(svn r15101) -Change [API CHANGE]: more consistant naming for consts:

   INVALID_TOWN_RATING        -> TOWN_RATING_INVALID
   INVALID_TRANSPORT          -> TRANSPORT_INVALID
   INVALID_ORDER              -> ORDER_INVALID
   INVALID_GROUP              -> GROUP_INVALID
   GROUP_ALL/DEFAULT          -> ALL/DEFAULT_GROUP
   VEHICLE_RAIL/ROAD/..       -> VT_RAIL/ROAD/..
   MY_COMPANY                 -> COMPANY_SELF
   FIRST/LAST/INVALID_COMPANY -> COMPANY_FIRST/LAST/INVALID

27 files changed, 132 insertions, 121 deletions

diff --git a/src/ai/ai_instance.cpp b/src/ai/ai_instance.cpp
index cfd952505..cc8893c9d 100644
--- a/src/ai/ai_instance.cpp
+++ b/src/ai/ai_instance.cpp
@@ -10,6 +10,7 @@
 #include "../string_func.h"
 #include "../settings_type.h"
 #include "../company_base.h"
+#include "../vehicle_base.h"
 #include "../saveload/saveload.h"
 #include "table/strings.h"
 
@@ -18,14 +19,14 @@
 #include "../script/squirrel_helper.hpp"
 #include "../script/squirrel_class.hpp"
 #include "../script/squirrel_std.hpp"
+
+#define DEFINE_SCRIPT_FILES
+
 #include "ai.hpp"
-#include "api/ai_controller.hpp"
 #include "ai_info.hpp"
 #include "ai_storage.hpp"
 #include "ai_instance.hpp"
 
-#define DEFINE_SCRIPT_FILES
-
 /* Convert all AI related classes to Squirrel data.
  * Note: this line a marker in squirrel_export.sh. Do not change! */
 #include "api/ai_abstractlist.hpp.sq"
diff --git a/src/ai/api/ai_bridge.cpp b/src/ai/api/ai_bridge.cpp
index 86eb5f6f1..56fe7061b 100644
--- a/src/ai/api/ai_bridge.cpp
+++ b/src/ai/api/ai_bridge.cpp
@@ -56,27 +56,27 @@ static void _DoCommandReturnBuildBridge1(class AIInstance *instance)
 	EnforcePrecondition(false, start != end);
 	EnforcePrecondition(false, ::IsValidTile(start) && ::IsValidTile(end));
 	EnforcePrecondition(false, TileX(start) == TileX(end) || TileY(start) == TileY(end));
-	EnforcePrecondition(false, vehicle_type == AIVehicle::VEHICLE_ROAD || vehicle_type == AIVehicle::VEHICLE_RAIL || vehicle_type == AIVehicle::VEHICLE_WATER);
-	EnforcePrecondition(false, vehicle_type != AIVehicle::VEHICLE_RAIL || AIRail::IsRailTypeAvailable(AIRail::GetCurrentRailType()));
+	EnforcePrecondition(false, vehicle_type == AIVehicle::VT_ROAD || vehicle_type == AIVehicle::VT_RAIL || vehicle_type == AIVehicle::VT_WATER);
+	EnforcePrecondition(false, vehicle_type != AIVehicle::VT_RAIL || AIRail::IsRailTypeAvailable(AIRail::GetCurrentRailType()));
 
 	uint type = 0;
 	switch (vehicle_type) {
-		case AIVehicle::VEHICLE_ROAD:
+		case AIVehicle::VT_ROAD:
 			type |= (TRANSPORT_ROAD << 15);
 			type |= (RoadTypeToRoadTypes((::RoadType)AIObject::GetRoadType()) << 8);
 			break;
-		case AIVehicle::VEHICLE_RAIL:
+		case AIVehicle::VT_RAIL:
 			type |= (TRANSPORT_RAIL << 15);
 			type |= (AIRail::GetCurrentRailType() << 8);
 			break;
-		case AIVehicle::VEHICLE_WATER:
+		case AIVehicle::VT_WATER:
 			type |= (TRANSPORT_WATER << 15);
 			break;
 		default: NOT_REACHED();
 	}
 
 	/* For rail and water we do nothing special */
-	if (vehicle_type == AIVehicle::VEHICLE_RAIL || vehicle_type == AIVehicle::VEHICLE_WATER) {
+	if (vehicle_type == AIVehicle::VT_RAIL || vehicle_type == AIVehicle::VT_WATER) {
 		return AIObject::DoCommand(end, start, type | bridge_id, CMD_BUILD_BRIDGE);
 	}
 
diff --git a/src/ai/api/ai_company.cpp b/src/ai/api/ai_company.cpp
index 9a426bd2b..4040ab9c1 100644
--- a/src/ai/api/ai_company.cpp
+++ b/src/ai/api/ai_company.cpp
@@ -19,14 +19,14 @@
 
 /* static */ AICompany::CompanyID AICompany::ResolveCompanyID(AICompany::CompanyID company)
 {
-	if (company == MY_COMPANY) return (CompanyID)((byte)_current_company);
+	if (company == COMPANY_SELF) return (CompanyID)((byte)_current_company);
 
-	return ::IsValidCompanyID((::CompanyID)company) ? company : INVALID_COMPANY;
+	return ::IsValidCompanyID((::CompanyID)company) ? company : COMPANY_INVALID;
 }
 
 /* static */ bool AICompany::IsMine(AICompany::CompanyID company)
 {
-	return ResolveCompanyID(company) == ResolveCompanyID(MY_COMPANY);
+	return ResolveCompanyID(company) == ResolveCompanyID(COMPANY_SELF);
 }
 
 /* static */ bool AICompany::SetCompanyName(const char *name)
@@ -52,7 +52,7 @@
 /* static */ const char *AICompany::GetName(AICompany::CompanyID company)
 {
 	company = ResolveCompanyID(company);
-	if (company == INVALID_COMPANY) return NULL;
+	if (company == COMPANY_INVALID) return NULL;
 
 	static const int len = 64;
 	char *company_name = MallocT<char>(len);
@@ -75,7 +75,7 @@
 
 	static const int len = 64;
 	char *president_name = MallocT<char>(len);
-	if (company != INVALID_COMPANY) {
+	if (company != COMPANY_INVALID) {
 		::SetDParam(0, company);
 		::GetString(president_name, STR_PRESIDENT_NAME, &president_name[len - 1]);
 	} else {
@@ -88,7 +88,7 @@
 /* static */ Money AICompany::GetCompanyValue(AICompany::CompanyID company)
 {
 	company = ResolveCompanyID(company);
-	if (company == INVALID_COMPANY) return -1;
+	if (company == COMPANY_INVALID) return -1;
 
 	return ::CalculateCompanyValue(::GetCompany((CompanyID)company));
 }
@@ -96,7 +96,7 @@
 /* static */ Money AICompany::GetBankBalance(AICompany::CompanyID company)
 {
 	company = ResolveCompanyID(company);
-	if (company == INVALID_COMPANY) return -1;
+	if (company == COMPANY_INVALID) return -1;
 
 	return ::GetCompany((CompanyID)company)->money;
 }
@@ -121,7 +121,7 @@
 	EnforcePrecondition(false, loan >= 0);
 	EnforcePrecondition(false, (loan % GetLoanInterval()) == 0);
 	EnforcePrecondition(false, loan <= GetMaxLoanAmount());
-	EnforcePrecondition(false, (loan - GetLoanAmount() + GetBankBalance(MY_COMPANY)) >= 0);
+	EnforcePrecondition(false, (loan - GetLoanAmount() + GetBankBalance(COMPANY_SELF)) >= 0);
 
 	if (loan == GetLoanAmount()) return true;
 
