working with parameters to turn on and off now, still haven't fixed the articulated vehicles exception though

src/lang/english.txt

@@ -1525,6 +1525,9 @@ STR_CONFIG_SETTING_ROAD_SIDE_HELPTEXT                           :Choose the driv
 STR_CONFIG_SETTING_ROAD_SIDE_LEFT                               :Drive on left
 STR_CONFIG_SETTING_ROAD_SIDE_RIGHT                              :Drive on right
 
+STR_CONFIG_SETTING_DIAGONAL_ROADS                               :Diagonal Roads: {STRING2}
+STR_CONFIG_SETTING_DIAGONAL_ROADS_HELPTEXT                      :Choose whether to turn smooth corners into diagonal roads
+
 STR_CONFIG_SETTING_HEIGHTMAP_ROTATION                           :Heightmap rotation: {STRING2}
 ###length 2
 STR_CONFIG_SETTING_HEIGHTMAP_ROTATION_COUNTER_CLOCKWISE         :Counter clockwise

src/roadveh_cmd.cpp

@@ -1315,7 +1315,7 @@ static bool RoadVehLeaveDepot(RoadVehicle *v, bool first)
 	v->direction = DiagDirToDir(dir);
 
 	Trackdir tdir = DiagDirToDiagTrackdir(dir);
-	const RoadDriveEntry *rdp = _road_drive_data[GetRoadTramType(v->roadtype)][(_settings_game.vehicle.road_side << RVS_DRIVE_SIDE) + tdir];
+	const RoadDriveEntry *rdp = _road_drive_data[GetRoadTramType(v->roadtype) + (_settings_game.vehicle.diagonal_roads * 2)][(_settings_game.vehicle.road_side << RVS_DRIVE_SIDE) + tdir];
 
 	int x = TileX(v->tile) * TILE_SIZE + (rdp[RVC_DEPOT_START_FRAME].x & 0xF);
 	int y = TileY(v->tile) * TILE_SIZE + (rdp[RVC_DEPOT_START_FRAME].y & 0xF);
@@ -1713,7 +1713,7 @@ bool IndividualRoadVehicleController(RoadVehicle *v, const RoadVehicle *prev)
 	/* Get move position data for next frame.
 	 * For a drive-through road stop use 'straight road' move data.
 	 * In this case v->state is masked to give the road stop entry direction. */
-	RoadDriveEntry rd = _road_drive_data[GetRoadTramType(v->roadtype)][(
+	RoadDriveEntry rd = _road_drive_data[GetRoadTramType(v->roadtype) + (_settings_game.vehicle.diagonal_roads * 2)][(
 		(HasBit(v->state, RVS_IN_DT_ROAD_STOP) ? v->state & RVSB_ROAD_STOP_TRACKDIR_MASK : v->state) +
 		(_settings_game.vehicle.road_side << RVS_DRIVE_SIDE)) ^ v->overtaking][v->frame + 1];
 
@@ -1812,7 +1812,7 @@ again:
 		}
 
 		/* Get position data for first frame on the new tile */
-		const RoadDriveEntry *rdp = _road_drive_data[GetRoadTramType(v->roadtype)][(dir + (_settings_game.vehicle.road_side << RVS_DRIVE_SIDE)) ^ v->overtaking];
+		const RoadDriveEntry *rdp = _road_drive_data[GetRoadTramType(v->roadtype) + (_settings_game.vehicle.diagonal_roads * 2)][(dir + (_settings_game.vehicle.road_side << RVS_DRIVE_SIDE)) ^ v->overtaking];
 
 		int x = TileX(tile) * TILE_SIZE + rdp[start_frame].x;
 		int y = TileY(tile) * TILE_SIZE + rdp[start_frame].y;
@@ -1928,7 +1928,7 @@ again:
 			return false;
 		}
 
-		const RoadDriveEntry *rdp = _road_drive_data[GetRoadTramType(v->roadtype)][(_settings_game.vehicle.road_side << RVS_DRIVE_SIDE) + dir];
+		const RoadDriveEntry *rdp = _road_drive_data[GetRoadTramType(v->roadtype) + (_settings_game.vehicle.diagonal_roads * 2)][(_settings_game.vehicle.road_side << RVS_DRIVE_SIDE) + dir];
 
 		int x = TileX(v->tile) * TILE_SIZE + rdp[turn_around_start_frame].x;
 		int y = TileY(v->tile) * TILE_SIZE + rdp[turn_around_start_frame].y;

src/settings_gui.cpp

@@ -2355,6 +2355,7 @@ static SettingsContainer &GetSettingsTree()
 			genworld->Add(new SettingEntry("game_creation.height_affects_rocks"));
 			genworld->Add(new SettingEntry("game_creation.tree_placer"));
 			genworld->Add(new SettingEntry("vehicle.road_side"));
+			genworld->Add(new SettingEntry("vehicle.diagonal_roads"));
 			genworld->Add(new SettingEntry("economy.larger_towns"));
 			genworld->Add(new SettingEntry("economy.initial_city_size"));
 			genworld->Add(new SettingEntry("economy.town_layout"));

src/settings_type.h

@@ -665,6 +665,7 @@ struct VehicleSettings {
 	Year   no_introduce_vehicles_after;      ///< do not introduce vehicles after this year
 	byte   extend_vehicle_life;              ///< extend vehicle life by this many years
 	byte   road_side;                        ///< the side of the road vehicles drive on
+	bool   diagonal_roads;                   ///< whether road corners are turned into diagonals
 	uint8  plane_crashes;                    ///< number of plane crashes, 0 = none, 1 = reduced, 2 = normal
 	bool   adjacent_crossings;               ///< enable closing of adjacent level crossings
 	bool   safer_crossings;                  ///< enable safer level crossings

src/table/settings/settings.ini

@@ -625,6 +625,14 @@ pre_cb   = CheckRoadSide
 post_cb  = RoadSideChanged
 cat      = SC_BASIC
 
+[SDT_BOOL]
+var      = vehicle.diagonal_roads
+flags    = SF_NO_NETWORK
+def      = false
+str      = STR_CONFIG_SETTING_DIAGONAL_ROADS
+strhelp  = STR_CONFIG_SETTING_DIAGONAL_ROADS_HELPTEXT
+cat      = SC_EXPERT
+
 ; Construction
 
 [SDT_VAR]