On Sun, 2012-08-26 at 20:30 +0200, Erik Johansson wrote: > On Sun, Aug 26, 2012 at 2:00 PM, Craig Wallace <[email protected]> wrote: > > On 26/08/2012 08:42, Markus Lindholm wrote: > >> > >> Also, no one has offered any other solution to the routing issue. The > >> divider tag has been proposed, but I think it has been demonstrated > >> not to work, as routing decision are made on the node and not on the > >> line. > > > > > > Where has it been demonstrated not to work? What do you mean by "routing > > decision are made on the node and not on the line"? > > Yes, the divider tag is probably not supported by any current routing > > software. But it would not be too hard to modify the software to allow for > > it. > > This is an area which has two ways instead of one: > http://osm.org/go/0bCzT1kfr-- > > Here is an route example: > http://map.project-osrm.org/1cL > > Without two ways you would be routed directly to the end point, but > with two ways you will be routed with the needed detour. It's > especially interesting if you go by bike but then it's more of a > psychological divider than a physical (which is another story). > > > > I don't like mapping like this, but I'm pragmatic and it does solve a > real problem, so I decided no to fight Markus on this. > So what is the recommendation for mapping this. > Its a difficult question.
The pragmatic approach I would take is the driver should follow the rules and let the satnav catch up. I must admit I have cheated here, and looked at streetview. The U-turn that the router has come up with looks very wrong to me, the road just isn't wide enough to complete the turn from the left lane. To do a U-turn from the right lane, across straight ahead traffic is dangerous. In this case the false dual carriageway seems wrong and gives a wrong impression of what is on the ground. I think the correct and safe answer is this http://map.project-osrm.org/1cX Outside of a built up area, using this method will give the false impression of the existence of dual carriageway and anyone using OSM as a map will expect a fast road and will find a slow one where overtaking is impossible. Phil _______________________________________________ Tagging mailing list [email protected] http://lists.openstreetmap.org/listinfo/tagging
