diff --git a/layers/transportation/etl_diagram.png b/layers/transportation/etl_diagram.png
index cea8f26..479b9ed 100644
Binary files a/layers/transportation/etl_diagram.png and b/layers/transportation/etl_diagram.png differ
diff --git a/layers/transportation/mapping.yaml b/layers/transportation/mapping.yaml
index d8cfe48..34984a0 100644
--- a/layers/transportation/mapping.yaml
+++ b/layers/transportation/mapping.yaml
@@ -42,18 +42,6 @@ generalized_tables:
     sql_filter: ST_IsValid(geometry)
     tolerance: ZRES13
 
-# etldoc: osm_highway_linestring_gen_z10 -> osm_highway_linestring_gen_z9
-  highway_linestring_gen_z9:
-    source: highway_linestring_gen_z10
-    sql_filter: (highway IN ('motorway', 'trunk', 'primary', 'secondary', 'motorway_link', 'trunk_link', 'primary_link', 'secondary_link') OR highway = 'construction' AND construction IN ('motorway', 'trunk', 'primary', 'secondary', 'motorway_link', 'trunk_link', 'primary_link', 'secondary_link')) AND NOT is_area
-    tolerance: ZRES10
-
-# etldoc: osm_highway_linestring_gen_z11 -> osm_highway_linestring_gen_z10
-  highway_linestring_gen_z10:
-    source: highway_linestring_gen_z11
-    sql_filter: (highway IN ('motorway', 'trunk', 'primary', 'secondary', 'motorway_link', 'trunk_link', 'primary_link', 'secondary_link') OR highway = 'construction' AND construction IN ('motorway', 'trunk', 'primary', 'secondary', 'motorway_link', 'trunk_link', 'primary_link', 'secondary_link')) AND NOT is_area
-    tolerance: ZRES11
-
 # etldoc: osm_highway_linestring -> osm_highway_linestring_gen_z11
   highway_linestring_gen_z11:
     source: highway_linestring
diff --git a/layers/transportation/transportation.sql b/layers/transportation/transportation.sql
index 416f8c8..6a60144 100644
--- a/layers/transportation/transportation.sql
+++ b/layers/transportation/transportation.sql
@@ -209,7 +209,7 @@ FROM (
          WHERE zoom_level = 8
          UNION ALL
 
-         -- etldoc: osm_highway_linestring_gen_z9  ->  layer_transportation:z9
+         -- etldoc: osm_transportation_merge_linestring_gen_z9  ->  layer_transportation:z9
          SELECT osm_id,
                 geometry,
                 highway,
@@ -234,12 +234,11 @@ FROM (
                 mtb_scale,
                 NULL AS surface,
                 z_order
-         FROM osm_highway_linestring_gen_z9
+         FROM osm_transportation_merge_linestring_gen_z9
          WHERE zoom_level = 9
-           AND ST_Length(geometry) > ZRes(11)
          UNION ALL
 
-         -- etldoc: osm_highway_linestring_gen_z10  ->  layer_transportation:z10
+         -- etldoc: osm_transportation_merge_linestring_gen_z10  ->  layer_transportation:z10
          SELECT osm_id,
                 geometry,
                 highway,
@@ -264,12 +263,11 @@ FROM (
                 mtb_scale,
                 NULL AS surface,
                 z_order
-         FROM osm_highway_linestring_gen_z10
+         FROM osm_transportation_merge_linestring_gen_z10
          WHERE zoom_level = 10
-           AND ST_Length(geometry) > ZRes(11)
          UNION ALL
 
-         -- etldoc: osm_highway_linestring_gen_z11  ->  layer_transportation:z11
+         -- etldoc: osm_transportation_merge_linestring_gen_z11  ->  layer_transportation:z11
          SELECT osm_id,
                 geometry,
                 highway,
@@ -294,9 +292,8 @@ FROM (
                 mtb_scale,
                 NULL AS surface,
                 z_order
-         FROM osm_highway_linestring_gen_z11
+         FROM osm_transportation_merge_linestring_gen_z11
          WHERE zoom_level = 11
-           AND ST_Length(geometry) > ZRes(12)
          UNION ALL
 
          -- etldoc: osm_highway_linestring  ->  layer_transportation:z12
diff --git a/layers/transportation/update_transportation_merge.sql b/layers/transportation/update_transportation_merge.sql
index 94ba324..2a46c75 100644
--- a/layers/transportation/update_transportation_merge.sql
+++ b/layers/transportation/update_transportation_merge.sql
@@ -12,6 +12,92 @@ CREATE INDEX IF NOT EXISTS osm_highway_linestring_highway_partial_idx
     ON osm_highway_linestring (highway)
     WHERE highway IN ('motorway', 'trunk', 'primary', 'construction');
 
