Anti-ram Fencing

Considerations for selection, installation to prevent vehicle attacks

• By Scott Espensen
• Oct 01, 2017

Vehicle ramming attacks are on the rise in the United States and abroad. Already in 2017, there have been no less than seven major attacks worldwide resulting in 24 people dead and another 153 injured. Shortly after a driver used his car as a weapon in Times Square, ISIS released a video calling for lone-wolf terrorist attacks in U.S. cities. As a result of this recent trend, many government agencies at the federal, state and local levels are assessing vulnerabilities at their facilities and public spaces.

When it comes to protecting pedestrians in public spaces, passive bollards have long served as a successful preventive method to stop vehicles from encroaching areas such as sidewalks, tourist attractions and parks because they allow unrestricted walking access. Bollards are manufactured in a wide array of architectural shapes, finishes and sizes, which allows them to blend in or even complement the surrounding environment.

Securing property boundaries to prevent vehicle ramming attacks, on the other hand, typically involves the use of anti-ram fencing, which is a more cost effective and practical solution than bollards where longer runs are required. Anti-ram fencing is ideal for restricting unauthorized vehicle access to a facility and for protecting office buildings, critical infrastructure, hazardous materials and people in high-risk areas adjacent to roadways or parking lots where free access for pedestrians is not required.

Understanding How Crash Test Standards and Ratings Apply to Anti-Ram Fencing

When selecting anti-ram vehicle fencing, consideration should be given to how a system was designed and tested to ensure that it meets the applicable threat conditions. In addition, understanding the various testing standards simplifies the process of comparing crash ratings between different manufacturers’ products, or even different products offered by the same manufacturer. It’s important to note that the standards referenced below are designed for testing vehicle barriers against head-on attacks as opposed to testing conducted for highway barriers, which often measure the effects of a glancing blow.

U.S. crash test standards for vehicle barriers have evolved a great deal over the years. The U.S. Department of State (DOS) pioneered anti-ram vehicle barrier testing and developed a rating system and test standard that was published in April 1985, and later revised in 2003. While the initial rating system, SD-STD-02.01, allowed for different penetration distances that occurred from a medium-duty truck, the 2003 revision (SD-STD-02.01 Rev A) required that all barriers receiving a DOS certification allow no more than 1 meter of vehicle test bed penetration beyond the inside of the barrier. The DOS test method used a 15,000 pound medium-duty truck as the test vehicle.

In 2009, the DOS retired SD-STD-02.01 Rev A and stated that all new barriers should be tested to ASTM International standards in order to be considered for embassy projects. ASTM is an international standards organization that has over 12,000 standards implemented globally. F2656-15 is the most recent standard to which anti-ram vehicle barriers are tested, and a corresponding performance rating is assigned based on testing results.

ASTM ratings are assigned based on three variables—test vehicle type, vehicle speed and vehicle penetration distance. Test vehicles span six style and weight categories, from a small passenger car (2,430 pounds) to a heavy goods vehicle (65,000 pounds). Vehicles are impacted into the barrier at speeds ranging from 30 to 60 mph. Finally, the penetration distance of the vehicle into the barrier falls into one of three categories—from less than 1 meter (P1) up to 30 meters (P3).

While all new barriers being considered for embassy projects should be tested to ASTM standards, the DOS SD-STD-02.01 Rev A ratings are still used frequently in project specifications. These ratings were assigned based on impact speed, similar to ASTM ratings. Products successfully tested with vehicles travelling at 30 mph were assigned a K4 rating, at 40 mph a K8 rating, and at 50 mph a K12 rating.

Property owners should first seek to understand the threat conditions for the particular site they want to secure, and then make a determination as to the performance level required. For reference, the DOS typically requires that barriers used on embassy projects must be tested with a medium-duty truck (15,000 pounds) traveling 50 mph and have less than a 1 meter penetration distance, which is equivalent to the ASTM F2656 M50-P1 rating.

Separately, the Department of Defense maintains a list of vehicle barriers and fencing that are approved for use. While the DOD doesn’t have its own unique crash testing standard, the U.S. Army Corps of Engineers reviews crash test reports and independently validates the barriers. It’s important to note that not every product that obtains a crash test performance rating is placed on DOD Anti-Ram Vehicle Barrier List.

Differentiating the Various Types of Anti-Ram Fencing

Choosing an anti-ram fence largely comes down to two options—post and beam or cable-based—and the differences lie right in the name.

