How a revolving door meters passage
A revolving door turns around a vertical central shaft. Several panels, called wings, extend from that shaft to the curved outer wall, dividing the doorway into small compartments. As one person or a few people step into a compartment, they push the panels forward; the next group must wait for the door to turn far enough to reach an opening.
That geometry limits how many people can pass through in a single burst. Unlike a wide, open doorway, it does not offer one broad gap that a crowd can rush through all at once. The door’s rotation creates a steady sequence of small openings, so entry tends to happen in batches.
A shared entrance, with a built-in pace
Revolving doors can also carry people in both directions at the same time: someone entering occupies one compartment while someone leaving uses another. The panels keep those flows separated rather than forcing everyone to negotiate one opening. In busy buildings, that can make movement more orderly, though the door still depends on people taking turns and pushing at a manageable pace.
The control is mechanical, not a guarantee against crowding. If people press too closely, move too quickly, or cannot use the revolving door comfortably, the entrance needs another way through. But when used as intended, its compartments do something a plain doorway cannot: they turn an open passage into a sequence of limited spaces, making the crowd’s movement easier to meter.
