last frame inside this tile. */
			if (frame != TILE_SIZE - 1) return VETSB_CONTINUE;
			switch (v->type) {
				case VEH_TRAIN: {
					Train *t = Train::From(v);
					t->track = TRACK_BIT_WORMHOLE;
					ClrBit(t->gv_flags, GVF_GOINGUP_BIT);
					ClrBit(t->gv_flags, GVF_GOINGDOWN_BIT);
					break;
				}
				case VEH_ROAD: {
					RoadVehicle *rv = RoadVehicle::From(v);
					rv->state = RVSB_WORMHOLE;
					/* There are no slopes inside bridges / tunnels. */
					ClrBit(rv->gv_flags, GVF_GOINGUP_BIT);
					ClrBit(rv->gv_flags, GVF_GOINGDOWN_BIT);
					break;
				}
				case VEH_SHIP:
					Ship::From(v)->state = TRACK_BIT_WORMHOLE;
					break;
				default: NOT_REACHED();
			}
			return VETSB_ENTERED_WORMHOLE;
		} else if (vdir == ReverseDiagDir(dir)) {
			v->tile = tile;
			switch (v->type) {
				case VEH_TRAIN: {
					Train *t = Train::From(v);
					if (t->track == TRACK_BIT_WORMHOLE) {
						t->track = DiagDirToDiagTrackBits(vdir);
						return VETSB_ENTERED_WORMHOLE;
					}
					break;
				}
				case VEH_ROAD: {
					RoadVehicle *rv = RoadVehicle::From(v);
					if (rv->state == RVSB_WORMHOLE) {
						rv->state = DiagDirToDiagTrackdir(vdir);
						rv->frame = 0;
						return VETSB_ENTERED_WORMHOLE;
					}
					break;
				}
				case VEH_SHIP: {
					Ship *ship = Ship::From(v);
					if (ship->state == TRACK_BIT_WORMHOLE) {
						ship->state = DiagDirToDiagTrackBits(vdir);
						return VETSB_ENTERED_WORMHOLE;
					}
					break;
				}
				default: NOT_REACHED();
			}
		}
	}
	return VETSB_CONTINUE;
}
static CommandCost TerraformTile_TunnelBridge(TileIndex tile, DoCommandFlag flags, int z_new, Slope tileh_new)
{
	if (_settings_game.construction.build_on_slopes && AutoslopeEnabled() && IsBridge(tile) && GetTunnelBridgeTransportType(tile) != TRANSPORT_WATER) {
		DiagDirection direction = GetTunnelBridgeDirection(tile);
		Axis axis = DiagDirToAxis(direction);
		CommandCost res;
		int z_old;
		Slope tileh_old = GetTileSlope(tile, &z_old);
		/* Check if new slope is valid for bridges in general (so we can safely call GetBridgeFoundation()) */
		if ((direction == DIAGDIR_NW) || (direction == DIAGDIR_NE)) {
			CheckBridgeSlopeSouth(axis, &tileh_old, &z_old);
			res = CheckBridgeSlopeSouth(axis, &tileh_new, &z_new);
		} else {
			CheckBridgeSlopeNorth(axis, &tileh_old, &z_old);
			res = CheckBridgeSlopeNorth(axis, &tileh_new, &z_new);
		}
		/* Surface slope is valid and remains unchanged? */
		if (res.Succeeded() && (z_old == z_new) && (tileh_old == tileh_new)) return CommandCost(EXPENSES_CONSTRUCTION, _price[PR_BUILD_FOUNDATION]);
	}
	return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
}
extern const TileTypeProcs _tile_type_tunnelbridge_procs = {
	DrawTile_TunnelBridge,           // draw_tile_proc
	GetSlopePixelZ_TunnelBridge,     // get_slope_z_proc
	ClearTile_TunnelBridge,          // clear_tile_proc
	NULL,                            // add_accepted_cargo_proc
	GetTileDesc_TunnelBridge,        // get_tile_desc_proc
	GetTileTrackStatus_TunnelBridge, // get_tile_track_status_proc
	NULL,                            // click_tile_proc
	NULL,                            // animate_tile_proc
	TileLoop_TunnelBridge,           // tile_loop_proc
	ChangeTileOwner_TunnelBridge,    // change_tile_owner_proc
	NULL,                            // add_produced_cargo_proc
	VehicleEnter_TunnelBridge,       // vehicle_enter_tile_proc
	GetFoundation_TunnelBridge,      // get_foundation_proc
	TerraformTile_TunnelBridge,      // terraform_tile_proc
};