Imagine for a second that you’re in one of those double lane drive thrus that eventually converge at the window.

(Excuse the confusing numbering)
Let’s say that:
- Car 3 was the first car at the menu, followed by car 1 at the adjacent menu
- Car 3 finishes their order and pulls up to the window
- Car 2 pulls up to the menu where car 3 was and they finish ordering just a moment before car 1 finishes
Who should be next to pull up to the window? Does car 2 pause and allow for car 1 to finish so that the lanes at the window alternate? Or does car 2 pull up as soon as there order is finished?