diff --git a/src/clear_cmd.cpp b/src/clear_cmd.cpp
--- a/src/clear_cmd.cpp
+++ b/src/clear_cmd.cpp
@@ -127,7 +127,7 @@ static void DrawTile_Clear(TileInfo *ti)
 	DrawBridgeMiddle(ti);
 }
 
-static int GetSlopePixelZ_Clear(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Clear(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	int z;
 	Slope tileh = GetTilePixelSlope(tile, &z);
diff --git a/src/elrail.cpp b/src/elrail.cpp
--- a/src/elrail.cpp
+++ b/src/elrail.cpp
@@ -233,7 +233,7 @@ static int GetPCPElevation(TileIndex til
 	 */
 
 	int z = GetSlopePixelZ(TileX(tile) * TILE_SIZE + std::min<int8>(x_pcp_offsets[PCPpos], TILE_SIZE - 1),
-	                       TileY(tile) * TILE_SIZE + std::min<int8>(y_pcp_offsets[PCPpos], TILE_SIZE - 1));
+	                       TileY(tile) * TILE_SIZE + std::min<int8>(y_pcp_offsets[PCPpos], TILE_SIZE - 1), true);
 	/* Round the Z to the nearest half tile height. */
 	static const uint HALF_TILE_HEIGHT = TILE_HEIGHT / 2;
 	return (z + HALF_TILE_HEIGHT / 2) / HALF_TILE_HEIGHT * HALF_TILE_HEIGHT;
@@ -491,7 +491,7 @@ static void DrawRailCatenaryRailway(cons
 		 * down to the nearest full height change.
 		 */
 		AddSortableSpriteToDraw(wire_base + sss->image_offset, PAL_NONE, ti->x + sss->x_offset, ti->y + sss->y_offset,
-			sss->x_size, sss->y_size, sss->z_size, (GetSlopePixelZ(ti->x + sss->x_offset, ti->y + sss->y_offset) + 4) / 8 * 8 + sss->z_offset,
+			sss->x_size, sss->y_size, sss->z_size, (GetSlopePixelZ(ti->x + sss->x_offset, ti->y + sss->y_offset, true) + 4) / 8 * 8 + sss->z_offset,
 			IsTransparencySet(TO_CATENARY));
 	}
 }
diff --git a/src/ground_vehicle.hpp b/src/ground_vehicle.hpp
--- a/src/ground_vehicle.hpp
+++ b/src/ground_vehicle.hpp
@@ -134,7 +134,7 @@ struct GroundVehicle : public Specialize
 	 */
 	inline void UpdateZPositionAndInclination()
 	{
-		this->z_pos = GetSlopePixelZ(this->x_pos, this->y_pos);
+		this->z_pos = GetSlopePixelZ(this->x_pos, this->y_pos, true);
 		ClrBit(this->gv_flags, GVF_GOINGUP_BIT);
 		ClrBit(this->gv_flags, GVF_GOINGDOWN_BIT);
 
@@ -143,7 +143,7 @@ struct GroundVehicle : public Specialize
 			 * direction it is sloped, we get the 'z' at the center of
 			 * the tile (middle_z) and the edge of the tile (old_z),
 			 * which we then can compare. */
-			int middle_z = GetSlopePixelZ((this->x_pos & ~TILE_UNIT_MASK) | (TILE_SIZE / 2), (this->y_pos & ~TILE_UNIT_MASK) | (TILE_SIZE / 2));
+			int middle_z = GetSlopePixelZ((this->x_pos & ~TILE_UNIT_MASK) | (TILE_SIZE / 2), (this->y_pos & ~TILE_UNIT_MASK) | (TILE_SIZE / 2), true);
 
 			if (middle_z != this->z_pos) {
 				SetBit(this->gv_flags, (middle_z > this->z_pos) ? GVF_GOINGUP_BIT : GVF_GOINGDOWN_BIT);
@@ -200,7 +200,7 @@ struct GroundVehicle : public Specialize
 		if (HasBit(this->gv_flags, GVF_GOINGUP_BIT) || HasBit(this->gv_flags, GVF_GOINGDOWN_BIT)) {
 			if (T::From(this)->HasToUseGetSlopePixelZ()) {
 				/* In some cases, we have to use GetSlopePixelZ() */
-				this->z_pos = GetSlopePixelZ(this->x_pos, this->y_pos);
+				this->z_pos = GetSlopePixelZ(this->x_pos, this->y_pos, true);
 				return;
 			}
 			/* DirToDiagDir() is a simple right shift */
@@ -220,7 +220,7 @@ struct GroundVehicle : public Specialize
 			this->z_pos += HasBit(this->gv_flags, GVF_GOINGUP_BIT) ? d : -d;
 		}
 
