Hi. MCliquid
Probably not, but at the beginning of a roundabout, you would have
to drive against traffic to do a u-turn,......having the roundabout there, to do it
the safe and legal way... but indeed, it is sometimes possible to do a
u-turn in front of a roundabout, without having to drive against traffic, if
you are not already at the beginning of the roundabout, or are blocked by
markings, or a white line on the road separating the backwards and forward lines / roads.
But using the roundabout, is usually the better option, and the safest...

Sometimes the navigational system performs a u-turn even on a motorway,
because the motorway is in 2 directions, even when it has separate lanes divided
by markings or a line.
So the navigational system suggests a u-turn, ....instead of using the roundabout,
just because the possibility of a u-turn is almost always automatically added..
suggesting that there are no further obstacles like a white separating line on the road,
or a sign....
But you are right.
Not 13 u-turn signs, but that does not mean you can actually perform a u-turn...on
that particular peace of road, so if a roundabout is close, it is always better to use that,
so the navigational system needs to know that too, so making a particular peace of road,
with no u-turns, because a roundabout is close, when navigating with OSM+ is the better option
Thanks for the comment.
Hans.