diff --git a/src/elrail.cpp b/src/elrail.cpp
index 108dc419cf..15ff1b0fac 100644
--- a/src/elrail.cpp
+++ b/src/elrail.cpp
@@ -165,20 +165,20 @@ static TrackBits MaskWireBits(TileIndex t, TrackBits tracks)
 /**
  * Get the base wire sprite to use.
  */
-static inline SpriteID GetWireBase(TileIndex tile, bool upper_halftile = false)
+static inline SpriteID GetWireBase(TileIndex tile, TileContext context = TCX_NORMAL)
 {
 	const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(tile));
-	SpriteID wires = GetCustomRailSprite(rti, tile, RTSG_WIRES, upper_halftile);
+	SpriteID wires = GetCustomRailSprite(rti, tile, RTSG_WIRES, context);
 	return wires == 0 ? SPR_WIRE_BASE : wires;
 }
 
 /**
  * Get the base pylon sprite to use.
  */
-static inline SpriteID GetPylonBase(TileIndex tile, bool upper_halftile = false)
+static inline SpriteID GetPylonBase(TileIndex tile, TileContext context = TCX_NORMAL)
 {
 	const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(tile));
-	SpriteID pylons = GetCustomRailSprite(rti, tile, RTSG_PYLONS, upper_halftile);
+	SpriteID pylons = GetCustomRailSprite(rti, tile, RTSG_PYLONS, context);
 	return pylons == 0 ? SPR_PYLON_BASE : pylons;
 }
 
@@ -300,7 +300,7 @@ static void DrawCatenaryRailway(const TileInfo *ti)
 	AdjustTileh(ti->tile, &tileh[TS_HOME]);
 
 	SpriteID pylon_normal = GetPylonBase(ti->tile);
-	SpriteID pylon_halftile = (halftile_corner != CORNER_INVALID) ? GetPylonBase(ti->tile, true) : pylon_normal;
+	SpriteID pylon_halftile = (halftile_corner != CORNER_INVALID) ? GetPylonBase(ti->tile, TCX_UPPER_HALFTILE) : pylon_normal;
 
 	for (DiagDirection i = DIAGDIR_BEGIN; i < DIAGDIR_END; i++) {
 		static const uint edge_corners[] = {
@@ -439,7 +439,7 @@ static void DrawCatenaryRailway(const TileInfo *ti)
 	}
 
 	SpriteID wire_normal = GetWireBase(ti->tile);
-	SpriteID wire_halftile = (halftile_corner != CORNER_INVALID) ? GetWireBase(ti->tile, true) : wire_normal;
+	SpriteID wire_halftile = (halftile_corner != CORNER_INVALID) ? GetWireBase(ti->tile, TCX_UPPER_HALFTILE) : wire_normal;
 	Track halftile_track;
 	switch (halftile_corner) {
 		case CORNER_W: halftile_track = TRACK_LEFT; break;
@@ -501,14 +501,14 @@ void DrawCatenaryOnBridge(const TileInfo *ti)
 
 	height = GetBridgeHeight(end);
 
-	SpriteID wire_base = GetWireBase(start);
+	SpriteID wire_base = GetWireBase(end, TCX_ON_BRIDGE);
 
 	AddSortableSpriteToDraw(wire_base + sss->image_offset, PAL_NONE, ti->x + sss->x_offset, ti->y + sss->y_offset,
 		sss->x_size, sss->y_size, sss->z_size, height + sss->z_offset,
 		IsTransparencySet(TO_CATENARY)
 	);
 
-	SpriteID pylon_base = GetPylonBase(start);
+	SpriteID pylon_base = GetPylonBase(end, TCX_ON_BRIDGE);
 
 	/* Finished with wires, draw pylons
 	 * every other tile needs a pylon on the northern end */
diff --git a/src/newgrf_commons.cpp b/src/newgrf_commons.cpp
index 5a1de575f0..c5a2ebea90 100644
--- a/src/newgrf_commons.cpp
+++ b/src/newgrf_commons.cpp
@@ -21,6 +21,7 @@
 #include "station_map.h"
 #include "tree_map.h"
 #include "tunnelbridge_map.h"
+#include "variables.h"
 #include "core/mem_func.hpp"
 