-		assert(this->z_pos == GetSlopePixelZ(this->x_pos, this->y_pos));
+		assert(this->z_pos == GetSlopePixelZ(this->x_pos, this->y_pos, true));
 	}
 
 	/**
diff --git a/src/industry_cmd.cpp b/src/industry_cmd.cpp
--- a/src/industry_cmd.cpp
+++ b/src/industry_cmd.cpp
@@ -385,7 +385,7 @@ static void DrawTile_Industry(TileInfo *
 	}
 }
 
-static int GetSlopePixelZ_Industry(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Industry(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	return GetTileMaxPixelZ(tile);
 }
diff --git a/src/landscape.cpp b/src/landscape.cpp
--- a/src/landscape.cpp
+++ b/src/landscape.cpp
@@ -343,11 +343,22 @@ uint GetPartialPixelZ(int x, int y, Slop
 	return z;
 }
 
-int GetSlopePixelZ(int x, int y)
+/**
+ * Return world \c Z coordinate of a given point of a tile. Normally this is the
+ * Z of the ground/foundation at the given location, but in some cases the
+ * ground/foundation can differ from the Z coordinate that the (ground) vehicle
+ * passing over it would take. For example when entering a tunnel or bridge.
+ *
+ * @param x World X coordinate in tile "units".
+ * @param y World Y coordinate in tile "units".
+ * @param ground_vehicle Whether to get the Z coordinate of the ground vehicle, or the ground.
+ * @return World Z coordinate at tile ground (vehicle) level, including slopes and foundations.
+ */
+int GetSlopePixelZ(int x, int y, bool ground_vehicle)
 {
 	TileIndex tile = TileVirtXY(x, y);
 
-	return _tile_type_procs[GetTileType(tile)]->get_slope_z_proc(tile, x, y);
+	return _tile_type_procs[GetTileType(tile)]->get_slope_z_proc(tile, x, y, ground_vehicle);
 }
 
 /**
@@ -361,9 +372,9 @@ int GetSlopePixelZ(int x, int y)
 int GetSlopePixelZOutsideMap(int x, int y)
 {
 	if (IsInsideBS(x, 0, Map::SizeX() * TILE_SIZE) && IsInsideBS(y, 0, Map::SizeY() * TILE_SIZE)) {
-		return GetSlopePixelZ(x, y);
+		return GetSlopePixelZ(x, y, false);
 	} else {
-		return _tile_type_procs[MP_VOID]->get_slope_z_proc(INVALID_TILE, x, y);
+		return _tile_type_procs[MP_VOID]->get_slope_z_proc(INVALID_TILE, x, y, false);
 	}
 }
 
diff --git a/src/landscape.h b/src/landscape.h
--- a/src/landscape.h
+++ b/src/landscape.h
@@ -37,7 +37,7 @@ int GetSlopeZInCorner(Slope tileh, Corne
 Slope GetFoundationSlope(TileIndex tile, int *z = nullptr);
 
 uint GetPartialPixelZ(int x, int y, Slope corners);
-int GetSlopePixelZ(int x, int y);
+int GetSlopePixelZ(int x, int y, bool ground_vehicle = false);
 int GetSlopePixelZOutsideMap(int x, int y);
 void GetSlopePixelZOnEdge(Slope tileh, DiagDirection edge, int *z1, int *z2);
 
@@ -97,7 +97,7 @@ static inline Point RemapCoords(int x, i
  */
 static inline Point RemapCoords2(int x, int y)
 {
-	return RemapCoords(x, y, GetSlopePixelZ(x, y));
+	return RemapCoords(x, y, GetSlopePixelZ(x, y, false));
 }
 
 /**
diff --git a/src/object_cmd.cpp b/src/object_cmd.cpp
--- a/src/object_cmd.cpp
+++ b/src/object_cmd.cpp
@@ -486,7 +486,7 @@ static void DrawTile_Object(TileInfo *ti
 	DrawBridgeMiddle(ti);
 }
 
