diff --git a/vehicle_gui.c b/vehicle_gui.c
--- a/vehicle_gui.c
+++ b/vehicle_gui.c
@@ -421,7 +421,7 @@ static void train_engine_drawing_loop(in
 		const RailVehicleInfo *rvi = RailVehInfo(i);
 		const EngineInfo *info = &_engine_info[i];
 
-		if (p->engine_replacement[i] == INVALID_ENGINE && _player_num_engines[i] == 0 && show_outdated) continue;
+		if (!EngineHasReplacement(p, i) && _player_num_engines[i] == 0 && show_outdated) continue;
 
 		if (rvi->power == 0 && !show_cars)   // disables display of cars (works since they do not have power)
 			continue;
@@ -480,7 +480,7 @@ static void SetupScrollStuffForReplaceWi
 				const EngineInfo *info = &_engine_info[engine_id];
 
 				if (ENGINE_AVAILABLE && RailVehInfo(engine_id)->power && e->railtype == railtype) {
-					if (_player_num_engines[engine_id] > 0 || p->engine_replacement[engine_id] != INVALID_ENGINE) {
+					if (_player_num_engines[engine_id] > 0 || EngineHasReplacement(p, engine_id)) {
 						if (sel[0] == 0) selected_id[0] = engine_id;
 						count++;
 						sel[0]--;
@@ -503,7 +503,7 @@ static void SetupScrollStuffForReplaceWi
 
 			do {
 				info = &_engine_info[engine_id];
-				if (_player_num_engines[engine_id] > 0 || p->engine_replacement[engine_id] != INVALID_ENGINE) {
+				if (_player_num_engines[engine_id] > 0 || EngineHasReplacement(p, engine_id)) {
 					if (sel[0] == 0) selected_id[0] = engine_id;
 					count++;
 					sel[0]--;
@@ -536,7 +536,7 @@ static void SetupScrollStuffForReplaceWi
 
 			do {
 				info = &_engine_info[engine_id];
-				if (_player_num_engines[engine_id] > 0 || p->engine_replacement[engine_id] != INVALID_ENGINE) {
+				if (_player_num_engines[engine_id] > 0 || EngineHasReplacement(p, engine_id)) {
 					if (sel[0] == 0) selected_id[0] = engine_id;
 					count++;
 					sel[0]--;
@@ -571,7 +571,7 @@ static void SetupScrollStuffForReplaceWi
 
 			do {
 				info = &_engine_info[engine_id];
-				if (_player_num_engines[engine_id] > 0 || p->engine_replacement[engine_id] != INVALID_ENGINE) {
+				if (_player_num_engines[engine_id] > 0 || EngineHasReplacement(p, engine_id)) {
 					count++;
 					if (sel[0] == 0) selected_id[0] = engine_id;
 					sel[0]--;
@@ -650,7 +650,7 @@ static void DrawEngineArrayInReplaceWind
 
 				do {
 					info = &_engine_info[engine_id];
-					if (_player_num_engines[engine_id] > 0 || p->engine_replacement[engine_id] != INVALID_ENGINE) {
+					if (_player_num_engines[engine_id] > 0 || EngineHasReplacement(p, engine_id)) {
 						if (IS_INT_INSIDE(--pos, -w->vscroll.cap, 0)) {
 							DrawString(x+59, y+2, GetCustomEngineName(engine_id), sel[0]==0 ? 0xC : 0x10);
 							DrawRoadVehEngine(x+29, y+6, engine_id, _player_num_engines[engine_id] > 0 ? SPRITE_PALETTE(PLAYER_SPRITE_COLOR(_local_player)) : PALETTE_CRASH);
@@ -687,7 +687,7 @@ static void DrawEngineArrayInReplaceWind
 
 				do {
 					info = &_engine_info[engine_id];
-					if (_player_num_engines[engine_id] > 0 || p->engine_replacement[engine_id] != INVALID_ENGINE) {
+					if (_player_num_engines[engine_id] > 0 || EngineHasReplacement(p, engine_id)) {
 						if (IS_INT_INSIDE(--pos, -w->vscroll.cap, 0)) {
 							DrawString(x+75, y+7, GetCustomEngineName(engine_id), sel[0]==0 ? 0xC : 0x10);
 							DrawShipEngine(x+35, y+10, engine_id, _player_num_engines[engine_id] > 0 ? SPRITE_PALETTE(PLAYER_SPRITE_COLOR(_local_player)) : PALETTE_CRASH);
@@ -722,7 +722,7 @@ static void DrawEngineArrayInReplaceWind
 
 				do {
 					info = &_engine_info[engine_id];
-					if (_player_num_engines[engine_id] > 0 || p->engine_replacement[engine_id] != INVALID_ENGINE) {
+					if (_player_num_engines[engine_id] > 0 || EngineHasReplacement(p, engine_id)) {
 						if (sel[0] == 0) selected_id[0] = engine_id;
 						if (IS_INT_INSIDE(--pos, -w->vscroll.cap, 0)) {
 							DrawString(x+62, y+7, GetCustomEngineName(engine_id), sel[0]==0 ? 0xC : 0x10);
@@ -835,7 +835,7 @@ static void ReplaceVehicleWndProc(Window
 				if (selected_id[0] == -1 ||
 						selected_id[1] == -1 ||
 						selected_id[0] == selected_id[1] ||
-						p->engine_replacement[selected_id[0]] == selected_id[1]) {
+						EngineReplacement(p, selected_id[0]) == selected_id[1]) {
 					SETBIT(w->disabled_state, 4);
 				} else {
 					CLRBIT(w->disabled_state, 4);
@@ -845,7 +845,7 @@ static void ReplaceVehicleWndProc(Window
 				//    The left list (existing vehicle) is empty
 				// or The selected vehicle has no replacement set up
 				if (selected_id[0] == -1 ||
-						p->engine_replacement[selected_id[0]] == INVALID_ENGINE) {
+						!EngineHasReplacement(p, selected_id[0])) {
 					SETBIT(w->disabled_state, 6);
 				} else {
 					CLRBIT(w->disabled_state, 6);
@@ -863,10 +863,10 @@ static void ReplaceVehicleWndProc(Window
 
 				// sets up the string for the vehicle that is being replaced to
 				if (selected_id[0] != -1) {
-					if (p->engine_replacement[selected_id[0]] == INVALID_ENGINE) {
+					if (!EngineHasReplacement(p, selected_id[0])) {
 						SetDParam(0, STR_NOT_REPLACING);
 					} else {
-						SetDParam(0, GetCustomEngineName(p->engine_replacement[selected_id[0]]));
+						SetDParam(0, GetCustomEngineName(EngineReplacement(p, selected_id[0])));
 					}
 				} else {
 					SetDParam(0, STR_NOT_REPLACING_VEHICLE_SELECTED);