[OSM-newbies] Question about how to connection correctly highway links

[Roger Calvert]

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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>

-- 
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Roger Calvert
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