Index: resources/data/validator/combinations.mapcss
===================================================================
--- resources/data/validator/combinations.mapcss	(revision 17884)
+++ resources/data/validator/combinations.mapcss	(working copy)
@@ -6,6 +6,19 @@
   set unpaved_surface;
 }
 
+way!:closed[highway][layer][layer!=0][!bridge][!tunnel][!covered][highway!~/steps|elevator/],
+way!:closed[railway][layer][layer!=0][!bridge][!tunnel][!covered],
+way!:closed[waterway][layer][layer!=0][!bridge][!tunnel][!covered] {
+  throwWarning: tr("inspect to confirm a {1} tag is necessary on this {0}. If so, add either {2}, {3}, {4} or any other tags complimentary to {5}", "{2.key}", "{3.key}", "{4.key}=*", "{5.key}=*", "{6.key}=*", "{3.key}=*");
+  group: tr("suspicious tag combination");
+  assertMatch: "way highway=tertiary layer=2";
+  assertMatch: "way waterway=stream layer=-1";
+  assertMatch: "way railway=rail layer=2";
+  assertNoMatch: "way highway=tertiary layer=2 bridge=yes";
+  assertNoMatch: "way waterway=stream layer=-1 tunnel=yes";
+  assertNoMatch: "way railway=rail layer=2 bridge=yes";
+}
+
 /* {0.key} without {1.key} (warning level) */
 way[junction                   ][!highway][junction!=yes][!area:highway],
 way[living_street              ][!highway],