--- a/src/autoreplace_cmd.cpp
+++ b/src/autoreplace_cmd.cpp
@@ -24,6 +24,69 @@
 
 #include "table/strings.h"
 
+/** Figure out if two engines got at least one type of cargo in common (refitting if needed)
+ * @param engine_a one of the EngineIDs
+ * @param engine_b the other EngineID
+ * @param type the type of the engines
+ * @return true if they can both carry the same type of cargo (or at least one of them got no capacity at all)
+ */
+static bool EnginesGotCargoInCommon(EngineID engine_a, EngineID engine_b, VehicleType type)
+{
+	uint32 available_cargos_a = GetUnionOfArticulatedRefitMasks(engine_a, type, true);
+	uint32 available_cargos_b = GetUnionOfArticulatedRefitMasks(engine_b, type, true);
+	return (available_cargos_a == 0 || available_cargos_b == 0 || (available_cargos_a & available_cargos_b) != 0);
+}
+
+/**
+ * Checks some basic properties whether autoreplace is allowed
+ * @param from Origin engine
+ * @param to Destination engine
+ * @param player Player to check for
+ * @return true if autoreplace is allowed
+ */
+bool CheckAutoreplaceValidity(EngineID from, EngineID to, PlayerID player)
+{
+	/* First we make sure that it's a valid type the user requested
+	 * check that it's an engine that is in the engine array */
+	if (!IsEngineIndex(from) || !IsEngineIndex(to)) return false;
+
+	/* we can't replace an engine into itself (that would be autorenew) */
+	if (from == to) return false;
+
+	VehicleType type = GetEngine(from)->type;
+
+	/* check that the new vehicle type is available to the player and its type is the same as the original one */
+	if (!IsEngineBuildable(to, type, player)) return false;
+
+	switch (type) {
+		case VEH_TRAIN: {
+			const RailVehicleInfo *rvi_from = RailVehInfo(from);
+			const RailVehicleInfo *rvi_to   = RailVehInfo(to);
+
+			/* make sure the railtypes are compatible */
+			if ((GetRailTypeInfo(rvi_from->railtype)->compatible_railtypes & GetRailTypeInfo(rvi_to->railtype)->compatible_railtypes) == 0) return false;
+
+			/* make sure we do not replace wagons with engines or vise versa */
+			if ((rvi_from->railveh_type == RAILVEH_WAGON) != (rvi_to->railveh_type == RAILVEH_WAGON)) return false;
+			break;
+		}
+
+		case VEH_ROAD:
+			/* make sure that we do not replace a tram with a normal road vehicles or vise versa */
+			if (HasBit(EngInfo(from)->misc_flags, EF_ROAD_TRAM) != HasBit(EngInfo(to)->misc_flags, EF_ROAD_TRAM)) return false;
+			break;
+
+		case VEH_AIRCRAFT:
+			/* make sure that we do not replace a plane with a helicopter or vise versa */
+			if ((AircraftVehInfo(from)->subtype & AIR_CTOL) != (AircraftVehInfo(to)->subtype & AIR_CTOL)) return false;
+			break;
+
+		default: break;
+	}
+
+	/* the engines needs to be able to carry the same cargo */
+	return EnginesGotCargoInCommon(from, to, type);
+}
 
 /*
  * move the cargo from one engine to another if possible

--- a/src/autoreplace_func.h
+++ b/src/autoreplace_func.h
@@ -100,4 +100,6 @@
 	return RemoveEngineReplacement(&p->engine_renew_list, engine, group, flags);
 }
 
+bool CheckAutoreplaceValidity(EngineID from, EngineID to, PlayerID player);
+
 #endif /* AUTOREPLACE_FUNC_H */

--- a/src/autoreplace_gui.cpp
+++ b/src/autoreplace_gui.cpp
@@ -23,7 +23,6 @@
 #include "engine_base.h"
 #include "window_gui.h"
 #include "engine_gui.h"
-#include "articulated_vehicles.h"
 
 #include "table/sprites.h"
 #include "table/strings.h"
@@ -99,19 +98,6 @@
 	InvalidateWindowClassesData(WC_BUILD_VEHICLE); // The build windows needs updating as well
 }
 
