I think I have read it correctly.
https://www.openstreetmap.org/node/5408566797
It is easy to determine this shared node is part of the roundabout as
well as the entrance from Wapping & can exit along Commercial, or if
required, continue around the roundabout:
How is this different from, say, two side roads joining a main road at
the same node?,
Or even cross-roads. The router has to check to find out what road it's
crossing & find the appropriate exit, which, in the case of cross-roads,
will be on the same node.
DaveF
On 14/02/2018 16:17, Maarten Deen wrote:
On 2018-02-14 15:53, Dave F wrote:
Hi
Could anyone give me an explanation for this line from
https://wiki.openstreetmap.org/wiki/Tag:junction=roundabout
"Each road has to be connected with the roundabout in a separate
node—that is, between these nodes a segment of the roundabout is
required."
I see no requirement for a separate segment:
* When a entering road shares a node with a roundabout then the
router knows it's entered that roundabout by reading the tags on the
circular way.
* Whilst on that node, the router checks to see if there are any
suitable exits. If there are, then it leaves the roundabout.
* If not, it continues going around until it finds an appropriate
exit.
I'm not sure if you read the requirement right, but this tells mappers
not to connect the entry and exit road on the same node. If you were
to map it that way, the router will not see that you enter a
roundabout and need to exit at the first exit. It will just tell you
to go right.
It is not (what I think you think) that there needs to be a separate
way between entrance and exit, the roundabout can be mapped as one way
in total.
Maarten
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