@@ -154,7 +154,7 @@
 /* static */ TileIndex AICompany::GetCompanyHQ(CompanyID company)
 {
 	company = ResolveCompanyID(company);
-	if (company == INVALID_COMPANY) return INVALID_TILE;
+	if (company == COMPANY_INVALID) return INVALID_TILE;
 
 	TileIndex loc = ::GetCompany((CompanyID)company)->location_of_HQ;
 	return (loc == 0) ? INVALID_TILE : loc;
@@ -168,7 +168,7 @@
 /* static */ bool AICompany::GetAutoRenewStatus(CompanyID company)
 {
 	company = ResolveCompanyID(company);
-	if (company == INVALID_COMPANY) return false;
+	if (company == COMPANY_INVALID) return false;
 
 	return ::GetCompany((CompanyID)company)->engine_renew;
 }
@@ -181,7 +181,7 @@
 /* static */ int16 AICompany::GetAutoRenewMonths(CompanyID company)
 {
 	company = ResolveCompanyID(company);
-	if (company == INVALID_COMPANY) return 0;
+	if (company == COMPANY_INVALID) return 0;
 
 	return ::GetCompany((CompanyID)company)->engine_renew_months;
 }
@@ -194,7 +194,7 @@
 /* static */ uint32 AICompany::GetAutoRenewMoney(CompanyID company)
 {
 	company = ResolveCompanyID(company);
-	if (company == INVALID_COMPANY) return 0;
+	if (company == COMPANY_INVALID) return 0;
 
 	return ::GetCompany((CompanyID)company)->engine_renew_money;
 }
diff --git a/src/ai/api/ai_company.hpp b/src/ai/api/ai_company.hpp
index 2497e43b7..bc08e9630 100644
--- a/src/ai/api/ai_company.hpp
+++ b/src/ai/api/ai_company.hpp
@@ -16,17 +16,21 @@ public:
 
 	/** Different constants related to CompanyID. */
 	enum CompanyID {
-		INVALID_COMPANY = -1, //!< An invalid company.
-		FIRST_COMPANY   = 0, //!< The first available company.
-		LAST_COMPANY    = 7, //!< The last available company.
-		MY_COMPANY      = 8, //!< Constant that gets resolved to the correct company index for your company.
+		COMPANY_INVALID = -1, //!< An invalid company.
+
+#ifdef DEFINE_SCRIPT_FILES
+		COMPANY_FIRST   = 0, //!< The first available company.
+		COMPANY_LAST    = ::MAX_COMPANIES, //!< The last available company.
+#endif /* DEFINE_SCRIPT_FILES */
+
+		COMPANY_SELF    = 254, //!< Constant that gets resolved to the correct company index for your company.
 	};
 
 	/**
 	 * Resolved the given company index to the correct index for the company. If
-	 *  the company index was MY_COMPANY it will be resolved to the index of
+	 *  the company index was COMPANY_SELF it will be resolved to the index of
 	 *  your company. If the company with the given index does not exist it will
-	 *  return INVALID_COMPANY.
+	 *  return COMPANY_INVALID.
 	 * @param company The company index to resolve.
 	 * @return The resolved company index.
 	 */
@@ -62,7 +66,7 @@ public:
 	/**
 	 * Get the name of the given company.
 	 * @param company The company to get the name for.
-	 * @pre ResolveCompanyID(company) != INVALID_COMPANY
+	 * @pre ResolveCompanyID(company) != COMPANY_INVALID
 	 * @return The name of the given company.
 	 */
 	static const char *GetName(CompanyID company);
@@ -79,7 +83,7 @@ public:
 	/**
 	 * Get the name of the president of the given company.
 	 * @param company The company to get the president's name for.
-	 * @pre ResolveCompanyID(company) != INVALID_COMPANY
+	 * @pre ResolveCompanyID(company) != COMPANY_INVALID
 	 * @return The name of the president of the given company.
 	 */
 	static const char *GetPresidentName(CompanyID company);
@@ -130,7 +134,7 @@ public:
 	/**
 	 * Gets the current value of the given company.
 	 * @param company The company to get the company value of.
-	 * @pre ResolveCompanyID(company) != INVALID_COMPANY
+	 * @pre ResolveCompanyID(company) != COMPANY_INVALID
 	 * @return The current value of the given company.
 	 */
 	static Money GetCompanyValue(CompanyID company);
@@ -138,7 +142,7 @@ public:
 	/**
 	 * Gets the bank balance. In other words, the amount of money the given company can spent.
 	 * @param company The company to get the bank balance of.
-	 * @pre ResolveCompanyID(company) != INVALID_COMPANY
+	 * @pre ResolveCompanyID(company) != COMPANY_INVALID
 	 * @return The actual bank balance.
 	 */
 	static Money GetBankBalance(CompanyID company);
@@ -158,8 +162,8 @@ public:
 	/**
 	 * Return the location of a company's HQ.
 	 * @param company The company the get the HQ of.
-	 * @pre ResolveCompanyID(company) != INVALID_COMPANY.
-	 * @return The tile of the company's HQ, this tile is the most nothern tile of that HQ, or INVALID_TILE if there is no HQ yet.
+	 * @pre ResolveCompanyID(company) != COMPANY_INVALID.
+	 * @return The tile of the company's HQ, this tile is the most nothern tile of that HQ, or TILE_INVALID if there is no HQ yet.
 	 */
 	static TileIndex GetCompanyHQ(CompanyID company);
 
@@ -173,7 +177,7 @@ public:
 	/**
 	 * Return whether autorenew is enabled for a company.
 	 * @param company The company to get the autorenew status of.
-	 * @pre ResolveCompanyID(company) != INVALID_COMPANY.
+	 * @pre ResolveCompanyID(company) != COMPANY_INVALID.
 	 * @return True if autorenew is enabled.
 	 */
 	static bool GetAutoRenewStatus(CompanyID company);
@@ -188,7 +192,7 @@ public:
 	/**
 	 * Return the number of months before/after max age to autorenew an engine for a company.
 	 * @param company The company to get the autorenew months of.
-	 * @pre ResolveCompanyID(company) != INVALID_COMPANY.
+	 * @pre ResolveCompanyID(company) != COMPANY_INVALID.
 	 * @return The months before/after max age of engine.
 	 */
 	static int16 GetAutoRenewMonths(CompanyID company);
@@ -203,7 +207,7 @@ public:
 	/**
 	 * Return the minimum money needed to autorenew an engine for a company.
 	 * @param company The company to get the autorenew money of.
-	 * @pre ResolveCompanyID(company) != INVALID_COMPANY.
+	 * @pre ResolveCompanyID(company) != COMPANY_INVALID.
 	 * @return The minimum required money for autorenew to work.
 	 */
 	static uint32 GetAutoRenewMoney(CompanyID company);
diff --git a/src/ai/api/ai_company.hpp.sq b/src/ai/api/ai_company.hpp.sq
index 0f0bb5ccf..9f5bfe4b5 100644
--- a/src/ai/api/ai_company.hpp.sq
+++ b/src/ai/api/ai_company.hpp.sq
@@ -21,10 +21,10 @@ void SQAICompany_Register(Squirrel *engine) {
 	SQAICompany.PreRegister(engine);
 	SQAICompany.AddConstructor<void (AICompany::*)(), 1>(engine, "x");
 
