Good morning,

Could you tell me how to treat a roundabout in so far as a roundabout is a gyratory in OSM?
In these conditions if we can’t use the tag junction=roundabout how can we navigate when we arrive at a roundabout in every sense?
For example, the roundabout Place de la porte de Saint Cloud in Paris can’t be considered as roundabout and compared to the other navigation softwares such as Google maps and Bing maps the navigation is not precise.
Maybe a new identifier would be necessary such as “junction=go round” for example.

Thank you very much for your answer.


Gyratory systems are not roundabouts, they are traffic circles. Unfortunately the only way of correctly showing these is a simple circle of roads, so routing software doesn’t think in terms of exit numbers. The other problem is that people are likely to incorrectly correct them by tagging them as roundabouts!

This is the site

Thank you for the answer.
Since gyratory systems aren’t roundabouts, how can we identify them when we arrive on this roundabout in a broad sens?
This is in contradiction with the tag “junction=roundabout”.
For the “Place de la Porte de Saint Cloud” which isn’t a gyratory system the tag" junction=roundabout" has been refused by a community member.
For all kinds of “roundabouts” could we have the following information: " Enter the roundabout and turn on the 3rd street" for example?
Thank you for your answers.

The tag “junction=roundabout” is reserved for gyratory systems.
With the tag “junction=circular” do we have the following information as an example " Enter the roundabout and turn on the 3rd street"?
In these cases, OSM will be in accordance with the other navigation softwares and when entering in a roundabout on site the voice guidance with will not give erroneous directions compare to the way to follow as its the case currently.

What is the main difference between a roundabout and a gyratory?

Can I see the difference in the satellite background image?

Does a gyratory has a different traffic sign than a roundabout when entering it with a car (other than the three white arrows on blue background)?


If you examine the tags for example regarding the “Place de la Porte de Saint Cloud” in Paris you will see that in the note it is mentioned “Not a roundabout pas un giratoire” because historically it has been done like that; so the only way to consider a roundabout that isn’t a gyratory is to use as indicated in the OSM data base “junction=circular”.

I’m still stuck with your initial question. Could you please explain what a “gyratory” is or is not, opposed to a “roundabout”. I am not familiar with the term.

I think there may be country specific issues here. In the UK, junction=roundabout SHOULD NOT be used for gyratory systems.

@FvGordon: according to wikipedia

There are (at least!) two kinds of places where traffic goes in a circle: Those that have special signage (in Europe, this is typically a circular blue sign with white arrows going in a circle) that assigns priority to traffic already in the circle, and those that are just circular roads with no special rules, meaning that the traffic entering the circle has priority because it is coming from the right (or left, in the UK and a few other places). In OSM, junction=roundabout is reserved for the first kind, with traffic already in the circle having priority.

There is room for linguistic confusion here. In France, I believe that a “carrefour giratoire” refers to the first type (junction=roundabout in OSM) while apparently the British use “gyratory system” to mean something else. In everyday English, the terms “roundabout”, “traffic circle”, “gyratory” and probably a few others seem to be thrown around with little respect for legal definitions, and I suspect that the same is true in French (giratoire, rond-point, …) (it certainly is in Swedish, though luckily, the second type is scarce here).

So I agree with TZorn — this thread needs definitions!

Edit: A “the” should have been a “be”.

I think that the soluion for a roundabout in every sens, would be to solve any ambiguity, to have in OSM “junction=roundabout”,whatever the giratory systems or circular roads.
Remark:this proposal has been refused by an OSM member in charge of the database. This leads on site to a discrepancy between the way to follow and the voice guidance for circular roads that consequently are treated as normal roads when entering in a roundabout in every sens.

The general rule is to use british english (in this case for good reasons as usage even within the US varies), Beware of false friends (faux amis) :

Roundabout: a topologically circular path where traffic on the path has priority over traffic entering the path. As others have said in Europe this is marked by a standard sign. Entry points should have give way (yield) markings: in Britain dashed white lines. In the US these are usually called modern roundabouts.

Gyratory: a oneway system which is also a topologically circular path, but where traffic on the path does not necessarily have priority. The best known one in the UK is the Hangar Lane Gyratory System. Usually access and priorities are controlled by traffic signals, and thus most entries will have a stop markings. I suspect that junction=gyratory should be reserved for places where the path is signal controlled. NOTE: Many roundabouts in Britain now have traffic signals controlling flow both on to the path and within the path. These are still generally tagged as roundabouts even though they are properly gyratory systems. I suspect in the event of failure of the lights British drivers would still treat them as roundabouts.

Other circular roads with different properties with respect to priorities and management of access should not receive one of the above tags. I suspect that using junction=traffic_circle would be a potentially suitable tag. The historic exemplar for me would be the Rond Point d’Etoile (Arc de Triomphe) in Paris. The example given very much fits into this category.

The problem is one of working out how to manage the differences for data consumers. All three types can validly have routes described as " take the 3rd exit", but have very different properties for things like lane tags or calculation of delay times.

One other useful clue as to whether it’s valid to tag something as a roundabout or not is the presence of bus stops. These rotary junctions are usually significant interchange locations for buses. Allowing any vehicle to stop goes against the basic principle of roundabouts. So bus stops located on the actual junction suggest that junction=roundabout is inappropriate.

traffic_circle is not currently in the possibilities for junction in the database but junction=circular is in it. Could we use it?

I don’t understand what you mean by “in the database”. There is no database of valid tags.

When you want to modify for example a “roundabout” in OSM, several tags are available such as:
and others.

I think you are confusing a particular editor with OSM. I can add any lexically valid key with any lexically valid value to a road or junction. Even iD will allow you to do that, although it is, maybe, less obvious than JOSM.

I agree with you:it was a short cut but my question remains.

For the “roundabouts” with junction=circular in OSM the navigation with OSRM is correct in so far as a 'roundabout" is considered as it is. However, the navigation with Mapzen is incorrect due to the fact that there is no more the “roundabout” notion when we enter in it but only a place to take with the imprecision that results from this, compared to Google maps and Bing maps.
Would we have the same problem with junction=gyratory?
Remark: I suppose that currently is based on Mapzen for the navigation. uses OSRM.