Breakdowns Broken down trains affect one direction up to all but one directions.
Low cost, low space consumption and relatively high efficiency
Roundabout with PBS and bridges
This slight modification allows crossing trains not to interfere with each other.
Without bridges, both the grain [A] and steel train [B] would go through the roundabout, causing one of both trains to wait for the other one to pass by. The additional paths for trains just going straight ahead increase the roundabout's efficiency even more, without need of additional space!