Generally, the size of the entrance in question dictates about how many turnstiles are needed. Therefore, the larger the entrance, the more turnstiles will be needed. Alternatively, post and rail systems can be used as a substitute to fill gaps if a continuous line of turnstiles is not desired or necessary for the amount of traffic encountered.
Similar to entrance size, it is crucial to consider throughput and peak traffic at an entrance when determining how many turnstiles are needed for a project (throughput can be defined as the speed at which individuals can enter the facility, usually expressed as people per minute). If you install more turnstiles, your throughput speed will increase because more turnstile lanes allows for more passes per minute. Notably, under normal conditions a typical turnstile should handle a throughput of approximately 20 people per minute, so there will be no lane congestion if 20 or less people pass through a turnstile in any given minute. Throughput should be calculated at peak traffic times.
All readers (card readers, biometric scanners, et cetera) take time to process credentials; this read rate further dictates the throughput of a turnstile. For example, if a card reader takes 3 seconds to process credentials and unlock a turnstile after a card is swiped, then that 3 seconds should be accounted for when determining a turnstile’s throughput.
The Americans with Disabilities Act (ADA) of 1990 ensures that people with disabilities have the same opportunities as everyone else. This means that handicapped individuals should have the same ease of entry into a facility as everyone else. Therefore, ADA compliant gates should also be considered when deciding how many turnstiles are needed for a project. Generally, each access point at a facility should have at least one alternate entryway for those in wheelchairs, with walkers, or with other special accommodations needed. NOTE: ADA gates are also great for entryways with a large amount of cargo and tools going in and out because the extra space allows hand trucks and other large, awkward objects easy passage.
The equation below makes it possible to determine the most efficient number of turnstiles needed for an entrance by calculating the exact number of turnstiles needed during peak traffic (the time when entry/exit volume is the highest). This quantity of turnstiles calculated will be able to handle maximum traffic without causing any congestion.
M= The peak time period in minutes
N= Number of entrants during the peak time period
T= throughput of a certain turnstile model (in seconds per person)- including all added time for readers
L= Quantity of turnstile lanes needed
(N/M)= Total Entrants per minute
(60/T)= Entrants per turnstile per minute
Let’s say you recorded the number of people passing through your entrance during your building’s peak period. You found that your facility’s peak period is from 8:00AM to 9:00AM (M=60). You observed 2400 people entering the building (N=2400) during that time. You also know that the turnstile you plan to buy has a throughput of 3 seconds per person (T=3).
To find the number of turnstiles needed (L), you calculate that there are 40 entrants per minute (2400 entrants/60 minutes) at your facility. You also notice that since a person can pass through a turnstile in 3 seconds, then 20 people can pass through a turnstile per minute (60/T). Finally, if 40 people enter your facility per minute and each turnstile allows 20 entrants per minute, you calculate that you need 2 turnstiles (L) to accommodate for the total amount of people.
N= 2400 People
M= 60 Minutes