diff --git a/openttd.h b/openttd.h
index 9ed4db102d..5dd28c909d 100644
--- a/openttd.h
+++ b/openttd.h
@@ -35,26 +35,28 @@ typedef struct Town Town;
 typedef struct NewsItem NewsItem;
 typedef struct Industry Industry;
 typedef struct DrawPixelInfo DrawPixelInfo;
-typedef uint16 VehicleID;
-typedef uint16 StationID;
-typedef uint16 RoadStopID;
-typedef uint16 TownID;
-typedef uint16 IndustryID;
-typedef uint16 DepotID;
-typedef uint16 WaypointID;
-typedef uint16 OrderID;
 typedef byte PlayerID;
 typedef byte VehicleOrderID;  ///< The index of an order within its current vehicle (not pool related)
 typedef byte CargoID;
 typedef byte LandscapeID;
-typedef uint16 StringID;
 typedef uint32 SpriteID;      ///< The number of a sprite, without mapping bits and colortables
 typedef uint32 PalSpriteID;   ///< The number of a sprite plus all the mapping bits and colortables
 typedef uint32 CursorID;
 typedef uint16 EngineID;
-typedef uint16 EngineRenewID;
-typedef uint16 SignID;
 typedef uint16 UnitID;
+typedef uint16 StringID;
+
+/* IDs used in Pools */
+typedef uint16 VehicleID;
+typedef uint16 StationID;
+typedef uint16 RoadStopID;
+typedef uint16 TownID;
+typedef uint16 IndustryID;
+typedef uint16 DepotID;
+typedef uint16 WaypointID;
+typedef uint16 OrderID;
+typedef uint16 SignID;
+typedef uint16 EngineRenewID;
 
 typedef union DestinationID {
 	StationID station;