Digital data has to be physically located somewhere i.e. country, state, building, servers with access control. Which require perimeter and internal controls. Without physical control the data stored on them is vulnerable as malicious people can do whatever they want from destroying it, altercation, disclose it. Physical controls are your first line of defense.
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You work as an independent consultant within physical security, you are hired to choose a location for an IT start company that just received a multi-million dollar government contract to provide cloud services. Although the company will handle non-sensitive information you will provide consultations as the information was sensitive.
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Tips:
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- FEMA Perimeter Security Design
perimeter security design 4
4-1Perimeter security design
4.1 intrOductiOn
p
erimeter security is designed to protect employees, visitors, and
building functions and services from threats such as unauthor-
ized vehicles approaching close to or penetrating high-risk
buildings. The key element in protecting buildings from a vehicular
bomb is the establishment of appropriate stand-off distance, depending
on the size of the threat and the building characteristics. This is accom-
plished by a protective barrier system placed to provide at least minimum
required stand-off. In an urban situation, this is often not possible, and al-
ternative measures must be taken. These are discussed in Chapter 6
.
The barrier may be along the site property line or, within a large site or
campus, placed independently of the property line. When along the prop-
erty line, the barrier forms the interface between public and private space,
and thus, in an urban setting, it may have major visual and functional im-
pacts on city amenities. If the barrier is within the site, it may have a major
impact on the visual appeal of the site and the experience of the ap-
proach to the building.
A perimeter security design involves two main elements: the perimeter
barrier that prevents unauthorized vehicles and pedestrians from en-
tering the site, and access control points at which vehicles and pedestrians
can be screened and, if necessary, inspected before they pass through the
barrier. Barrier system design and types of barriers are described in this
chapter. Access control points are described in Chapter 5, Section 5.3,
and Chapter 6, Section 6.5, for open and urban sites, respectively.
The following are suggested as some of the goals of perimeter security
planning:
m To provide an appropriate balance between the need to accommodate
perimeter security for sensitive buildings and their occupants, and the
need to maintain the vitality of the public realm.
m To provide security in the context of streetscape enhancement and
public realm beautification, rather than as a separate or redundant
system of components whose only purpose is security.
*
Perimeter security design4-2
m To expand the palette of elements that can gracefully or
unobtrusively provide perimeter security in a manner that does not
clutter the public realm, while avoiding the monotony of endless
lines of jersey barriers or bollards which only evoke defensiveness
(see Section 4.6.2 for an example of an innovative unobtrusive
security element).
m To produce a coherent strategy for deploying specific families
of streetscape and security elements in which priority is given to
achieving aesthetic continuity along streets, rather than solutions
selected solely by the needs of a particular building under the
jurisdiction of one owner or agency.
m To provide perimeter security in a manner that does not impede
the city’s commerce and vitality, nor excessively restrict or impede
operational use of sidewalks or pedestrian and vehicular mobility, or
impact the health of existing trees.
Perimeter protection may participate in all three layers of defense.
The first layer applies when the access control is outside the property
line. The second layer applies when there is controlled access around
a building within the property line. The third layer applies to under-
ground parking, or parking underneath a plaza (see Chapter 6, Section
6.4). It also applies when the access control is at the building face.
Perimeter security protection is accomplished by design strategies that
use a variety of methods to protect the site. The two following sections
provide some broad guidelines for the design of barrier systems and de-
tails of the characteristics of barriers currently in use.
4.2 BArrier system design
4.2.1 issues Of BArrier systems design
t
he architecture and the landscaping of the site entry elements
are the first part (and may be the only part) of the project that is
visible. As such, they introduce the identity of the site and its ar-
chitectural style and quality, and impart a sense of welcome or “stay away”
(Figure 4-1).
Sidewalks should be open and accessible to pedestrians to the greatest ex-
tent possible, and security elements should not interfere with circulation,
particularly in crowded locations.
Perimeter security design 4-3
Issues to be considered in the design of the barrier system include:
m To ensure protection to the desired level, the design and selection of
barriers should be based directly on the design base threat assessed for
the project, as well as available countermeasures and their ability to
mitigate risk.
m The barrier layout at sidewalks should be such that a constant clear
path of 8 feet or 50% of the sidewalk, whichever is the greater, should
be maintained.
m For buildings with a yard, security elements should be placed in or at
the edge of the yard depending on available space and stand-off.
m All necessary security elements should be installed to minimize
obstruction of the clear path. If it is necessary for space reasons to place
elements at the curb they should be placed in an available amenity strip
adjacent to most curbs, since this space is already designated for street
furniture and trees and is not part of the existing clear path.
m Any security (or other) object placed on the curb should be at
least two feet from the curb line to allow for door opening and to
facilitate passenger vehicle pick-up and drop-offs, if this can be done
anywhere along the curb. However, the most effective placement
is at a maximum of two feet: this allows the barrier to engage the
engine block and mass of an approaching vehicle before the tires have
impacted the curb and begun to launch it over the barrier. Ideally,
drop-off points should be located in pull-over or stopping points
where the setback is greatest. At a distance of more than two feet, the
curb can become a major factor in barrier height requirements and in
reducing their effectiveness.
Figure 4-1:
custom bollards match
the architecture at a
defended corner.
Perimeter security design4-4
m A bollard barrier system is less intrusive if it is short in length and
thoughtfully integrated into the entire perimeter security system. The
bollard materials should harmonize with the building architecture.
Figure 4-2 shows a small row of bollards protecting a building entrance.
The custom-designed stainless steel bollards harmonize well with the
building architecture.
m Monotonous repetition of a single element should be avoided. Block
after block of the same element, no matter how attractive, does not
create good design (Figures 4-3 and 4-4). When a continuous line of
bollards approaches 100 feet, they should be interspersed with other
streetscape elements, such as hardened benches, planters, or trees.
Figure 4-2:
stainless steel covers
on bollards harmonize
with the building
entrance.
Figure 4-3:
monotonous
repetition of bollards
Perimeter security design 4-5
m Hydraulic barriers, drop arm beams and the complete system including
security gatehouses are visually intrusive. Wherever possible, such entry
controls should be located in access roads and service alleys.
m The use of a combination of barrier types establishes a flexible design
palette that responds to security requirements in accordance with
diverse perimeter conditions (Figure 4-5).
Figure 4-4:
these bollards resemble a wall.
sOurce: ncPc)
Figure 4-5:
top: combination of
low retaining walls
and low bollards.
Bottom, left:
combination of
oversize bollard
and large planters
placed on very wide
sidewalk. Bottom,
right: combination of
tree and bollards.
Perimeter security design4-6
Opportunities to add a palette of elements, such as varied bollard types,
engineered sculptured forms, hardened street furniture, low walls, and
judicious landscaping can all assist in creating a functional yet attractive
barrier that will enhance the setting. Solutions that integrate a number of
appropriate perimeter barriers into the overall site design will be more
successful (Figure 4-6).
The graphic box following shows varied bollard sizes combined with other
elements to reduce the monotony of a long curbside barrier system.
