Crash Course in Traffic Control
Using Turnstiles to Direct Pedestrian Traffic
Turnstiles provide control and directional flow of pedestrian traffic inside any given structure. This form of gate permits access to only one individual at a time, allowing security professionals to monitor incoming and outgoing patrons.
“A turnstile gives true one-for-one access control; whereas a gate or a door, once activated and opened, can allow multiple entries. A turnstile will relock itself after each passage, ensuring only one person passes through for each activation,” says Jonathan Watson, director of international sales for Alvarado Manufacturing Co. Inc. of Chino, Calif. Watson, who has spent 10 years with Alvarado, has been involved in access control projects for many professional sports facilities and several college universities.
“For most medium to high security applications for access control or time and attendance, facilities will opt to use turnstiles for general populace and have a gate to the side in order that ‘exceptions’ to the norm will have a means of entry,” Watson says. “But for lobby access and facility entry, the advent of optical turnstiles with acceptable passage widths — either barrier-free or with drop-arm or retractable wing barriers —have allowed companies to use a single device for everyone.”
Turnstiles are a successful method for controlling directional flow of pedestrians. One-way, exit-only or entry-only turnstiles are available for secure passages in or out of a facility. However, turnstiles are available in a variety of types, some of which are more appropriate for a given facility than another.
For perimeter control, full-height turnstiles should be used to prevent patrons from jumping over the barriers. For lobby and access control, waist-high or optical turnstiles are more appropriate. Turnstiles also serve as a means to protect property and increase loss prevention; however, while restricting access into a building, emergency escape plans need to be well thought-out as well.
“Safety concerns must be considered with respect to facilities, and the ability to safely exit a building in an emergency is paramount. This is why all of our interior optical barrier turnstiles allow for emergency manual force opening,” says Watson. “All of our turnstiles allow for alarm inputs and can be set to automatically open in event of a power loss.”
Guarding Against Pedestrian and Vehicular Tailgating
Tailgating has been a concern for both traffic control barriers and turnstiles. Once a vehicle has approached the guard shack, the risk of tailgating becomes a security concern. If permission is granted for an authorized vehicle to enter the restricted area, an unauthorized vehicle can also receive access by tailgating the vehicle into the premise.
“There is another phenomenon with aggressive tailgating where the trailing vehicle will actually push the other vehicle through,” Dickinson says.
In order to prevent tailgating, inductive loop detectors (ILD) can be embedded within the barricade system. ILDs consist of one or more loops of wire embedded in the pavement and connected to a control box. When a vehicle passes over a loop, the presence of the vehicle is detected. ILDs can be used to detect the presence, passage, count and occupancy of a vehicle.
“We can make stringent access control where only one car can get through a gate, or we can make it extremely stringent where you can’t get a car through,” says Dickinson. “We have the ability to moderate that.”
Infrared detectors can also be used to prevent tailgating si
tuations. These types of detectors are typically deployed in high security environments and are used in conjunction with sally port barricades. Sally ports consist of two sets of barricades with only one barricade being lowered at a time. This forces the vehicle to enter a small, secure space while the second barricade is lowered. This method makes it impossible for an unauthorized vehicle to tailgate and enter the premise behind an authorized vehicle.
“Sally ports are used a lot in U.S. embassies,” says Dickinson. “Even if someone tailgates, they can’t get in.”
Turnstiles follow similar measures in preventing tailgating from occurring. Tailgating is addressed with the use of a physical barrier preventing an individual from entering through a turnstile without authorized access.
“With optical turnstiles, tailgating is detected by infrared beams. In Alvarado’s turnstiles, a series of horizontal beams determines the presence of a person. If a second person is crossing the beams without first presenting access credentials, they will be detected as an attempting violation,” says Watson. “Optical turnstiles with barriers combine the best of both worlds in their ability to detect tailgating attempts and decrease the rate of unauthorized entries by physically resetting the barrier after each authorized passage.”
Combining additional security system features with vehicular and pedestrian access control barriers will create an even more effective tailgating solution and guard against unwanted access.
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