Gate Protection – Mitigation against hostile entry

The world has become a dangerous place. The threat of terrorist attacks and other forms of violence is very real. A preferred tactic intruders implement is to use some form of heavy vehicle to crash through the gate or other security structure that has been installed to prevent access to a property. Commercial, industrial and military facilities as well as other large installations have to implement strict security measures to safeguard their properties and protect the people and assets housed within them. Facilities that do not have an effective crash barrier in place may be unable to prevent a potentially catastrophic attack.

A crash barrier is a security gate or similar structure specifically designed and constructed to prevent vehicles from penetrating the perimeter of a facility.

Type

• Bollards
• Barriers

Bollards are posts arranged in a line, at predetermined intervals, to prevent unauthorized vehicles from accessing a property. Bollards are generally used at facilities such as government and military installations that are vulnerable to a terrorist attack.

There are several types of bollards viz:

• Removable temporary bollards
• Collapsible Bollards
• Fixed Crash Bollards
  • Concrete Crash Bollards
  • Architectural Bollards
  • Stainless Steel Bollards

Bollards may be of a fixed nature or could be retractable. Retractable bollards are deployed where there is a need to permit authorized vehicles to enter or exit the premise. These can be raised or lowered as per the requirements.

Innovations in bollard design have led to the development of shallow mount crash-rated bollards that are able to withstand extremely high impacts with a shallow foundation. The spring action enables the bollard to bend and absorb the energy, and then return to its original start position after impact.

Barriers / Blockers
A crash gate or beam is a barrier that opens and closes manually or automatically to permit entry and exit. These are deployed at high-security facilities such as airports, correctional facilities and military installations.

Cantilever slide gate: Cantilever style gates are deployed where there is sufficient space on one side of the opening to slide (horizontally) the gate open. No ground tracks or overhead supports are necessary. Cantilever gates are supported by two or four posts installed on one side of the roadway/opening and can be operated automatically or manually.

Vertical lift gate: The vertical lift gate is deployed where there is not sufficient space for a slide gate to open and can be operated either automatically or manually.

Overhead slide gate: An overhead slide gate is supported by an overhead beam and track system. It also slides to one side of the opening to open. Although the overhead beam and track creates an overhead restriction, the system is designed to allow tractor trailer and bus type vehicles to pass through. If space/width is a concern, overhead slide gates require less overall space for a given clear opening than cantilever systems. They can be operated either automatically or manually.

Swing gate: The swing gate is supported by a post and hinges. They are most appropriate for gate openings having limited activity that do not require automation. While it is possible to automate a swing gate, those that are crash rated can only swing toward the unsecured/public side to open. Because the gate swings out (toward entering traffic) entering vehicles are set back a considerable distance from the gate to allow for its swing path. Given the setback distance and time required for the swing gate to complete its open cycle, security is compromised.

Crash beam systems
These rotate 90 degrees, upwards, to open. These are available in various specifications and are even capable of stopping a heavy vehicle dead in its tracks. They can be operated either automatically or manually. Manually operated systems include counter weights to enable a single person to easily open or close the device. Unlike a crash gate, beams are intended to provide security against approaching vehicles only, not pedestrians.

Road Blockers
Road Blockers are designed to offer an impact-resistant barrier to vehicle access. These are deployed at ‘High Security’ sites. Such installations may range from car parks through to anti-terrorist protection of defence sites. These blockers are available in various designs depending on the application. They range from simple, low cost, rising kerb for relatively low volume usage to heavy-duty, anti-terrorist road blockers for frequent operation.

Crash Rating
These ratings are based on the U.S. Department of State (DOS) SD-STD-02.01. This standard uses a “K” rating to measure the stopping power of a barrier in relation to the speed and weight of a vehicle that crashes into it. The standard K rating weight for a vehicle was established at 15,000 lbs. The original DoS standard included “distance of penetration” levels L3 (3 ft. or less), L2 (3 ft. to 20 ft.) and L1 (20 ft. to 50 ft.). The new standard eliminated levels L1 and L2, and established an allowable penetration of no more than 1 meter (3.3 ft.).

As the State Department no longer certifies crash tests, The American Society for Testing and Materials (ASTM) ratings are now the standard for crash test ratings. These are used to measure both speed and penetration. Under ASTM International Designation F 2656-07, the speed ratings are differentiated based on the type of vehicle, such as a passenger vehicle, pickup truck, light-duty vehicle, etc.:

Small passenger car (C) (2430lbs):
• C40 (40mph) (38.0-46.9 mph)
• C50 (50mph) (47.0-56.9 mph)
• C60 (60mph) (57.0mph-above)

Pickup truck (P)2300 (5070lbs):
• PU40 (40 mph) (38.0-46.9 mph)
• PU50 (50 mph) (47.0-56.9 mph)
• PU60 (60 mph) (57.0-above mph)

Medium-duty truck (M) (15 000lbs):
• M3050 (30 mph) (28.0-37.9 mph)
• M4065 (40 mph) (38.0-46.9 mph)
• M5080 (50 mph) (47.0-above mph)

Heavy goods vehicle (H) (65 000lbs):
• H30 (30 mph) (28.0-37.9 mph)
• H40 (40 mph) (38.0-46.9 mph)
• H50 (50 mph) (47.0-above mph)

A “P” rating is assigned to indicate the distance of penetration of the test vehicle upon impact with the barrier. The four classification levels are as follows:
• P1: < 1 m (3.3 ft.)
• P2: 1.01 to 7 m (3.31 to 23.0 ft.)
• P3: 7.01 to 30 m (23.1 to 98.4 ft.)
• P4: 30 m (98 ft.) or greater

As an example, a PU40 P1 crash barrier could stop a pickup truck travelling at 40 mph with a penetration distance no greater than 3.3 ft. An H50 P3 crash barrier would be capable of stopping a heavy goods vehicle moving at 50 mph with a penetration distance between 23.1 and 98.4 ft.

Barrier Selection
Careful consideration of the following factors is necessary:
• The vulnerability of the facility to a vehicle attack.
• The high-vulnerability areas.
• Traffic analyses around the facility – such as the most likely types of attack vehicles and     potential paths vehicles may take to approach.
• The size of the opening and available space on the side.
• Level or levels of crash protection required

This risk assessment will provide a better understanding of the types of vehicles that pose the biggest threat to the facility. This will help determine the best crash barrier and rating that will meet the site conditions. Reputable crash barrier manufactures offer products that clearly indicate which (if any) of the DoS/ASTM testing standards they comply wit

Article by Kiron Kunte

Kiron Kunte has over 35 years of design and solutions experience, in Security, Telephony and Networking infrastructure. He is a graduate of IIT Bombay, a Fellow of the Institute of Engineers and has a post-graduate diploma, from Bombay University, in Systems Management. He is professionally certified in the design and engineering of Data Centres, IP Telephony, Video surveillance and Structured Cabling solutions. He heads Norik Konsult, a practice that offers advisory, design and system planning help to upgrade or build a new Telephony, Security and Networking infrastructure.

For more information contact:
www.norikkonsult.com