#74 - Turn Lanes in Washington DC (Archived)

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This project was archived.

Mapping turn Lanes on highways secondary and up in Washington DC

Created by Jothirnadh - Updated - Priority: medium


Entities to Map
turn:lanes, turn:lanes:forward, turn:lanes:backward
Changeset Comment
Add missing turn lanes from satellite imagery in Washington DC https://github.com/mapbox/mapping/issues/180
When saving your work, please leave the default comment but add what you actually mapped, for example "added buildings and a residential road".

Mapbox , Bing, USGS

JOSM Workflow


  • Activate the following in from JOSM preferences > Map Settings
  • Map Paint Styles: Lanes and road attributes
  • Tagging Presets: lane attributes
  • Filter out non road features with boundary: | leisure: | landuse: | waterway: | amenity: | natural: | building:
  • Add inverse filter: highway=motorway|trunk|primary|secondary|*link|motorway_link or untagged
  • Read http://wiki.openstreetmap.org/wiki/Key:turn:lanes
  • Read https://github.com/mapbox/mapping/wiki/Mapping-guide-for-turn-lanes-from-imagery
  • Install the 🔪 tool in JOSM to easily split the roads: https://wiki.openstreetmap.org/wiki/JOSM/Plugins/Knife-tool
  • Use the Turn lanes tagging Plugin in JOSM Preferences>Plugins
  • If there is a missing road at the junction representing the turn lane make sure to map the missing road as well


  • Check the roads for turn lanes at exits and entry points
  • Split the road into segments based on the total number of lanes for the segment
  • For each road segment tag the turn lanes based on the road markings in the direction of the way. Eg. turn:lanes=left|through|right. See OSM turn:lanes
  • For bi-directional segments, use turn:lanes:backward= and turn:lanes:forward= to specify turn lanes in each direction.
  • Verify correct tagging using the Lane attributes style

Issues to keep in mind:

  • For QA and edge cases in turn lanes mapping and how to handle them(parking lanes, splitting roads for start and end of turn lanes, handling of dual carriageways, etc) look into the QA for turn lane data document.
  • Priority area is having 3-inch recent Mapbox imagery, outside of the priority area let's continue using Bing/USGS for mapping

Changeset Comment: Add missing turn lanes from satellite imagery in DC https://github.com/mapbox/mapping/issues/180

Source: Mapbox, Bing, USGS


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