 /** Constructor of generic class
@@ -283,7 +284,7 @@ void IndustryTileOverrideManager::SetEntitySpec(const IndustryTileSpec *its)
  * @param upper_halftile If true, query upper halftile in case of rail tiles.
  * @return value corresponding to the grf expected format:
  *         Terrain type: 0 normal, 1 desert, 2 rainforest, 4 on or above snowline */
-uint32 GetTerrainType(TileIndex tile, bool upper_halftile)
+uint32 GetTerrainType(TileIndex tile, TileContext context)
 {
 	switch (_settings_game.game_creation.landscape) {
 		case LT_TROPIC: return GetTropicZone(tile);
@@ -291,27 +292,41 @@ uint32 GetTerrainType(TileIndex tile, bool upper_halftile)
 			bool has_snow;
 			switch (GetTileType(tile)) {
 				case MP_CLEAR:
+					/* During map generation the snowstate may not be valid yet, as the tileloop may not have run yet. */
+					if (_generating_world) goto genworld;
 					has_snow = IsSnowTile(tile) && GetClearDensity(tile) >= 2;
 					break;
 
 				case MP_RAILWAY: {
+					/* During map generation the snowstate may not be valid yet, as the tileloop may not have run yet. */
+					if (_generating_world) goto genworld; // we do not care about foundations here
 					RailGroundType ground = GetRailGroundType(tile);
-					has_snow = (ground == RAIL_GROUND_ICE_DESERT || (upper_halftile && ground == RAIL_GROUND_HALF_SNOW));
+					has_snow = (ground == RAIL_GROUND_ICE_DESERT || (context == TCX_UPPER_HALFTILE && ground == RAIL_GROUND_HALF_SNOW));
 					break;
 				}
 
 				case MP_ROAD:
+					/* During map generation the snowstate may not be valid yet, as the tileloop may not have run yet. */
+					if (_generating_world) goto genworld; // we do not care about foundations here
 					has_snow = IsOnSnow(tile);
 					break;
 
 				case MP_TREES: {
+					/* During map generation the snowstate may not be valid yet, as the tileloop may not have run yet. */
+					if (_generating_world) goto genworld;
 					TreeGround ground = GetTreeGround(tile);
 					has_snow = (ground == TREE_GROUND_SNOW_DESERT || ground == TREE_GROUND_ROUGH_SNOW) && GetTreeDensity(tile) >= 2;
 					break;
 				}
 
 				case MP_TUNNELBRIDGE:
-					has_snow = HasTunnelBridgeSnowOrDesert(tile);
+					if (context == TCX_ON_BRIDGE) {
+						has_snow = (GetBridgeHeight(tile) > GetSnowLine());
+					} else {
+						/* During map generation the snowstate may not be valid yet, as the tileloop may not have run yet. */
+						if (_generating_world) goto genworld; // we do not care about foundations here
+						has_snow = HasTunnelBridgeSnowOrDesert(tile);
+					}
 					break;
 
 				case MP_STATION:
@@ -324,6 +339,7 @@ uint32 GetTerrainType(TileIndex tile, bool upper_halftile)
 
 				case MP_VOID:
 				case MP_WATER:
+				genworld:
 					has_snow = (GetTileZ(tile) > GetSnowLine());
 					break;
 
diff --git a/src/newgrf_commons.h b/src/newgrf_commons.h
index df277b4b03..3c0ae571ef 100644
--- a/src/newgrf_commons.h
+++ b/src/newgrf_commons.h
@@ -16,6 +16,13 @@
 
 #include "tile_cmd.h"
 
+/** Contextx for tile accesses */
+enum TileContext {
+	TCX_NORMAL,         ///< Nothing special.
+	TCX_UPPER_HALFTILE, ///< Querying information about the upper part of a tile with halftile foundation.
+	TCX_ON_BRIDGE,      ///< Querying information about stuff on the bridge (via some bridgehead).
+};
+
 /**
  * Maps an entity id stored on the map to a GRF file.
  * Entities are objects used ingame (houses, industries, industry tiles) for
@@ -101,7 +108,7 @@ extern HouseOverrideManager _house_mngr;
 extern IndustryOverrideManager _industry_mngr;
 extern IndustryTileOverrideManager _industile_mngr;
 
