diff --git a/src/newgrf/newgrf_act0_railtypes.cpp b/src/newgrf/newgrf_act0_railtypes.cpp
index 9db6f6c7b5..0ab9fdbb9e 100644
--- a/src/newgrf/newgrf_act0_railtypes.cpp
+++ b/src/newgrf/newgrf_act0_railtypes.cpp
@@ -29,14 +29,15 @@ static ChangeInfoResult RailTypeChangeInfo(uint first, uint last, int prop, Byte
 	ChangeInfoResult ret = CIR_SUCCESS;
 
 	extern RailTypeInfo _railtypes[RAILTYPE_END];
+	const auto &type_map = _cur_gps.grffile->railtype_map;
 
-	if (last > RAILTYPE_END) {
-		GrfMsg(1, "RailTypeChangeInfo: Rail type {} is invalid, max {}, ignoring", last, RAILTYPE_END);
+	if (last > std::size(type_map)) {
+		GrfMsg(1, "RailTypeChangeInfo: Rail type {} is invalid, max {}, ignoring", last, std::size(type_map));
 		return CIR_INVALID_ID;
 	}
 
 	for (uint id = first; id < last; ++id) {
-		RailType rt = _cur_gps.grffile->railtype_map[id];
+		RailType rt = type_map[id];
 		if (rt == INVALID_RAILTYPE) return CIR_INVALID_ID;
 
 		RailTypeInfo *rti = &_railtypes[rt];
@@ -163,9 +164,10 @@ static ChangeInfoResult RailTypeReserveInfo(uint first, uint last, int prop, Byt
 	ChangeInfoResult ret = CIR_SUCCESS;
 
 	extern RailTypeInfo _railtypes[RAILTYPE_END];
+	auto &type_map = _cur_gps.grffile->railtype_map;
 
-	if (last > RAILTYPE_END) {
-		GrfMsg(1, "RailTypeReserveInfo: Rail type {} is invalid, max {}, ignoring", last, RAILTYPE_END);
+	if (last > std::size(type_map)) {
+		GrfMsg(1, "RailTypeReserveInfo: Rail type {} is invalid, max {}, ignoring", last, std::size(type_map));
 		return CIR_INVALID_ID;
 	}
 
@@ -182,7 +184,7 @@ static ChangeInfoResult RailTypeReserveInfo(uint first, uint last, int prop, Byt
 					rt = AllocateRailType(rtl);
 				}
 
-				_cur_gps.grffile->railtype_map[id] = rt;
+				type_map[id] = rt;
 				break;
 			}
 
@@ -199,10 +201,10 @@ static ChangeInfoResult RailTypeReserveInfo(uint first, uint last, int prop, Byt
 				break;
 
 			case 0x1D: // Alternate rail type label list
-				if (_cur_gps.grffile->railtype_map[id] != INVALID_RAILTYPE) {
+				if (type_map[id] != INVALID_RAILTYPE) {
 					int n = buf.ReadByte();
 					for (int j = 0; j != n; j++) {
-						_railtypes[_cur_gps.grffile->railtype_map[id]].alternate_labels.push_back(std::byteswap(buf.ReadDWord()));
+						_railtypes[type_map[id]].alternate_labels.push_back(std::byteswap(buf.ReadDWord()));
 					}
 					break;
 				}
diff --git a/src/newgrf/newgrf_act0_roadtypes.cpp b/src/newgrf/newgrf_act0_roadtypes.cpp
index d655c99b7e..2eff6b05fd 100644
--- a/src/newgrf/newgrf_act0_roadtypes.cpp
+++ b/src/newgrf/newgrf_act0_roadtypes.cpp
@@ -30,10 +30,10 @@ static ChangeInfoResult RoadTypeChangeInfo(uint first, uint last, int prop, Byte
 	ChangeInfoResult ret = CIR_SUCCESS;
 
 	extern RoadTypeInfo _roadtypes[ROADTYPE_END];
-	std::array<RoadType, ROADTYPE_END> &type_map = (rtt == RTT_TRAM) ? _cur_gps.grffile->tramtype_map : _cur_gps.grffile->roadtype_map;
+	const auto &type_map = (rtt == RTT_TRAM) ? _cur_gps.grffile->tramtype_map : _cur_gps.grffile->roadtype_map;
 
-	if (last > ROADTYPE_END) {
-		GrfMsg(1, "RoadTypeChangeInfo: Road type {} is invalid, max {}, ignoring", last, ROADTYPE_END);
+	if (last > std::size(type_map)) {
+		GrfMsg(1, "RoadTypeChangeInfo: Road type {} is invalid, max {}, ignoring", last, std::size(type_map));
 		return CIR_INVALID_ID;
 	}
 
@@ -151,10 +151,10 @@ static ChangeInfoResult RoadTypeReserveInfo(uint first, uint last, int prop, Byt
 	ChangeInfoResult ret = CIR_SUCCESS;
 
 	extern RoadTypeInfo _roadtypes[ROADTYPE_END];
-	std::array<RoadType, ROADTYPE_END> &type_map = (rtt == RTT_TRAM) ? _cur_gps.grffile->tramtype_map : _cur_gps.grffile->roadtype_map;
+	auto &type_map = (rtt == RTT_TRAM) ? _cur_gps.grffile->tramtype_map : _cur_gps.grffile->roadtype_map;
 
-	if (last > ROADTYPE_END) {
-		GrfMsg(1, "RoadTypeReserveInfo: Road type {} is invalid, max {}, ignoring", last, ROADTYPE_END);
+	if (last > std::size(type_map)) {
+		GrfMsg(1, "RoadTypeReserveInfo: Road type {} is invalid, max {}, ignoring", last, std::size(type_map));
 		return CIR_INVALID_ID;
 	}
 
diff --git a/src/newgrf/newgrf_act3.cpp b/src/newgrf/newgrf_act3.cpp
index 2f060c1fca..3ec90c87b7 100644
--- a/src/newgrf/newgrf_act3.cpp
+++ b/src/newgrf/newgrf_act3.cpp
@@ -268,7 +268,8 @@ struct RailTypeMapSpriteGroupHandler : MapSpriteGroupHandler {
 	{
 		if (cid >= RTSG_END) return;
 
-		RailType railtype = local_id < RAILTYPE_END ? _cur_gps.grffile->railtype_map[local_id] : INVALID_RAILTYPE;
+		const auto &type_map = _cur_gps.grffile->railtype_map;
+		RailType railtype = local_id < std::size(type_map) ? type_map[local_id] : INVALID_RAILTYPE;
 		if (railtype == INVALID_RAILTYPE) return;
 
 		extern RailTypeInfo _railtypes[RAILTYPE_END];
@@ -286,8 +287,8 @@ struct RoadTypeMapSpriteGroupHandler : MapSpriteGroupHandler {
 	{
 		if (cid >= ROTSG_END) return;
 
-		std::array<RoadType, ROADTYPE_END> &type_map = (TRoadTramType == RTT_TRAM) ? _cur_gps.grffile->tramtype_map : _cur_gps.grffile->roadtype_map;
-		RoadType roadtype = local_id < ROADTYPE_END ? type_map[local_id] : INVALID_ROADTYPE;
+		const auto &type_map = (TRoadTramType == RTT_TRAM) ? _cur_gps.grffile->tramtype_map : _cur_gps.grffile->roadtype_map;
+		RoadType roadtype = local_id < std::size(type_map) ? type_map[local_id] : INVALID_ROADTYPE;
 		if (roadtype == INVALID_ROADTYPE) return;
 
 		extern RoadTypeInfo _roadtypes[ROADTYPE_END];