Index: resources/styles/default/lines
===================================================================
--- resources/styles/default/lines	(revision 3792)
+++ resources/styles/default/lines	(working copy)
@@ -77,11 +77,12 @@
 highway=* {name '${name}' | '${ref}' }
 
 # Flag unpaved roads.
-highway=*
-& (surface=cobblestone | surface=compacted | surface=dirt |
-   surface=earth | surface=grass | surface=grass_paver |
-   surface=gravel | surface=grit | surface=ground | surface=mud |
-   surface=pebblestone | surface=sand | surface=unpaved |
+highway=* & 
+( (surface=* & surface!=asphalt & surface!=paved & surface!=sett & 
+    surface!=concrete & surface!=concrete:lanes & surface!=concrete:plates & 
+    surface!=paving_stones  & surface!=cobblestone  & 
+   	surface!=cobblestone:flattened  & surface!=metal  & surface!=wood
+   ) |
    mtb:scale=* |
    tracktype ~ 'grade[2-6]' |
    smoothness ~ '.*(bad|horrible|impassable)' |