--- a/aircraft_cmd.c
+++ b/aircraft_cmd.c
@@ -1124,7 +1124,7 @@
 	}
 
 	if (v->current_order.type == OT_GOTO_DEPOT &&
-			(v->current_order.flags & (OF_UNLOAD | OF_FULL_LOAD)) == (OF_UNLOAD | OF_FULL_LOAD) &&
+			(v->current_order.flags & (OF_PART_OF_ORDERS | OF_SERVICE_IF_NEEDED)) == (OF_PART_OF_ORDERS | OF_SERVICE_IF_NEEDED) &&
  			!VehicleNeedsService(v)) {
 			v->cur_order_index++;
 		}

--- a/order.h
+++ b/order.h
@@ -1,5 +1,8 @@
 /* $Id$ */
 
+/** @file order.h
+  */
+
 #ifndef ORDER_H
 #define ORDER_H
 
@@ -19,29 +22,44 @@
 
 /* Order flags -- please use OFB instead OF and use HASBIT/SETBIT/CLEARBIT */
 
-/* Order flag masks - these are for direct bit operations */
-enum {
+/** Order flag masks - these are for direct bit operations */
+enum OrderFlagMasks {
 	//Flags for stations:
-	OF_TRANSFER       = 0x1,
-	OF_UNLOAD         = 0x2,
-	OF_FULL_LOAD      = 0x4, // Also used when to force an aircraft into a depot
+	/** vehicle will transfer cargo (i. e. not deliver to nearby industry/town even if accepted there) */
+	OF_TRANSFER           = 0x1,
+	/** If OF_TRANSFER is not set, drop any cargo loaded. If accepted, deliver, otherwise cargo remains at the station.
+      * No new cargo is loaded onto the vehicle whatsoever */
+	OF_UNLOAD             = 0x2,
+	/** Wait for full load of all vehicles, or of at least one cargo type, depending on patch setting
+	  * @todo make this two different flags */
+	OF_FULL_LOAD          = 0x4,
 
 	//Flags for depots:
-	OF_PART_OF_ORDERS	= 0x2,
-	OF_HALT_IN_DEPOT  = 0x4,
+	/** The current depot-order was initiated because it was in the vehicle's order list */
+	OF_PART_OF_ORDERS	  = 0x2,
+	/** if OF_PART_OF_ORDERS is not set, this will cause the vehicle to be stopped in the depot */
+	OF_HALT_IN_DEPOT      = 0x4,
+	/** if OF_PART_OF_ORDERS is set, this will cause the order only be come active if the vehicle needs servicing */
+	OF_SERVICE_IF_NEEDED  = 0x4, //used when OF_PART_OF_ORDERS is set.
 
 	//Common flags
-	OF_NON_STOP  = 0x8
+	/** This causes the vehicle not to stop at intermediate OR the destination station (depending on patch settings)
+	  * @todo make this two different flags */
+	OF_NON_STOP           = 0x8
 };
 
-/* Order flags bits - these are for the *BIT macros */
+/** Order flags bits - these are for the *BIT macros
+  * for descrption of flags, see OrderFlagMasks
+  * @see OrderFlagMasks
+  */
 enum {
-	OFB_TRANSFER       = 0,
-	OFB_UNLOAD         = 1,
-	OFB_FULL_LOAD      = 2,
-	OFB_PART_OF_ORDERS = 1,
-	OFB_HALT_IN_DEPOT  = 2,
-	OFB_NON_STOP       = 3
+	OFB_TRANSFER          = 0,
+	OFB_UNLOAD            = 1,
+	OFB_FULL_LOAD         = 2,
+	OFB_PART_OF_ORDERS    = 1,
+	OFB_HALT_IN_DEPOT     = 2,
+	OFB_SERVICE_IF_NEEDED = 2,
+	OFB_NON_STOP          = 3
 };
 
 

--- a/roadveh_cmd.c
+++ b/roadveh_cmd.c
@@ -630,7 +630,7 @@
 	}
 
 	if (v->current_order.type == OT_GOTO_DEPOT &&
-			(v->current_order.flags & (OF_UNLOAD | OF_FULL_LOAD)) == (OF_UNLOAD | OF_FULL_LOAD) &&
+			(v->current_order.flags & (OF_PART_OF_ORDERS | OF_SERVICE_IF_NEEDED)) == (OF_PART_OF_ORDERS | OF_SERVICE_IF_NEEDED) &&
 			!VehicleNeedsService(v)) {
 		v->cur_order_index++;
 	}

--- a/ship_cmd.c
+++ b/ship_cmd.c
@@ -220,7 +220,7 @@
 	}
 
 	if (v->current_order.type == OT_GOTO_DEPOT &&
-			(v->current_order.flags & (OF_UNLOAD | OF_FULL_LOAD)) == (OF_UNLOAD | OF_FULL_LOAD) &&
+			(v->current_order.flags & (OF_PART_OF_ORDERS | OF_SERVICE_IF_NEEDED)) == (OF_PART_OF_ORDERS | OF_SERVICE_IF_NEEDED) &&
 			!VehicleNeedsService(v)) {
 		v->cur_order_index++;
 	}

--- a/train_cmd.c
+++ b/train_cmd.c
@@ -2156,7 +2156,7 @@
 	}
 
 	if (v->current_order.type == OT_GOTO_DEPOT &&
-			(v->current_order.flags & (OF_UNLOAD | OF_FULL_LOAD)) ==  (OF_UNLOAD | OF_FULL_LOAD) &&
+			(v->current_order.flags & (OF_PART_OF_ORDERS | OF_SERVICE_IF_NEEDED)) ==  (OF_PART_OF_ORDERS | OF_SERVICE_IF_NEEDED) &&
 			!VehicleNeedsService(v)) {
 		v->cur_order_index++;
 	}