Index: src/train_cmd.cpp
===================================================================
--- src/train_cmd.cpp	(Revision 20902)
+++ src/train_cmd.cpp	(Arbeitskopie)
@@ -2861,14 +2861,14 @@
 };
 
 /** Modify the speed of the vehicle due to a change in altitude */
-static inline void AffectSpeedByZChange(Train *v, byte old_z)
+static inline void AffectSpeedByZChange(Train *v, int32 old_z)
 {
 	if (old_z == v->z_pos || _settings_game.vehicle.train_acceleration_model != AM_ORIGINAL) return;
 
 	const RailtypeSlowdownParams *rsp = &_railtype_slowdown[v->railtype];
 
 	if (old_z < v->z_pos) {
-		v->cur_speed -= (v->cur_speed * rsp->z_up >> 8);
+		v->cur_speed -= ((uint32)(v->cur_speed * rsp->z_up) >> 8);
 	} else {
 		uint16 spd = v->cur_speed + rsp->z_down;
 		if (spd <= v->max_speed) v->cur_speed = spd;
@@ -3317,7 +3317,7 @@
 		v->y_pos = gp.y;
 
 		/* update the Z position of the vehicle */
-		byte old_z = v->UpdateInclination(gp.new_tile != gp.old_tile, false);
+		int32 old_z = v->UpdateInclination(gp.new_tile != gp.old_tile, false);
 
 		if (prev == NULL) {
 			/* This is the first vehicle in the train */
Index: src/elrail.cpp
===================================================================
--- src/elrail.cpp	(Revision 20902)
+++ src/elrail.cpp	(Arbeitskopie)
@@ -204,7 +204,7 @@
  * @param PCPpos The PCP of the tile.
  * @return The Z position of the PCP.
  */
-static byte GetPCPElevation(TileIndex tile, DiagDirection PCPpos)
+static int32 GetPCPElevation(TileIndex tile, DiagDirection PCPpos)
 {
 	/* The elevation of the "pylon"-sprite should be the elevation at the PCP.
 	 * PCPs are always on a tile edge.
@@ -220,8 +220,11 @@
 	 * Also note that the result of GetSlopeZ() is very special on bridge-ramps.
 	 */
 
-	byte z = GetSlopeZ(TileX(tile) * TILE_SIZE + min(x_pcp_offsets[PCPpos], TILE_SIZE - 1), TileY(tile) * TILE_SIZE + min(y_pcp_offsets[PCPpos], TILE_SIZE - 1));
-	return (z + 2) & ~3; // this means z = (z + TILE_HEIGHT / 4) / (TILE_HEIGHT / 2) * (TILE_HEIGHT / 2);
+	int32 z = GetSlopeZ(TileX(tile) * TILE_SIZE + min(x_pcp_offsets[PCPpos], TILE_SIZE - 1), TileY(tile) * TILE_SIZE + min(y_pcp_offsets[PCPpos], TILE_SIZE - 1));
+	z = (z + TILE_HEIGHT / 4) / (TILE_HEIGHT / 2) * (TILE_HEIGHT / 2);
+	return z;
+	/* Removed because this bit magic almost surely does no longer work with int32.
+	 * return (z + 2) & ~3; // this means z = (z + TILE_HEIGHT / 4) / (TILE_HEIGHT / 2) * (TILE_HEIGHT / 2); */
 }
 
 /**
@@ -311,7 +314,7 @@
 		SpriteID pylon_base = (halftile_corner != CORNER_INVALID && HasBit(edge_corners[i], halftile_corner)) ? pylon_halftile : pylon_normal;
 		TileIndex neighbour = ti->tile + TileOffsByDiagDir(i);
 		Foundation foundation = FOUNDATION_NONE;
-		byte elevation = GetPCPElevation(ti->tile, i);
+		int32 elevation = GetPCPElevation(ti->tile, i);
 
 		/* Here's one of the main headaches. GetTileSlope does not correct for possibly
 		 * existing foundataions, so we do have to do that manually later on.*/