[Talk-GB] Spurious No U turns in GB

[David Woolley]

On 27/06/18 15:30, SK53 wrote:
> # Junctions with islands which also cause a single carriageway to split 
> and merge around the junction.
> #

I would definitely agree that this is tagging for the renderer, and wrong.

However, I can think of a case like this where you might well get 
attention from the police, for a dangerous manoeuvre, if you U-turned at 
any time but the early hours.  I seem to remember that one of the 
routers thinks this is a good place for a U-turn.

Obviously the correct thing is for routers to use a heuristic to detect 
that if two one way roads join at a very acute angle, they shouldn't 
route from one to the other, or should give it a large penalty, but it 
does beg the question as to whether OSM should allow router hints.

The problem with hints is that, like "too dangerous for cycles, so mark 
as no cycling" they are subjective, and the router should really be 
looking at the topology to infer a that this is really a dual carriageway.