Two tracks. Both are going in the same direction. One filled with cargo and a train on the move. The other empty and waiting. Waiting for what? Another train to come along? Could you send two trains along these tracks at the same time? Do they converge somewhere ahead? Do they split and go in different directions? I know very little about railroads.
One interpretation of these tracks is that they represent capacity in life. I have a set amount of capacity for work, home, family, fun, and other aspects of my life. Maybe I have two tracks, and the trains of different commitments need to take turns. Perhaps, I fill both rails all the time. Could I build more train tracks? Would I want to?