Antonyms of “intersection ”

This is not a single word, but in mathematics, conceptually you are after the symmetric difference:

In mathematics, the symmetric difference, also known as the disjunctive union, of two sets is the set of elements which are in either of the sets and not in their intersection.
_Wikipedia

The reference article provides a nice illustration:

For traffic or roads, I thought about roundabout, which is a way to get to a cross street without a direct intersection, or a track, which is a closed circuit used for racing, thus theoretically lacks an intersection.