diff -r f02afc46afa8 -r 87f2238f47d4 src/ai/api/ai_tile.cpp
--- a/src/ai/api/ai_tile.cpp	Sat Jun 07 22:57:00 2008 +0000
+++ b/src/ai/api/ai_tile.cpp	Sat Jun 07 23:05:36 2008 +0000
@@ -12,6 +12,7 @@
 #include "../../station_func.h"
 #include "../../command_type.h"
 #include "../../settings_type.h"
+#include "../../player_func.h"
 #include "../../road_map.h"
 
 /* static */ bool AITile::IsBuildable(TileIndex tile)
@@ -19,18 +20,15 @@
 	if (!::IsValidTile(tile)) return false;
 
 	switch (::GetTileType(tile)) {
-		default: return true;
-		case MP_VOID:
-		case MP_HOUSE:
-		case MP_STATION:
-		case MP_INDUSTRY:
-		case MP_UNMOVABLE:
-		case MP_WATER: return false;
-
+		default: return false;
+		case MP_CLEAR: return true;
 		case MP_ROAD:
 			/* Depots aren't considered buildable */
 			if (::GetRoadTileType(tile) == ROAD_TILE_DEPOT) return false;
-			return true;
+			if (CountBits(GetAllRoadBits(tile)) != 1) return false;
+			if (IsRoadOwner(tile, ROADTYPE_ROAD, OWNER_TOWN)) return true;
+			if (IsRoadOwner(tile, ROADTYPE_ROAD, _current_player)) return true;
+			return false;
 	}
 }