-/** Figure out if two engines got at least one type of cargo in common (refitting if needed)
- * @param engine_a one of the EngineIDs
- * @param engine_b the other EngineID
- * @param type the type of the engines
- * @return true if they can both carry the same type of cargo (or at least one of them got no capacity at all)
- */
-static bool EnginesGotCargoInCommon(EngineID engine_a, EngineID engine_b, VehicleType type)
-{
-	uint32 available_cargos_a = GetUnionOfArticulatedRefitMasks(engine_a, type, true);
-	uint32 available_cargos_b = GetUnionOfArticulatedRefitMasks(engine_b, type, true);
-	return (available_cargos_a == 0 || available_cargos_b == 0 || (available_cargos_a & available_cargos_b) != 0);
-}
-
 /**
  * Window for the autoreplacing of vehicles.
  */
@@ -143,10 +129,6 @@
 		if (draw_left && show_engines) {
 			/* Ensure that the railtype is specific to the selected one */
 			if (rvi->railtype != this->sel_railtype) return false;
-		} else {
-			/* Ensure that it's a compatible railtype to the selected one (like electric <-> diesel)
-			 * The vehicle do not have to have power on the railtype in question, only able to drive (pulled if needed) */
-			if (!IsCompatibleRail(rvi->railtype, this->sel_railtype)) return false;
 		}
 		return true;
 	}
@@ -177,13 +159,7 @@
 				/* Skip drawing the engines we don't have any of and haven't set for replacement */
 				if (num_engines == 0 && EngineReplacementForPlayer(GetPlayer(_local_player), eid, selected_group) == INVALID_ENGINE) continue;
 			} else {
-				/* This is for engines we can replace to and they should depend on what we selected to replace from */
-				if (!IsEngineBuildable(eid, type, _local_player)) continue; // we need to be able to build the engine
-				if (!EnginesGotCargoInCommon(eid, this->sel_engine[0], type)) continue; // the engines needs to be able to carry the same cargo
-
-				/* Road vehicles can't be replaced by trams and vice-versa */
-				if (type == VEH_ROAD && HasBit(EngInfo(this->sel_engine[0])->misc_flags, EF_ROAD_TRAM) != HasBit(e->info.misc_flags, EF_ROAD_TRAM)) continue;
-				if (eid == this->sel_engine[0]) continue; // we can't replace an engine into itself (that would be autorenew)
+				if (!CheckAutoreplaceValidity(this->sel_engine[0], eid, _local_player)) continue;
 			}
 
 			*list->Append() = eid;

--- a/src/players.cpp
+++ b/src/players.cpp
@@ -717,21 +717,7 @@
 
 			if (!IsValidGroupID(id_g) && !IsAllGroupID(id_g) && !IsDefaultGroupID(id_g)) return CMD_ERROR;
 			if (new_engine_type != INVALID_ENGINE) {
-				/* First we make sure that it's a valid type the user requested
-				 * check that it's an engine that is in the engine array */
-				if (!IsEngineIndex(new_engine_type)) return CMD_ERROR;
-
-				/* check that the new vehicle type is the same as the original one */
-				if (GetEngine(old_engine_type)->type != GetEngine(new_engine_type)->type) return CMD_ERROR;
-
-				/* make sure that we do not replace a plane with a helicopter or vise versa */
-				if (GetEngine(new_engine_type)->type == VEH_AIRCRAFT &&
-						(AircraftVehInfo(old_engine_type)->subtype & AIR_CTOL) != (AircraftVehInfo(new_engine_type)->subtype & AIR_CTOL)) {
-					return CMD_ERROR;
-				}
-
-				/* make sure that the player can actually buy the new engine */
-				if (!HasBit(GetEngine(new_engine_type)->player_avail, _current_player)) return CMD_ERROR;
+				if (!CheckAutoreplaceValidity(old_engine_type, new_engine_type, _current_player)) return CMD_ERROR;
 
 				cost = AddEngineReplacementForPlayer(p, old_engine_type, new_engine_type, id_g, flags);
 			} else {