Tag:junction=roundabout

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+/-Mini-osm-logo.png junction=roundabout

One example for junction=roundabout

Description

A roundabout is a road junction where the traffic goes around an island in the middle.

Used on these elements

Can not be attached on nodes Can be attached on ways Can not be attached on areas Unknown or not included in the template

Useful combination
Implies
Status

Undefined

A roundabout is a road junction where the traffic goes around an island in the middle, and the traffic on the roundabout has right of way. Roundabouts can be anywhere from tiny (the island is just painted on the road surface) to huge with several lanes.

Small roundabouts are just represented as a node which is tagged highway=mini_roundabout.

Contents

How to Map

Mapping-Features-Roundabout-Double-Carriageway.png

There are different ways of representing roundabouts depending on their size. The segments in the way must go around the roundabout in the direction the traffic flows, but there is no need to tag them as oneway=*. The way should then be tagged with junction=roundabout.

The way should also be tagged with the same highway=* tag as the connecting streets. If there are several streets of different importance connecting to the roundabout, you should usually use the one with greater importance (so a roundabout connecting unclassified roads and a primary road should be tagged as highway=primary). A roundabout must have a highway=* tag in order for routing software to use it.

If there is a longer way with several larger roundabouts in between, you have to break up the way into chunks. See the examples for more information.

Roundabouts may also be split for other reasons, for instance: to tag part of the roundabout as a bridge, of if each part of the roundabout is part of different bus routes.

Multi-segment-junctions (Proposal)

If a roundabout consists out of several segments, we have to use a relation to group them. See also

for an alternative proposal.

Tags

Key Value Explanation
type route
route junction
junction roundabout

Members

Way or Node Role Recurrence? Discussion
Way (blank) two or more the ways making up the roundabout.

Examples

Feature Example Example Rendering
A standard size roundabout with up to four exits can be drawn simply using four nodes in a diamond shape. A road can be connected to each of the nodes. A larger roundabout may benefit from using eight or even more nodes.
A standard roundabout with four exits
Mapping-Features-Roundabout-Simple.png
Where a dual carriageway connects to a roundabout, there should be two nodes on the roundabout in place of just one.
Dual Carriageway with Roundabout
Mapping-Features-Roundabout-Double-Carriageway.png
In many cases the road approaching a roundabout may split into two separated carriageways (technically, this is called a flare). If these are of a significant size (at least more than just a pedestrian island) then you may want to draw some or all of these out distinctly like the following example. Each of these flares would be a separate way (tagged as one way).
A roundabout with separated entrances and exits
Mapping-Features-Roundabout-Flare.png

See also

If you want to know more about the design of roundabouts in the United Kingdom then this pdf document (Highways Agency Design Manual for Roads and Bridges -Volume 6, Section 2, Part 3, Geometric Design of Roundabouts) is the definitive reference.

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