diff --git a/layers/transportation/class.sql b/layers/transportation/class.sql
index 6e4e7e1..ff83b9b 100644
--- a/layers/transportation/class.sql
+++ b/layers/transportation/class.sql
@@ -32,3 +32,12 @@ CREATE OR REPLACE FUNCTION railway_class(railway TEXT) RETURNS TEXT AS $$
         ELSE NULL
     END;
 $$ LANGUAGE SQL IMMUTABLE STRICT;
+
+-- Limit service to only the most important values to ensure
+-- we always know the values of service
+CREATE OR REPLACE FUNCTION service_value(service TEXT) RETURNS TEXT AS $$
+    SELECT CASE
+        WHEN service IN ('spur', 'yard', 'siding', 'crossover', 'driveway', 'alley', 'parking_aisle') THEN service
+        ELSE NULL
+    END;
+$$ LANGUAGE SQL IMMUTABLE STRICT;
diff --git a/layers/transportation/layer.sql b/layers/transportation/layer.sql
index fdd0e50..0ce4270 100644
--- a/layers/transportation/layer.sql
+++ b/layers/transportation/layer.sql
@@ -80,7 +80,8 @@ RETURNS TABLE(osm_id bigint, geometry geometry, class text, subclass text, ramp
         -- etldoc: osm_highway_linestring       ->  layer_transportation:z13
         -- etldoc: osm_highway_linestring       ->  layer_transportation:z14_
         SELECT
-            osm_id, geometry, highway, NULL AS railway, service,
+            osm_id, geometry, highway, NULL AS railway,
+            service_value(service) AS service,
             is_bridge, is_tunnel, is_ford, is_ramp, is_oneway, z_order
         FROM osm_highway_linestring
         WHERE NOT is_area AND (
@@ -96,7 +97,8 @@ RETURNS TABLE(osm_id bigint, geometry geometry, class text, subclass text, ramp
         -- etldoc: osm_railway_linestring       ->  layer_transportation:z13
         -- etldoc: osm_railway_linestring       ->  layer_transportation:z14
         SELECT
-            osm_id, geometry, NULL AS highway, railway, service,
+            osm_id, geometry, NULL AS highway, railway,
+            service_value(service) AS service,
             is_bridge, is_tunnel, is_ford, is_ramp, is_oneway, z_order
         FROM osm_railway_linestring
         WHERE zoom_level = 13 AND (railway='rail' AND service = '')