Figure 4-6:
A combination of
barrier types for
a variety of threat
conditions. Vehicle
access to this building
is prevented by custom
designed bollards, a
sculptured concrete
barrier, fences and
trees
sOurce: design: deLLA
VALLe + BernHeimer
ArcHitects
BOLLARD VARIATIONS AS PART OF THE STREETSCAPE
small and large bollards, trees and plants. in a few years
the trees will dominate the
streetscape (right).
Bollards, trees, and lamp
standards (below).
Perimeter security design 4-7
m The placement of barriers at corners, driveways, sally ports, stairs, and
handicapped ramps requires careful attention.
m Barriers at the edges of soil slopes need to be investigated carefully.
m Corners need creative design, for example, to
increase the area to account for pedestrian
queuing while interspersing effective barriers
that can consist of non-obvious objects,
such as traffic signals, signs, lighting, etc. In
addition, corners can offer the opportunity to
consider barrier design in depth to facilitate
pedestrian flow and protection while
preventing vehicle entry.
Space for several functions are important consid-
erations: (1) pedestrians to circulate during the
green signal phase, (2) a pedestrian holding area during the red signal
phase, (3) vehicles turning the corner, and (4) people joining in the
queue at the red signal phase. These space requirements demand that
sidewalk corners be kept clear of obstructions. Reduction of corner space
can lead to people using the roadbed as a waiting area. Sidewalk corners
(defined as the space created by extending lines to the edge of the side-
walk) should be free of objects. No part of a corner curb cut should have
any security elements. Wrap-around corners (stretches from the edge of
one curb cut to the edge of the adjacent one) at rounded sidewalk cor-
ners should not be permitted.
m Emergency evacuation and access are important considerations.
The primary goal of perimeter security is to provide facilities with a
layer of barrier protection. However, the same protection that keeps
dangerous vehicles or people away could also keep first responders
from approaching the building quickly and enabling people to exit
rapidly.
m Landscape materials can soften and naturalize the appearance of
many types of constructed barriers, improving their appearance and
compatibility with the surrounding areas (Figure 4-7).
m When possible, position gates and perimeter boundary fences outside
the blast vulnerability envelope.
m For high-risk buildings, barriers should be provided at site and
building entries. Vehicles should not be permitted to park next to the
perimeter walls of the secured area.
corners can be vulnerable points for
vehicle bomb attacks. they are often the
area of greatest approach speed, greatest
number of approach avenues, and most
perpendicular impact. unless they are
carefully designed to impede bomb-laden
vehicles, it may be possible for an attacker
to drive onto the sidewalk and proceed
unimpeded to an intended target.
Perimeter security design4-8
m In case of an elevated risk, vehicles can be used as very temporary
physical barriers when placed in front of buildings or across access
roads, but they are very detrimental to the character of an entry when
used as a long-term risk mitigation measure.
Case Study 5 describes a large agency complex in Washington, D.C., that
features an arcaded crescent that wraps around two sides of the building
and encloses an internal garden space. This creative security barrier
makes a positive contribution to the urban environment.
Figure 4-7:
Low and high
walls softened with
landscaping.
CASE STUDY 5: A MAJOR GOVERNMENT BUILDING
1.0 INTRODUCTION
this new government building using
innovative security barriers is located at
the intersection of two major streets in a
city’s industrial area that is undergoing
urban renewal. the complex is designed
to engage the street edges, with an
entrance across from a nearby transit
center. retail facilities border to the east,
while a trellised garden wall to the south
animates the street edges in addition to
enhancing the perimeter security.
Perimeter security design 4-9
CASE STUDY 5: A MAJOR GOVERNMENT BUILDING (continued)
1.1 Project Scope
the building program includes general office space, training rooms, laboratories, a library, an
auditorium, underground parking, and auxiliary services. A three-story, planted, arcaded crescent
wraps around the north and west boundaries, enclosing an internal garden space. Loading docks
and an inspection booth are integrated into the architecture and garden walls.
1.2 Project Team
moshe safdie and Associates with OPX Architecture, Associate Architects
1.3 Project Schedule
completed in 2007
2.0 DESIGN APPROACH
2.1 Issues Addressed
m security needs of a major
government building
m Limited space in existing urban
context
2.2 Security Strategy
First Layer of Defense
m unusual perimeter arcade, which
provides attractive, integrated
security
m entry controls and screening
Second Layer of Defense
m Walls with attractive security
fencing
Third Layer of Defense
m Building architecture incorporates
risk mitigation measures
3.0 BLENDING WITH THE NEIGHBORHOOD CONTEXT
m nice transition from neighborhood low-rise buildings
m Arcade and landscaped plaza adds amenity
4.0 INNOVATIONS AND BEST PRACTICES
m A mix of barriers and deterrents designed within the context of the site and its surroundings
provides multiple layers of protection and creates an amenity for the neighborhood
m security is part of the aesthetic of the architectural design, an integral component, instead of
an afterthought
Perimeter security design4-10
4.2.2 BArrier crAsh test stAndArds
There is a wide variety of design methods and devices that can be used to
provide protection. The site risk analysis (see Chapter 2) will provide in-
formation on the nature of the threat to be mitigated, and the designer
needs to know the relative performance of the methods that are available
so that appropriate choices can be made for the various conditions that
will be encountered. Since this publication is primarily concerned with
protecting buildings from bomb-carrying vehicles, effectiveness in stop-
ping vehicle entry is a critical performance parameter.
The crash testing standard in common use was developed by the
Department of State (DOS). To obtain DOS certification, the vehicle bar-
rier must be tested by an independent crash test facility to meet DOS
standards. The test specifies perpendicular barrier impact by a 15,000-lb.
(6810 kg.) diesel truck.
Initially, the DOS standard provided for three levels of intrusion:
m Level 3: Allows intrusion of the vehicle 36 inches (0.91 m) into the
barrier
m Level 2: Allows intrusion of the vehicle 20 feet (6.1 m) into the barrier
m Level 1: Allows intrusion of the vehicle 50 feet (15.2 m) into the barrier
In February 2003, the standard was revised, and levels 1 and 2 were de-
leted. The standard currently provides certification for three classes of
protection:
Certification Class Speed (mph) Speed (kph)
K12 50 mph 80 kph
K8 40 mph 65 kph
K4 30 mph 48 kph
To become certified with a DOS “K” rating, the 15,000-lb. vehicle must
achieve one of the K-rating speeds, and the bed of the truck must not
penetrate the barrier by more than 36 inches. The test vehicle is a me-
dium-duty truck such as those that any driver with a commercial license
and a credit card can buy or rent. Note that the amount of intrusion is
measured to the front of the cargo bed of the truck, where explosives
would typically be located (Figure 4-8).
Perimeter security design 4-11
This limited penetration is appropriate for the
DOS because their facilities have usually been
located in high-density areas with little or no set-
back. In open sites with more adequate setback,
deeper penetration may be acceptable, and agen-
cies, such as the DoD or the DOE, or the private
sector, may reinstate deeper penetration levels in
the new ASTM standard under development (see
below). Where the setback is extremely limited,
every foot of penetration is critical.
