Hi- I'm a user, not developer, trying to clean up the data in my area to make it more usable for routing and directions.
Several times now I have come across a situation that seems wrong, and has not improved by itself in the last year or two as far as I can tell. That is where routers want you to make a U-turn on a highway link. My most recent example is here: http://maps.cloudmade.com/?lat=45.418666&lng=-122.321563&zoom=16&directions=45.41881686582581,-122.32349395751953,45.4324308667588,-122.36778259277344&travel=car&styleId=1 and here: http://nroets.dev.openstreetmap.org/demo/?lat=45.42567&lon=-122.34394&zoom=13&markers=!45.41879,-122.32406!45.43276,-122.37054&v=motorcar&fast=1 and it looks like others have found it to be an issue before also: http://wiki.openstreetmap.org/wiki/Talk:Gosmore#Illegal_Routing I understand that I could make a new turn restriction relation for each end of every single highway onramp in the world. However, it seems like that is a redundant waste of effort if we can identify a default pattern. My Garmin StreetPilot C330, though old and creaky at this point, works great on OSM maps from mkgmap, and doesn't do this. But it has a number of configurable settings, including "no U turn" which I enable. It seems to me, however, that choosing U-turns or not as a personal preference is nice, but it should always avoid giving a U turn in situations that just would not be possible to drive. It seems like we should be able to identify some rules where a router would never give out U-turns. I don't know exactly what those would be, but I have some ideas. highway=*_link, particularly if it is oneway=yes, seems like an obvious one. On those, it should clearly take the one closest to straight-on. For example, if you have one direction less than +/- 45 degrees and another over +/- 135 degrees from the last bearing on the *_link road, the router should never choose the U-turn over 135 degrees. I would be REALLY nice, also, if different routing engines worked the same way for this issue. Anyone have ideas on how we can solve this in a good way? - Alan -- Alan Millar [email protected] _______________________________________________ Routing mailing list [email protected] http://lists.openstreetmap.org/listinfo/routing
