--- a/src/autoreplace_gui.cpp	Sun Feb 03 20:23:59 2008 +0000
+++ b/src/autoreplace_gui.cpp	Mon Feb 04 11:28:12 2008 +0000
@@ -80,7 +80,7 @@
 void InvalidateAutoreplaceWindow(EngineID e, GroupID id_g)
 {
 	Player *p = GetPlayer(_local_player);
-	byte type = GetEngine(e)->type;
+	VehicleType type = GetEngine(e)->type;
 	uint num_engines = GetGroupNumEngines(_local_player, id_g, e);
 
 	if (num_engines == 0 || p->num_engines[e] == 0) {
@@ -175,7 +175,7 @@
 {
 	EngineID e;
 	EngineID selected_engine = INVALID_ENGINE;
-	byte type = w->window_number;
+	VehicleType type = (VehicleType)w->window_number;
 	byte i = draw_left ? 0 : 1;
 
 	EngineList *list = &WP(w, replaceveh_d).list[i];

--- a/src/build_vehicle_gui.cpp	Sun Feb 03 20:23:59 2008 +0000
+++ b/src/build_vehicle_gui.cpp	Mon Feb 04 11:28:12 2008 +0000
@@ -81,9 +81,11 @@
 };
 
 /* Setup widget strings to fit the different types of vehicles */
-static void SetupWindowStrings(Window *w, byte type)
+static void SetupWindowStrings(Window *w, VehicleType type)
 {
 	switch (type) {
+		default: NOT_REACHED();
+
 		case VEH_TRAIN:
 			w->widget[BUILD_VEHICLE_WIDGET_CAPTION].data    = STR_JUST_STRING;
 			w->widget[BUILD_VEHICLE_WIDGET_LIST].tooltips   = STR_8843_TRAIN_VEHICLE_SELECTION;
@@ -92,6 +94,7 @@
 			w->widget[BUILD_VEHICLE_WIDGET_RENAME].data     = STR_8820_RENAME;
 			w->widget[BUILD_VEHICLE_WIDGET_RENAME].tooltips = STR_8845_RENAME_TRAIN_VEHICLE_TYPE;
 			break;
+
 		case VEH_ROAD:
 			w->widget[BUILD_VEHICLE_WIDGET_CAPTION].data    = STR_9006_NEW_ROAD_VEHICLES;
 			w->widget[BUILD_VEHICLE_WIDGET_LIST].tooltips   = STR_9026_ROAD_VEHICLE_SELECTION;
@@ -100,6 +103,7 @@
 			w->widget[BUILD_VEHICLE_WIDGET_RENAME].data     = STR_9034_RENAME;
 			w->widget[BUILD_VEHICLE_WIDGET_RENAME].tooltips = STR_9035_RENAME_ROAD_VEHICLE_TYPE;
 			break;
+
 		case VEH_SHIP:
 			w->widget[BUILD_VEHICLE_WIDGET_CAPTION].data    = STR_9808_NEW_SHIPS;
 			w->widget[BUILD_VEHICLE_WIDGET_LIST].tooltips   = STR_9825_SHIP_SELECTION_LIST_CLICK;
@@ -108,6 +112,7 @@
 			w->widget[BUILD_VEHICLE_WIDGET_RENAME].data     = STR_9836_RENAME;
 			w->widget[BUILD_VEHICLE_WIDGET_RENAME].tooltips = STR_9837_RENAME_SHIP_TYPE;
 			break;
+
 		case VEH_AIRCRAFT:
 			w->widget[BUILD_VEHICLE_WIDGET_CAPTION].data    = STR_A005_NEW_AIRCRAFT;
 			w->widget[BUILD_VEHICLE_WIDGET_LIST].tooltips   = STR_A025_AIRCRAFT_SELECTION_LIST;
@@ -890,7 +895,7 @@
 	EngList_Sort(&bv->eng_list, _sorter[bv->vehicle_type][bv->sort_criteria]);
 }
 
-static void DrawVehicleEngine(byte type, int x, int y, EngineID engine, SpriteID pal)
+static void DrawVehicleEngine(VehicleType type, int x, int y, EngineID engine, SpriteID pal)
 {
 	switch (type) {
 		case VEH_TRAIN:    DrawTrainEngine(   x, y, engine, pal); break;

--- a/src/depot_gui.cpp	Sun Feb 03 20:23:59 2008 +0000
+++ b/src/depot_gui.cpp	Mon Feb 04 11:28:12 2008 +0000
@@ -519,9 +519,11 @@
  * Only use this if it's the same widget, that's used for more than one vehicle type and it needs different text/sprites
  * Vehicle specific text/sprites, that's in a widget, that's only shown for one vehicle type (like sell whole train) is set in the widget array
  */
-static void SetupStringsForDepotWindow(Window *w, byte type)
+static void SetupStringsForDepotWindow(Window *w, VehicleType type)
 {
 	switch (type) {
+		default: NOT_REACHED();
+
 		case VEH_TRAIN:
 			w->widget[DEPOT_WIDGET_CAPTION].data      = STR_8800_TRAIN_DEPOT;
 			w->widget[DEPOT_WIDGET_STOP_ALL].tooltips = STR_MASS_STOP_DEPOT_TRAIN_TIP;

--- a/src/engine.cpp	Sun Feb 03 20:23:59 2008 +0000
+++ b/src/engine.cpp	Mon Feb 04 11:28:12 2008 +0000
@@ -403,22 +403,19 @@
 }
 
 
-/*
- * returns true if an engine is valid, of the specified type, and buildable by
- * the given player, false otherwise
- *
- * engine = index of the engine to check
- * type   = the type the engine should be of (VEH_xxx)
- * player = index of the player
+/** Check if an engine is buildable.
+ * @param engine index of the engine to check.
+ * @param type   the type the engine should be.
+ * @param player index of the player.
+ * @return True if an engine is valid, of the specified type, and buildable by
+ *              the given player.
  */
-bool IsEngineBuildable(EngineID engine, byte type, PlayerID player)
+bool IsEngineBuildable(EngineID engine, VehicleType type, PlayerID player)
 {
-	const Engine *e;
-
 	/* check if it's an engine that is in the engine array */
 	if (!IsEngineIndex(engine)) return false;
 
-	e = GetEngine(engine);
+	const Engine *e = GetEngine(engine);
 
 	/* check if it's an engine of specified type */
 	if (e->type != type) return false;

--- a/src/engine.h	Sun Feb 03 20:23:59 2008 +0000
+++ b/src/engine.h	Mon Feb 04 11:28:12 2008 +0000
@@ -168,7 +168,7 @@
 void LoadCustomEngineNames();
 void DeleteCustomEngineNames();
 
-bool IsEngineBuildable(EngineID engine, byte type, PlayerID player);
+bool IsEngineBuildable(EngineID engine, VehicleType type, PlayerID player);
 CargoID GetEngineCargoType(EngineID engine);
 
 enum {
@@ -185,14 +185,14 @@
 	ROAD_ENGINES_INDEX      = NUM_TRAIN_ENGINES,
 };
 
-static inline EngineID GetFirstEngineOfType(byte type)
+static inline EngineID GetFirstEngineOfType(VehicleType type)
 {
 	const EngineID start[] = {0, ROAD_ENGINES_INDEX, SHIP_ENGINES_INDEX, AIRCRAFT_ENGINES_INDEX};
 
 	return start[type];
 }
 
-static inline EngineID GetLastEngineOfType(byte type)
+static inline EngineID GetLastEngineOfType(VehicleType type)
 {
 	const EngineID end[] = {
 		NUM_TRAIN_ENGINES,