+-- etldoc: osm_highway_linestring_gen_z11 ->  osm_transportation_merge_linestring_gen_z11
+DROP MATERIALIZED VIEW IF EXISTS osm_transportation_merge_linestring_gen_z11 CASCADE;
+CREATE MATERIALIZED VIEW osm_transportation_merge_linestring_gen_z11 AS
+(
+SELECT (ST_Dump(geometry)).geom AS geometry,
+       NULL::bigint AS osm_id,
+       highway,
+       construction,
+       is_bridge,
+       is_tunnel,
+       is_ford,
+       z_order,
+       bicycle,
+       foot,
+       horse,
+       mtb_scale,
+       layer
+FROM (
+         SELECT ST_LineMerge(ST_Collect(geometry)) AS geometry,
+                highway,
+                construction,
+                is_bridge,
+                is_tunnel,
+                is_ford,
+                min(z_order) AS z_order,
+                bicycle,
+                foot,
+                horse,
+                mtb_scale,
+                layer
+         FROM osm_highway_linestring_gen_z11
+         WHERE ST_IsValid(geometry)
+         GROUP BY highway, construction, is_bridge, is_tunnel, is_ford, bicycle, foot, horse, mtb_scale, layer
+     ) AS highway_union
+    ) /* DELAY_MATERIALIZED_VIEW_CREATION */;
+CREATE INDEX IF NOT EXISTS osm_transportation_merge_linestring_gen_z11_geometry_idx
+    ON osm_transportation_merge_linestring_gen_z11 USING gist (geometry);
+
+-- etldoc: osm_transportation_merge_linestring_gen_z11 -> osm_transportation_merge_linestring_gen_z10
+DROP MATERIALIZED VIEW IF EXISTS osm_transportation_merge_linestring_gen_z10 CASCADE;
+CREATE MATERIALIZED VIEW osm_transportation_merge_linestring_gen_z10 AS
+(
+SELECT ST_Simplify(geometry, ZRes(12)) AS geometry,
+       osm_id,
+       highway,
+       construction,
+       is_bridge,
+       is_tunnel,
+       is_ford,
+       z_order,
+       bicycle,
+       foot,
+       horse,
+       mtb_scale,
+       layer
+FROM osm_transportation_merge_linestring_gen_z11
+WHERE highway NOT IN ('tertiary', 'tertiary_link') 
+      OR highway = 'construction' AND construction NOT IN ('tertiary', 'tertiary_link')
+    ) /* DELAY_MATERIALIZED_VIEW_CREATION */;
+CREATE INDEX IF NOT EXISTS osm_transportation_merge_linestring_gen_z10_geometry_idx
+    ON osm_transportation_merge_linestring_gen_z10 USING gist (geometry);
+
+-- etldoc: osm_transportation_merge_linestring_gen_z10 -> osm_transportation_merge_linestring_gen_z9
+DROP MATERIALIZED VIEW IF EXISTS osm_transportation_merge_linestring_gen_z9 CASCADE;
+CREATE MATERIALIZED VIEW osm_transportation_merge_linestring_gen_z9 AS
+(
+SELECT ST_Simplify(geometry, ZRes(11)) AS geometry,
+       osm_id,
+       highway,
+       construction,
+       is_bridge,
+       is_tunnel,
+       is_ford,
+       z_order,
+       bicycle,
+       foot,
+       horse,
+       mtb_scale,
+       layer
+FROM osm_transportation_merge_linestring_gen_z10
+WHERE highway NOT IN ('tertiary', 'tertiary_link') 
+      OR highway = 'construction' AND construction NOT IN ('tertiary', 'tertiary_link')
+    ) /* DELAY_MATERIALIZED_VIEW_CREATION */;
+CREATE INDEX IF NOT EXISTS osm_transportation_merge_linestring_gen_z9_geometry_idx
+    ON osm_transportation_merge_linestring_gen_z9 USING gist (geometry);
+
 -- etldoc: osm_highway_linestring ->  osm_transportation_merge_linestring
 DROP MATERIALIZED VIEW IF EXISTS osm_transportation_merge_linestring CASCADE;
 CREATE MATERIALIZED VIEW osm_transportation_merge_linestring AS
@@ -188,4 +274,4 @@ CREATE CONSTRAINT TRIGGER trigger_refresh
     ON transportation.updates
     INITIALLY DEFERRED
     FOR EACH ROW
-EXECUTE PROCEDURE transportation.refresh();
\ No newline at end of file
+EXECUTE PROCEDURE transportation.refresh();
diff --git a/layers/transportation_name/etl_diagram.png b/layers/transportation_name/etl_diagram.png
index 7ed7a04..dacb8c1 100644
Binary files a/layers/transportation_name/etl_diagram.png and b/layers/transportation_name/etl_diagram.png differ