Editing Revolving door (section)

==Security==
[[File:Revolvingdoors.ogv|thumb |alt=A video of a pair of revolving doors, one revolving clockwise, one revolving counterclockwise|An unusual pair of revolving doors at [[City Hall, Southwark|City Hall]] in [[London]]: one revolves clockwise; the other revolves counterclockwise. ]]

Revolving doors can also be used as security devices to restrict entry to a single person at a time if the spacing between the doors is small enough.  This is in contrast to a normal door which allows a second person to easily "[[Piggybacking (security)|tailgate]]" behind an authorized person. Extreme security can require a particular type of bullet-resistant glass.

Sometimes a revolving door is designed for [[one-way traffic]]. An example is the now-common usage in [[airports]] to prevent a person from bypassing [[airport security]] checkpoints by entering the exit. Such doors are designed with a [[brake]] that is activated by a sensor should someone enter from the incorrect side. The door also revolves backwards to permit that person to exit, while also notifying security of the attempt.

[[File:TR-a.JPG|thumb|upright|A one-way High Entrance&thinsp;/&thinsp;Exit Turnstile]]
[[Turnstile]] exit-only doors are also often used in [[Subway (rail)|subways]] and other [[rapid transit]] facilities to prevent people from bypassing fare payment.  They are similarly used at large [[sports stadium]]s, [[theme park|amusement park]]s, and other such venues, to allow pedestrians to exit freely, but not to enter without paying admission fees.  These doors usually work mechanically, with the door panels constructed of horizontal bars which pass through a "wall" of interlacing (interdigitated) bars, allowing the door leaves to pass through, but blocking people from illegally entering through the exit.