How to tag road junction names and traffic signal names? Background: In some countries (Japan, Korea, Ivory Coast…) people orient themselves in the local area using the names of road junctions (like crossroads or roundabouts) or traffic signals rather then the names of streets. While street names also exist, they are not important for orientation. (Note: This is about orientation in the local area, thus different from the names of motorway junctions who’s names serve for orientation at large distances.)
Use case: This information is necessary for rendering maps and can be useful for turn-to-turn navigation. Current situation: We have the tags highway=traffic_signals (for traffic signals on road junctions or at straight roads – typical for Japan) and junction=yes (for road junctions with or without traffic signals – typical for Ivory Coast) in use at OSM. Both tags are almost exclusively used on nodes. They can be used together with name=*. This works quite well for simple crossroads (example: http://wiki.openstreetmap.org/wiki/File:Junction_yes_example_1.png ) Shortcomings of the current situation: It isn’t defined how to tag more complex cases. This should be made clear – also because we want to have a suitable rendering for this in openstreetmap-carto ( http://github.com/gravitystorm/openstreetmap-carto/issues/374). Ideas for road junction names (countries like Ivory Coast): Example: http://wiki.openstreetmap.org/wiki/File:Junction_yes_example_2.png is a junction in Ivory Coast. How can we tag the junction? If we make a node at the red point (centre of the junction), this will be fine for rendering (rendering the name at the position of the red point), but not as easy for turn-to-turn navigation because the point is not part of a way. We could also tag the four nodes where the ways cross. This will be fine for turn-to-turn navigation, but not as easy for rendering (sorting out duplicates because you should render the name only once, not four times). Furthermore, you have to provide the same information four times (and you can make a spelling mistake four times). You could also use a new relation type, which contains the four nodes where the ways cross. This is a clean solution, but complicates to use for beginners, and complicate for a quite simple task like adding a name of a junction. We could also make an area (closed way) around the junction area, sharing nodes with all incoming and outgoing ways. This would be less “clean” tagging than a relation would, but it is much easier to use for beginners, and be still quite easy to process for rendering and (I think) also routing. (PS: Another type of “complex junctions” are roundabouts like http://www.openstreetmap.org/#map=19/5.35590/-4.07360 in Ivory Coast. You will not use the name=* tag on the way that makes up the roundabout itself because this would render like in western countries as a label of the street itself. Instead, you need something different that renders bigger – so the tagging should also provide a solution for this use case.) Ideas for traffic signal names (countries like Japan): On the ground, each traffic signal in complex crossroads seems to have its own sign showing the name. Searching a little bit around, I’ve found at http://gis.19327.n5.nabble.com/Crossroad-names-td5754463.html > As theory, the names of Japanese traffic signals are given to each > signals, not to a junction. > (and basically, the signals on a same junction has same names) However, rendering each name four times may not be very nice. Google and Bing display the name only once ( http://tools.geofabrik.de/mc/#18/34.3847/132.4542&num=4&mt0=mapnik&mt1=google-map&mt2=bing-map&mt3=geofabrik-topo), in the middle of the crossroad. They even display the traffic signal icon only once. Currently, in OSM there seem to be for Japan the name at each of the nodes where the ways cross. How can we get a clean and reliable tagging here, which is suitable for rendering and turn-to-turn navigation? Lukas Sommer
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