The lack of a universally accepted testing and certification process for bar-
riers has hindered the development of components that are uniquely
designed and appropriate for well-planned streetscapes. Typical testing
methods today include a computer simulation, using finite-element analysis,
followed by an actual crash test at a controlled facility. Computer simulations
can help refine design details and reduce overall costs. However, the live
crash tests are generally needed to verify the performance of the barrier.
Oftentimes, security projects are designed under tight deadlines with lim-
ited budgets, so that few tested barriers are readily available. The result is
that only a limited number of “off-the-shelf” items, such as bollards and
concrete barriers, are available, and they may not be appropriate for every
location. To prevent such occurrences, the design effort in a major project
should include time and money for the design and testing of custom pe-
rimeter security elements in the early stages of the planning process.
A key aspect of testing an element is the availability of a proper standard
by which to measure its effectiveness. Until recently, the general standard
used was one created by the Department of State for overseas locations,
utilized for domestic purposes. The standard does not provide for much
flexibility in design. To address this, ASTM International has developed
recent experience has shown that terrorists
are making increasing use of a “double tap”
tactic in which the first vehicle is intended
to breach the barrier so that a second
vehicle can pass through and get close to
the building. careful design and control
is necessary to prevent the first or second
vehicle from entering the setback area.
Figure 4-8:
Barrier test intrusion
limit.
Perimeter security design4-12
a new standard (WK 2534, Standard Test Method for Vehicle Crash Testing of
Perimeter Barriers and Gates) to expand upon the DOS crash test standard.
To meet the diverse needs of the various groups that will use the new anti-
ram standard, the types of test vehicles and test conditions included in the
standard need to be expanded, and longer stopping distances will be re-
instated for use on open sites where more space is available for greater
stand-off distance.
The new standard will include additional vehicle sizes. The smallest will
be a uni-body sedan that might be able to slip between bollards that
would stop a larger and heavier vehicle, such as a single-unit truck or
tractor-trailer. Another vehicle to be considered in the standard is a
3/4-ton (2000 kg) pickup truck. The largest vehicle will be a 60,000-lb.
(27 metric ton) tractor-trailer or dump truck, which would test the limits
of the barrier.
4.2.3 determining BArrier design criteriA
The security design criteria required for a barrier are largely deter-
mined by key information obtained in the following steps in the risk
assessment process:
1. Threat analysis should provide the following Design Basis Threat (see
Chapter 2, Section 2.2.2, Step 1 of the FEMA Risk Assessment Steps) :
m Vehicle size, weight, speed.
m Bomb size (weapon yield in pounds of TNT equivalent) and
worst-case stand-off distance.
2. Vulnerability analysis provides:
m Building envelope and structural information that contribute
to the determination of the appropriate stand-off distance,
and that enable possible tradeoff between alternative building
characteristics and stand-off distances to be evaluated and costed.
m Information on available stand-off distances.
m Information on the possible reduction of vehicle speed through
the existing or modified characteristics of approach roads.
m Limitations imposed by underground utilities.
m Information on the types of soil, which affect barrier
standards.
Other criteria relating to planning, architectural, and streetscape issues
are discussed in the following sections.
Perimeter security design 4-13
4.3 BArrier mAteriALs And types
4.3.1 mAteriALs
t
here are four commonly used building materials for perimeter bar-
riers: steel, cast iron, reinforced concrete, and cast stone. Natural
materials such as rocks, trees, plants and earth forms may also be
incorporated in a barrier system.
m Steel or cast iron can be used in almost any design and are usually
easier to install than other materials. They are very strong and,
compared to concrete, permit a smaller barrier to stop a vehicle. Steel
and cast-iron barriers require more maintenance than other materials,
such as concrete, and routine painting is necessary to prevent rust.
m Reinforced concrete barriers take more time and manpower to install,
but require little maintenance and are typically less expensive than
steel or cast iron. Because concrete structures are commonly found
in urban environments, this material is often more compatible with
the surrounding context. Reinforced concrete barriers can be both
poured-in-place and precast.
m Stone or granite security elements must be larger than steel or
reinforced concrete elements and are often used in enclosed
earthen walls or as benches. Granite is very durable and attractive,
complementing the architecture of many buildings.
4.3.2 BArrier types
There are two basic categories of barriers: passive (fixed) and active
(operable).
Passive barriers are fixed in place, do not allow for vehicle entry, and are
used to provide perimeter protection away from vehicle access points. For
jurisdictional purposes, they may typically be categorized into four types:
m Devices placed within the property lines of a building; they are usually
not subject to city rules or regulations.
m Devices that are installed in the public right-of-way and that are under
the jurisdiction of local planning and transportation regulations.
m Devices installed in privately maintained and privately owned public
spaces (such as plazas built on private property in exchange for floor
area bonuses) are usually under the jurisdiction of the local planning
department.
Perimeter security design4-14
m Devices installed on federal and state land are not required to comply
with local regulations, although typically federal and state agencies
work cooperatively with local departments.
Passive barriers include:
m Walls, berms, and ha-ha barriers
m Engineered planters
m Fixed bollards, heavy objects, reinforced street furniture, fixtures, and
trees
m Water obstacles
m Jersey barriers in fixed and anchored installations
m Fences
These are listed in approximate order of typical impact ratings, with the
highest first. Examples of crash ratings for engineered barriers are given
in the type descriptions below.
Active barriers are used at vehicular access control points within a perim-
eter barrier system, or at the entry to specific buildings within a site, such
as a parking structure or a parking garage within an occupied building,
to provide a barrier for vehicle screening or inspection; they can be op-
erated to allow vehicle passage. Catalog items can be obtained with DOS
system ratings to resist various levels of impacts. The descriptive termi-
nology varies among manufacturers.
m Rotating wedge systems
m Rising-wedge barricades
m Retractable bollards
m Crash beams
m Crash gates
m Surface-mounted wedges and plates
These are listed in approximate order of typical impact ratings, with the
highest first. Examples of crash ratings for each type of barrier are given
in the type descriptions below.
Active barriers are mechanical devices produced by a number of special-
ized manufacturers. Examples of each type are illustrated below to show
designers their typical characteristics. Active devices must be used in con-
junction with signage, light signals, gatehouses and security personnel:
Perimeter security design 4-15
these provide a challenging task to design an integrated grouping of ob-
jects that are in tune with the building and site.
In addition, some innovative barrier systems have been developed in re-
sponse to design and cost-related demands. These include both active and
passive devices:
m The NOGO system
m The Tiger Trap
m The Turntable
4.4 pAssiVe BArriers
4.4.1 WALLs, excAVAtiOns, Berms, ditches,
And hA-hA’s
Description, Purpose, and Performance
t
he hardened (or engineered) wall group includes retaining walls
and freestanding walls. These may be constructed of reinforced or
mass concrete, concrete masonry, brick, and natural stone, or other
materials typically reinforced with steel. Walls may be designed to include
sections of perforated walls or discontinuous walls to achieve improved
appearance while still satisfying security requirements.