-uint32 GetTerrainType(TileIndex tile, bool upper_halftile = false);
+uint32 GetTerrainType(TileIndex tile, TileContext context = TCX_NORMAL);
 TileIndex GetNearbyTile(byte parameter, TileIndex tile);
 uint32 GetNearbyTileInformation(TileIndex tile);
 
diff --git a/src/newgrf_railtype.cpp b/src/newgrf_railtype.cpp
index 9aa6e2b544..7f35982caa 100644
--- a/src/newgrf_railtype.cpp
+++ b/src/newgrf_railtype.cpp
@@ -45,7 +45,7 @@ static uint32 RailTypeGetVariable(const ResolverObject *object, byte variable, b
 	}
 
 	switch (variable) {
-		case 0x40: return GetTerrainType(tile, object->u.routes.upper_halftile);
+		case 0x40: return GetTerrainType(tile, object->u.routes.context);
 		case 0x41: return 0;
 		case 0x42: return IsLevelCrossingTile(tile) && IsCrossingBarred(tile);
 	}
@@ -63,7 +63,7 @@ static const SpriteGroup *RailTypeResolveReal(const ResolverObject *object, cons
 	return NULL;
 }
 
-static inline void NewRailTypeResolver(ResolverObject *res, TileIndex tile, bool upper_halftile)
+static inline void NewRailTypeResolver(ResolverObject *res, TileIndex tile, TileContext context)
 {
 	res->GetRandomBits = &RailTypeGetRandomBits;
 	res->GetTriggers   = &RailTypeGetTriggers;
@@ -72,7 +72,7 @@ static inline void NewRailTypeResolver(ResolverObject *res, TileIndex tile, bool
 	res->ResolveReal   = &RailTypeResolveReal;
 
 	res->u.routes.tile = tile;
-	res->u.routes.upper_halftile = upper_halftile;
+	res->u.routes.context = context;
 
 	res->callback        = CBID_NO_CALLBACK;
 	res->callback_param1 = 0;
@@ -83,7 +83,7 @@ static inline void NewRailTypeResolver(ResolverObject *res, TileIndex tile, bool
 	res->count           = 0;
 }
 
-SpriteID GetCustomRailSprite(const RailtypeInfo *rti, TileIndex tile, RailTypeSpriteGroup rtsg, bool upper_halftile)
+SpriteID GetCustomRailSprite(const RailtypeInfo *rti, TileIndex tile, RailTypeSpriteGroup rtsg, TileContext context)
 {
 	assert(rtsg < RTSG_END);
 
@@ -92,7 +92,7 @@ SpriteID GetCustomRailSprite(const RailtypeInfo *rti, TileIndex tile, RailTypeSp
 	const SpriteGroup *group;
 	ResolverObject object;
 
-	NewRailTypeResolver(&object, tile, upper_halftile);
+	NewRailTypeResolver(&object, tile, context);
 
 	group = SpriteGroup::Resolve(rti->group[rtsg], &object);
 	if (group == NULL || group->GetNumResults() == 0) return 0;
diff --git a/src/newgrf_railtype.h b/src/newgrf_railtype.h
index 40f772c034..622c14e5a9 100644
--- a/src/newgrf_railtype.h
+++ b/src/newgrf_railtype.h
@@ -4,8 +4,9 @@
 #define NEWGRF_RAILTYPE_H
 
 #include "rail.h"
+#include "newgrf_commons.h"
 
-SpriteID GetCustomRailSprite(const RailtypeInfo *rti, TileIndex tile, RailTypeSpriteGroup rtsg, bool upper_halftile = false);
+SpriteID GetCustomRailSprite(const RailtypeInfo *rti, TileIndex tile, RailTypeSpriteGroup rtsg, TileContext context = TCX_NORMAL);
 
 uint8 GetReverseRailTypeTranslation(RailType railtype, const GRFFile *grffile);
 
diff --git a/src/newgrf_spritegroup.h b/src/newgrf_spritegroup.h
index 5f63ed6ad2..61c03ff350 100644
--- a/src/newgrf_spritegroup.h
+++ b/src/newgrf_spritegroup.h
@@ -22,6 +22,7 @@
 #include "newgrf_callbacks.h"
 #include "newgrf_generic.h"
 #include "newgrf_storage.h"
+#include "newgrf_commons.h"
 
