Love the way that sometimes three or four people are converging on a point and, through only slight changes in each persons walking speed and direction, they move smoothly past each other without any visible break in their gait.
The whole effect looks planned, the people following predetermined, invisibly marked paths, sometimes missing each other by the smallest gap.

Suppose it’s an example of strangers subconsciously acting together as a unit – no conscious decision, just an awareness on each persons part of the others’ movements.