2009/7/31 Greg Troxel <[email protected]>: > I see Trunk as almost motorway, but a little deficient. Definitely has > to be divided by at least some concrete (== dual carriageway), and > mostly limited access with infrequent at-grade intersections. Urban > areas are so crowded that roads that meet this definition have to be > basically motorway like but probably more curvy with lanes that aren't > wide enough, and have too many on/offramps.
This is illustrative of the problem we have in OSM of so many tagging norms. Because this _isn't_ the way trunk is used in many other countries. In Ireland, we tag our roads by and large by administrative class, not by quality (though there is quite good correlation between the two). For this reason, our highway=trunk sections can be anything from motorway-grade roads down to quite poor single-carriageways. They can also be surface roads in towns. I know that German tagging norms have overloaded the interpretation of trunk, something I was never happy with. Annoyingly, the German mappers can't seem to agree on exactly what extra must-haves apply to a highway=trunk. Some claim it should imply motor_road=yes, others insist on grade-separated junctions, others still on near-motorway characteristics. My point here is that we need to be very careful before we assume any consensus or even any possibility for real consensus. We have already diverged on country lines in our interpretations of the highway tag and it seems likely that any routing application will need to infer quite a bit based on knowledge of local tagging norms. If consensus is to be pursued, I am strongly in favour of the existing highway tag being used to convey what I'm going to call road "class", by which I mean its official classification, importance, routing significance, whatever. Other aspects related to the quality of the road or its suitability for any particular kind of vehicle or user can readily be accommodated using other tags, some of which are already widely used. We have, for instance, tagging norms for: Prohibitions on use Max and min speeds height, width or weight restrictions Number of lanes Width of carriageway whether single or dual-carriageway (not through tagging, but we can tell) Grade separation or otherwise of junctions (through examination of whether single or dual-carriageway and evaluation of turn restrictions) Surface And even smoothness, for those who require it So I urge: * DON'T blindly adopt a tagging idiom from another language just because they have been more specific * DON'T adopt a change to tagging norms that will break a lot of existing work * DON'T have sneaky edits to the wiki that don't reflect actual consensus * DO look to evolve current practice in safe, sane steps towards something that solves real problems with current practice * DO document on the wiki the kinds of problems we are actually trying to solve (hard to have a useful discussion without this) Dermot -- -------------------------------------- Iren sind menschlich _______________________________________________ talk mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk
