This is basically two normal roundabouts, one inside the other, with traffic direction the opposite way in the inner lane. Or a two-lane roundabout. It allows you to spend less time on the roundabout if you want to take the junction to your right, as you would usually have to go to your left and do an almost complete lap.

Compare reaching your parent on a singly-linked list to a doubly-linked list. Being able to traverse in either direction may provide significant performance boosts...