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.