Figure 4-9 shows a reinforced concrete barrier wall that incorporates art
work on its face, and Figure 4-10 shows a barrier wall integral with the
building face in an urban site.
Figure 4-9:
reinforced wall barrier
with artwork.
sOurce: PHOeniX, AriZOnA,
POLice dePArtment, tOdd
WHite
Perimeter security design4-16
Walls can be engineered to provide any desired level of performance.
It should be noted that concrete can become fragmented by an explo-
sion and turn into projectiles that may cause serious damage to life and
property.
Berms, excavations, and ditches can be effectively used to stop vehicles
from penetrating the restricted territory. Triangular ditches and hillside
cuts are easy to construct and can be effective against a wide range of ve-
hicle types. Side hill cuts are variations of the triangular ditch, adapted
to side hill locations, and have the same advantages and limitations. With
this type of construction, a vehicle will be trapped when the front end
falls into the ditch and the undercarriage is hung up on the leading edge
of the ditch. Although untested, soil and rock can absorb large amounts
of kinetic energy. Typical configurations and dimensions are shown in
Figure 4-11. Both the configurations and dimensions should be carefully
studied in relation to the types of vehicles expected to be encountered
and the desired level of protection.
Figure 4-10:
reinforced concrete
barrier wall with
artwork at the scottish
Parliament, edinburgh.
sOurce: enric, mireLLes,
BenedAttA, tAgLiABue
(emBt) And rmJm, JOint-
Venture ArcHitects,
PHOtO: ducciO
mALAgAmBA
Perimeter security design 4-17
The ha-ha is a form of barrier that originated for aesthetic purposes in
17th century England. The barrier was used to prevent cattle from wan-
dering up to a country mansion, while at the same time the barrier wall
was invisible to the house. This strategy has been adapted for use as a se-
curity barrier, most notably around the new setting for the Washington
Monument. Here it replaces an unsightly circle of Jersey barriers and
allows an unimpeded view of its surroundings from the base of the mon-
ument. Viewed from outside the site from below, the Jersey barriers are
replaced by an elegantly detailed masonry wall. A happy historical refer-
ence is that Washington’s home at Mount Vernon used ha-ha’s for their
original purpose (Figure 4-12)
Figure 4-11:
excavations, berms,
and ditches.
sOurce: AFter dOd
HAndBOOK:
seLectiOn And APPLicAtiOn
OF VeHicLe BArriers, miL-
HdBK-1013/14, 1999
Perimeter security design4-18
Installation
Although mass may provide an effective barrier in such walls as heavy
masonry installed in a ha-ha, typical concrete walls require heavy rein-
forcing. Figure 4-13 shows a typical engineering detail of a low anti-ram
wall and indicates the necessary dimensions and reinforcing for effective
performance.
Design Implications
Unless carefully placed and designed, barrier walls can be intrusive
elements. They should, as far as possible, only be used where a wall is es-
sential, and where efforts are made by design and materials to reduce the
negative impact. Ha-ha’s are an effective way of providing a non-intrusive
barrier that can be integrated into the landscape.
Figure 4-12:
Top: Ha-ha diagram
(sOurce: ncPc).
Center left: Jersey
barriers at the
Washington
monument.
Center right and bottom:
Ha-ha’s at the
Washington
monument.
Perimeter security design 4-19
4.4.2 engineered pLAnters
Description, Purpose, and Performance
Well-designed planters can form an effective vehicle barrier. Planters
located on the surface rely on friction to stop or delay a vehicle, and
will be pushed aside by any heavy or fast-moving vehicle; displaced
planters may become dangerous projectiles. Engineered planters need
considerable reinforcing and below-grade depth to be effective and
become fixed elements in the landscape design. The planter shown
provides DOS K12 performance (Figure 4-14).
Protection may also be enhanced by the use of crash-rated bollards con-
cealed in planters (Figure 4-15).
Figure 4-13:
engineering detail of anti-ram low wall, to
illustrate concept only; dimensions and reinforcing
will vary.
sOurce: dOs
Perimeter security design4-20
Installation
Some security guidelines for planter system installation are:
m Rectangular planters should be no more than two feet wide, and
circular planters should be no more than three feet wide. The
horizontal dimension of rectangular planters should not exceed six
feet. These, however, are not the best sizes for viable plantings.
Figure 4-14:
typical engineering
detail of reinforced
planter with dOs
K12 performance,
to illustrate concept
only; dimensions and
reinforcing will vary.
sOurce: dOs
Figure 4-15:
Planter with concealed
crash-rated bollards.
sOurce: WAusAu tiLe
Perimeter security design 4-21
m A maximum distance of four feet, depending on the kind of traffic
anticipated, should be maintained between planters and other
permanent streetscape elements including, but not limited to, fire
hydrants, light poles, mailboxes, trees etc. Any greater distance will
allow a small car with a few hundred pounds of explosives to pass
through.
m Planters should be oriented in a direction parallel to the curb or
primary flow of pedestrian traffic. In no case should a planter or line
of planters be placed perpendicular to the curb.
m Landscaping within planters should be kept below two-and-a-half
feet, except when special use requirements call for increased
foliage (Figure 4-16). In addition, planters should not have enough
vegetation to hide a package six inches thick, a briefcase, or a
knapsack.
m Planters should contain live landscaping at all times and be regularly
cleaned of trash and debris.
m Planters should not be used in high pedestrian traffic areas. In these
locations, bollards or other less obtrusive objects are appropriate.
m Planter design, location, and maintenance should create viable
conditions for healthy plants. These include adequate water
or irrigation, appropriate soil mixture, and selection of plants
appropriate to be grown in planters. Seasonal characteristics and
ultimate size of plant material shape the choices.
Figure 4-16:
Large planters as a
barrier. the small
planters de-emphasize
the scale for the open-
air restaurant. despite
the large planters,
the effective sidewalk
width remains wide.
Perimeter security design4-22
Design Implications
Planters can have a heavy impact on pedestrian movement, reducing the
effective sidewalk width — the portion of the sidewalk that can be effec-
tively used by pedestrians, defined as the width of the sidewalk minus
the width of obstructions and the distance people stay away from them.
However, well-designed and placed planters can have multiple functions
and be civic amenities.
4.4.3 fixed BOLLArds
Description, Purpose, and Performance
A bollard is a vehicle barrier consisting of a cylinder, usually made of steel
and filled with concrete placed on end in a deep concrete footing in the
ground to prevent vehicles from passing, but allowing the entrance of pe-
destrians and bicycles. Bollards are also constructed of steel sections and
reinforced concrete. An anti-ram bollard system must be designed to ef-
fectively arrest the vehicle and its cargo as quickly as possible and not
create an opening for a second vehicle.
