On Apr 18, 2022, at 6:50 PM, Andrew Hughes <ahhug...@gmail.com> wrote: > We're using OSM and pgrouting and it's GREAT! > > Something that I have found difficult to come to terms with, is assigning a > "default speed" for unclassified roads (without a maxspeed tag). This is > because in metro area's these are most-likely to be 50kph. However, out in > regional areas these are likely to be 100kph.
This is an interesting “edge” that OSM seems to bump up against every now and then, sometimes rather public (like on a talk-list), sometimes less so, but it still happens. The following is a bit fuzzy, please allow me a bit of leeway. What I have noticed is that there are “defaults” in a legal jurisdiction for an activity (such as “driving through a residential zone in the state of X”) where that implies 40 km/hr, or 25 MPH, or some such. What OSM seems to continue to struggle to do is to somehow capture this idea, whether in tagging, in wiki, in “understood defaults” or in some combination of the above (and/or more inputs). While it might seem like this can be done and/or is a good idea, it can break down as a wider audience (of OSM downstream users / renderers / routers / use cases) struggles to “parse what is.” By the latter, what I mean is that the combination of ambiguously “understood to apply” defaults (whether legal, in OSM somehow, like in a wiki, or other) become murky. It isn’t always clear what to do because of what is tagged (and what might be, or isn’t, or could be) and understood. Please, I urge all to be careful when we make assumptions based on “well, in Western Australia…” (for example) because this is a commercial zone, we can assume a speed limit on an unclassified road. Sometimes it’s safe / effective / realistic to assume defaults apply, much of the time it is not, and such assumptions are folly. It can be difficult to even describe these, as I struggle for words as I type here. So, if you’re going to do this, you have to imagine that you can imagine all future, downstream use-cases. Maybe you can, maybe you can’t. Be careful. _______________________________________________ Talk-au mailing list Talk-au@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-au
