I got two more validation ideas, now that mkgmap is not complaining about roundabouts, oneways or turn restrictions in finland.osm.bz2. Both should be easy to implement. Dead end check 3: Check dead ends in bidirectional streets. Consider the following situation where AB joins the oneway street CB: A============B<----------C Normally, this is legitimate. However, if there is a turn restriction (via=B, from=AB) that prevents the U-turn ABA, AB would be a dead end. Another idea: complain about redundant or impossible turn restrictions. A restriction whose "from" or "to" role is against the direction of a oneway, is impossible. For example, only_straight_on (from=AB, via=B, to=CB). An impossible restriction may also be redundant, meaning that it does not restrict anything: no_u_turn (from=CB, via=B, to=CB). If there are no other ways joining at B, the following would be redundant: only_straight_on (from=CB, via=B, to=BA). I came across some of these situations in a crossing in Vaasa. There were other oneway errors in the area, but these I had to notice myself. JOSM Validator did not complain. Best regards, Marko