A typical fixed anti-ram bollard consists of a ½-inch thick steel pipe, eight
inches in diameter projecting about 30 inches above grade and buried
about 48 inches in a continuous strip foundation (Figure 4-17).
The bollard shown in Figure 4-17 would be capable of stopping a 4,500-lb.
vehicle traveling at 30 mph. Rated bollards are also available that would
provide protection up to DOS K12 level.
Figure 4-17:
diagram of typical
bollard installation. to
illustrate concept only:
dimensions and
reinforcing will vary.
sOurce: dOs
Perimeter security design 4-23
Bollards can be specified with ornamental steel trim attached directly to
the bollard or with selected cast sleeves of aluminum, iron, or bronze that
slip over the crash tube. Bollards can be galvanized against corrosion and
fitted with internal illumination for increased visibility. Figure 4-18 shows
a number of decorative bollards with high-performance ratings. Bollards
may be custom designed for an individual project to harmonize with the
materials and form of the building, but to ensure adequate protection,
they would need to be tested by an independent laboratory (Figure 4-19).
.
Figure 4-18:
decorative bollards
with high-performance
ratings.
sOurces: tOP LeFt And
rigHt: secureusA, inc.
BOttOm LeFt: deLtA
scientiFic cOrP.
Figure 4-19:
custom-designed steel
bollards that match
the design of their
buildings
Perimeter security design4-24
Commonly used decorative bollards without deep foundations do not
have anti-ram capacity, though they may provide some deterrence value
by making the building look more protected than it is.
Installation
The need for bollards to penetrate several feet into the ground may cause
problems with below-ground utilities whose location may not be known
with certainty (Figure 4-20).
If underground utilities make the installation of conventional bollard
foundations too difficult, a possible solution is to use bollards with a wide
shallow base and a system of beams below the pavement to provide resis-
tance against overturning (Figure 4-21).
Figure 4-20:
installation of fixed
bollard line. note the
depth and size of the
excavation.
sOurce: secureusA, inc.
Figure 4-21:
example of bollards
with a wide shallow
base and a system of
beams.
sOurce: rsA PrOtectiVe
tecHnOLOgies
Perimeter security design 4-25
Design Implications
Bollards are by their nature an intrusion into the streetscape. A bollard
system must be very thoughtfully designed, limited in extent and well in-
tegrated into the perimeter security design and the streetscape in order to
minimize its visual impact
The visual impact of bollards can be reduced by limiting height to no
more than 2 feet 6 inches. However, the height of the curb and its po-
sition relative to the bollard also relates to the bollard height. This and
other site specific conditions such as road surface grade, may help to
maintain an effective bollard for impact while making the bollard appear
visually less obtrusive. In addition, the design basis threat, in terms of ve-
hicle size and speed, also influences bollard height. In no case should
bollards exceed a height of 38 inches inclusive of any decorative sleeve.
A bollard reduces the effective sidewalk width in a pedestrian zone by the
width of the curb to bollard (typically 24 inches, plus the width of the bol-
lard). In several high-pedestrian and narrow-sidewalk areas of a central
business district, the reduction in effective sidewalk width can prove critical.
Other bollard system guidelines are:
m Spacing between 36 and 48 inches depending on the kind of traffic
expected and the needs of pedestrians, people with strollers and
wheel chairs and the elderly must be considered.
m In long barrier systems, the bollards should be interspersed with
other streetscape elements such as hardened benches, light poles, or
decorative planters.
m They should be kept clear of ADA access ramps and the corner
quadrants at streets.
m They should be arranged in a linear fashion in which the center of the
bollards is parallel to the center line of existing streets.
4.4.4 heAVy OBjects And trees
Description, Purpose, and Performance
Heavy objects, such as large sculptural objects, massive boulders, earthen
berms or concrete forms with unassailable slopes, and dense planting
and trees can be used in a similar way to bollards to prevent vehicles from
passing, while allowing the passage of pedestrians and bicycles. To ensure
that such barriers can effectively reduce the threat level, engineering de-
sign and/or evaluation is necessary. For example existing dense thickets of
mature trees can be incorporated into a perimeter system (Figure 4-22).
Perimeter security design4-26
Specially designed objects that also serve a practical and aesthetic purpose
can be used as effective barriers (Figures 4-23, 4-24, 4-25, and 4-26).
Figure 4-23:
combination low
retaining wall and
sculptural object as a
barrier system.
Figure 4-22:
groups of mature
palm trees as
protection from
vehicular intrusion.
sOurce: PHOeniX
POLice dePArtment,
AriZOnA center, rOuse
deVeLOPment cO.
Perimeter security design 4-27
Figure 4-24:
decorative obelisk at the approach to a civic
Plaza.
sOurce: PHOeniX, AriZOnA, POLice dePt., tOdd WHite.
Figure 4-25:
group of engineered
sculptured objects as a
barrier.
sOurce: PHOeniX, AriZOnA,
POLice dePt., tOdd WHite.
Perimeter security design4-28
Figure 4-27 shows the use of custom bollards in combination with large
rocks. The rocks have symbolic meaning as part of the landscaping of the
space but are also engineered barriers.
Figure 4-26:
An array of rocks form
an effective barrier.
Figure 4-27:
selected rocks and custom bollards as
barriers: scale and placement provide
nonintrusive security.
Perimeter security design 4-29
Installation
Objects used as barriers will need varying degrees of embedment and rein-
forcement, depending on their weight, footprint, and height/width ratio.
Design Implications
The use of natural features such as rocks, or man-made objects such as
sculpture, provides opportunities for creating barriers that can enhance
the visual environment, effectively delineate pathways, clarify public and
private space, and provide protection in an unobtrusive manner.
4.4.5 WAter OBstAcLes
Description, Purpose, and Performance
One of the oldest forms of site security design is that of water. Used in the
form of artificial or natural lakes, ponds, rivers, and fountains, water can
be an effective and beautiful choice for a barrier. The configuration of the
channel can be designed as an effective “tank trap,” or walls of the pool
or mass of the fountain can be engineered to stop a vehicle. The water
can be presented in a variety of ways — flat and smooth or enhanced with
movement by falls or fountains. Water features generally require ongoing
maintenance with filters, pumps, cleaning, etc. (Figure 4-28).
Figure 4-28:
this proposal for
the re-design of
the Washington
monument grounds
uses water to create
a barrier. the
meandering canal is
quite beautiful as well
as functional.
sOurce: micHAeL VAn
VAndenBurgH And
AssOciAtes
Perimeter security design4-30
An example of a water barrier in an urban setting is also shown in Chapter
6, Section 6.4, Figure 6-19.
4.4.6 jersey BArriers
Description, Purpose, and Performance
A Jersey barrier is a standardized precast concrete element originally de-
veloped in the 1940s and 1950s by New Jersey, California, and other states
as a median barrier to prevent vehicle crossovers into oncoming traffic.
The New Jersey barrier became the most widely used and gave its name
to the generic barrier type. Subsequently, the barrier was widely used for
temporary protection in highway and other construction projects, and
came into wide use after September 11, 2001, as an anti-ram and traffic
control barrier against terrorist attack.
