Fixing not connected u-turns and u-turns via node inside a way

[annakulikowa]

Background

As part of on-going work to improve the quality of OpenStreetMap data, our team detected a bunch of incorrect u-turn restrictions all around the world. To collect such data, we've parsed specific restrictions around the world (from_way = to_way, and nodes as via).

We are going to focus on predominantly 2 types of cases:

1. U-turns have a via-point inside the way ~ 120 cases

Now	Expected

2. Restrictions with the via point far away from the indicated way ~430 cases. Example

Our actions:

1. Investigate OSM groundtruth sources (Mapilarry, Bing, OpenStreetCam) to confirm if the turn-restriction exists now.
2. If the groundtruth confirms turn-restriction existing, remove the incorrect restriction members and and the correct one to it.
3. If the groundtruth doesn't confirm turn-restriction existing, remove all members from incorrect restriction. Notes for community might be added to get additional information on turn restrictions we are not able to prove by ourselves.

Tools

We are going to edit this area with the help of OSM ID using satellite images provided by Esri, Bing, Maxar and Photo overlays Bing Streetside, Mapillary, OpenStreetCam. Hashtag #mbx_uturns will be used to mark changeset associated with this project.

Timeframe

We are going to deliver edits by the end of the next week.

Contact Person

We welcome feedback, suggestions, and insights from local mappers. If you have questions about this work, or a specific edit by our team, please reach out to Anna at hannakulikova@mapbox.com or post a comment in a changeset.

[annakulikowa]

Reviewing incorrect u-turns is completed, here are some results of our work:

Fixing not connected u-turns:

403 cases when u-turns have a via-point that was far away from the indicated way were reviewed.

Region statistic:

• Asia - 188 cases (47%)
• Europe - 102 (25%)
• North America - 67 (16%)
• Africa - 29 (7%)
• Central America - 7 (2%)
• Australia and Oceania - 6 (2%)
• South America - 4 (1%)

Statistic of fixes:

• 395 turn restrictions were removed (98%) as we were not able to prove their current existence using OSM groundtruth sources.
• 8 turn restrictions were removed and correct restrictions were set by using OSM groundtruth sources (2%). Also 66 cases with via-node inside a way were found among all 403 restrictions (16%) due to an issue with parsing script.

Correction rate by regions:

• Central America - 14,3% (1 fixed item / 7 all cases)
• North America - 6,0% (4/67)
• Asia - 1,1% (2/188)
• Europe - 1,0% (1/102)
• other regions - 0%

In 1 case note for the community has been added to get additional information on turn restrictions we are not able to prove by ourselves.

Fixing u-turns with via-point inside the way:

120 cases when u-turns have a via-point inside the way.

Region statistic:

• Asia - 57 cases (47%)
• Africa - 20 (17%)
• Europe - 20 (17%)
• North America - 14 (12%)
• Central America - 5 (4%)
• South America - 4 (3%)

Statistic of fixes:

• 105 turn restrictions were removed (87,5%) as we were not able to prove their current existence using OSM groundtruth sources.
• 15 turn restrictions were removed and correct restrictions were set by using OSM groundtruth sources (12,5%).

Correction rate by regions:

• North America - 43% (6 fixed items / 14 all cases)
• Central America - 20% (1/5)
• Africa - 15% (3/20)
• Europe - 10% (2/20). Also 3 restrictions were removed with notes (it means that restrictions were defined but there weren't groundtruth sources to map this restrictions).
• Asia - 5% (3/57)
• South America - 0% (0/4).

High correction rate in North America is explained by the fact that there are a lot of good sources in OSM for this region.

Next steps:

On week 23 we are going to parse u-turn restrictions one more time to double-check the issue existing.