Turning restrictions issue

The BRouter does honour access restrictions of OSM ways, if they are attributes of the ways themselves. I.e. it will not lead you toward a road your vehicle is not allowed to go along. Not true anymore - implemented in Brouter 1.4.8 for car profiles by default, RD5 navigation data needs update if older than 24-NOV-2016. Still marked as incomplete.

But some restrictions are expressed as relation between ways, when restriction applicability depends on where are you coming from. E.g. you are coming toward a T junction from the South. The road to West has generally allowed access. BUT, there is only allowed turning right from the North, but not turning left from the South, where you are coming from.

In such a case, the Brouter will for now fail, routing you to otherwise allowed road, where you have actually forbidden access, given by the geometry of the traffic rules.

See more on OpenStreetMap wiki page for Relation:restriction.