Between any two operations there is a buffer, and it is almost always sitting on the floor, a staging area that grew into a permanent one. It works until the mix changes, and then it is the reason the line waits. Shuttle storage puts that buffer inside a controlled, dense structure that feeds production on demand. Upstream and downstream stop waiting on each other, work-in-progress leaves the production hall, and the space you get back is the most expensive space in the building.