The barriers are not easily adaptable: they come in standard lengths of
12.5 and 20 feet, making their use somewhat inflexible, and they must
be carefully installed or they may create undesirable spaces where they
overlap, and reduce sidewalks to non-navigable widths (Figure 4-29).
Jersey barriers were thought to provide protection through their mass
— a 12-foot barrier weighs approximately 5,700 pounds — but if placed
on the surface, they are ineffective against vehicular attack. To be effec-
tive, they need embedment and vertical anchorage by steel reinforcing
through the foundation.
The Jersey barrier shown in Figure 4-30 is capable of stopping a 4,000-lb.
vehicle traveling at 50 mph and a 12,000-lb. vehicle traveling at 25 mph.
Note that the barrier is embedded about 12 inches and anchored to the
concrete slab with reinforcing bars: in this installation, the barriers essen-
tially become permanent (Figure 4-30).
Figure 4-29: Jersey barriers: pedestrian disruption at the White House (left) and on a d.c. street (right).
Perimeter security design 4-31
Installation
When installed on a sidewalk, a Jersey barrier reduces the effective side-
walk width by three-and-a-half feet, plus whatever distance it is placed from
the curb. Some installations can be dangerous in the event of an emer-
gency evacuation, particularly when several barriers are connected without
breaks, because there is no easy way for pedestrians to move past them.
Design Implications
Relatively inexpensive and readily available, Jersey barriers became ubiqui-
tous in the protection of public buildings and monuments in Washington,
New York, and elsewhere. However, their often awkward placement may
degrade the beauty of the urban scene and disrupt access and movement
for those on affected streets and sidewalks. Their most effective use is on a
temporary basis.
4.4.7 fences
Description, Purpose, and Performance
Fences are a traditional choice for security barriers, primarily intended
to discourage or delay intruders or serve as a barrier against stand-off
weapons (e.g., rocket-propelled grenades) or hand-thrown weapons such
as grenades or fire-bombs. Familiar fence types include:
m Chain-link
m Monumental fences (metal)
Figure 4-30:
Jersey barrier
dimensions and
installation for high
level of protection.
sOurce: dOd
HAndBOOK: SELECTION
AND APPLICATION OF
VEHICLE BARRIERS, miL-
HdBK-1013/14, 1999
Perimeter security design4-32
m Anti-climb (CPTED) fence
m Wire (barbed, barbed tape or concertina, triple-standard concertina,
tangle-foot)
Descriptions of these fence types can be found in FEMA 426, Section 2.4.1.
These fencing types are primarily intended to delay intrusion; they pro-
vide limited protection against vehicles unless specially designed to be
crash-rated.
Fencing can also incorporate various types of sensing devices that will
relay warning of an intruder to security personnel. Concealed intrusion
detection systems are also available, incorporating buried field units and
sensor cables.
Fences can also be constructed as engineered anti-ram systems. A typical
solution is to use cable restraints to stop the vehicle: these can be placed
at bumper height within the fence, hidden in planting. The cable needs
to be held in place using bollards and anchored to the ground at the ends
(Figure 4-31).
High-security cable fencing is available that can provide protection to the
original DOS Standards of providing an L1 rating (20 to 50 feet penetra-
tion) or L2 rating (3 to 20 feet penetration).
Figure 4-31:
Layout of cable
barrier, used in
conjunction with fence
or planting.
sOurce: dOd HAndBOOK:
seLectiOn And APPLicAtiOn
OF VeHicLe BArriers, miL-
HdBK-1013/14, 1999
Perimeter security design 4-33
Installation
Cable system fences allow considerable deflection before vehicles are
stopped; vehicles will be able to partially penetrate the site before re-
sistance occurs. The amount of deflection is based upon the distance
between the concrete “deadmen” — typically about 200 feet. As a re-
sult, the siting requirements for fences and gates that incorporate a cable
system differ slightly from other types of walls and fences. The designer
should take this into consideration when these types of systems are being
considered. Conventional fences with crash ratings can also be provided
(Figure 4-32).
Design Implications
Fences for the protection of property have a long history and have also
often been elements of great beauty. Modern fences are governed more
by function and cost, but variations of historic fence design have been
used as barriers for important historic buildings. The appearance of less
attractive fencing can be improved by planting.
4.4.8 reinfOrced street furniture And
fixtures
Description, Purpose, and Performance
Common streetscape elements can be reinforced to serve as anti-ram
barriers. These elements can be designed to be “hardened” so that they
function both as amenities and as components of physical building perim-
eter security. The structural design, spacing, shape and detailing of the
perimeter security components must be designed to address the required
Figure 4-32:
crash-rated fence.
sOurce: AmeristAr Fence
PrOducts inc.
Perimeter security design4-34
level of protection for a particular building. Typical elements that lend
themselves to this approach include hardened street furniture, fences or
fence walls, plinth walls (low retaining walls), bollards, planters, light stan-
dards, bus shelters etc (Figure 4-33).
Figure 4-33: streetscape elements suitable for hardening as security elements
sOurce: ncPc
Perimeter security design 4-35
To date, bollards have tended to become ubiquitous as perimeter barrier
systems. Security device manufacturers have found sufficient demand to
justify development and testing of active and passive bollards. They have
also responded to design demands by providing decorative covers in a
number of materials, which has greatly improved their appearance, but
there is need for more variety in barrier system design. This variety can
be provided by the use of hardened streetscape elements, but this ap-
proach has been limited due to the lack of tested and certified examples.
Development of such elements is important to enable the design of an at-
tractive and secure urban environment. An improvised example of this
approach, using crash rated bollards concealed between two benches, is
shown below ((Figure 4-34).
Supplementing bollards with common other reinforced streetscape compo-
nents such as lamp standards, bus shelters, and kiosks can assist in relating
security design to the community context. Such components would need
testing to ensure acceptable performance, but the use of custom-designed
components would enhance the streetscape and add an additional level of
safety to pedestrians against everyday traffic accidents. Some example of
these applications are shown in the following graphic boxes.
Figure 4-34:
Outdoor seating
reinforced with hidden
bollards.
sOurce: secure usA, inc.
CUSTOM STREET FURNITURE BARRIERS
Perimeter security design4-36
CUSTOM STREET FURNITURE BARRIERS (continued)
Perimeter security design 4-37
An example of a custom-designed streetscape feature is that of reinforced
glass seating that provides a considerable level of protection, looks at-
tractive, and can be illuminated to provide additional night protection at
locations such as bus stops (Figure 4-35).
