[talk-au] Roundabouts and routing

[Craig Feuerherdt]

As per email below, intersection_simple.jpg is the method I have adopted.
Agree with multiple nodes on straight roads, I have been fixing them up as I
find them.
Separated ways is an interesting one and people do it differently. I am of
the opinion that they have to be 'physically separate' ie there must be some
barrier (island) between them (other than a solid white line - which can be
seen in the link to the OSM map of the intersection under current debate, in
the north-west corner - compare the nearmap image with the OSM image for
entry into the club(?) from the east-bound lane). Having said that, where a
painted island (greater than a car width approximately) exists that
separates lanes I have taken that as a physical separation as well. The
painted barriers have the same restrictions as physical ones ie can only
turn right at specified places etc.
My motto is Keep It Simple, don't over-engineer the representation - use
tags & relations to describe the nuances.
Craig - not Chris ;-)


> > The intersection shown in the links below is an interesting case. As it
> is
> > currently mapped in OSM, the mapper is showing the turning posibilities
> at
> > the intersection (and to a lesser extent that the turning lanes have
> their
> > own separate traffic light sequences). To my mind this is over mapping.
> > While the intersection is displayed neatly at smaller scales, at the
> largest
> > scale it is not pleasant (not saying it is wrong!). I am wondering if
> anyone
> > has routed through this intersection with a garmin - what happens? Is it
> > correct? I suspect in the scenario where you were travelling south and
> > wished to turn right (west) into Christine Avenue you would be told to
> "turn
> > right into 'to Christine Avenue', continue along Christine Avenue" which
> > isn't correct. The intent of the mapper (as far as I can ascertain) was
> to
> > indicate "move into right lane, turn right into Christine Avenue".
>
> I have not changed the current intersection in osm but here are two screen
> shots of the intersection in josm.
>
> http://www.4x4falcon.com/osm/junctions/intersection_messy.jpg
> http://www.4x4falcon.com/osm/junctions/intersection_simple.jpg
>
> The second shows exactly the same from a map point of view as the first and
> also routes correctly.
>
> It's not necessary to map all the turning lanes and is much easier to read
> on the screen and if printed out in paper form.
>
> If you call this intersection up in garmin, navit, gpsdrive etc when in
> routing mode it's a real mess and becomes unusable.
>
> Likewise it's not necessary to have multiple nodes on a straight section of
> road (unless it's really long).  As an example I just came across one
> straight road that was 150m long. It had 6 nodes on it where it could have
> been drawn with three. One at each end of the road and one where it
> intersected with the second carriageway of the dual carriageway road it
> joins.
>
> Like Chris said this is overmapping.
>
> --
> Cheers
> Ross
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