-	SQAICompany.DefSQConst(engine, AICompany::INVALID_COMPANY, "INVALID_COMPANY");
-	SQAICompany.DefSQConst(engine, AICompany::FIRST_COMPANY,   "FIRST_COMPANY");
-	SQAICompany.DefSQConst(engine, AICompany::LAST_COMPANY,    "LAST_COMPANY");
-	SQAICompany.DefSQConst(engine, AICompany::MY_COMPANY,      "MY_COMPANY");
+	SQAICompany.DefSQConst(engine, AICompany::COMPANY_INVALID, "COMPANY_INVALID");
+	SQAICompany.DefSQConst(engine, AICompany::COMPANY_FIRST,   "COMPANY_FIRST");
+	SQAICompany.DefSQConst(engine, AICompany::COMPANY_LAST,    "COMPANY_LAST");
+	SQAICompany.DefSQConst(engine, AICompany::COMPANY_SELF,    "COMPANY_SELF");
 
 	SQAICompany.DefSQStaticMethod(engine, &AICompany::GetClassName,         "GetClassName",         1, "x");
 	SQAICompany.DefSQStaticMethod(engine, &AICompany::ResolveCompanyID,     "ResolveCompanyID",     2, "xi");
diff --git a/src/ai/api/ai_engine.cpp b/src/ai/api/ai_engine.cpp
index c3f3aed3e..443f03482 100644
--- a/src/ai/api/ai_engine.cpp
+++ b/src/ai/api/ai_engine.cpp
@@ -79,7 +79,7 @@
 /* static */ bool AIEngine::CanPullCargo(EngineID engine_id, CargoID cargo_id)
 {
 	if (!IsValidEngine(engine_id)) return false;
-	if (GetVehicleType(engine_id) != AIVehicle::VEHICLE_RAIL) return false;
+	if (GetVehicleType(engine_id) != AIVehicle::VT_RAIL) return false;
 	if (!AICargo::IsValidCargo(cargo_id)) return false;
 
 	return (::RailVehInfo(engine_id)->ai_passenger_only != 1) || AICargo::HasCargoClass(cargo_id, AICargo::CC_PASSENGERS);
@@ -225,13 +225,13 @@
 
 /* static */ AIVehicle::VehicleType AIEngine::GetVehicleType(EngineID engine_id)
 {
-	if (!IsValidEngine(engine_id)) return AIVehicle::VEHICLE_INVALID;
+	if (!IsValidEngine(engine_id)) return AIVehicle::VT_INVALID;
 
 	switch (::GetEngine(engine_id)->type) {
-		case VEH_ROAD:     return AIVehicle::VEHICLE_ROAD;
-		case VEH_TRAIN:    return AIVehicle::VEHICLE_RAIL;
-		case VEH_SHIP:     return AIVehicle::VEHICLE_WATER;
-		case VEH_AIRCRAFT: return AIVehicle::VEHICLE_AIR;
+		case VEH_ROAD:     return AIVehicle::VT_ROAD;
+		case VEH_TRAIN:    return AIVehicle::VT_RAIL;
+		case VEH_SHIP:     return AIVehicle::VT_WATER;
+		case VEH_AIRCRAFT: return AIVehicle::VT_AIR;
 		default: NOT_REACHED();
 	}
 }
@@ -239,7 +239,7 @@
 /* static */ bool AIEngine::IsWagon(EngineID engine_id)
 {
 	if (!IsValidEngine(engine_id)) return false;
-	if (GetVehicleType(engine_id) != AIVehicle::VEHICLE_RAIL) return false;
+	if (GetVehicleType(engine_id) != AIVehicle::VT_RAIL) return false;
 
 	return ::RailVehInfo(engine_id)->power == 0;
 }
@@ -247,7 +247,7 @@
 /* static */ bool AIEngine::CanRunOnRail(EngineID engine_id, AIRail::RailType track_rail_type)
 {
 	if (!IsValidEngine(engine_id)) return false;
-	if (GetVehicleType(engine_id) != AIVehicle::VEHICLE_RAIL) return false;
+	if (GetVehicleType(engine_id) != AIVehicle::VT_RAIL) return false;
 	if (!AIRail::IsRailTypeAvailable(track_rail_type)) return false;
 
 	return ::IsCompatibleRail((::RailType)::RailVehInfo(engine_id)->railtype, (::RailType)track_rail_type);
@@ -256,7 +256,7 @@
 /* static */ bool AIEngine::HasPowerOnRail(EngineID engine_id, AIRail::RailType track_rail_type)
 {
 	if (!IsValidEngine(engine_id)) return false;
-	if (GetVehicleType(engine_id) != AIVehicle::VEHICLE_RAIL) return false;
+	if (GetVehicleType(engine_id) != AIVehicle::VT_RAIL) return false;
 	if (!AIRail::IsRailTypeAvailable(track_rail_type)) return false;
 
 	return ::HasPowerOnRail((::RailType)::RailVehInfo(engine_id)->railtype, (::RailType)track_rail_type);
@@ -265,7 +265,7 @@
 /* static */ AIRoad::RoadType AIEngine::GetRoadType(EngineID engine_id)
 {
 	if (!IsValidEngine(engine_id)) return AIRoad::ROADTYPE_INVALID;
-	if (GetVehicleType(engine_id) != AIVehicle::VEHICLE_ROAD) return AIRoad::ROADTYPE_INVALID;
+	if (GetVehicleType(engine_id) != AIVehicle::VT_ROAD) return AIRoad::ROADTYPE_INVALID;
 
 	return HasBit(::EngInfo(engine_id)->misc_flags, EF_ROAD_TRAM) ? AIRoad::ROADTYPE_TRAM : AIRoad::ROADTYPE_ROAD;
 }
@@ -273,7 +273,7 @@
 /* static */ AIRail::RailType AIEngine::GetRailType(EngineID engine_id)
 {
 	if (!IsValidEngine(engine_id)) return AIRail::RAILTYPE_INVALID;
-	if (GetVehicleType(engine_id) != AIVehicle::VEHICLE_RAIL) return AIRail::RAILTYPE_INVALID;
+	if (GetVehicleType(engine_id) != AIVehicle::VT_RAIL) return AIRail::RAILTYPE_INVALID;
 
 	return (AIRail::RailType)(uint)::RailVehInfo(engine_id)->railtype;
 }
@@ -281,7 +281,7 @@
 /* static */ bool AIEngine::IsArticulated(EngineID engine_id)
 {
 	if (!IsValidEngine(engine_id)) return false;
-	if (GetVehicleType(engine_id) != AIVehicle::VEHICLE_ROAD && GetVehicleType(engine_id) != AIVehicle::VEHICLE_RAIL) return false;
+	if (GetVehicleType(engine_id) != AIVehicle::VT_ROAD && GetVehicleType(engine_id) != AIVehicle::VT_RAIL) return false;
 