-static int GetSlopePixelZ_Object(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Object(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	if (IsObjectType(tile, OBJECT_OWNED_LAND)) {
 		int z;
diff --git a/src/pathfinder/npf/npf.cpp b/src/pathfinder/npf/npf.cpp
--- a/src/pathfinder/npf/npf.cpp
+++ b/src/pathfinder/npf/npf.cpp
@@ -245,8 +245,8 @@ static uint NPFSlopeCost(AyStarNode *cur
 	/* Get the height on both sides of the tile edge.
 	 * Avoid testing the height on the tile-center. This will fail for halftile-foundations.
 	 */
-	int z1 = GetSlopePixelZ(x1 + dx4, y1 + dy4);
-	int z2 = GetSlopePixelZ(x2 - dx4, y2 - dy4);
+	int z1 = GetSlopePixelZ(x1 + dx4, y1 + dy4, true);
+	int z2 = GetSlopePixelZ(x2 - dx4, y2 - dy4, true);
 
 	if (z2 - z1 > 1) {
 		/* Slope up */
diff --git a/src/pathfinder/yapf/yapf_road.cpp b/src/pathfinder/yapf/yapf_road.cpp
--- a/src/pathfinder/yapf/yapf_road.cpp
+++ b/src/pathfinder/yapf/yapf_road.cpp
@@ -40,12 +40,12 @@ protected:
 		/* height of the center of the current tile */
 		int x1 = TileX(tile) * TILE_SIZE;
 		int y1 = TileY(tile) * TILE_SIZE;
-		int z1 = GetSlopePixelZ(x1 + TILE_SIZE / 2, y1 + TILE_SIZE / 2);
+		int z1 = GetSlopePixelZ(x1 + TILE_SIZE / 2, y1 + TILE_SIZE / 2, true);
 
 		/* height of the center of the next tile */
 		int x2 = TileX(next_tile) * TILE_SIZE;
 		int y2 = TileY(next_tile) * TILE_SIZE;
-		int z2 = GetSlopePixelZ(x2 + TILE_SIZE / 2, y2 + TILE_SIZE / 2);
+		int z2 = GetSlopePixelZ(x2 + TILE_SIZE / 2, y2 + TILE_SIZE / 2, true);
 
 		if (z2 - z1 > 1) {
 			/* Slope up */
diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -2550,7 +2550,7 @@ void DrawTrainDepotSprite(int x, int y, 
 	DrawRailTileSeqInGUI(x, y, dts, offset, 0, palette);
 }
 
-static int GetSlopePixelZ_Track(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Track(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	if (IsPlainRail(tile)) {
 		int z;
diff --git a/src/road_cmd.cpp b/src/road_cmd.cpp
--- a/src/road_cmd.cpp
+++ b/src/road_cmd.cpp
@@ -1886,7 +1886,7 @@ void UpdateNearestTownForRoadTiles(bool 
 	}
 }
 
-static int GetSlopePixelZ_Road(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Road(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 
 	if (IsNormalRoad(tile)) {
diff --git a/src/roadveh_cmd.cpp b/src/roadveh_cmd.cpp
--- a/src/roadveh_cmd.cpp
+++ b/src/roadveh_cmd.cpp
@@ -277,7 +277,7 @@ CommandCost CmdBuildRoadVehicle(DoComman
 		int y = TileY(tile) * TILE_SIZE + TILE_SIZE / 2;
 		v->x_pos = x;
 		v->y_pos = y;
-		v->z_pos = GetSlopePixelZ(x, y);
+		v->z_pos = GetSlopePixelZ(x, y, true);
 
 		v->state = RVSB_IN_DEPOT;
 		v->vehstatus = VS_HIDDEN | VS_STOPPED | VS_DEFPAL;
diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -510,12 +510,12 @@ static uint FixVehicleInclination(Vehicl
 		case INVALID_DIR: break;
 		default: NOT_REACHED();
 	}
-	byte entry_z = GetSlopePixelZ(entry_x, entry_y);
+	byte entry_z = GetSlopePixelZ(entry_x, entry_y, true);
 
 	/* Compute middle of the tile. */
 	int middle_x = (v->x_pos & ~TILE_UNIT_MASK) + TILE_SIZE / 2;
 	int middle_y = (v->y_pos & ~TILE_UNIT_MASK) + TILE_SIZE / 2;
-	byte middle_z = GetSlopePixelZ(middle_x, middle_y);
+	byte middle_z = GetSlopePixelZ(middle_x, middle_y, true);
 
