ZMW bedoelt denk ik forward/backward role op route relaties, dat is iets waar je idd op moet letten als je de wegrichting omdraait en er zit toevallig zo’n relatie op die weg:
http://wiki.openstreetmap.org/wiki/Relations/Routes#Members

if a route should only be followed in one direction for some or all of its length, the “role” can indicate this for some or all of the constituent ways. “forward” means the route follows this way only in the direction of the way and “backward” means the route runs only against the direction of the way.