 	return CountArticulatedParts(engine_id, true) != 0;
 }
@@ -289,7 +289,7 @@
 /* static */ AIAirport::PlaneType AIEngine::GetPlaneType(EngineID engine_id)
 {
 	if (!IsValidEngine(engine_id)) return AIAirport::PT_INVALID;
-	if (GetVehicleType(engine_id) != AIVehicle::VEHICLE_AIR) return AIAirport::PT_INVALID;
+	if (GetVehicleType(engine_id) != AIVehicle::VT_AIR) return AIAirport::PT_INVALID;
 
 	return (AIAirport::PlaneType)::AircraftVehInfo(engine_id)->subtype;
 }
diff --git a/src/ai/api/ai_event_types.hpp b/src/ai/api/ai_event_types.hpp
index 13c004d97..9c0e8a396 100644
--- a/src/ai/api/ai_event_types.hpp
+++ b/src/ai/api/ai_event_types.hpp
@@ -400,7 +400,7 @@ public:
 	 * Get the CompanyID of the company that has been bought.
 	 * @return The CompanyID of the company that has been bought.
 	 * @note: The value below is not valid anymore as CompanyID, and
-	 *  AICompany::ResolveCompanyID will return INVALID_COMPANY. It's
+	 *  AICompany::ResolveCompanyID will return COMPANY_COMPANY. It's
 	 *  only usefull if you're keeping track of company's yourself.
 	 */
 	AICompany::CompanyID GetOldCompanyID() { return old_owner; }
diff --git a/src/ai/api/ai_gamesettings.cpp b/src/ai/api/ai_gamesettings.cpp
index 81b187d73..b3b4fb85a 100644
--- a/src/ai/api/ai_gamesettings.cpp
+++ b/src/ai/api/ai_gamesettings.cpp
@@ -29,10 +29,10 @@
 /* static */ bool AIGameSettings::IsDisabledVehicleType(AIVehicle::VehicleType vehicle_type)
 {
 	switch (vehicle_type) {
-		case AIVehicle::VEHICLE_RAIL:  return _settings_game.ai.ai_disable_veh_train;
-		case AIVehicle::VEHICLE_ROAD:  return _settings_game.ai.ai_disable_veh_roadveh;
-		case AIVehicle::VEHICLE_WATER: return _settings_game.ai.ai_disable_veh_ship;
-		case AIVehicle::VEHICLE_AIR:   return _settings_game.ai.ai_disable_veh_aircraft;
+		case AIVehicle::VT_RAIL:  return _settings_game.ai.ai_disable_veh_train;
+		case AIVehicle::VT_ROAD:  return _settings_game.ai.ai_disable_veh_roadveh;
+		case AIVehicle::VT_WATER: return _settings_game.ai.ai_disable_veh_ship;
+		case AIVehicle::VT_AIR:   return _settings_game.ai.ai_disable_veh_aircraft;
 		default:                       return true;
 	}
 }
diff --git a/src/ai/api/ai_group.cpp b/src/ai/api/ai_group.cpp
index a6365450b..5dc676303 100644
--- a/src/ai/api/ai_group.cpp
+++ b/src/ai/api/ai_group.cpp
@@ -23,7 +23,7 @@
 
 /* static */ AIGroup::GroupID AIGroup::CreateGroup(AIVehicle::VehicleType vehicle_type)
 {
-	if (!AIObject::DoCommand(0, (::VehicleType)vehicle_type, 0, CMD_CREATE_GROUP, NULL, &AIInstance::DoCommandReturnGroupID)) return INVALID_GROUP;
+	if (!AIObject::DoCommand(0, (::VehicleType)vehicle_type, 0, CMD_CREATE_GROUP, NULL, &AIInstance::DoCommandReturnGroupID)) return GROUP_INVALID;
 
 	/* In case of test-mode, we return GroupID 0 */
 	return (AIGroup::GroupID)0;
@@ -38,7 +38,7 @@
 
 /* static */ AIVehicle::VehicleType AIGroup::GetVehicleType(GroupID group_id)
 {
-	if (!IsValidGroup(group_id)) return AIVehicle::VEHICLE_INVALID;
+	if (!IsValidGroup(group_id)) return AIVehicle::VT_INVALID;
 
 	return (AIVehicle::VehicleType)((::VehicleType)::GetGroup(group_id)->vehicle_type);
 }
@@ -80,14 +80,14 @@
 
 /* static */ int32 AIGroup::GetNumEngines(GroupID group_id, EngineID engine_id)
 {
-	if (!IsValidGroup(group_id) && group_id != DEFAULT_GROUP && group_id != ALL_GROUP) return -1;
+	if (!IsValidGroup(group_id) && group_id != GROUP_DEFAULT && group_id != GROUP_ALL) return -1;
 
 	return GetGroupNumEngines(_current_company, group_id, engine_id);
 }
 
 /* static */ bool AIGroup::MoveVehicle(GroupID group_id, VehicleID vehicle_id)
 {
-	EnforcePrecondition(false, IsValidGroup(group_id) || group_id == DEFAULT_GROUP);
+	EnforcePrecondition(false, IsValidGroup(group_id) || group_id == GROUP_DEFAULT);
 	EnforcePrecondition(false, AIVehicle::IsValidVehicle(vehicle_id));
 
 	return AIObject::DoCommand(0, group_id, vehicle_id, CMD_ADD_VEHICLE_GROUP);
@@ -107,7 +107,7 @@
 
 /* static */ bool AIGroup::SetAutoReplace(GroupID group_id, EngineID engine_id_old, EngineID engine_id_new)
 {
-	EnforcePrecondition(false, IsValidGroup(group_id) || group_id == ALL_GROUP);
+	EnforcePrecondition(false, IsValidGroup(group_id) || group_id == GROUP_ALL);
 	EnforcePrecondition(false, AIEngine::IsValidEngine(engine_id_new));
 
 	return AIObject::DoCommand(0, 3 | (group_id << 16), (engine_id_new << 16) | engine_id_old, CMD_SET_AUTOREPLACE);
@@ -115,14 +115,14 @@
 
 /* static */ EngineID AIGroup::GetEngineReplacement(GroupID group_id, EngineID engine_id)
 {
-	if (!IsValidGroup(group_id) && group_id != ALL_GROUP) return ::INVALID_ENGINE;
+	if (!IsValidGroup(group_id) && group_id != GROUP_ALL) return ::INVALID_ENGINE;
 
 	return ::EngineReplacementForCompany(GetCompany(_current_company), engine_id, group_id);
 }
 
