Ever been stuck a drivethru where there's a long line-up and traffic is just inching along? We need for extra drivethru windows to be able to open up, and allow cars to divert to those extra windows.
Suppose our FastFood eatery has 4 sides. There will be a drivethru lane going by a drivethru window
on one side. That lane needs to be able to branch off to another drivethru window on an adjacent side, so that cars in queue can divert out there, should the extra window open up.
Just as supermarkets will open up additional checkout lanes when there's a high load of customers waiting, likewise drivethrus need to be able to open up additional windows to serve higher demand periods, and to have forking lanes where cars can turn off to, in order to get to these additional drivethru windows.