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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