This diary post last week outlined an overarching goal of making OpenStreetMap navigable, and our intent to investigate and add missing turn-restrictions in Berlin, Stuttgart, and Wolfsburg using Mapillary as a source. We received some good questions from the local OpenStreetMap community about using Mapillary as a source. Considering the concerns of the community, we did a preliminary research on the Mapillary imagery to ascertain their recency. We want to share our findings here.
Here is an animation showing Mapillary traces in Berlin, Stuttgart, and Wolfsburg spanning the last six months (March - August 2016). Not surprisingly, Berlin was found to have the best Mapillary coverage. The coverage in Stuttgart and Wolfsburg was sparse in comparison.

Berlin2 Berlin Mapillary Coverage

Stuttgart2 Stuttgart Mapillary Coverage

Wolfsburg Wolfsburg Mapillary Coverage

Recency of Imagery

When adding data on OpenStreetMap using any type of source, recency is an important aspect to consider. The plan is to add data on OpenStreetMap only if Mapillary imagery is more recent than when the turn-restriction was added. If this is not the case, or there was a recent change in the area, the intent is to add a note, and rely on the knowledge of the local community to verify accuracy. Based on this approach, here are a few cases where turn-restrictions could be added. To the best of our knowledge, these are valid turn-restrictions that are not added on OpenStreetMap. To do this, we’re using the OSM Navigation Map to detect turn-restrictions, and their absolute positions using Mapillary. We’d appreciate if anyone with knowledge of these areas can verify if these detected signs are in fact correct or not.

screen shot 2016-08-23 at 11 48 50 am

We had carried out our preliminary research in reviewing Mapillary detected turn restrictions in these 3 cities, using OSM navigation map. We time boxed this task to 2 hours with two people working on Berlin and one each working on Stuttgart & Wolfsburg. We were able to find 25 missing turn restrictions out of the 110 we reviewed. Turn restrictions are categorised as valid/invalid/redundant based on the Mapillary detected signboards and by the OSM data present.

Case 1:

screen shot 2016-08-23 at 12 03 25 pm Missing No Left Turn (Link to OSM note)

Case 2:

screen shot 2016-08-23 at 12 08 56 pm Missing No U Turn (Link to OSM note)

Case 3:

image Missing only_straight_on (Link to OSM note)


screen shot 2016-08-23 at 12 45 20 pm

Missing only_straight_on (Link to OSM note)


screen shot 2016-08-23 at 12 54 41 pm Missing only_right_on (Link to OSM map)

Also, some other missing cases are listed here.

While we reviewed turn restrictions that can be mapped using Mapillary, we also verified some of the existing turn restrictions and encountered few cases where community feedback would help

Case 1:

  • In the case below, the image shows that there are restriction signages for each lane
  • Also the turn restriction added was a no_u_turn, which did not show up in the Mapillary.
  • In such a case, what is the approach community would suggest?

screen shot 2016-08-23 at 4 07 49 pm Link to the map.

Case 2

  • In this case the signboard is showing only_staright_on but it was added as two separate turn restrictions, no_left_run & no_right_turn.
  • As per the German wiki it should have been added as only_straight_on.
  • We would like to get feedback on adding such turn restrictions, what is the general convention the community follows?

screen shot 2016-08-23 at 5 38 25 pm Link to the map

Case 3

  • We have observed a no_straight_on restriction which seemed odd as it was on a dual carriage way with highway=teritiary tag.
  • We could not verify this with Mapillary images, as there was none on the road. It would be great this can be verified by the local mappers.

screen shot 2016-08-23 at 5 52 39 pm Link to the map

Based on the community feedback received, we are ready to add OSM notes for the missing turn restrictions if the community has no issue with this and also open to getting any thoughts you have on improving the OSM Navigation Map whether it’s feature requests, or bug fixes here.

Thank you :)


From Mapbox Data Team


Comment from Nakaner on 24 August 2016 at 17:05

U-Turns are forbidden at road crossing Borsigstraße/Heilbronner Str. in Stuttgart if you come from Friedrichswahl because there is a restricted area painted on the street.

That’s why u-turns are prohibited here but allowed here (coming from Plieningen doing a u-turn back to Plieningen). There is a no-passing line (road centre marking without gaps) painted after the traffic island at node 1.

Turn restrictions can be implicit in Germany.

Comment from Jojo4u on 25 August 2016 at 11:23

The turn restriction at Borsigstraße/Heilbronner Str. is now wrong, the road was changed in 2012/2013. Now the restricted area is not in the way of a u-turn, just compare the aerial images 2013/2015 and 2011 (slider right top) here: Comparing with Streetview: even in 2008 when the restricted area was in place there was no sign present.

Unfortunately the view on the restricted area on all Mapillary images is blocked by cars. Since OSM is only [allowed to use the 2011 Stuttgart arial images] ( we have a difficult here. In this unclear situation I would create a note and leave to local mappers.

If the situation is more clear (unrestricted recent Mapillary view, edits are older) I would directly delete the restriction. There a quite a view mappers watching changesets in Stuttgart - if you make big mistake it will be noticed.

In Germany turning is not allowed if (refering to 1. A sign forbids it 2. A “Intersection arrows” is present and does not point in your direction 3. A “Restricted zone” or a “solid center line” will be crossed

Comment from nammala on 1 September 2016 at 14:36

Thanks for your valuable feedback. Have followed the instructions during our updating process.

cheers, Krishna

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