diff --git a/geo_app/schema.py b/geo_app/schema.py
index 376af89..2e1bc6b 100644
--- a/geo_app/schema.py
+++ b/geo_app/schema.py
@@ -541,14 +541,21 @@ class Query(graphene.ObjectType):
             COLLECT WITH COUNT INTO length
             RETURN length
         """
-        cursor = db.aql.execute(aql, bind_vars={
+        bind_vars = {
             'transport_type': transport_type,
             'country': country,
-            'west': west,
-            'south': south,
-            'east': east,
-            'north': north,
-        })
+        }
+
+        # Only add bounds to bind_vars if they are used
+        if west is not None and south is not None and east is not None and north is not None:
+            bind_vars.update({
+                'west': west,
+                'south': south,
+                'east': east,
+                'north': north,
+            })
+
+        cursor = db.aql.execute(aql, bind_vars=bind_vars)
         return next(cursor, 0)
 
     def resolve_hub_countries(self, info):