[talk-au] Roundabouts and routing

[Ross Scanlon]

> 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