Find out if crossroad or 3-way-intersection

Question

I'm trying to find out the type of a crossroad / intersection in overpass by given coordinates (simple 4-way-crossroad or 3-way-intersection aka Y/T intersection).

Wanted to count the way-id's I'm getting via json later in program code (4 = simple crossroad, 3 = Y or T) using the following query: http://overpass-turbo.eu/s/NyD

[out:json][timeout:15];
way["highway"](around:1,48.7986003,11.3759673);
foreach ->.w {
  node(w.w);(way(bn);- .w;)->.wd;
  out body geom;
};

Problem: This only works if a street ends at the crossroad / intersection or at least turns into another way-id. In this example there's a street which reaches from north to south and east. The east way got another way-id so that's not a problem. But from north to south it's just one way (so only one id). Result: I'm counting 3 but it should be 4 for this type of crossroad.

How do I solve this problem or is there a better way to identify the type of a crossroad / intersection?

Thank you very much!

crosspost: https://gis.stackexchange.com/questions/340207/find-out-if-crossroad-or-3-way-intersection — scai, Oct 30 '19 at 09:40
Similar question: https://stackoverflow.com/questions/58478621/filtering-intersections-to-4-way-intersections-t-junctions-and-other-using — mmd, Nov 02 '19 at 10:03

score 2 · Accepted Answer · answered Oct 30 '19 at 09:16

You have to look at the junction node, too.

Some examples:

If the node is part of two ways and..

these ways have other nodes before and after this node ID then you have a 4-way-junction.
only one way has other nodes before and after this node ID then you have a 3-way-junction
none of these ways have other nodes before and after this node ID then it is not a junction. Instead, the way continues with a different ID.

If the node is part of n ways and it is the last or first node of all these ways then you have a n-way-junction.

There will be some more cases than the ones mentioned above. Take a sheet of paper, draw some ways and their nodes onto it to get a better visualization of the data.

I'm not sure if this simple approach will work for all cases, though.

Thanks, works quite well. For more than two ways I'm looking additionally if the junction node is equal to the first or last node of a way. 2 or 4 occurences mean 4-way, otherwise 3-way. That fits for me for now. — Youkai, Nov 07 '19 at 12:03

Find out if crossroad or 3-way-intersection

1 Answers1