 /**
  * Gets the value of a so-called newgrf "register".
@@ -341,8 +342,8 @@ struct ResolverObject {
 			uint8 station_size;
 		} generic;
 		struct {
-			TileIndex tile;
-			bool upper_halftile;           ///< Are we resolving sprites for the upper halftile?
+			TileIndex tile;                ///< Tracktile. For track on a bridge this is the southern bridgehead.
+			TileContext context;           ///< Are we resolving sprites for the upper halftile, or on a bridge?
 		} routes;
 	} u;
 
diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
index 4a8fda85a9..2aeb3c5026 100644
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -1756,7 +1756,7 @@ static void DrawTrackDetails(const TileInfo *ti, const RailtypeInfo *rti)
 {
 	/* Base sprite for track fences.
 	 * Note: Halftile slopes only have fences on the upper part. */
-	SpriteID base_image = GetCustomRailSprite(rti, ti->tile, RTSG_FENCES, IsHalftileSlope(ti->tileh));
+	SpriteID base_image = GetCustomRailSprite(rti, ti->tile, RTSG_FENCES, IsHalftileSlope(ti->tileh) ? TCX_UPPER_HALFTILE : TCX_NORMAL);
 	if (base_image == 0) base_image = SPR_TRACK_FENCE_FLAT_X;
 
 	switch (GetRailGroundType(ti->tile)) {
@@ -1915,8 +1915,8 @@ static void DrawTrackBitsOverlay(TileInfo *ti, TrackBits track, const RailtypeIn
 
 	if (IsValidCorner(halftile_corner)) {
 		DrawFoundation(ti, HalftileFoundation(halftile_corner));
-		overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY, true);
-		ground = GetCustomRailSprite(rti, ti->tile, RTSG_GROUND, true);
+		overlay = GetCustomRailSprite(rti, ti->tile, RTSG_OVERLAY, TCX_UPPER_HALFTILE);
+		ground = GetCustomRailSprite(rti, ti->tile, RTSG_GROUND, TCX_UPPER_HALFTILE);
 
 		/* Draw higher halftile-overlay: Use the sloped sprites with three corners raised. They probably best fit the lightning. */
 		Slope fake_slope = SlopeWithThreeCornersRaised(OppositeCorner(halftile_corner));
diff --git a/src/tunnelbridge_cmd.cpp b/src/tunnelbridge_cmd.cpp
index 0968de9e1f..98db3bc9f5 100644
--- a/src/tunnelbridge_cmd.cpp
+++ b/src/tunnelbridge_cmd.cpp
@@ -1221,7 +1221,7 @@ void DrawBridgeMiddle(const TileInfo *ti)
 	} else if (transport_type == TRANSPORT_RAIL) {
 		const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(rampsouth));
 		if (rti->UsesOverlay()) {
-			SpriteID surface = GetCustomRailSprite(rti, ti->tile, RTSG_BRIDGE);
+			SpriteID surface = GetCustomRailSprite(rti, rampsouth, RTSG_BRIDGE, TCX_ON_BRIDGE);
 			if (surface != 0) {
 				AddSortableSpriteToDraw(surface + axis, PAL_NONE, x, y, 16, 16, 0, bridge_z, IsTransparencySet(TO_BRIDGES));
 			}
@@ -1364,12 +1364,17 @@ static void TileLoop_TunnelBridge(TileIndex tile)
 {
 	bool snow_or_desert = HasTunnelBridgeSnowOrDesert(tile);
 	switch (_settings_game.game_creation.landscape) {
-		case LT_ARCTIC:
-			if (snow_or_desert != (GetTileZ(tile) > GetSnowLine())) {
+		case LT_ARCTIC: {
+			/* As long as we do not have a snow density, we want to use the density
+			 * from the entry endge. For tunnels this is the lowest point for bridges the highest point.
+			 * (Independent of foundations) */
+			uint z = IsBridge(tile) ? GetTileMaxZ(tile) : GetTileZ(tile);
+			if (snow_or_desert != (z > GetSnowLine())) {
 				SetTunnelBridgeSnowOrDesert(tile, !snow_or_desert);
 				MarkTileDirtyByTile(tile);
 			}
 			break;
+		}
 
 		case LT_TROPIC:
 			if (GetTropicZone(tile) == TROPICZONE_DESERT && !snow_or_desert) {