 	/* middle_z == entry_z, no height change. */
 	if (middle_z == entry_z) return 0;
@@ -1249,7 +1249,7 @@ bool AfterLoadGame()
 					case DIAGDIR_SW: if ((v->x_pos & 0xF) != TILE_SIZE - 1) continue; break;
 					case DIAGDIR_NW: if ((v->y_pos & 0xF) !=  0)            continue; break;
 				}
-			} else if (v->z_pos > GetSlopePixelZ(v->x_pos, v->y_pos)) {
+			} else if (v->z_pos > GetSlopePixelZ(v->x_pos, v->y_pos, true)) {
 				v->tile = GetNorthernBridgeEnd(v->tile);
 				v->UpdatePosition();
 			} else {
@@ -2515,7 +2515,7 @@ bool AfterLoadGame()
 			if (!IsTunnelTile(vtile)) continue;
 
 			/* Are we actually in this tunnel? Or maybe a lower tunnel? */
-			if (GetSlopePixelZ(v->x_pos, v->y_pos) != v->z_pos) continue;
+			if (GetSlopePixelZ(v->x_pos, v->y_pos, true) != v->z_pos) continue;
 
 			/* What way are we going? */
 			const DiagDirection dir = GetTunnelBridgeDirection(vtile);
@@ -2661,7 +2661,7 @@ bool AfterLoadGame()
 				/* In old versions, z_pos was 1 unit lower on bridge heads.
 				 * However, this invalid state could be converted to new savegames
 				 * by loading and saving the game in a new version. */
-				v->z_pos = GetSlopePixelZ(v->x_pos, v->y_pos);
+				v->z_pos = GetSlopePixelZ(v->x_pos, v->y_pos, true);
 				DiagDirection dir = GetTunnelBridgeDirection(v->tile);
 				if (v->type == VEH_TRAIN && !(v->vehstatus & VS_CRASHED) &&
 						v->direction != DiagDirToDir(dir)) {
@@ -2675,7 +2675,7 @@ bool AfterLoadGame()
 
 			/* If the vehicle is really above v->tile (not in a wormhole),
 			 * it should have set v->z_pos correctly. */
-			assert(v->tile != TileVirtXY(v->x_pos, v->y_pos) || v->z_pos == GetSlopePixelZ(v->x_pos, v->y_pos));
+			assert(v->tile != TileVirtXY(v->x_pos, v->y_pos) || v->z_pos == GetSlopePixelZ(v->x_pos, v->y_pos, true));
 		}
 
 		/* Fill Vehicle::cur_real_order_index */
@@ -3183,7 +3183,7 @@ bool AfterLoadGame()
 					int y = TileY(closestDepot.location) * TILE_SIZE + TILE_SIZE / 2;
 					u->x_pos = x;
 					u->y_pos = y;
-					u->z_pos = GetSlopePixelZ(x, y);
+					u->z_pos = GetSlopePixelZ(x, y, true);
 
 					u->vehstatus |= VS_HIDDEN;
 					u->state = RVSB_IN_DEPOT;
diff --git a/src/station_cmd.cpp b/src/station_cmd.cpp
--- a/src/station_cmd.cpp
+++ b/src/station_cmd.cpp
@@ -3269,7 +3269,7 @@ void StationPickerDrawSprite(int x, int 
 	DrawRailTileSeqInGUI(x, y, t, st == STATION_WAYPOINT ? 0 : total_offset, 0, pal);
 }
 
-static int GetSlopePixelZ_Station(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Station(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	return GetTileMaxPixelZ(tile);
 }
diff --git a/src/tile_cmd.h b/src/tile_cmd.h
--- a/src/tile_cmd.h
+++ b/src/tile_cmd.h
@@ -73,7 +73,19 @@ struct TileDesc {
  * @param ti Information about the tile to draw
  */
 typedef void DrawTileProc(TileInfo *ti);
-typedef int GetSlopeZProc(TileIndex tile, uint x, uint y);
+
+/**
+ * Tile callback function signature for obtaining the world \c Z coordinate of a given
+ * point of a tile.
+ *
+ * @param tile The queries tile for the Z coordinate.
+ * @param x World X coordinate in tile "units".
+ * @param y World Y coordinate in tile "units".
+ * @param ground_vehicle Whether to get the Z coordinate of the ground vehicle, or the ground.
+ * @return World Z coordinate at tile ground (vehicle) level, including slopes and foundations.
+ * @see GetSlopePixelZ
+ */
+typedef int GetSlopeZProc(TileIndex tile, uint x, uint y, bool ground_vehicle);
 typedef CommandCost ClearTileProc(TileIndex tile, DoCommandFlag flags);
 
