diff --git a/src/clear_map.h b/src/clear_map.h
--- a/src/clear_map.h
+++ b/src/clear_map.h
@@ -5,6 +5,7 @@
 
 #include "macros.h"
 #include "tile.h"
+#include "bridge_map.h"
 
 /* ground type, m5 bits 2...4
  * valid densities (bits 0...1) in comments after the enum
@@ -123,12 +124,17 @@ static inline void SetFenceSW(TileIndex 
 
 static inline void MakeClear(TileIndex t, ClearGround g, uint density)
 {
+	/* If this is a non-bridgeable tile, clear the bridge bits while the rest
+	 * of the tile information is still here. */
+	if (!MayHaveBridgeAbove(t)) SB(_m[t].extra, 6, 2, 0);
+
 	SetTileType(t, MP_CLEAR);
 	SetTileOwner(t, OWNER_NONE);
 	_m[t].m2 = 0;
 	_m[t].m3 = 0;
 	_m[t].m4 = 0 << 5 | 0 << 2;
 	SetClearGroundDensity(t, g, density);
+	SB(_m[t].extra, 2, 4, 0);
 }
 
 
diff --git a/src/terraform_gui.c b/src/terraform_gui.c
--- a/src/terraform_gui.c
+++ b/src/terraform_gui.c
@@ -76,12 +76,8 @@ static void GenerateRockyArea(TileIndex 
 	BEGIN_TILE_LOOP(tile, size_x, size_y, TileXY(sx, sy)) {
 		switch (GetTileType(tile)) {
 			case MP_CLEAR:
-				MakeClear(tile, CLEAR_ROCKS, 3);
-				break;
-
 			case MP_TREES:
 				MakeClear(tile, CLEAR_ROCKS, 3);
-				ClearBridgeMiddle(tile);
 				break;
 
 			default: continue;
diff --git a/src/tree_cmd.c b/src/tree_cmd.c
--- a/src/tree_cmd.c
+++ b/src/tree_cmd.c
@@ -587,7 +587,6 @@ static void TileLoop_Trees(TileIndex til
 					case TREE_GROUND_ROUGH: MakeClear(tile, CLEAR_ROUGH, 3); break;
 					default: MakeClear(tile, CLEAR_SNOW, GetTreeDensity(tile)); break;
 				}
-				ClearBridgeMiddle(tile);
 			}
 			break;