Point graph collision avoidance

Could you possibly point me in the right direction?
I have an A* point graph which lays out some paths and crossings. I have gameobjects navigating the paths in both directions.
Is there a simple way to see that a path is blocked by another gameobject, stop and wait for the path to be clear again and proceed?
Thank you.

I’ll show an example of what i’m trying to achieve.
Object a should to move to position 1 and object b to position 2. The point graph is shown with the green lines. At the moment, the objects collide at position c but I’d like to check for the overlapping paths and wait on the previous node (before potential collision) until the path is clear and then proceed again.
Can you give me any ideas what to use or where to look, im still a beginner.