I would like to share a new MapRoulette challenge type (Bulgaria - Fix Incorrect Junctions on Roundabouts). We’ve developed new checks aimed at identifying and correcting cases where two or more highways are connected to the same node on a roundabout.
According to the [OSM wiki documentation], highways entering and exiting a roundabout should never connect to the same node on that roundabout.
Why is this important? Fixing such situations will enable routing applications that rely on OSM data to correctly recognise the situation, providing improved guidance when entering or exiting a roundabout.The Leads were detected based on a query of OSM data.
We compared the number of highways entering and exiting a roundabout to find situations with a high number of highways or a low number of highways that are part of junction=roundabout or junction=circular. We excluded pedestrian paths, cycleways and roads that are located on different levels (bridges, tunnels).I trust you’ll find this challenge valuable for enhancing OpenStreetMap in Bulgaria.
There are currently 132 tasks distributed throughout the country. If you believe it adds value, we may be able to add more tasks.
I took a quick look at the flagged items. Overall it does point at some interesting ways that some things are mapped. There are just two cases for which I think that we can’t fix (or rather shouldn’t). They are at nodes 1119209513 and 6302060459. The junction is built in such a way, that if you are coming from the north, you will go straight (if you want to go south). Then if you want to continue south, on the second junction you just continue straight on (you don’t turn left and then exit right). If the entry and exit nodes are apart, routers would suggest a zig-zag route (turn right, instantly turn left, turn left left, instantly turn right) which is not a good situation IMHO. Other than that, I haven’t noticed any other problems.
How about cases where it’s not a way entering and another exiting the roundabout at the same node, but 2 exits on the same node, like this case Node: 3356886821 | OpenStreetMap ? Is that an issue?
Only yesterday fixed one flagged by Osmose as ‘shortcut’. The surprising thing is, done by a long time mapper i.e. should know. Why it’s done? Maybe it’s easier on the route relation mapping, no cutting up of the roundabout ring for the on-via-to. Anyway, Osmose can be used to set a filter on this issue.
It should be fine since Node: 247889287 | OpenStreetMap isn’t/wasn’t flagged. But keep in mind that Stochna gara is marked as junction=circular unlike your example (which has junction=roundabout). It might make a difference in TomTom’s algorithm.
Thank you @Dimitar155 : really appreciate your attention to the challenge, please do not hesitate to open our eyes on all types of scenarios so we can make our challenges more validated and smarter
This challenge is now complete. There were a few cases where I doubted that the junction was really a roundabout, but I assumed the mapper who created it has local knowledge.