Add a dedicated setting to enable ship collision avoidance.

src/lang/english.txt

@@ -1253,6 +1253,8 @@ STR_CONFIG_SETTING_STOP_ON_COMPETITOR_ROAD_HELPTEXT             :Allow construct
 STR_CONFIG_SETTING_DYNAMIC_ENGINES_EXISTING_VEHICLES            :{WHITE}Changing this setting is not possible when there are vehicles
 STR_CONFIG_SETTING_INFRASTRUCTURE_MAINTENANCE                   :Infrastructure maintenance: {STRING2}
 STR_CONFIG_SETTING_INFRASTRUCTURE_MAINTENANCE_HELPTEXT          :When enabled, infrastructure causes maintenance costs. The cost grows over-proportional with the network size, thus affecting bigger companies more than smaller ones
+STR_CONFIG_SETTING_SHIP_COLLISION_AVOIDANCE                     :Ships avoid collisions: {STRING2}
+STR_CONFIG_SETTING_SHIP_COLLISION_AVOIDANCE_HELPTEXT            :When enabled, ships try to avoid passing through each other. Requires 90° turns to be forbidden.
 
 STR_CONFIG_SETTING_NEVER_EXPIRE_AIRPORTS                        :Airports never expire: {STRING2}
 STR_CONFIG_SETTING_NEVER_EXPIRE_AIRPORTS_HELPTEXT               :Enabling this setting makes each airport type stay available forever after its introduction

src/settings_gui.cpp

@@ -1612,6 +1612,7 @@ static SettingsContainer &GetSettingsTree()
 				physics->Add(new SettingEntry("vehicle.roadveh_slope_steepness"));
 				physics->Add(new SettingEntry("vehicle.smoke_amount"));
 				physics->Add(new SettingEntry("vehicle.plane_speed"));
+				physics->Add(new SettingEntry("vehicle.ship_collision_avoidance"));
 			}
 
 			SettingsPage *routing = vehicles->Add(new SettingsPage(STR_CONFIG_SETTING_VEHICLES_ROUTING));

src/settings_type.h

@@ -462,6 +462,7 @@ struct VehicleSettings {
 	byte   extend_vehicle_life;              ///< extend vehicle life by this many years
 	byte   road_side;                        ///< the side of the road vehicles drive on
 	uint8  plane_crashes;                    ///< number of plane crashes, 0 = none, 1 = reduced, 2 = normal
+	bool   ship_collision_avoidance;         ///< ships try to avoid colliding with each other
 };
 
 /** Settings related to the economy. */

src/ship_cmd.cpp

@@ -620,7 +620,7 @@ static void ShipController(Ship *v)
 			if (track == INVALID_TRACK) goto reverse_direction;
 
 			/* Try to avoid collision and keep distance between each other. */
-			if (_settings_game.pf.forbid_90_deg && DistanceManhattan(v->dest_tile, gp.new_tile) > 3) {
+			if (_settings_game.pf.forbid_90_deg && _settings_game.vehicle.ship_collision_avoidance && DistanceManhattan(v->dest_tile, gp.new_tile) > 3) {
 				if (HasVehicleOnPos(gp.new_tile, NULL, &FindShipOnTile) ||
 						HasVehicleOnPos(TileAddByDiagDir(gp.new_tile, _diagdir_to_next_tile[track][diagdir]), NULL, &FindShipOnTile)) {
 

src/table/settings.ini

@@ -1138,6 +1138,15 @@ strhelp  = STR_CONFIG_SETTING_PLANE_CRASHES_HELPTEXT
 strval   = STR_CONFIG_SETTING_PLANE_CRASHES_NONE
 cat      = SC_BASIC
 
+[SDT_BOOL]
+base     = GameSettings
+var      = vehicle.ship_collision_avoidance
+def      = true
+str      = STR_CONFIG_SETTING_SHIP_COLLISION_AVOIDANCE
+strhelp  = STR_CONFIG_SETTING_SHIP_COLLISION_AVOIDANCE_HELPTEXT
+patxname = ""ship_collision_avoidance.vehicle.ship_collision_avoidance""
+cat      = SC_BASIC
+
 ; station.join_stations
 [SDT_NULL]
 length   = 1