diff --git a/media/baseset/openttd.grf b/media/baseset/openttd.grf
index e3ebf2dd67..9e08fb17c3 100644
Binary files a/media/baseset/openttd.grf and b/media/baseset/openttd.grf differ
diff --git a/media/baseset/openttd/oneway.nfo b/media/baseset/openttd/oneway.nfo
index 46f3b8f947..56d2e2809a 100644
--- a/media/baseset/openttd/oneway.nfo
+++ b/media/baseset/openttd/oneway.nfo
@@ -4,10 +4,24 @@
 // See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 //
    -1 * 0	 0C "One way road graphics"
-   -1 * 3	 05 09 06
-   -1 sprites/oneway.png 8bpp  34    8  24  16 -12  -8 normal
-   -1 sprites/oneway.png 8bpp  66    8  24  16 -12  -8 normal
-   -1 sprites/oneway.png 8bpp  98    8  24  16 -12  -8 normal
-   -1 sprites/oneway.png 8bpp 130    8  24  16 -12  -8 normal
-   -1 sprites/oneway.png 8bpp 162    8  24  16 -12  -8 normal
-   -1 sprites/oneway.png 8bpp 194    8  24  16 -12  -8 normal
+   -1 * 3	 05 09 12
+   -1 sprites/oneway.png 8bpp  34    8  24  16 -10   -9 normal
+   -1 sprites/oneway.png 8bpp  66    8  24  16 -13   -7 normal
+   -1 sprites/oneway.png 8bpp  98    8  24  16 -12   -8 normal
+   -1 sprites/oneway.png 8bpp 130    8  24  16 -15  -10 normal
+   -1 sprites/oneway.png 8bpp 162    8  24  16 -12   -9 normal
+   -1 sprites/oneway.png 8bpp 194    8  24  16 -11   -8 normal
+
+   -1 sprites/oneway.png 8bpp  34   40  24  16 -13  -10 normal
+   -1 sprites/oneway.png 8bpp  66   40  24  16 -12   -8 normal
+   -1 sprites/oneway.png 8bpp  98   40  24  16 -12   -9 normal
+   -1 sprites/oneway.png 8bpp 130   40  24  16 -11   -8 normal
+   -1 sprites/oneway.png 8bpp 162   40  24  16  -9  -10 normal
+   -1 sprites/oneway.png 8bpp 194   40  24  16 -10   -9 normal
+
+   -1 sprites/oneway.png 8bpp  34   72  24  16  -8  -11 normal
+   -1 sprites/oneway.png 8bpp  66   72  24  16 -11   -5 normal
+   -1 sprites/oneway.png 8bpp  98   72  24  16 -12   -8 normal
+   -1 sprites/oneway.png 8bpp 130   72  24  16 -12   -5 normal
+   -1 sprites/oneway.png 8bpp 162   72  24  16 -14  -10 normal
+   -1 sprites/oneway.png 8bpp 194   72  24  16 -12   -8 normal
diff --git a/media/baseset/openttd/oneway.png b/media/baseset/openttd/oneway.png
index 15542af856..843747677f 100644
Binary files a/media/baseset/openttd/oneway.png and b/media/baseset/openttd/oneway.png differ
diff --git a/src/newgrf.cpp b/src/newgrf.cpp
index 5f1991ae6e..692ef30850 100644
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -6274,9 +6274,17 @@ static void GraphicsNew(ByteReader *buf)
 		if (offset <= depot_no_track_offset && offset + num > depot_no_track_offset) _loaded_newgrf_features.tram = TRAMWAY_REPLACE_DEPOT_NO_TRACK;
 	}
 
