I've split a lot of roundabouts to accommodate a lot of routes — usually in the USA's "midwestern" region where there are many roundabouts and for USBRs, our national-level bicycle routes, respectively. I usually split at the roundabout's nodes where they "need" splitting for that particular route's elements to "be routed correctly." This follows from my (and other human editors') habit of splitting ways "as needed." For example, if the roundabout needed to be split on "only" two or four nodes (to accommodate a 90˚ turn, for example, in both directions) that's what I do. If another route (say a bus route that uses the same roundabout) needs to go in all four directions (starting from any direction, 0˚, 90˚, 180˚ and 270˚) then THAT route's human author should split the roundabout on four nodes (or eight if traffic is bidirectional on dual carriageways). There isn't any real harm in having "too many" splits, except for maybe some confusion by beginning editors of maybe needlessly over-splitting. Make it make sense for other human editors (or even software which consume such data, like renderers or especially routers) and you (and present and future software) should be OK. And other human editors tend to see this and get in the (good) habit of "splitting up to and only 'as needed,' but no further."
I can see how a routing software (voice) could envision a 270˚ turn through a roundabout coming up ahead and turn that (logically) into a voice command to "turn right." (Or 90˚ for "turn left," as you Aussies drive on the left, different than us Yanks who drive on the right). I think OSM is fine now and will be fine in the future using this approach — it has worked for me for over a decade of routing through roundabouts in OSM. And others seem to "pick up on it" and do the same in other roundabouts. (Your mileage may vary with that last point). Things like "where to split and how much?" and "how many nodes in this curve?" tend to evolve to take care of themselves over time (as humans "spread good seeds" to other human editors). But while over-splitting and over-node-ing does happen, I don't think it is a huge problem. stevea, California _______________________________________________ Talk-au mailing list [email protected] https://lists.openstreetmap.org/listinfo/talk-au
