|Feature : Junctions|
|Related to junctions between roads|
See Editing Standards and Conventions#Junctions for editing basics.
A simple intersection is represented by the ways for the two roads sharing a common node.
Dual carriageway intersections
When a single carriageway intersects a dual carriageway (on the same level), the junction is represented by two nodes and a small section of the single carriageway (left image). When two dual carriageways intersect, the junction is represented by four nodes and four small sections (right image).
When all sections of a carriageway have the same attributes, they can be represented by a single OSM-way going through. Once attributes are different, such as having turn:lanes=* or destination=* mapped, they become split into individual OSM-ways.
Representing a road area by a linear OSM-way is an abstraction for routability. In analogy, the four nodes and the inner way sections of a dual carriageway junction are an abstraction from the real junction area (grey in the example images), also required for routing. This can however lead to problems for assigning the name=* tag. Obviously, the pink segments m and n in the pictures can be named as A-road without a conflict. On the other hand, the blue segments p and q might be named either B-road or C-road, or given no name at all. Similarly, the destination=* should be tagged on the outer segments where things are unambiguous.
Roundabouts should be tagged as junction=roundabout. Small roundabouts where the middle can be traversed by vehicles should be tagged as highway=mini_roundabout.
Intersections with stop signs should be tagged highway=stop. Intersections with traffic signals should be tagged highway=traffic_signals.
Mapbox recommendations on mapping junctions
A ford (where automobiles, pedestrians, or horses enter the water to cross a stream or river) should be tagged as ford=*.
Rail/road level crossings
Rail/road level crossings should be tagged as railway=level_crossing.
Pedestrian road crossings
- Main article: Crossings
Pedestrian road crossings (UK: zebra crossings; US: crosswalks) should be tagged as highway=crossing. Pedestrian rail crossings should be tagged railway=crossing.
- highway=junction: Proposal for mapping the extent of junctions and to reduce the number of needed relations