+	/* If the baseset or grf only provides sprites for flat tiles (pre #10282), duplicate those for use on slopes. */
+	bool dup_oneway_sprites = ((type == 0x09) && (offset + num <= SPR_ONEWAY_SLOPE_N_OFFSET));
+
 	for (; num > 0; num--) {
 		_cur.nfo_line++;
-		LoadNextSprite(replace == 0 ? _cur.spriteid++ : replace++, *_cur.file, _cur.nfo_line);
+		int load_index = (replace == 0 ? _cur.spriteid++ : replace++);
+		LoadNextSprite(load_index, *_cur.file, _cur.nfo_line);
+		if (dup_oneway_sprites) {
+			DupSprite(load_index, load_index + SPR_ONEWAY_SLOPE_N_OFFSET);
+			DupSprite(load_index, load_index + SPR_ONEWAY_SLOPE_S_OFFSET);
+		}
 	}
 
 	_cur.skip_sprites = skip_num;
diff --git a/src/road.h b/src/road.h
index c34579b5bb..c3fcc30ca9 100644
--- a/src/road.h
+++ b/src/road.h
@@ -66,6 +66,7 @@ enum RoadTypeSpriteGroup {
 	ROTSG_DEPOT,          ///< Optional: Depot images
 	ROTSG_reserved3,      ///<           Placeholder, if we add road fences (for highways).
 	ROTSG_ROADSTOP,       ///< Required: Drive-in stop surface
+	ROTSG_ONEWAY,         ///< Optional: One-way indicator images
 	ROTSG_END,
 };
 
diff --git a/src/road_cmd.cpp b/src/road_cmd.cpp
index dda2f2fa2a..94b4423a15 100644
--- a/src/road_cmd.cpp
+++ b/src/road_cmd.cpp
@@ -1606,7 +1606,17 @@ static void DrawRoadBits(TileInfo *ti)
 	if (road_rti != nullptr) {
 		DisallowedRoadDirections drd = GetDisallowedRoadDirections(ti->tile);
 		if (drd != DRD_NONE) {
-			DrawGroundSpriteAt(SPR_ONEWAY_BASE + drd - 1 + ((road == ROAD_X) ? 0 : 3), PAL_NONE, 8, 8, GetPartialPixelZ(8, 8, ti->tileh));
+			SpriteID oneway = GetCustomRoadSprite(road_rti, ti->tile, ROTSG_ONEWAY);
+
+			if (oneway == 0) oneway = SPR_ONEWAY_BASE;
+
+			if ((ti->tileh == SLOPE_NE) || (ti->tileh == SLOPE_NW)) {
+				oneway += SPR_ONEWAY_SLOPE_N_OFFSET;
+			} else if ((ti->tileh == SLOPE_SE) || (ti->tileh == SLOPE_SW)) {
+				oneway += SPR_ONEWAY_SLOPE_S_OFFSET;
+			}
+
+			DrawGroundSpriteAt(oneway + drd - 1 + ((road == ROAD_X) ? 0 : 3), PAL_NONE, 8, 8, GetPartialPixelZ(8, 8, ti->tileh));
 		}
 	}
 
diff --git a/src/table/sprites.h b/src/table/sprites.h
index b0e61b5d02..407a7a2d87 100644
--- a/src/table/sprites.h
+++ b/src/table/sprites.h
@@ -290,8 +290,10 @@ static const SpriteID SPR_TRAMWAY_DEPOT_NO_TRACK       = SPR_TRAMWAY_BASE + 113;
 static const uint16 TRAMWAY_SPRITE_COUNT = 119;
 
 /** One way road sprites */
-static const SpriteID SPR_ONEWAY_BASE = SPR_TRAMWAY_BASE + TRAMWAY_SPRITE_COUNT;
-static const uint16 ONEWAY_SPRITE_COUNT = 6;
+static const SpriteID SPR_ONEWAY_BASE           = SPR_TRAMWAY_BASE + TRAMWAY_SPRITE_COUNT;
+static const SpriteID SPR_ONEWAY_SLOPE_N_OFFSET = 6;
+static const SpriteID SPR_ONEWAY_SLOPE_S_OFFSET = 12;
+static const uint16 ONEWAY_SPRITE_COUNT = 18;
 
 /** Tunnel sprites with grass only for custom railtype tunnel. */
 static const SpriteID SPR_RAILTYPE_TUNNEL_BASE = SPR_ONEWAY_BASE + ONEWAY_SPRITE_COUNT;