Reviewing navigation data in France

Posted by BharataHS on 9 September 2016 in English (English). Last updated on 19 September 2016.

One of the prime applications of maps is navigation. In order to make OpenStreetMap more reliable for navigation, the team Mapbox has been improving the data in the map by adding missing turn restrictions, exits and destinations across the world. Recently, we mapped most of the gaps in the data across US cities as well as 5 cities each in Canada and Germany. In the entire process, we worked closely with the local community by taking inputs in the form of suggestions and guidance on improving our workflow and resources.

Continuing from our previous work in Europe, we did an initial research on France to get estimate of existing navigation data. These are the 5 cities we want to start with,

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Our initial assessment shows that there are very few turn-restrictions mapped overall, and a majority of what is present is “only-straight” or “only-right” rather than the common “no-right-turn” or “no-left-turn”.

Data Sources for Mapping

Mapillary Imagery

We use Mapillary as the primary source for adding turn restrictions. Overall, Paris has the best Mapillary coverage which would allow for bridging any gaps in data. This is followed by Lyon, where coverage is less dense, but could still be used to cover some gaps, if any.

screen shot 2016-09-09 at 7 43 14 pm

We came across these situations while reviewing the data using Mapillary images, where we were unable to perceive these signage representations.

[1] Mapping conditional turn restrictions

There is a no left turn but with a condition for except service vehicles. But it is only mapped as no-left-turn. How should we be mapping this?


[2] Similar to the above case, is this sign a combination of all the three or are they individual signs? How do we interpret sign like these in general?

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[3] Exit numbers

There seems to be signs with only_arrows along with an E below it. They are mostly located on higher classification of roads. What do these signs signify?


[4] We encountered multiple restriction signs, What is the background behind these signs and what is the ideal way to handle these?


Although most of these turn restrictions are mapped, there are still many conditional turn restrictions that could be added and a few existing turn restrictions that could be validated for improving data quality on OpenStreetMap. It would be great if community can answer our questions and help us understand the above scenarios better. Looking forward to hear your suggestions and comments on this.

We’re going to be at SOTM in Brussels next week. Catch up with @jinalfoflia @ramyaragupathy @pratikyadav @geohacker and @planemad on the latest data team projects at Mapbox!

Thank you.

Comment from gileri on 9 September 2016 at 18:56

Some answers as I’m french and haven’t forgot the entirety of traffic laws :)

[1] For the general public, this is a no-left-turn. “Service” means specially authorized vehicle, so I think that a general no-left-turn is ok.

[2] The distance from the sign to the danger or restriction is defined strictly, that’s why multiple independant signs can be stacked. In this case, those signs does not follow the legal requirements, so they are just indication without a legal standing. The first sign is to indicate what is there (Civilian Protection, a kind of state-run emergency services), the second one is “Generic Danger”, with a subtext explaining that emergency vehicles can enter the road, and you’ve already explained the third.

[3] The upper “double-sign” means that vehickles transporting dangerous materials (filled orange) must turn right. The “E” sign means that the upcoming tunnel is class “E” by european standards, meaning that almost every truck with dangerous stuff can’t go in that tunnel.

[4] This is a straight-only restriction. Maybe three oneways join to a fourth oneway, or maybe the turn radius is too short to turn.

Comment from cquest on 10 September 2016 at 08:50

[1] the highway=service on the left is restricted to “Protection Civile” (rescue service) No turn restriction here to add, only access=emergency to add

[2] these signs are not standard at all (too small, too close from the crossing, etc)… just forget them ;)

[3] [4] same as gileri

Comment from gileri on 10 September 2016 at 11:12

I concur with cquest for [1], as the general public is not allowed to go on that stretch of road from anywhere, so a turn restriction would be redundant.

Comment from BharataHS on 19 September 2016 at 11:54

@cquest and @gileri, thank you for clarifying these special cases.

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