As well as "You can't do this" and "You must do this" we need "You may do this (that normally you can't)". Where I live, you can't do a U-turn at traffic lights unless there's a sign that says you can. If we try and mark this by putting relations at every light banning U-turns, we'll just end up with the no-street name problem - how can you tell the difference between somewhere you can do a u-turn and somewhere that hasn't been mapped. If we can mark the places you can turn, then it matches the signs, and we can preprocess the data to something routers can use.
There's a challenge for the router dev's as well. Add an option to your routing software that disables u-turns at traffic lights unless a restriction specifically allows it. You'll be ahead of both of the commercial GPS devices I've tried. Stephen 2008/11/30 Frederik Ramm <[EMAIL PROTECTED]>: > Hi, > > Nic Roets wrote: >> At T junctions the ambiguity is resolved using >> restriction=no_left_turn/no_right_turn. > > For the record, I am strongly opposed to automated processing of the > "restriction" except to see if it is "only..." or "no...". > > I want a situation where the two parts of the road are unambiguously > identified by the "from" and "to" members, meaning that if any of these > do not start/end at the junction they have to be split. > > The "restriction" tag would then be used to check whether I can "ONLY" > go from "from" to "to", or whether I can "NOT" go from "from" to "to". > Whatever follows after "no_" or "only_" can be used to paint nice > matching signs on a map or to give voice commands, but should not be > used to identify which ways the restiction applies to! > > Bye > Frederik > > -- > Frederik Ramm ## eMail [EMAIL PROTECTED] ## N49°00'09" E008°23'33" > > _______________________________________________ > talk mailing list > talk@openstreetmap.org > http://lists.openstreetmap.org/listinfo/talk > _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
