I would generally agree with all your points. A slightly more formal definition (though not fully rigorous) for me would be: a circular route is one in which, from any boarding area, you can return to the same boarding area without being forced to disembark.
I say boarding area rather than point because of the fairly frequent case where the dropoff and pickup points serve the same area (such as a train station) but are not necessarily identical. The example I gave in the other thread, I believe, is marketed that way because people are indeed supposed to leave the bus, though I would imagine that since most people use weekly or monthly passes, most drivers would probably look the other way. https://www.openstreetmap.org/relation/8140184 Thorsten's description is good, but technically pretty much any bus route is a roundtrip (circular) topologically. A typical route is: A -> B -> C -> (forced disembark) -> C' -> B' -> A' -> (forced disembark) -> A ... Typically B and B' are on opposite sides of a two-way street. That's the simplest example. Topologically it's the same as a circular route, because the bus makes a U turn at each end and continues. So it's a question of marketing and general public understanding, more than mathematical rigor. But the variations are bewildering. Personally, I track circular routes for validation purposes. As I understand Public Transport version 2, every route variant requires a route master, even if the master has only one variant. So masters with one variant are oddballs; most routes have at least two. A master with only one variant is typically either (a) a circular route (so I mark them in my private database), (b) a PTv1 route (thus needing an upgrade), or (c) an error (thus needing further investigation). I would mark the OSM example above in my data as a circular route, so I won't flag it as needing further work, but it would not meet my more formal definition of a circular route, because of the forced disembark, so I would not consider it as qualifying for a "roundtrip=yes" tag. If there is sentiment to change the name of the tag, I would suggest "route:circular=yes". (There are "only" 25000 in the OSM data, so it might be manageable.) I don't like "circular=yes" because it's so vague. (example: building=silo circular=yes ?) On Fri, May 25, 2018 at 1:23 PM, Peter Elderson <pelder...@gmail.com> wrote: > Oops, I didn't think this topic would generate so much response, even > though I charged a bit in the first mail. > > Let me try to make some sense of it. I have seen enough use cases, I think. > > a. There are two use cases which use the actual definition on the wiki: a > geagraphically closed route, start-point=end-point. One is about marking > routes as roundtrips based on JOSM validation, then monitoring if the chain > had broken so you can fix it. The other is marking an unfinished route as > roundtrip in order to detect it for completion. To me, this is almost the > same use case. > > b. A range of use cases are opposite: a geographical roundtrip has to be > regarded as non-roundtrip, or a geographical non-roundtrip has to be > regarded as a roundtrip anyway. > > Could we agree that the wiki should cover b.? > I think this does not exclude a. > > If anyone judges that a geographical roundtrip should explicitly be tagged > as roundtrip=yes, ok. > do think that when one of the use cases under b. applies, then you have > an exception to what the map says, with a reason. Then this takes > precedence over the geographical default. > This could be a geographical roundtrip tagged as roundtrip=no for whatever > reason, or a geographical non-roundtrip tagged as roundtrip=yes, for > whatever reason. It would be nice to know the reason, of course. For my > part, "everybody/nobody here calls this a circular line" is reason enough. > > Could we agree on that too? > > If so, all that remains is add this to the wiki. > > -- > Vr gr Peter Elderson > > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging > >
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