Figure 4-35:
reinforced and
illuminated glass bench
model.
sOurce: rOgers mArVeL
ArcHitects, LLc
CUSTOM STREET FURNITURE BARRIERS (continued)
Perimeter security design4-38
4.5 ActiVe BArriers
4.5.1 retrActABLe BOLLArds
Description, Purpose, and Performance
A
retractable bollard system consists of one or more rising bollards
operating independently or in groups of two or more units. The
bollard is a below-ground assembly consisting of a foundation
structure and a heavy cylindrical bollard that can be raised or lowered
by a buried hydraulic or pneumatic power unit, controlled remotely by
a range of access control devices. Manually operated systems are also
available: these are counter-balanced and lock in the up or down posi-
tion. Typical retractable bollards are 12 to 13 inches in diameter, up to 35
inches high, and are usually mounted about three feet apart, depending
on the type of traffic. Figure 4-36 shows typical installations of retractable
bollards, with fixed bollards to each side of the retractable array.
Figure 4-36:
typical retractable bollard systems at a service entry (left) and a parking garage (right). note the fixed
bollards to each side of the retractable arrays.
Retractable bollards are used in high-traffic entry and exit lanes where
vehicle screening is necessary, at site entrances, and at entries to
parking garages and building services. Unlike rising or rotating wedge
barriers, the entry is freely accessible to pedestrians when the bollards
are raised.
Normal bollard operating speed is field adjustable and ranges from 3.0
to 10.0 seconds. Emergency operating systems can raise bollards to the
guard position from fully down in 1.5 seconds.
Retractable bollards are available crash rated up to DOS K12 standard.
Perimeter security design 4-39
Installation
Retractable bollards are expensive because they need deep and broad ex-
cavation for the bollards and operating equipment. Figure 4-37 shows a
single bollard installation and the installation requirements for a set of
bollards.
Figure 4-37:
retractable bollard
installation section
(top) and installation
requirements for
power and control
of a set of bollards
(bottom).
sOurce: deLtA scientiFic
cOrP.
Perimeter security design4-40
m Retractable bollards are a relatively unobtrusive barrier, which need
only be raised when screening is necessary, although at a time of
heightened threat they can remain in their raised position. A variety of
ornamental sleeves can be provided. Retractable bollards are generally
accompanied by fixed bollards at the sides, and a secure control booth
is necessary for security personnel.
4.5.2 rising Wedge BArriers
Description, Purpose, and Performance
Wedge barriers, sometimes called rotating plate barriers, consist of a metal
plate installed in a roadway that can be raised or lowered by an attendant
usually located in a booth next to the metal plate, thus regulating vehicle
access to the street across which it is installed. These barriers can be crash
rated and can effectively stop vehicles. Their primary purpose is to create
a restricted area by regulating vehicle access, rather than to block an area
from all vehicles. Shallow foundation systems are available rated to DOS
K12 standard. Raised height is from about 21 inches to 38 inches, and a
standard width is 10 feet. In the retracted position, the heavy steel ramp will
support any permitted road transport vehicle axle loadings. The moving
plate is raised and lowered by a hydraulic or pneumatic system (Figure 4-38).
Figure 4-38:
rising wedge barriers.
sOurce: deLtA scientiFic
cOrP.
Perimeter security design 4-41
Installation
Wedge barriers can be surface mounted, or mounted in a shallow excava-
tion about 18 inches deep. In the latter installation, the barricade plate is
flush with the road surface when retracted. The power unit can be config-
ured to operate one or more barricades and can be operated by a range
of optional remote control inputs. In surface-mounted installations, all
components are mounted above grade; no cutting or excavation is re-
quired on good concrete surfaces.
Mobile wedge barriers are also available that can be moved into position
by a medium-sized pickup truck in 15 minutes. These can form an effec-
tive element of a planned temporary barrier to respond to a heightened
threat level (Figure 4-39).
Design Implications
Rising wedge barriers were one of the earliest active barrier systems to be
developed. They are somewhat utilitarian in appearance, compared to re-
tractable bollards or rotating wedge systems.
These barriers effectively restrict vehicular through movement, but care
must be taken to ensure that limitations on the passage of screened bicy-
cles, cars and emergency vehicles are minimized. Like all active barriers,
mobile wedge barriers must be attended at all times.
Figure 4-39:
mobile wedge barrier.
sOurce: deLtA scientiFic
cOrP.
Perimeter security design4-42
4.5.3 rOtAting Wedge systems
Description, Purpose, and Performance
These systems are similar in action to the rising wedge blocker outlined
in Section 4.5.2 but have a curved front face, providing a better appear-
ance, and are embedded to a grater depth. The height of the obstacle is
between 24 and 28 inches, and a standard width is 10 feet. The obstacle is
operated hydraulically by heavy duty rams. Operating time is about three
seconds per movement (Figure 4-40).
Figure 4-40: typical rotating wedge barrier dimensions and installation requirements.
sOurce: deLtA scientiFic cOrP.
Installation
The pit to receive the system is approximately 5 feet wide, 40 inches deep,
and about 6 inches wider than the width of the obstacle. The hydraulic
mechanism can be located up to 50 feet away from the barrier.
Design Implications
Appearance depends on the layout and design of any accompanying fixed
barriers and control booths, the design of operating buttresses, and the
color and pattern of the barrier (Figure 4-41).
Perimeter security design 4-43
4.5.4 drOp Arm crAsh BeAms
Description, Purpose, and Performance
Drop-arm crash beams are a greatly strengthened version of barriers fa-
miliar at parking garage entries and the like. To create a crash barrier, the
assembly consists of a steel crash beam, support and pivot assembly, cast-
in-place concrete buttress, and locking and anchoring mechanisms. In
addition, crash-rated beams incorporate a high-strength steel cable, which
is attached to both buttresses when the arm is in a down position. Clear
opening range is from about 10 to 24 feet. The arm is raised and lowered
using a hydraulic or pneumatic system, or manually with a counter-bal-
anced arm (Figure 4-42).
Figure 4-42:
drop-arm crash beam.
Figure 4-41:
rotating wedge installation with typical manufacturer’s jazz pattern (left), rotating plate barrier with stop
sign in an elegant font combined with well-designed fixed low bollards (right).
Perimeter security design4-44
While crash-rated drop beams can be obtained, their performance is typ-
ically less effective than other active systems, although barriers can be
obtained with a certified K12 performance rating.
4.5.5 crAsh gAtes
Description, Purpose, and Performance
Crash-rated gates can be obtained that operate without contact with the
ground, while others use a rack-and-pinion drive across a V-groove. Swing
versions are also available. Clear opening range is from about 12 feet to
30 feet. Typical heights are 7 feet to 9 feet (Figure 4-43). Crash ratings up
to DOS K12 can be obtained.
Figure 4-43: typical gate installation (left); sliding gate with K12 crash rating (right).
sOurce: deLtA scientiFic cOrP.
4.5.6 surfAce-mOunted rOtAting pLAtes
Description, Purpose, and Performance
Surface-mounted wedges and plates are modular bolt-down barrier sys-
tems in which all components are mounted above grade, and no cutting
or excavation is needed on most concrete surfaces. The moving plate or
wedge is raised and lowered by a hydraulic, pneumatic or electro-mechan-
ical drive. A typical unit incorporates a single buttress with a ramp width
of 10 feet and a raised height of 21 to 28 inches. Dual buttress systems
have a width of about 18 feet. These systems can be installed quickly and
removed easily. Some systems incorporate a drop arm and traffic lights for
additional safety (Figure 4-44).
