[OSM-talk] Divided/Non-Divided Intersection

[Dylan Semler]

On Thu, Jul 22, 2010 at 5:57 AM, andrzej zaborowski <balrogg at gmail.com>wrote:

> On 11 July 2010 10:23, Maarten Deen <mdeen at xs4all.nl> wrote:
> > If you have a layout like this (use a fixed-width font):
> >
> >     | |
> > A----+-+
> >     | +----B
> > C----+-+
> >     | |
> >
> > And you want to go from B to A, why would routing software say "go
> straight
> > on" and not "go right, then go left"?
>
> My opinion is that it is a routing software issue after all.  When a
> road segment is just about 5m long, the software should just skip it
> in the driving directions and look at the angle between the A and the
> B roads.  It can go as far as doing what Alan said, i.e. join all of
> the nodes in a junction (a concentration of nodes where roads meet)
> into a single node, possibly in the preprocessing phase.  I don't
> agree that this should be done in OSM data, it will prevent more
> clever routing direction being given when more clever routing software
> is written (e.g. software telling your car where to stop to wait for
> green light, which lane to take etc).
>
> The lengths need to be chosen carefully because in e.g. pedestrian
> routing, 5m may be significant (say you're looking for an exit from a
> maze).  A car can't even make turns that tight, and you're interested
> in the bigger picture when you reach a junction, the routing is not
> clever enough to get you through a junction anyway.
>
> >
> > And option is to map it like this:
> >     | |
> > A----+ |
> >     |\|
> >     | +----B
> >     |/|
> > C----+ |
> >     | |
>
>
How about grouping all of the nodes of the intersection into a relation?
 Routing software can treat it as a single intersection and the map can
reflect how the roads are actually laid.
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