With highways we can tag their width. I don’t see in the wiki that we can tag turning circles with a diameter spec. Has this ever been considered? In the default osm rendering they are usually rendered way too small.
Rendering is a separate issue - we don’t consider road or bridge width for rendering in OSM Carto. The issue might be with mini-rounds, since real round has always a proper diameter thanks to rendering the road shape, not a circle. Did I understand your problem?
While the OSM Carto, and probably many other renders, may not use that information I can see where a very detailed map could benefit from properly rendering both the road width and turning circle diameters. So I think tagging a turning circle with a diameter makes a lot of sense. You may want to sound that out on the tagging email list (expect to get a lot of noise back).
There is a
tag but that gives values in millimeters. https://wiki.openstreetmap.org/wiki/Key%3Adiameter I would expect that a tag with values in meters would be more useful.
Adding a diameter tag to the turning circle makes a lot of sense. If there’s ambiguity about the default unit, one can always add it explicitly, e.g.
diameter = 7 m
It probably isn’t going to be supported by default osm rendering style (OSM Carto) anytime soon, though, as that style uses road width to signal importance rather than physical width. Other renderers will be able to make good use of such data though!
Turning circles are not the same thing as roundabouts.