SomeoneElse <[email protected]> writes: > Presumably the argument for tagging "maxspeed=60mph" where it's actually > signed > as "national" is that it's too hard for routers to figure out whether > something's a single or dual carriageway? I'm not sure why we have to depart > from the "on-the-ground" rule in this case - if it's not obvious that > something's a dual carriageway surely that's a tag that should be added, not > some curious code value stored against a tag (source:maxspeed) that's usually > used for something else entirely?
As the author of an OSM data consumer (the router "Routino") I think that distinguishing between single and dual carriageways is mostly irrelevant in the argument for preferring numeric values for maxspeed tags. The real reason which I see, and which is much more difficult to handle, is when you consider that there are ~200 countries in the world and they each might have their own speed limits. If everybody tags their local part of the world with numeric limits we create a database that anybody, anywhere, can use without any knowledge of foreign legislation. If we tag with local conventions then we end up with something suitable only for a tiny fraction of the potential users. I agree that extra tags for dual-carriageways are preferable to infering that information from the speed limit. Trying to deduce whether a road is a single or dual-carriageway from the speed limit is bound to fail, not least because of those dual-carriageways that have 60mph limits. For the record, Routino doesn't allow you to prefer dual-carriageways when routing but you can select to prefer multi-lane roads (those that use the "lanes" tag) which largely has the same effect. Perhaps we need some "UK national speed limits" tagging presets for JOSM to encourage people to use a consistent set of tags (if we can ever agree). Andrew. ---------------------------------------------------------------------- Andrew M. Bishop [email protected] http://www.routino.org/ _______________________________________________ Talk-GB mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-gb
