In OSM, there are
These features all have in common that they can be represented as a circular slub in the road-way at the node position where it is tagged.
On the default mapnik map, the first two look like this.

In the vector-datasource though, they are not included, so it cannot be rendered. I think it would make sense to include it in one way or another because it is useful to see if one can easily turn at the end of dead end street or not.
In OSM, there are
highway=turning_circlehighway=turning_loophighway=mini_roundaboutThese features all have in common that they can be represented as a circular slub in the road-way at the node position where it is tagged.
On the default mapnik map, the first two look like this.

In the vector-datasource though, they are not included, so it cannot be rendered. I think it would make sense to include it in one way or another because it is useful to see if one can easily turn at the end of dead end street or not.