 /* static */ bool AIGroup::StopAutoReplace(GroupID group_id, EngineID engine_id)
 {
-	EnforcePrecondition(false, IsValidGroup(group_id) || group_id == ALL_GROUP);
+	EnforcePrecondition(false, IsValidGroup(group_id) || group_id == GROUP_ALL);
 
 	return AIObject::DoCommand(0, 3 | (group_id << 16), (::INVALID_ENGINE << 16) | engine_id, CMD_SET_AUTOREPLACE);
 }
diff --git a/src/ai/api/ai_group.hpp b/src/ai/api/ai_group.hpp
index 84569c562..51a4c47aa 100644
--- a/src/ai/api/ai_group.hpp
+++ b/src/ai/api/ai_group.hpp
@@ -20,9 +20,9 @@ public:
 	 */
 	enum GroupID {
 		/* Values are important, as they represent the internal state of the game (see group_type.h). */
-		ALL_GROUP = 0xFFFD,     //!< All vehicles are in this group.
-		DEFAULT_GROUP = 0xFFFE, //!< Vehicles not put in any other group are in this one.
-		INVALID_GROUP = 0xFFFF, //!< An invalid group id.
+		GROUP_ALL = 0xFFFD,     //!< All vehicles are in this group.
+		GROUP_DEFAULT = 0xFFFE, //!< Vehicles not put in any other group are in this one.
+		GROUP_INVALID = 0xFFFF, //!< An invalid group id.
 	};
 
 	/**
diff --git a/src/ai/api/ai_group.hpp.sq b/src/ai/api/ai_group.hpp.sq
index 3556f5cc9..94be736b0 100644
--- a/src/ai/api/ai_group.hpp.sq
+++ b/src/ai/api/ai_group.hpp.sq
@@ -21,9 +21,9 @@ void SQAIGroup_Register(Squirrel *engine) {
 	SQAIGroup.PreRegister(engine);
 	SQAIGroup.AddConstructor<void (AIGroup::*)(), 1>(engine, "x");
 
-	SQAIGroup.DefSQConst(engine, AIGroup::ALL_GROUP,     "ALL_GROUP");
-	SQAIGroup.DefSQConst(engine, AIGroup::DEFAULT_GROUP, "DEFAULT_GROUP");
-	SQAIGroup.DefSQConst(engine, AIGroup::INVALID_GROUP, "INVALID_GROUP");
+	SQAIGroup.DefSQConst(engine, AIGroup::GROUP_ALL,     "GROUP_ALL");
+	SQAIGroup.DefSQConst(engine, AIGroup::GROUP_DEFAULT, "GROUP_DEFAULT");
+	SQAIGroup.DefSQConst(engine, AIGroup::GROUP_INVALID, "GROUP_INVALID");
 
 	SQAIGroup.DefSQStaticMethod(engine, &AIGroup::GetClassName,                "GetClassName",                1, "x");
 	SQAIGroup.DefSQStaticMethod(engine, &AIGroup::IsValidGroup,                "IsValidGroup",                2, "xi");
diff --git a/src/ai/api/ai_map.hpp b/src/ai/api/ai_map.hpp
index dbf3db08f..bf903a37e 100644
--- a/src/ai/api/ai_map.hpp
+++ b/src/ai/api/ai_map.hpp
@@ -14,7 +14,7 @@ class AIMap : public AIObject {
 public:
 #ifdef DEFINE_SCRIPT_FILES
 	enum MapType {
-		TILE_INVALID = INVALID_TILE, //!< An invalid tile for every function.
+		TILE_INVALID = INVALID_TILE, //!< Invalid TileIndex.
 	};
 #endif /* DEFINE_SCRIPT_FILES */
 
diff --git a/src/ai/api/ai_order.cpp b/src/ai/api/ai_order.cpp
index f48c5e392..1f30688e4 100644
--- a/src/ai/api/ai_order.cpp
+++ b/src/ai/api/ai_order.cpp
@@ -45,15 +45,15 @@ static OrderType GetOrderTypeByTile(TileIndex t)
 
 /* static */ bool AIOrder::IsValidVehicleOrder(VehicleID vehicle_id, OrderPosition order_position)
 {
-	return AIVehicle::IsValidVehicle(vehicle_id) && order_position >= 0 && (order_position < ::GetVehicle(vehicle_id)->GetNumOrders() || order_position == CURRENT_ORDER);
+	return AIVehicle::IsValidVehicle(vehicle_id) && order_position >= 0 && (order_position < ::GetVehicle(vehicle_id)->GetNumOrders() || order_position == ORDER_CURRENT);
 }
 
 /* static */ AIOrder::OrderPosition AIOrder::ResolveOrderPosition(VehicleID vehicle_id, OrderPosition order_position)
 {
-	if (!AIVehicle::IsValidVehicle(vehicle_id)) return INVALID_ORDER;
+	if (!AIVehicle::IsValidVehicle(vehicle_id)) return ORDER_INVALID;
 
-	if (order_position == CURRENT_ORDER) return (AIOrder::OrderPosition)::GetVehicle(vehicle_id)->cur_order_index;
-	return (order_position >= 0 && order_position < ::GetVehicle(vehicle_id)->GetNumOrders()) ? order_position : INVALID_ORDER;
+	if (order_position == ORDER_CURRENT) return (AIOrder::OrderPosition)::GetVehicle(vehicle_id)->cur_order_index;
+	return (order_position >= 0 && order_position < ::GetVehicle(vehicle_id)->GetNumOrders()) ? order_position : ORDER_INVALID;
 }
 
 
@@ -87,7 +87,7 @@ static OrderType GetOrderTypeByTile(TileIndex t)
 
 	const Order *order;
 	const Vehicle *v = ::GetVehicle(vehicle_id);
-	if (order_position == CURRENT_ORDER) {
+	if (order_position == ORDER_CURRENT) {
 		order = &v->current_order;
 	} else {
 		order = v->GetFirstOrder();
@@ -110,7 +110,7 @@ static OrderType GetOrderTypeByTile(TileIndex t)
 	if (!IsValidVehicleOrder(vehicle_id, order_position)) return AIOF_INVALID;
 
 	const Order *order;
-	if (order_position == CURRENT_ORDER) {
+	if (order_position == ORDER_CURRENT) {
 		order = &::GetVehicle(vehicle_id)->current_order;
 	} else {
 		order = ::GetVehicle(vehicle_id)->GetFirstOrder();
@@ -144,7 +144,7 @@ static OrderType GetOrderTypeByTile(TileIndex t)
 /* static */ bool AIOrder::InsertOrder(VehicleID vehicle_id, OrderPosition order_position, TileIndex destination, AIOrder::AIOrderFlags order_flags)
 {
 	/* IsValidVehicleOrder is not good enough because it does not allow appending. */
-	if (order_position == CURRENT_ORDER) order_position = AIOrder::ResolveOrderPosition(vehicle_id, order_position);
+	if (order_position == ORDER_CURRENT) order_position = AIOrder::ResolveOrderPosition(vehicle_id, order_position);
 
 	EnforcePrecondition(false, AIVehicle::IsValidVehicle(vehicle_id));
 	EnforcePrecondition(false, order_position >= 0 && order_position <= ::GetVehicle(vehicle_id)->GetNumOrders());
diff --git a/src/ai/api/ai_order.hpp b/src/ai/api/ai_order.hpp
index fbda26892..c4e9f99be 100644
--- a/src/ai/api/ai_order.hpp
+++ b/src/ai/api/ai_order.hpp
@@ -71,8 +71,8 @@ public:
 
