OpenStreetMap
From the Wiki (osm.wiki/Tag:junction%3Droundabout):
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.
Simple, isn't it?
Well, burtobot (aka me) has just finished its first pass through the nation's (GB mainland) roundabouts. My aim was to sanitise the roundabouts sufficiently so that they become usable from the routing point of view (correct roundabout direction, usable flare roads, etc.)
Having just fixed over 500 roundabouts, I am amazed (and not a little depressed) by the shoddy mapping some people are doing. True, a lot of roundabouts are real works of art (and would be great if they happened to have the right direction!), but far too many are just plain ugly and completely broken from the routing point of view.
So folks, even if you don't want/need a routable map, please take a few minutes to visit the roundabouts on the map in your location and fix up the problems you will find there.
Thanks,
Mark
Discussion
Comment from wallclimber21 on 2 October 2009 at 22:23
According to the wiki, oneway=yes is implied. IOW, it's not necessary, but it also doesn't hurt, so I wouldn't worry about it.
It's a fact of life that most people only tag ways with a highway type, a name and, if necessary, oneway. Anything beyond that is gravy but unlikely.
I've mapped many thousands of ways and I'm aware of many additional tags, but I didn't know that the junction=roundabout has to be assigned. (In the US, roundabouts are very rare, so there's no real need to know about them anyway.) It's unrealistic to expect that everyone knows about all tags.
As for being depressed about shoddy mapping: someone contributed some of his spare time to create an account and enter a feature in a shared database for the greater good. Even if shoddy, it gives other the opportunity to improve on it. That's better than no feature at all, right? Looking at it this way makes it easier not to avoid depression. :-)
Comment from wallclimber21 on 2 October 2009 at 22:24
s/not to avoid depression/to avoid depression/
Comment from Gregory Williams on 3 October 2009 at 08:50
Just seen that you fixed some broken roundabout tagging on the A20 (A bit where the roundabout tag had managed to leak onto the road beyond the roundabout). Thanks for that.
Comment from marscot on 3 October 2009 at 18:37
I ve started to review all roundabouts that I have done and tweeked them.
as rule I now add the tage lit= yes/no to all highways/round about/ it maybe used in the future to show a map of all the lit and unlit roads on a map.