[Talk-GB] No U-turn on a long stretch of road

Edward Bainton bainton.ete at gmail.com
Sat Dec 5 14:27:43 UTC 2020

Sorry I should have made clear

Rather than seeking to capture a subjective jmt in the map, I'm trying to
capture "no U-turn" signs that are shopping this long stretch, .

I agree a driver should use their discretion. Equally where it's actually
prohibited do we want to capture that?

On Sat, 5 Dec 2020, 12:57 David Woolley, <forums at david-woolley.me.uk> wrote:

> On 05/12/2020 12:39, Edward Bainton wrote:
> > Any established tagging system?
> >
> > The turn restriction wiki
> > <https://wiki.openstreetmap.org/wiki/Relation:restriction> envisages
> > turn restrictions at junctions only; my case is along the length of a
> > major road (~3km). There's no barrier to prevent it, but presumably
> > routing engines ought to know that route correction after a wrong turn
> > will have to wait until the next roundabout.
> >
> That's a subjective judgement, so would be tagging for the renderer.
> The renderer (in this case a router) should be using some sort of
> heuristic like only  permitting U turns on residential or service roads,
> and giving a heavy weighting to the use of formal junctions at the the
> expense of distance travelled.  A real human would consider actual
> traffic levels and sight distances but they would be difficult to
> capture on the map and time and season dependent.
> I think No U Turn signs tend only to be used where traffic volumes or
> junction structures, might otherwise suggest U turns were acceptable.
> I don't think any driver (or autonomous vehicle) should be making U
> Turns based solely on the instructions of an automated router.
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