I recently ran across a neighborhood in Southern California with a large number of what I would call cul-de-sacs that happen to have a center island for plants. While the road would look like a loop (or a single-point roundabout, I would assume we would map something like this as a cul-de-sac as described in the new great Junction Style Guide from WeeeZer14.
If this is the consensus thinking, I believe we should add the following to the style guide:
# Cul-de-sac (add to current) - Show an image of a cul-de-sac with a center island and clarify this should be mapped as a dead-end as if the island was not there. Explain it is for simplicity and a loop or roundabout is unnecessary.
# Loop (add to current) - Note that a very small loop (we should give some recommended radius) with an island in the center should be mapped as a cul-de-sac. Tell them to see the example above.
# Roundabout (add to linked article on roundabouts) - In the Roundabout article add a section on when a road is NOT a roundabout. It can show the same example from the Junction Style Guide and refer them back to the style guide to create a loop or a cul-de-sac. We should also note the problem with a single looped segment roundabout and how to fix/prevent it.
Note I also sent a PM to the user in the permalink with all the unverified roads to review the road creation documentation to actually get the roads active. It looks like the base map created most of this neighborhood with loops, but the user was changing them to roundabouts.