Sometimes, a line shouldn't be connected to the other side

[liberostelios]

When a road intersects with a dual carriageway, sometimes it might not be possible to turn both ways because of some physical barrier. I think we should discuss about it as something that is dealt "automatically" since in those cases the dual carriageways will be modelled as two individual single ways in OSM, therefore this is taken care already.

Minor issue: we didn't check if there are cases that are still modelled as a dual carriageway with a single line and there are semantics to denote turning restrictions.