diff --git a/data.yml b/data.yml
index e809b33..fab9daa 100644
--- a/data.yml
+++ b/data.yml
@@ -68,34 +68,8 @@ Layer:
       max_size: 512
       password: osm
       port: 5432
-      srid: ''
-      table: |-
-        ( SELECT *
-          FROM (
-            SELECT * FROM road_z4 WHERE z(!scale_denominator!) BETWEEN 4 AND 5
-            UNION ALL
-            SELECT * FROM road_z5 WHERE z(!scale_denominator!) = 5
-            UNION ALL
-            SELECT * FROM road_z6 WHERE z(!scale_denominator!) = 6
-            UNION ALL
-            SELECT * FROM road_z7 WHERE z(!scale_denominator!) = 7
-            UNION ALL
-            SELECT * FROM road_z8 WHERE z(!scale_denominator!) = 8
-            UNION ALL
-            SELECT ST_Simplify(geom, 200), class FROM road_z9 WHERE z(!scale_denominator!) = 9
-            UNION ALL
-            SELECT ST_Simplify(geom, 120), class FROM road_z10 WHERE z(!scale_denominator!) = 10
-            UNION ALL
-            SELECT ST_Simplify(geom, 50), class FROM road_z11 WHERE z(!scale_denominator!) = 11
-            UNION ALL
-            SELECT ST_Simplify(geom, 20), class FROM road_z12 WHERE z(!scale_denominator!) = 12
-            UNION ALL
-            SELECT * FROM road_z13 WHERE z(!scale_denominator!) = 13
-            UNION ALL
-            SELECT * FROM road_z14 WHERE z(!scale_denominator!) >= 14
-          ) AS road
-          WHERE geom && !bbox!
-        ) AS data
+      srid: 900913
+      table: (SELECT * FROM layer_road(!bbox!, z(!scale_denominator!))) AS t
       type: postgis
       user: osm
     description: Buildings
diff --git a/schema/layers/road.sql b/schema/layers/road.sql
index 0767f69..30eee11 100644
--- a/schema/layers/road.sql
+++ b/schema/layers/road.sql
@@ -1,8 +1,8 @@
 CREATE OR REPLACE FUNCTION ne_road_class(type VARCHAR) RETURNS VARCHAR AS $$
   SELECT CASE type
-	WHEN 'Major Highway' THEN 'motorway'
-	WHEN 'Secondary Highway' THEN 'trunk'
-	WHEN 'Road' THEN 'primary'
+    WHEN 'Major Highway' THEN 'motorway'
+    WHEN 'Secondary Highway' THEN 'trunk'
+    WHEN 'Road' THEN 'primary'
     ELSE type
   END;
 $$ LANGUAGE SQL IMMUTABLE;
@@ -10,13 +10,13 @@ $$ LANGUAGE SQL IMMUTABLE;
 CREATE OR REPLACE VIEW ne_10m_global_roads AS (
     SELECT geom, scalerank, ne_road_class(type) AS class
     FROM ne_10m_roads
-	WHERE continent <> 'North America'
+    WHERE continent <> 'North America'
       AND featurecla = 'Road'
       AND type IN ('Major Highway', 'Secondary Highway', 'Road')
     UNION ALL
     SELECT geom, scalerank, ne_road_class(type) AS class
     FROM ne_10m_roads_north_america
-	WHERE type IN ('Major Highway', 'Secondary Highway', 'Road')
+    WHERE type IN ('Major Highway', 'Secondary Highway', 'Road')
 );
 
 CREATE OR REPLACE VIEW road_z4 AS (
@@ -92,3 +92,32 @@ CREATE OR REPLACE VIEW road_z14 AS (
     SELECT way AS geom, class::text
     FROM road_areas
 );
+
+CREATE OR REPLACE FUNCTION layer_road(bbox geometry, zoom_level int)
+RETURNS TABLE(geom geometry, class text) AS $$
+    WITH zoom_levels AS (
+        SELECT * FROM road_z4 WHERE zoom_level BETWEEN 4 AND 5
+        UNION ALL
+        SELECT * FROM road_z5 WHERE zoom_level = 5
+        UNION ALL
+        SELECT * FROM road_z6 WHERE zoom_level = 6
+        UNION ALL
+        SELECT * FROM road_z7 WHERE zoom_level = 7
+        UNION ALL
+        SELECT * FROM road_z8 WHERE zoom_level = 8
+        UNION ALL
+        SELECT ST_Simplify(geom, 200), class FROM road_z9 WHERE zoom_level = 9
+        UNION ALL
+        SELECT ST_Simplify(geom, 120), class FROM road_z10 WHERE zoom_level = 10
+        UNION ALL
+        SELECT ST_Simplify(geom, 50), class FROM road_z11 WHERE zoom_level = 11
+        UNION ALL
+        SELECT ST_Simplify(geom, 20), class FROM road_z12 WHERE zoom_level = 12
+        UNION ALL
+        SELECT * FROM road_z13 WHERE zoom_level = 13
+        UNION ALL
+        SELECT * FROM road_z14 WHERE zoom_level >= 14
+    )
+    SELECT geom, class::text FROM zoom_levels
+    WHERE geom && bbox;
+$$ LANGUAGE SQL IMMUTABLE;