|highway = mini_roundabout|
|A road junction where the traffic goes around a painted circle or traversable island and has right of way.|
|Used on these elements|
|Status: In use|
|Tools for this tag|
A mini-roundabout is a special type of roundabout in which the middle can be traversed by vehicles, and is typically used where there is only limited space available. Road traffic flows in one direction around a point in the middle, and the traffic in the roundabout has right-of-way. The middle of a mini-roundabout is usually only a painted circle, but there might also be a low, fully traversable (mountable) dome or island. If there is only a single vehicle, or two vehicles traveling in opposite directions, it is common - but not necessary legal in all countries - to drive straight across the middle rather than going around. In particular, large vehicles are allowed to drive across the center island if otherwise not possible due to their dimensions.
Please pay attention to the section "Possible misinterpretations" to differentiate between roundabouts, mini-roundabouts, turning circles and further road features.
How to map
Add the tag highway=mini_roundabout directly on the junction node where two or more ways intersect. The key direction=clockwise/anticlockwise could be added to reduce the need of assumptions about local traffic flows. In case the traffic flow is clockwise, the tag direction=clockwise should be added as the default rendering of major renderers is anti-clockwise.
Mini-roundabouts are usually indicated by signposts, like e.g. one of these:
The following table shows a selection of classical mini-roundabouts: they all are one-ways with either a painted circle or a fully traversable island in the middle, and the traffic within the mini-roundabout has right-of-way. Please note, that the key direction=* only needs to be specified if the traffic flow on the mini-roundabout is clockwise as the default value for this key in conjunction with mini-roundabouts is anti-clockwise.
In OpenStreetMap we have several tags that describe different circular and widened road features. Perhaps the three tags which are most commonly confused with each other are:
- junction=roundabout for roundabouts
- highway=mini_roundabout for mini-roundabouts
- highway=turning_circle for turning circles
Because of incomplete or ambiguous documentation, misinterpretation or just for the sake of simplicity they were often used in situations, where they do not apply. The major differences between the three are:
- A roundabout is a one-way street with right-of-way and a non-traversable center island.
- A mini-roundabout is a one-way street with right-of-way and a traversable center island. In particular, large vehicles are allowed to drive across the center island if otherwise not possible due to their dimensions, i.e. it might be impossible for a large vehicle to drive through a roundabout but possible to drive through a mini-roundabout with the same dimensions.
- A turning circle is a widened space on a two-way street without any center island (or at least a fully traversable island). The absence of a center island allows also large vehicles to turn around.
Another term sometimes mistaken for a roundabout is a traffic circle: contrary to roundabouts, the entering traffic is controlled by stop signs, traffic signals, or is not formally controlled. This wikipedia article explains the difference of a roundabout and a traffic circle according to the United States traffic engineers. In OSM traffic circles are usually not indicated by specific tags.
A very common question is: "Why is it important to follow this tagging guideline if the map looks good even when tagged differently?"
The answer is: The map is not everything. There exist a lot more applications which process our data and these tags have different implications e.g. for routers. So if you tag a small roundabout as a mini-roundabout or a loop at the end of a street as a turning circle, it might look ok on the map but will break other applications. So please don't think of this as annoyance and try to use the most fitting tags in each situation.
The following table presents the preferred tagging for the most common situations and also tries to clarify some ambiguities.
|A standard roundabout with a large, non-traversable center island.|
|Small, but not a mini-roundabout. Although it is preferred to tag this the same way as a large roundabout, for the sake of simplicity it is acceptable to tag this with a single node with junction=roundabout. In this case the tag direction=* should be specified, as its default value is anti-clockwise when used in conjunction with a roundabout.|
|A classical mini-roundabout where the center is only a painted circle. The tag direction=* should be specified, as its default value is anti-clockwise when used in conjunction with a mini-roundabout.|
|Large, but a mini-roundabout. The center island is traversable and without signposts.|
|Also a classical mini-roundabout with a slightly raised but still fully traversable center island.|
|This photo shows a round place with a traversable island in the middle, but this is neither a mini-roundabout nor a roundabout, but instead a turning circle, which allows large vehicles to turn around. Please bear in mind that a turning circle can have any shape, but never a non-traversable island.|
|Don't let the island confuse you: there are indications neither of a one-way nor of right-of-way, so this is just a junction with an island used for traffic calming.|
|Watch the arrows closely - this is also just a junction with traffic calming.|
|Obviously a place for vehicles to turn around. But because of the island, it is not a turning circle (which must not have an island), so this should be mapped as a loop. For the sake of simplicity the tag highway=turning_loop on a single node is currently under discussion.|
Note to data consumers
Due to a lack of clarity in the documentation for several years, smaller roundabouts or turning loops have often been tagged with
highway=mini_roundabout, rather than using
highway=turning_loop. Data consumers therefore should be cautious to assume the center of a junction tagged with
highway=mini_roundabout can be traversed by large vehicles, especially if the tag was added before June 2012.
- Wikipedia article about mini-roundabouts
- UK Highways Agency Design Manual for Roads and Bridges - Volume 6, Section 2, Part 3: Geometric Design of Roundabouts: Mini-roundabouts are explained on page 3/2
- US Federal Highway Administration Safety Program - Technical Summary - Mini-Roundabouts
- Wikipedia article about traffic circles