 	/** Different constants related to the OrderPosition */
 	enum OrderPosition {
-		CURRENT_ORDER = 0xFF, //!< Constant that gets resolved to the current order.
-		INVALID_ORDER = -1,   //!< An invalid order.
+		ORDER_CURRENT = 0xFF, //!< Constant that gets resolved to the current order.
+		ORDER_INVALID = -1,   //!< An invalid order.
 	};
 
 	/**
@@ -88,7 +88,7 @@ public:
 	 * Resolves the given order index to the correct index for the given vehicle.
 	 *  If the order index was CURRENT_ORDER it will be resolved to the index of
 	 *  the current order (as shown in the order list). If the order with the
-	 *  given index does not exist it will return INVALID_ORDER.
+	 *  given index does not exist it will return ORDER_INVALID.
 	 * @param vehicle_id The vehicle to check the order index for.
 	 * @param order_position The order index to resolve.
 	 * @pre AIVehicle::IsValidVehicle(vehicle_id).
diff --git a/src/ai/api/ai_order.hpp.sq b/src/ai/api/ai_order.hpp.sq
index 4128ae029..bb2089dee 100644
--- a/src/ai/api/ai_order.hpp.sq
+++ b/src/ai/api/ai_order.hpp.sq
@@ -42,8 +42,8 @@ void SQAIOrder_Register(Squirrel *engine) {
 	SQAIOrder.DefSQConst(engine, AIOrder::AIOF_UNLOAD_FLAGS,                                "AIOF_UNLOAD_FLAGS");
 	SQAIOrder.DefSQConst(engine, AIOrder::AIOF_LOAD_FLAGS,                                  "AIOF_LOAD_FLAGS");
 	SQAIOrder.DefSQConst(engine, AIOrder::AIOF_INVALID,                                     "AIOF_INVALID");
-	SQAIOrder.DefSQConst(engine, AIOrder::CURRENT_ORDER,                                    "CURRENT_ORDER");
-	SQAIOrder.DefSQConst(engine, AIOrder::INVALID_ORDER,                                    "INVALID_ORDER");
+	SQAIOrder.DefSQConst(engine, AIOrder::ORDER_CURRENT,                                    "ORDER_CURRENT");
+	SQAIOrder.DefSQConst(engine, AIOrder::ORDER_INVALID,                                    "ORDER_INVALID");
 
 	AIError::RegisterErrorMap(STR_8831_NO_MORE_SPACE_FOR_ORDERS,         AIOrder::ERR_ORDER_TOO_MANY);
 	AIError::RegisterErrorMap(STR_0210_TOO_FAR_FROM_PREVIOUS_DESTINATIO, AIOrder::ERR_ORDER_TOO_FAR_AWAY_FROM_PREVIOUS_DESTINATION);
diff --git a/src/ai/api/ai_subsidy.cpp b/src/ai/api/ai_subsidy.cpp
index 893b65e7d..1d0ec65d1 100644
--- a/src/ai/api/ai_subsidy.cpp
+++ b/src/ai/api/ai_subsidy.cpp
@@ -25,7 +25,7 @@
 
 /* static */ AICompany::CompanyID AISubsidy::GetAwardedTo(SubsidyID subsidy_id)
 {
-	if (!IsAwarded(subsidy_id)) return AICompany::INVALID_COMPANY;
+	if (!IsAwarded(subsidy_id)) return AICompany::COMPANY_INVALID;
 
 	return (AICompany::CompanyID)((byte)GetStation(_subsidies[subsidy_id].from)->owner);
 }
diff --git a/src/ai/api/ai_tile.cpp b/src/ai/api/ai_tile.cpp
index fd694373f..29305af8a 100644
--- a/src/ai/api/ai_tile.cpp
+++ b/src/ai/api/ai_tile.cpp
@@ -146,9 +146,9 @@
 
 /* static */ AICompany::CompanyID AITile::GetOwner(TileIndex tile)
 {
-	if (!::IsValidTile(tile)) return AICompany::INVALID_COMPANY;
-	if (::IsTileType(tile, MP_HOUSE)) return AICompany::INVALID_COMPANY;
-	if (::IsTileType(tile, MP_INDUSTRY)) return AICompany::INVALID_COMPANY;
+	if (!::IsValidTile(tile)) return AICompany::COMPANY_INVALID;
+	if (::IsTileType(tile, MP_HOUSE)) return AICompany::COMPANY_INVALID;
+	if (::IsTileType(tile, MP_INDUSTRY)) return AICompany::COMPANY_INVALID;
 
 	return AICompany::ResolveCompanyID((AICompany::CompanyID)(byte)::GetTileOwner(tile));
 }
diff --git a/src/ai/api/ai_tile.hpp b/src/ai/api/ai_tile.hpp
index 298de75cb..151771cae 100644
--- a/src/ai/api/ai_tile.hpp
+++ b/src/ai/api/ai_tile.hpp
@@ -75,7 +75,7 @@ public:
 		TRANSPORT_WATER   =  2, //!< Tile with navigable waterways.
 		TRANSPORT_AIR     =  3, //!< Tile with airport.
 
-		INVALID_TRANSPORT = -1, //!< Tile without any transport type.
+		TRANSPORT_INVALID = -1, //!< Tile without any transport type.
 	};
 
 	/**
@@ -222,7 +222,7 @@ public:
 	 * Get the owner of the tile.
 	 * @param tile The tile to get the owner from.
 	 * @pre AIMap::IsValidTile(tile).
-	 * @return The CompanyID of the owner of the tile, or INVALID_COMPANY if
+	 * @return The CompanyID of the owner of the tile, or COMPANY_INVALID if
 	 *  there is no owner (grass/industry/water tiles, etc.).
 	 */
 	static AICompany::CompanyID GetOwner(TileIndex tile);
diff --git a/src/ai/api/ai_tile.hpp.sq b/src/ai/api/ai_tile.hpp.sq
index 920dc6543..78a888ca8 100644
--- a/src/ai/api/ai_tile.hpp.sq
+++ b/src/ai/api/ai_tile.hpp.sq
@@ -54,7 +54,7 @@ void SQAITile_Register(Squirrel *engine) {
 	SQAITile.DefSQConst(engine, AITile::TRANSPORT_ROAD,    "TRANSPORT_ROAD");
 	SQAITile.DefSQConst(engine, AITile::TRANSPORT_WATER,   "TRANSPORT_WATER");
 	SQAITile.DefSQConst(engine, AITile::TRANSPORT_AIR,     "TRANSPORT_AIR");
-	SQAITile.DefSQConst(engine, AITile::INVALID_TRANSPORT, "INVALID_TRANSPORT");
+	SQAITile.DefSQConst(engine, AITile::TRANSPORT_INVALID, "TRANSPORT_INVALID");
 
 	AIError::RegisterErrorMap(STR_1003_ALREADY_AT_SEA_LEVEL, AITile::ERR_TILE_TOO_HIGH);
 	AIError::RegisterErrorMap(STR_1003_ALREADY_AT_SEA_LEVEL, AITile::ERR_TILE_TOO_LOW);
diff --git a/src/ai/api/ai_town.cpp b/src/ai/api/ai_town.cpp
index 8c8ab9c02..921e5a73e 100644
--- a/src/ai/api/ai_town.cpp
+++ b/src/ai/api/ai_town.cpp
@@ -139,7 +139,7 @@
 
