Recently, a new undergroud trunk road opened near my house, which is not currently shown on OSM. It is designed in a way that the eastbound carriageway is directly on top of the westbound one, and both of them are located beneath narrow ground streets. Being new to OSM, I am puzzled about how to show this…
Any suggestions?
Just offset it to the side, doesn’t have to be exactly drawn on top of each other.
Hi, they can be drawn on top of each other as they are in reality, don’t join them together at nodes, (except where they might join up at the ends).
Tag them with the appropriate layer, the highway at ground level would be layer=0 so the layer is implied, it need not be tagged. Tag layer=-1 to the higher of the underground highways and tag layer=-2 to the lower one.
JOSM is easier than iD here, when there’s no snapping by default, and better object selecting.
See also the situation in Maastricht (The Netherlands) where also two tunnel are below grounflevel:
https://www.openstreetmap.org/query?lat=50.84117&lon=5.71728#map=16/50.8407/5.7150