[Talk-GB] Rendering problem (Osmarender layer)

[Richard Fairhurst]

Michael Collinson wrote:

> It never hurts to be pedantic with tagging!  Yes there was a tip
> about mapping a roundabout as the most major road connecting to it,
> i.e. directly connecting to or across it. So in your example it would
> almost certainly be highway=motorway_link.
>
> Though just to confuse things again slightly, I would normally
> consider a primary or trunk road passing across the roundabout to be
> "above" a motorway link and therefore map the roundabout as primary
> or trunk - I don't know if that is standard practice.

If there's a grade-separated interchange where (say) a trunk road,  
with roundabout, meets a motorway which flies over/passes under:

- the slip roads should be motorway_link (motorway restrictions apply)
- the roundabout should be trunk (motorway restrictions do not apply)

Otherwise you're going to get all sorts of problems with bike routing  
not being able to use the roundabout, etc.

FWIW the UK Government principle for road classification is actually  
quite a good one to follow: "if the road inexorably leads to a  
motorway, it must therefore be a motorway". There are some  
single-carriageway motorways for that reason. ;)

cheers
Richard