Thank you for the advice, that's indeed a lot better like that. Chain signals keep amazing me.

My junction is quite overkill, I have to agree, but I'd like to point out it should also improve the concurrent use of the roundabout for left turns, not just U-turns.

Anyway, your design is probably ...

I think you're right, a deadlock could indeed happen at the center. Although it should be rare compared to the kinds of deadlocks that this roundabout design protects against, your point is a good one.

An obvious but inefficient fix would consist in turning the whole center into one exclusion zone ...

I use the same blueprint for all my junctions for simplicity. My initial junction was a simple roundabout but, as the number of trains increased, I realized deadlocks could occur. I then upgraded to a new version which I'm sharing with you here. It's quite compact, enables U-turns and should be ...