[Tagging] Proper Tag for Not-a-Roundabout

Daniel Hofmann hofmann at mapbox.com
Mon Nov 7 14:30:00 UTC 2016


Over at OSRM we're not only doing Routing on OSM but also Guidance for
users once a suitable route is found. In order to make the user experience
great and the instructions pleasant to use we differentiate between

1/ Roundabouts
Think: "at the roundabout take the nth exit"

2/ Roundabout Intersections
These are roundabouts with up to four ways and turn angles which makes the
turns obvious.
Think: "at the roundabout turn left"

3/ Rotaries
These are large and named roundabouts.
Think: "at Meinplatz take the nth exit"

4/ Not-a-Roundabout (what this post is about)
There are situations where one of the entering road has right of way, which
disqualifies the scenario for being classified as a roundabout. The Wiki
has a section on these Not-a-Roundabouts:

http://wiki.openstreetmap.org/wiki/Tag:junction%3Droundabout#Not_a_roundabout
> In all these cases, the key “junction” is not necessary at all. You need
no special tagging.

Most of these Not-a-Roundabouts have a note on them, telling users not to
tag them as junction=roundabout as this is a common mistake. Here are two
examples in Berlin:

Bersarinplatz

http://www.openstreetmap.org/way/288767318#map=19/52.51849/13.45355&layers=D

http://www.openstreetmap.org/directions?engine=osrm_car&route=52.51786%2C13.45348%3B52.51918%2C13.45281#map=19/52.51852/13.45327

Kottbusser Tor

http://www.openstreetmap.org/way/159155852#map=19/52.49898/13.41881&layers=D

http://www.openstreetmap.org/directions?engine=osrm_car&route=52.49915%2C13.41952%3B52.49857%2C13.41852#map=19/52.49896/13.41865

As you can tell, for both of those situations the routing engine is not
able to issue special instructions since there is no tag to parse. And
parsing note tags for the occurrence of roundabout is not a solution ;)

With the current situations of having note="don't tag as roundabout"
pseudo-tags on most of those it would make sense to establish a proper
junction=not_a_roundabout tag (tag is up for discussion) software can parse
and make use of.

What's your opinion on Not-a-Roundabout?

Cheers,
Daniel J H
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