On Fri, Oct 29, 2010 at 2:45 AM, Peter Budny <[email protected]> wrote:
> That doesn't work; there are cases where it's ambiguous. If you look at > [1], US-278 runs along North Avenue (bottom) and Ponce de Leon Avenue > (top), connected by Monroe Drive (left) and Piedmont Avenue (right). > > The problem is that North Ave and Ponce de Leon are both oneway=no, > while Monroe and Piedmont are oneway=yes. So unless you run a routing > algorithm over the relation, you can't figure out just from the oneway > tags that US-278 westbound doesn't include North Avenue (which you would > otherwise assume from it being oneway=no). Someone, somewhere, has messed this up good an proper. I can't find the origins of this discussion to figure out where it's arisen from though. The situation you describe is easily dealt with using Route Relation roles "forward" and "backward" as per cycle routes, or bus routes, or every other route relation. See for example http://www.openstreetmap.org/?lat=51.88888&lon=0.89395&zoom=17&layers=00B0FTF It's clearly documented here: http://wiki.openstreetmap.org/wiki/Relation:route#Members and rendered on multiple maps. However, I see from elsewhere that people are making route relations in the US and filling the memberships with "west" and "south" and suchlike and then finding this causes problems. My advice is to stick to the route relation member roles that work for every other type of route, and if people reeeeaaaaalllly want to have separate routes for I5 East and I5 West then feel free (something that hasn't seemed necessary elsewhere) - but don't put the words "east" or "west" in the ref, add an additional tag to the relation for "overall direction" or something. But please, stick with the forward/backward stuff for route relations roles, it works well. Cheers, Andy _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
