diff --git a/OpenRA.FileFormats/Exts.cs b/OpenRA.FileFormats/Exts.cs
index 9c071b73e0..af2e5d98ef 100755
--- a/OpenRA.FileFormats/Exts.cs
+++ b/OpenRA.FileFormats/Exts.cs
@@ -225,6 +225,20 @@ namespace OpenRA
 		}
 
 		public static Rectangle Bounds(this Bitmap b) { return new Rectangle(0, 0, b.Width, b.Height); }
+
+		public static int ToBits(this IEnumerable<bool> bits)
+		{
+			var i = 0;
+			var result = 0;
+			foreach (var b in bits)
+				if (b)
+					result |= (1 << i++);
+				else
+					i++;
+			if (i > 33)
+				throw new InvalidOperationException("ToBits only accepts up to 32 values.");
+			return result;
+		}
 	}
 
 	public static class Enum<T>
diff --git a/OpenRA.Mods.RA/Move/Mobile.cs b/OpenRA.Mods.RA/Move/Mobile.cs
index 58180da219..f380906945 100755
--- a/OpenRA.Mods.RA/Move/Mobile.cs
+++ b/OpenRA.Mods.RA/Move/Mobile.cs
@@ -72,6 +72,15 @@ namespace OpenRA.Mods.RA.Move
 			return TerrainSpeeds[type].Cost;
 		}
 
+		public int GetMovementClass(TileSet tileset)
+		{
+			/* collect our ability to cross *all* terraintypes, in a bitvector */
+			var passability = tileset.Terrain.OrderBy(t => t.Key)
+				.Select(t => TerrainSpeeds.ContainsKey(t.Key) && TerrainSpeeds[t.Key].Cost < int.MaxValue);
+
+			return passability.ToBits();
+		}
+
 		public readonly Dictionary<SubCell, PVecInt> SubCellOffsets = new Dictionary<SubCell, PVecInt>()
 		{
 			{SubCell.TopLeft, new PVecInt(-7,-6)},