 /* static */ AICompany::CompanyID AITown::GetExclusiveRightsCompany(TownID town_id)
 {
-	if (!IsValidTown(town_id)) return AICompany::INVALID_COMPANY;
+	if (!IsValidTown(town_id)) return AICompany::COMPANY_INVALID;
 
 	return (AICompany::CompanyID)(int8)::GetTown(town_id)->exclusivity;
 }
@@ -170,9 +170,9 @@ extern uint GetMaskOfTownActions(int *nump, CompanyID cid, const Town *t);
 
 /* static */ AITown::TownRating AITown::GetRating(TownID town_id, AICompany::CompanyID company_id)
 {
-	if (!IsValidTown(town_id)) return INVALID_TOWN_RATING;
+	if (!IsValidTown(town_id)) return TOWN_RATING_INVALID;
 	AICompany::CompanyID company = AICompany::ResolveCompanyID(company_id);
-	if (company == AICompany::INVALID_COMPANY) return INVALID_TOWN_RATING;
+	if (company == AICompany::COMPANY_INVALID) return TOWN_RATING_INVALID;
 
 	const Town *t = ::GetTown(town_id);
 	if (!HasBit(t->have_ratings, company)) return TOWN_RATING_NONE;
diff --git a/src/ai/api/ai_town.hpp b/src/ai/api/ai_town.hpp
index 94ba91e17..f9152106f 100644
--- a/src/ai/api/ai_town.hpp
+++ b/src/ai/api/ai_town.hpp
@@ -81,7 +81,7 @@ public:
 		TOWN_RATING_VERY_GOOD,    ///< The company got an very good rating in the town.
 		TOWN_RATING_EXCELLENT,    ///< The company got an excellent rating in the town.
 		TOWN_RATING_OUTSTANDING,  ///< The company got an outstanding rating in the town.
-		INVALID_TOWN_RATING = -1, ///< The town rating for invalid towns/companies.
+		TOWN_RATING_INVALID = -1, ///< The town rating for invalid towns/companies.
 	};
 
 	/**
@@ -228,7 +228,7 @@ public:
 	 * @param town_id The town to check.
 	 * @pre IsValidTown(town_id).
 	 * @return The company that has the exclusive rights. The value
-	 *         AICompany::INVALID_COMPANY means that there are currently no
+	 *         AICompany::COMPANY_INVALID means that there are currently no
 	 *         exclusive rights given out to anyone.
 	 */
 	static AICompany::CompanyID GetExclusiveRightsCompany(TownID town_id);
@@ -267,7 +267,7 @@ public:
 	 * @param town_id The town to get the rating for.
 	 * @param company_id The company to get the rating for.
 	 * @pre IsValidTown(town_id).
-	 * @pre AICompany.ResolveCompanyID(company) != AICompany::INVALID_COMPANY.
+	 * @pre AICompany.ResolveCompanyID(company) != AICompany::COMPANY_INVALID.
 	 * @return The rating as shown to humans.
 	 */
 	static TownRating GetRating(TownID town_id, AICompany::CompanyID company_id);
diff --git a/src/ai/api/ai_town.hpp.sq b/src/ai/api/ai_town.hpp.sq
index 664503923..164f0ffa5 100644
--- a/src/ai/api/ai_town.hpp.sq
+++ b/src/ai/api/ai_town.hpp.sq
@@ -40,7 +40,7 @@ void SQAITown_Register(Squirrel *engine) {
 	SQAITown.DefSQConst(engine, AITown::TOWN_RATING_VERY_GOOD,        "TOWN_RATING_VERY_GOOD");
 	SQAITown.DefSQConst(engine, AITown::TOWN_RATING_EXCELLENT,        "TOWN_RATING_EXCELLENT");
 	SQAITown.DefSQConst(engine, AITown::TOWN_RATING_OUTSTANDING,      "TOWN_RATING_OUTSTANDING");
-	SQAITown.DefSQConst(engine, AITown::INVALID_TOWN_RATING,          "INVALID_TOWN_RATING");
+	SQAITown.DefSQConst(engine, AITown::TOWN_RATING_INVALID,          "TOWN_RATING_INVALID");
 
 	SQAITown.DefSQStaticMethod(engine, &AITown::GetClassName,               "GetClassName",               1, "x");
 	SQAITown.DefSQStaticMethod(engine, &AITown::GetMaxTownID,               "GetMaxTownID",               1, "x");
diff --git a/src/ai/api/ai_tunnel.cpp b/src/ai/api/ai_tunnel.cpp
index 1991ef89b..6c4c7b216 100644
--- a/src/ai/api/ai_tunnel.cpp
+++ b/src/ai/api/ai_tunnel.cpp
@@ -60,11 +60,11 @@ static void _DoCommandReturnBuildTunnel1(class AIInstance *instance)
 /* static */ bool AITunnel::BuildTunnel(AIVehicle::VehicleType vehicle_type, TileIndex start)
 {
 	EnforcePrecondition(false, ::IsValidTile(start));
-	EnforcePrecondition(false, vehicle_type == AIVehicle::VEHICLE_RAIL || vehicle_type == AIVehicle::VEHICLE_ROAD);
-	EnforcePrecondition(false, vehicle_type != AIVehicle::VEHICLE_RAIL || AIRail::IsRailTypeAvailable(AIRail::GetCurrentRailType()));
+	EnforcePrecondition(false, vehicle_type == AIVehicle::VT_RAIL || vehicle_type == AIVehicle::VT_ROAD);
+	EnforcePrecondition(false, vehicle_type != AIVehicle::VT_RAIL || AIRail::IsRailTypeAvailable(AIRail::GetCurrentRailType()));
 
 	uint type = 0;
-	if (vehicle_type == AIVehicle::VEHICLE_ROAD) {
+	if (vehicle_type == AIVehicle::VT_ROAD) {
 		type |= (TRANSPORT_ROAD << 9);
 		type |= RoadTypeToRoadTypes((::RoadType)AIObject::GetRoadType());
 	} else {
@@ -73,7 +73,7 @@ static void _DoCommandReturnBuildTunnel1(class AIInstance *instance)
 	}
 
 	/* For rail we do nothing special */
-	if (vehicle_type == AIVehicle::VEHICLE_RAIL) {
+	if (vehicle_type == AIVehicle::VT_RAIL) {
 		return AIObject::DoCommand(start, type, 0, CMD_BUILD_TUNNEL);
 	}
 
diff --git a/src/ai/api/ai_tunnel.hpp b/src/ai/api/ai_tunnel.hpp
index 625237905..6aa6ea4c0 100644
--- a/src/ai/api/ai_tunnel.hpp
+++ b/src/ai/api/ai_tunnel.hpp
@@ -50,7 +50,7 @@ public:
 	 * @param tile The tile that is an entrance to a tunnel or the tile where you may want to build a tunnel.
 	 * @pre AIMap::IsValidTile(tile).
 	 * @return The TileIndex that is the other end of the (would be) tunnel, or
-	 *  INVALID_TILE if no other end was found (can't build tunnel).
+	 *  TILE_INVALID if no other end was found (can't build tunnel).
 	 */
 	static TileIndex GetOtherTunnelEnd(TileIndex tile);
 
diff --git a/src/ai/api/ai_vehicle.cpp b/src/ai/api/ai_vehicle.cpp
index 9532e3caf..7427025af 100644
--- a/src/ai/api/ai_vehicle.cpp
+++ b/src/ai/api/ai_vehicle.cpp
@@ -7,6 +7,7 @@
 #include "ai_cargo.hpp"
 #include "ai_order.hpp"
 #include "ai_gamesettings.hpp"
+#include "ai_group.hpp"
 #include "../ai_instance.hpp"
 #include "../../openttd.h"
 #include "../../company_func.h"
@@ -323,21 +324,21 @@
 
