I think you need to add no-left and no-right turn restrictions where it
crosses the middle link.
Roger
On 16/12/2012 11:38, Sebastian Arcus wrote:
I have a question about how to correctly trace highway links at
junctions/intersections. Sometimes a link physically crosses over one
or two other lanes coming from the other direction of traffic, before
reaching the lane it is suppose to merge into. Now, these junction
points do exist in real life, but from the point of view of navigation
software, they are useless as one is not allowed to turn turn into any
of those lanes of traffic it crosses until it reaches the right lane
it is supposed to merge into.
My question is, should these junction/common points between paths
actually exist in OSM? Wouldn't it be better to draw the highway link
like it wouldn't actually intersect with those oncoming traffic lanes
- and just joined it to the final destination lane? I use Navit GPS -
and it sometimes assume I can turn into those oncoming traffic lanes
just because the common waypoint indicates there is a joint. Maybe
other GPS navigation software does the same mistake?
In case my explanation is a bit fuzzy, I will give an example. The
following relatively simple junction is in Liverpool:
http://www.openstreetmap.org/?lat=53.394271&lon=-2.982713&zoom=18
Imagine you are traveling northwards on Sefton Street towards the
junction. The right-most link (looking northwards, in the direction of
travel) is obviously a no-no as it is a one-way going south. However,
Navit suggested for some strange reason that I take the middle link,
and then turn immediately left on the first lane of traffic that the
link hits into Chaloner St and continue northward. In real life, that
is impossible, because that particular highway link (the middle one)
is only for crossing over the first two lanes of traffic it
encounters, and then merging with the far most one and continuing east
on Parliament Street.
My thinking was that if the middle link coming from Sefton Street
didn't have common waypoints/joints with the first two lanes, the
navigation software would have never had any reason to suggest such a
move. Those points are as good as non-existent in practice, as they
can't be used for turning left or right into those two lanes.
Could anybody with more experience weigh in on this with some pro's or
con's please.
Thanks,
Sebastian
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Roger Calvert
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