 /**
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -306,7 +306,7 @@ static void DrawTile_Town(TileInfo *ti)
 	}
 }
 
-static int GetSlopePixelZ_Town(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Town(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	return GetTileMaxPixelZ(tile);
 }
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -635,7 +635,7 @@ static CommandCost CmdBuildRailWagon(DoC
 
 		v->x_pos = x;
 		v->y_pos = y;
-		v->z_pos = GetSlopePixelZ(x, y);
+		v->z_pos = GetSlopePixelZ(x, y, true);
 		v->owner = _current_company;
 		v->track = TRACK_BIT_DEPOT;
 		v->vehstatus = VS_HIDDEN | VS_DEFPAL;
@@ -761,7 +761,7 @@ CommandCost CmdBuildRailVehicle(DoComman
 		v->owner = _current_company;
 		v->x_pos = x;
 		v->y_pos = y;
-		v->z_pos = GetSlopePixelZ(x, y);
+		v->z_pos = GetSlopePixelZ(x, y, true);
 		v->track = TRACK_BIT_DEPOT;
 		v->vehstatus = VS_HIDDEN | VS_STOPPED | VS_DEFPAL;
 		v->spritenum = rvi->image_index;
diff --git a/src/tree_cmd.cpp b/src/tree_cmd.cpp
--- a/src/tree_cmd.cpp
+++ b/src/tree_cmd.cpp
@@ -586,7 +586,7 @@ static void DrawTile_Trees(TileInfo *ti)
 }
 
 
-static int GetSlopePixelZ_Trees(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Trees(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	int z;
 	Slope tileh = GetTilePixelSlope(tile, &z);
diff --git a/src/tunnelbridge_cmd.cpp b/src/tunnelbridge_cmd.cpp
--- a/src/tunnelbridge_cmd.cpp
+++ b/src/tunnelbridge_cmd.cpp
@@ -1663,7 +1663,7 @@ void DrawBridgeMiddle(const TileInfo *ti
 }
 
 
-static int GetSlopePixelZ_TunnelBridge(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_TunnelBridge(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	int z;
 	Slope tileh = GetTilePixelSlope(tile, &z);
@@ -1672,18 +1672,14 @@ static int GetSlopePixelZ_TunnelBridge(T
 	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;
+		if (ground_vehicle) 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) {
+		if (ground_vehicle) {
 			int delta;
 
 			if (tileh != SLOPE_FLAT) return z + TILE_HEIGHT;
@@ -1881,7 +1877,7 @@ extern const byte _tunnel_visibility_fra
 
 static VehicleEnterTileStatus VehicleEnter_TunnelBridge(Vehicle *v, TileIndex tile, int x, int y)
 {
-	int z = GetSlopePixelZ(x, y) - v->z_pos;
+	int z = GetSlopePixelZ(x, y, true) - v->z_pos;
 
 	if (abs(z) > 2) return VETSB_CANNOT_ENTER;
 	/* Direction into the wormhole */
diff --git a/src/void_cmd.cpp b/src/void_cmd.cpp
--- a/src/void_cmd.cpp
+++ b/src/void_cmd.cpp
@@ -25,7 +25,7 @@ static void DrawTile_Void(TileInfo *ti)
 }
 
 
-static int GetSlopePixelZ_Void(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Void(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	/* This function may be called on tiles outside the map, don't assume
 	 * that 'tile' is a valid tile index. See GetSlopePixelZOutsideMap. */
diff --git a/src/water_cmd.cpp b/src/water_cmd.cpp
--- a/src/water_cmd.cpp
+++ b/src/water_cmd.cpp
@@ -936,7 +936,7 @@ void DrawShipDepotSprite(int x, int y, A
 }
 
 
-static int GetSlopePixelZ_Water(TileIndex tile, uint x, uint y)
+static int GetSlopePixelZ_Water(TileIndex tile, uint x, uint y, bool ground_vehicle)
 {
 	int z;
 	Slope tileh = GetTilePixelSlope(tile, &z);