Tripod Turnstile
A tripod turnstile is like a barrier with three revolving arms that are waist-high. It allows access to one person at a time. We have seen gates like these where they block you from entering without a card. Once you swipe it, only one person can pass through the barrier and it will deactivate itself immediately after the person has passed. It is made to allow only one-way human traffic. These can be spotted at metros or corporate offices. It is also good for security reasons.