Post and beam anti-ram fencing systems rely on a single steel, horizontal beam that is mounted between two anchor posts. These are typically spaced around 30 feet apart, depending on the crash rating and manufacturer. Post and beam systems that utilize tubular steel offer a clean, aesthetic look, and simple connection points with minimal hardware.

Cable-based fences use anchor and intermediate posts spaced as close as 8 feet apart, to which a tensioned cable is attached. The tensioned cable is relied upon to stop all vehicular threats, and is either exposed or often ornamentally hidden in the fence. Multiple runs of cable line the posts, and the amount of cable needed largely depends on the level of crash test certification that is desired. Cable-based fence may include tall pickets, which act as anti-pedestrian security and add another level of protection.

However, the real difference between the two types of fence lies in the installation.

Purchase Price vs. Total Cost

Purchasing an anti-ram perimeter security fence system is only half the financial battle to securing a property’s border against vehicle- borne attacks—what still looms is the cost of installation. Contractors, architects and owners can realize significant savings by looking beyond the initial purchase price of the fence system and exploring the steps, materials and equipment necessary to complete the project.

Extensive amounts of hardware, intermediate posts, wire rope and concrete are all requirements of traditional cable-based fence systems that drive up the total project cost and lengthen the construction schedule. Post and beam perimeter fences eliminate these components to cut installation costs nearly in half while still providing crash tested certification to ASTM F2656 standards.

More than a 1,000 meter span, a DOS K12 or ASTM F2656 M50-P1 cable-based fence system can include up to 20 anchor posts and 380 line posts, while supporting multiple runs of cable. With up to 400 post holes in just a 1,000 meter stretch, the cost of materials and labor hours begins to add up quickly when you consider that each hole requires auguring, concrete fill and a rebar cage.

To effectively prevent vehicles from penetrating the fence, spools of cable must be run in multiple lines—sometimes up to eight— through line posts and anchor posts in timeconsuming fashion. The whole system also requires a significant amount of hardware to maintain its safety standards, using cable clamps and nuts to tension each cable.

Furthermore, the maintenance and work isn’t finished when the cable-based fence install is complete. Cables must be checked and re-tensioned periodically to adjust tensioning and maintain the fence’s ability to prevent vehicle penetration.

All of this work is above and beyond what’s needed to install a post and beam anti-ram fence. A post and beam solution to the anti-ram fence installation dilemma is straightforward—simplicity in design.

Vertical anchor posts are spaced approximately 30 feet apart in the case of M50-P1 systems and rely on a single tubular beam to absorb the energy of a crash as opposed to multiple runs of wire rope and the line posts that support them. The result is 110 posts in a 1,000 meter span, versus the 400 posts used with a cable-based fence system. That’s nearly 75 percent less holes to dig—and that’s before factoring in the different-sized holes, and the time it takes to switch back and forth between auger bit sizes.

While the rebar cage must always be priced and built separately with a cablebased fence system, rebar sticks are included with some post and beam fence designs. To install, contractors simply insert the rebar into pre-drilled holes in the anchor posts. No extra expenses, no extra labor to build elaborate cages. In addition, post and beam fences are engineered to be extremely simple and efficient in terms of the hardware used and the effort required for construction.

The time-saving design, ultimately, leads to abundant savings. Digging 75 percent less post holes speaks for itself, but a post and beam fence directly saves time, and labor costs, in several other ways:

• Little or no time spent building rebar cages
• Post hole foundations are shallower than cable-based anchor posts, and require less concrete
• Installing a single beam, connected by one nut and one bolt on each post, versus multiple runs of cable

This simplicity in installation, coupled with high crash test standards, led a post and beam fence to being specified to protect a Saudi Aramco facility, the world’s largest oil and gas company, and a government property owned by Saudi Arabia. The Saudi Aramco crew installed the post and beam fence at a rate of 1,000 meters per week with a relatively small crew—this is a process that is two to three times faster than installing a cable-based fence system.

“Installation of a post and beam fence saved us a tremendous amount of time, at least 50 percent versus other fence systems,” says Peter Saroufim at BRC Industrial (Saudi) LTD, in Jeddah, Saudi Arabia. “There is less excavation and less concrete to use. The whole process is much simpler, and you’re left with a product that does an exceptional job of protecting a perimeter and will not need any maintenance once it’s installed.”

When it comes time to choose an anti-ram fence for preventing vehicle ramming attacks, considering all of these factors will determine the type of fence that is ultimately chosen. Focusing on requirements (required crash test ratings), financials (differing installation costs) and preferences (aesthetics of post and beam vs. cable-based) is a great basis to selecting the proper anti-ram fence.

This article originally appeared in the October 2017 issue of Security Today.