Benefits
From a business/revenue standpoint, turnstiles enable a venue to have an accurate, verifiable count of total attendance. From a security standpoint, they lead patrons to enter single-file, so security personnel have a clear view of each patron. This enables security to efficiently isolate potential trouble or to confiscate any prohibited materials. Thus, turnstiles are a tool which leads to a more safe and secure atmosphere throughout a site.
History and applications
Turnstiles were originally used, like other forms of stile, to allow human beings to pass while keeping sheep or other livestock penned in. The use of turnstiles in most modern applications has been credited to Clarence Saunders, who used them in his first Piggly Wiggly store.
A modern turnstile at Legoland Windsor. The user inserts a ticket or pass into the orange slot, from which a barcode is read; if access is to be granted, a sensor determines the speed with which the user passes through, and sets the electric motor to turn the turnstile at the corresponding speed.
Turnstiles often use ratchet mechanisms to allow the rotation of the stile in one direction allowing ingress but preventing rotation in the other direction. They are often designed to operate only after a payment has been made, usually by inserting a coin or token in a slot; or by swiping, or inserting, a paper ticket or electronically encoded card.
Turnstiles are often used for counting the numbers of people passing through a gate, even where payment is not involved. They are used extensively in this manner in amusement parks, in order to keep track of how many people enter and exit the park and ride each ride. The first major use of turnstiles at a sporting venue was at Hampden Park in Glasgow, Scotland. It is common for entry to public lavatories in the United Kingdom to be controlled by turnstiles.