Lane number and turn lane editing in Detroit

Since we started editing in Detroit, we focused on making OSM navigation ready. We started with the basics: road geometry, road name, turn restrictions, and then we were able to further build on this foundation by adding details like lanes and turn lanes. In the last four months, we focused on adding and updating the lane info (lane number and turn lane) on motorway, motorway_link, trunk, trunk_link, primary, primary_link, secondary, secondary_link roads in Detroit, Michigan.

For editing lanes and turn lanes we used JOSM, the TurnLanes-tagging Editor plugin and the Lane and road attributes map paint style.

We had two kinds of lane editing: unidirectional road editing, bidirectional road editing. The only difference between those two is the direction tag used in the second case, as you can see in the below table:

For every edited case, we used a simple workflow:

we split the way where the number of lanes changes
we checked and double-checked the aerial imagery to make sure we enter the correct number of lanes and add the appropriate lanes tag
we opened the turn lanes-tagging plugin and activated the Lane and road attributes map style
using the plugin, we selected the type of the road: Unidirectional road or Bidirectional road
we marked the number of lanes for each way needed
we marked the direction on each lane
before uploading the data, we checked again that the turn lanes that we had added were similar to the markings on the road!

The approach of the main cases we’ve met during our edits is exemplified in the next GIFs.

Editing the number of lanes

Adding both ways lane

In some particular cases, when there were doubts, we consulted the OSM community on Github and Talk-US.

While editing, we paid special attention to other already existing features (like route relations, turn restrictions, speed limits, etc). Because all Telenav Mapping team was involved in this project, we established from the beginning some rules, in order to have consistency in our edits:

Add a new lane only when you have a line marked on the road (use the satellite imagery, OSC photos to validate the marks).
Links without any marks on-road or without one-way tag should be edited as a bidirectional road, adding one lane on both driving directions.
Never add the turn lane before or after the continuous line mark on the road. The turn lane will be added starting from the beginning of the continuous line mark on the road.
We split and edit lane numbers even when we have small segments of ways.
The location of the junction nodes should be at the beginning of the continuous line marks.
We always add the yellow both-way lane.
We DO NOT add the yellow striped lanes and double marked line lanes.

The main sources used during the project were aerial imagery (Bing, Mapbox, NAIP, Digital Globe) and street-level imagery: OSC, Mapillary.

We worked on this issue for 2 months and succeeded to review a large part of the motorway, trunk, primary and secondary roads from the Detroit area, in order to add or update lane info. During this project, we managed to review 3100 miles and edit 1730 miles of roads.

Here’s how the number of miles of roads with lane information has increased during the project:

The edits we made cover a large area of the Wayne, Macomb and Oakland counties. In the GIF below you can see an evolution (difference between March and July) of our lane info edits in OpenStreetMap.

Heatmaps with our edits during the last four months:

When we finished editing lanes and turn lanes in Detroit, we started assessing the general quality of the lane info by using different approaches. Internally, we call this process quality assurance and we think it is vital to do it after the end of each project.

During the QA process, we edited lane info on about 400 miles of roads, and the main issues that we corrected were: