Based on the Biham-Middleton-Levine traffic model simulator, where certain cells move to the right, and other move down. Patterns emerge as all of the cells get gridlocked.
There are 2 kinds of cells: ones that try to move down, and those that try to move to the right. There are two phases to the movement here. First all of the cells moving down will move into the “7” cell if that is currently empty. Then, all of the cells that are moving to the right will move into the “5” cell if that is empty.