 /* static */ AIVehicle::VehicleType AIVehicle::GetVehicleType(VehicleID vehicle_id)
 {
-	if (!IsValidVehicle(vehicle_id)) return VEHICLE_INVALID;
+	if (!IsValidVehicle(vehicle_id)) return VT_INVALID;
 
 	switch (::GetVehicle(vehicle_id)->type) {
-		case VEH_ROAD:     return VEHICLE_ROAD;
-		case VEH_TRAIN:    return VEHICLE_RAIL;
-		case VEH_SHIP:     return VEHICLE_WATER;
-		case VEH_AIRCRAFT: return VEHICLE_AIR;
-		default:           return VEHICLE_INVALID;
+		case VEH_ROAD:     return VT_ROAD;
+		case VEH_TRAIN:    return VT_RAIL;
+		case VEH_SHIP:     return VT_WATER;
+		case VEH_AIRCRAFT: return VT_AIR;
+		default:           return VT_INVALID;
 	}
 }
 
 /* static */ AIRoad::RoadType AIVehicle::GetRoadType(VehicleID vehicle_id)
 {
 	if (!IsValidVehicle(vehicle_id)) return AIRoad::ROADTYPE_INVALID;
-	if (GetVehicleType(vehicle_id) != VEHICLE_ROAD) return AIRoad::ROADTYPE_INVALID;
+	if (GetVehicleType(vehicle_id) != VT_ROAD) return AIRoad::ROADTYPE_INVALID;
 
 	return (AIRoad::RoadType)::GetVehicle(vehicle_id)->u.road.roadtype;
 }
@@ -370,7 +371,7 @@
 
 /* static */ GroupID AIVehicle::GetGroupID(VehicleID vehicle_id)
 {
-	if (!IsValidVehicle(vehicle_id)) return ::INVALID_GROUP;
+	if (!IsValidVehicle(vehicle_id)) return AIGroup::GROUP_INVALID;
 
 	return ::GetVehicle(vehicle_id)->group_id;
 }
@@ -378,7 +379,7 @@
 /* static */ bool AIVehicle::IsArticulated(VehicleID vehicle_id)
 {
 	if (!IsValidVehicle(vehicle_id)) return false;
-	if (GetVehicleType(vehicle_id) != VEHICLE_ROAD && GetVehicleType(vehicle_id) != VEHICLE_RAIL) return false;
+	if (GetVehicleType(vehicle_id) != VT_ROAD && GetVehicleType(vehicle_id) != VT_RAIL) return false;
 
 	const Vehicle *v = ::GetVehicle(vehicle_id);
 	switch (v->type) {
diff --git a/src/ai/api/ai_vehicle.hpp b/src/ai/api/ai_vehicle.hpp
index 84ddb4734..1336e9efe 100644
--- a/src/ai/api/ai_vehicle.hpp
+++ b/src/ai/api/ai_vehicle.hpp
@@ -68,11 +68,15 @@ public:
 	 */
 	enum VehicleType {
 		/* Order IS important, as it now matches the internal state of the game for vehicle type */
-		VEHICLE_RAIL,           //!< Rail type vehicle.
-		VEHICLE_ROAD,           //!< Road type vehicle (bus / truck).
-		VEHICLE_WATER,          //!< Water type vehicle.
-		VEHICLE_AIR,            //!< Air type vehicle.
-		VEHICLE_INVALID = 0xFF, //!< Invalid vehicle type.
+		VT_RAIL,           //!< Rail type vehicle.
+		VT_ROAD,           //!< Road type vehicle (bus / truck).
+		VT_WATER,          //!< Water type vehicle.
+		VT_AIR,            //!< Air type vehicle.
+		VT_INVALID = 0xFF, //!< Invalid vehicle type.
+
+#ifdef DEFINE_SCRIPT_FILES
+		VEHICLE_INVALID = -1, //!< Invalid VehicleID.
+#endif /* DEFINE_SCRIPT_FILES */
 	};
 
 	/**
diff --git a/src/ai/api/ai_vehicle.hpp.sq b/src/ai/api/ai_vehicle.hpp.sq
index 87dce4893..babb85306 100644
--- a/src/ai/api/ai_vehicle.hpp.sq
+++ b/src/ai/api/ai_vehicle.hpp.sq
@@ -38,10 +38,11 @@ void SQAIVehicle_Register(Squirrel *engine) {
 	SQAIVehicle.DefSQConst(engine, AIVehicle::ERR_VEHICLE_NOT_IN_DEPOT,         "ERR_VEHICLE_NOT_IN_DEPOT");
 	SQAIVehicle.DefSQConst(engine, AIVehicle::ERR_VEHICLE_IN_FLIGHT,            "ERR_VEHICLE_IN_FLIGHT");
 	SQAIVehicle.DefSQConst(engine, AIVehicle::ERR_VEHCILE_NO_POWER,             "ERR_VEHCILE_NO_POWER");
-	SQAIVehicle.DefSQConst(engine, AIVehicle::VEHICLE_RAIL,                     "VEHICLE_RAIL");
-	SQAIVehicle.DefSQConst(engine, AIVehicle::VEHICLE_ROAD,                     "VEHICLE_ROAD");
-	SQAIVehicle.DefSQConst(engine, AIVehicle::VEHICLE_WATER,                    "VEHICLE_WATER");
-	SQAIVehicle.DefSQConst(engine, AIVehicle::VEHICLE_AIR,                      "VEHICLE_AIR");
+	SQAIVehicle.DefSQConst(engine, AIVehicle::VT_RAIL,                          "VT_RAIL");
+	SQAIVehicle.DefSQConst(engine, AIVehicle::VT_ROAD,                          "VT_ROAD");
+	SQAIVehicle.DefSQConst(engine, AIVehicle::VT_WATER,                         "VT_WATER");
+	SQAIVehicle.DefSQConst(engine, AIVehicle::VT_AIR,                           "VT_AIR");
+	SQAIVehicle.DefSQConst(engine, AIVehicle::VT_INVALID,                       "VT_INVALID");
 	SQAIVehicle.DefSQConst(engine, AIVehicle::VEHICLE_INVALID,                  "VEHICLE_INVALID");
 	SQAIVehicle.DefSQConst(engine, AIVehicle::VS_RUNNING,                       "VS_RUNNING");
 	SQAIVehicle.DefSQConst(engine, AIVehicle::VS_STOPPED,                       "VS_STOPPED");