diff --git a/src/micropolisj/engine/TileConstants.java b/src/micropolisj/engine/TileConstants.java
index 7023b01..6e571c4 100644
--- a/src/micropolisj/engine/TileConstants.java
+++ b/src/micropolisj/engine/TileConstants.java
@@ -171,10 +171,7 @@ public class TileConstants
 	public static final char TINYEXP = 860;
 	public static final char SOMETINYEXP = 864;
 	public static final char LASTTINYEXP = 867;
-	public static final char COALSMOKE1 = 916;
-	public static final char COALSMOKE2 = 920;
-	public static final char COALSMOKE3 = 924;
-	public static final char COALSMOKE4 = 928;
+	public static final char SMOKEBASE2 = 884;
 	public static final char FOOTBALLGAME1 = 932;
 	public static final char FOOTBALLGAME2 = 940;
 	public static final char VBRDG0 = 948;   //draw bridge tiles (vert)
@@ -466,12 +463,24 @@ public class TileConstants
 		return (tile == DIRT || ((tile & BULLBIT) != 0 && isCombustible(tile)));
 	}
 
+	/**
+	 * Note: does not include rail/road tiles.
+	 * @see #isRoadAny
+	 */
 	public static boolean isRoad(int tile)
 	{
 		int tmp = tile & LOMASK;
 		return (tmp >= ROADBASE && tmp < POWERBASE);
 	}
 
+	public static boolean isRoadAny(int tile)
+	{
+		int tmp = tile & LOMASK;
+		return (tmp >= ROADBASE && tmp < POWERBASE)
+			|| (tmp == HRAILROAD)
+			|| (tmp == VRAILROAD);
+	}
+
 	/**
 	 * Checks whether the tile is a road that will automatically change to connect to
 	 * neighboring roads.
@@ -532,6 +541,14 @@ public class TileConstants
 		return (tmp >= RAILBASE && tmp < RESBASE);
 	}
 
+	public static boolean isRailAny(int tile)
+	{
+		int tmp = tile & LOMASK;
+		return (tmp >= RAILBASE && tmp < RESBASE)
+			|| (tmp == RAILHPOWERV)
+			|| (tmp == RAILVPOWERH);
+	}
+
 	public static boolean isRailDynamic(int tile)
 	{
 		int tmp = tile & LOMASK;
@@ -618,29 +635,38 @@ public class TileConstants
 
 	public static boolean isCommercialZone(int tile)
 	{
-		assert isZoneCenter(tile);
 		return (tile & LOMASK) >= COMBASE &&
 			(tile & LOMASK) < INDBASE;
 	}
 
 	public static boolean isHospitalOrChurch(int tile)
 	{
-		assert isZoneCenter(tile);
 		return (tile & LOMASK) >= HOSPITAL &&
 			(tile & LOMASK) < COMBASE;
 	}
 
 	public static boolean isIndustrialZone(int tile)
 	{
-		assert isZoneCenter(tile);
-		return (tile & LOMASK) >= INDBASE &&
-			(tile & LOMASK) < PORTBASE;
+		int tmp = tile & LOMASK;
+		return (tmp >= INDBASE && tmp < PORTBASE)
+		|| (tmp >= SMOKEBASE && tmp < TINYEXP)
+		|| (tmp >= SMOKEBASE2 && tmp < FOOTBALLGAME1);
 	}
 
+	/** Note: does not include hospital/church.
+	 * @see #isHospitalOrChurch
+	 */
 	public static boolean isResidentialZone(int tile)
 	{
-		assert isZoneCenter(tile);
-		return (tile & LOMASK) < HOSPITAL;
+		return (tile & LOMASK) >= RESBASE &&
+			(tile & LOMASK) < HOSPITAL;
+	}
+
+	// includes hospital/church.
+	public static boolean isResidentialZoneAny(int tile)
+	{
+		int tmp = tile & LOMASK;
+		return (tile >= RESBASE && tile < COMBASE);
 	}
 
 	public static boolean isSpecialZone(int tile)
@@ -649,6 +675,12 @@ public class TileConstants
 		return (tile & LOMASK) >= PORTBASE;
 	}
 
+	/** Tile represents a part of any sort of building. */
+	public static boolean isZoneAny(int tile)
+	{
+		return (tile & LOMASK) >= RESBASE;
+	}
+
 	public static boolean isZoneCenter(int tile)
 	{
 		TileSpec spec = Tiles.get(tile & LOMASK);
diff --git a/src/micropolisj/gui/OverlayMapView.java b/src/micropolisj/gui/OverlayMapView.java
index 921fae1..a548932 100644
--- a/src/micropolisj/gui/OverlayMapView.java
+++ b/src/micropolisj/gui/OverlayMapView.java
@@ -301,26 +301,38 @@ public class OverlayMapView extends JComponent
 				int tile = engine.getTile(x,y) & LOMASK;
 				switch (mapState) {
 				case RESIDENTIAL:
-					if (tile >= COMBASE) { tile = DIRT; }
+					if (isZoneAny(tile) &&
+						!isResidentialZone(tile) &&
+						!isHospitalOrChurch(tile))
+					{
+						tile = DIRT;
+					}
 					break;
 				case COMMERCIAL:
-					if (tile > COMLAST || (tile >= RESBASE && tile < COMBASE)) { tile = DIRT; }
+					if (isZoneAny(tile) &&
+						!isCommercialZone(tile))
+					{
+						tile = DIRT;
+					}
 					break;
 				case INDUSTRIAL:
-					if ((tile >= RESBASE && tile < INDBASE) ||
-						(tile >= PORTBASE && tile < SMOKEBASE) ||
-						(tile >= TINYEXP && tile < 884) ||
-						tile >= FOOTBALLGAME1)
-						{ tile = DIRT; }
+					if (isZoneAny(tile) &&
+						!isIndustrialZone(tile))
+					{
+						tile = DIRT;
+					}
 					break;
 				case POWER_OVERLAY:
 					tile = checkPower(img, x, y, engine.getTile(x,y));
 					break;
 				case TRANSPORT:
 				case TRAFFIC_OVERLAY:
-					if (tile >= RESBASE ||
-						(tile >= 207 && tile <= LVPOWER10) ||
-						tile == 223) { tile = DIRT; }
+					if (isConstructed(tile)
+						&& !isRoadAny(tile)
+						&& !isRailAny(tile))
+					{
+						tile = DIRT;
+					}
 					break;
 				default:
 				}