Typical cycle time is three to four seconds with a 1.5 second emergency
cycle. High-performance systems are capable of a DOS K4 rating.
Perimeter security design 4-45
4.6 innOVAtiVe BArrier systems
A
fter September 11, 2001, designers outside the traditional
security industry began to develop systems that combine func-
tionality with better appearance and, in some cases, lower cost.
The use of the ha-ha, described in Section 4.4.1, is an example of a tradi-
tional barrier imaginatively adapted to meet a contemporary and quite
different need. Three innovative systems are described in Section 4.6.1.
The NOGO barrier and “TigerTrap” are passive systems, while the “Turn-
table” is an active barrier.
4.6.1 the nOgO BArrier
Originally designed for the Wall Street area of New York City, the NOGO
barrier is an example of a device that provides an effective vehicle bar-
rier, while also being visually attractive and useful to lean on, socialize or
enjoy a lunch around, and as such makes a positive contribution to the
streetscape. The NOGO barrier is part security device and part a public
art object and has been exhibited at the New York Museum of Modern
Art. While more expensive than bollards, these simple yet subtle bronze
forms of a beautiful material provide a lasting benefit to the street scene
(Figure 4-45). Combined with the Turntable (see below) the NOGO, can
also be part of an active anti-ram system.
Figure 4-44:
surface-mounted wedges: single buttress with lighting (left); dual buttress with drop arm (right).
sOurce: secureusA inc.
Perimeter security design4-46
4.6.2 the tigertrAp
The TigerTrap is a collapsible sidewalk and planting system designed to
reduce the impact of force protection on public space while maintaining
a high level of security. The TigerTrap employs a sub-grade collapsible
material, installed below at-grade paving or planting. The installation
is designed to withstand pedestrian traffic but fail under the weight of
a loaded vehicle. The collapsible material lowers the elevation of an at-
tacking vehicle, so that it may be stopped by a low bench or underground
foundation wall. The system employs a compressible concrete technology
developed as an aircraft arrestor system that is installed at the end of the
overrun section of runways, instead of net systems commonly used.
The system is designed for use in sites where there is considerable space
available. The TigerTrap has been crash tested by the U.S. Army Corps of
Engineers and has been demonstrated to be approximately equivalent to
the DOS K12 standard.
The system needs careful design to be effective against design threat ve-
hicles without blocking lighter vehicles such as golf carts and motorized
wheel chairs; it needs considerable length to be effective (Figures 4-46,
4-47).
Figure 4-45:
nOgO bronze
sculptured barriers.
sOurce: rOgers mArVeL
ArcHitects, LLc
Perimeter security design 4-47
4.6.3 the turntABLe VehicLe BArrier
The Turntable Barrier concept was designed specifically to overcome diffi-
culties of installation in an urban environment, by use of a state-of-the-art
technology in operable anti-ram devices, while fostering a positive pedes-
trian environment (Figure 4-48).
Figure 4-46:
the tigertrap concept.
sOurce: rOcK 12 security
ArcHitecture
Figure 4-47:
Planting cover layer
creates a tigertrap
planting with a rear
bench.
sOurce: rOcK 12 security
ArcHitecture
Perimeter security design4-48
The Turntable Vehicle Barrier is a shallow-foundation operable de-
vice designed to provide the function of retractable bollards without
deep foundations. The foundation requires less than 2 ½ feet of depth,
placing the installation above most underground utilities. The turn-
table employs a non-hydraulic friction wheel drive system, a proven
technology used in rotating structures all over the world that alleviates
many of the operational and maintenance difficulties associated with
hydraulic devices. The rotational movement, while rapid enough for se-
curity purposes, does not pose a pedestrian danger.
The turntable is presently undergoing an extensive program of crash
testing to obtain certification.
The surface of the turntable is designed to accept a paving layer to
match surrounding materials, and the impact posts can accept covers
of any shape and size, such as architectural metals, walls, or planters
(Figure 4-49).
Figure 4-48:
turntable designed for conditions where security devices do not fit easily amid the tangle of underground
utilities and infrastructure.
sOurce: rOcK 12 security ArcHitecture
Perimeter security design 4-49
Figure 4-49:
shallow depth allows the turntable to avoid
underground utilities. impact posts keep the street
open to pedestrians (top), and the turntable can
accept architectural covers on the impact posts and
matching paving to the surrounding roadway (right).
sOurce: rOcK 12 security ArcHitecture
4.7 cOncLusiOn
t
he design of the perimeter barrier system is one of the most im-
portant aspects of providing building security. Design practice has
evolved rapidly from the hasty installation of Jersey barriers after
September 11, 2001, to the more considered designed systems that repre-
sent today’s best practice.
Today’s best practices often involve imaginative use of both traditional
and new concepts and materials, in the attempt to balance the needs
of security with those of site amenity and everyday function. They have
been developed in response to the perceived shortcomings of initial so-
lutions. Too often these solutions, conceived to be temporary, lasted for
many years, and some have become all but permanent. To the extent
that this has happened, and the visual and functional quality of our en-
vironment has been de-humanized, it can be said that the terrorists have
gained a victory.
Perimeter security design4-50
Access and egress control points need careful design and location, be-
cause they weaken the security of the perimeter. On the other hand, a
second point of egress is necessary in case an egress point is shut down by
police action, bomb squad activities, or other incidents.
The examples in this publication show that imaginative design of barrier
systems can provide positive enhancement of the urban environment, by
more clearly defining the types of public and private space and by pro-
viding city goers with more protection from everyday traffic. Innovation
in barrier design is also underway, spurred on by the needs of special situ-
ations such as the New York financial district, which is both high risk and
historic. The aim should be to develop building protection methods that
are unobtrusive elements in a safe and attractive streetscape.
- FEMA 430: SITE AND URBAN DESIGN FOR SECURITY
- CHAPTER 4: PERIMETER SECURITY DESIGN
4.1 INTRODUCTION
4.2 BARRIER SYSTEM DESIGN
4.2.1 Issues of Barrier Systems Design
4.2.2 Barrier Crash Test Standards
4.2.3 Determining Barrier Design Criteria
4.3 BARRIER MATERIALS AND TYPES
4.3.1 Materials
4.3.2 Barrier types
4.4 PASSIVE BARRIERS
4.4.1 Walls, excavations, berms, ditches, and ha-ha’s
4.4.2 Engineered Planters
4.4.3 Fixed Bollards
4.4.4 Heavy Objects and Trees
4.4.5 Water Obstacles
4.4.6 Jersey Barriers
4.4.7 Fences
4.4.8 Reinforced Street Furniture and Fixtures
4.5 ACTIVE BARRIERS
4.5.1 Retractable Bollards
4.5.2 Rising Wedge Barriers
4.5.3 Rotating Wedge Systems
4.5.4 Drop Arm Crash Beams
4.5.5 Crash Gates
4.5.6 Surface-Mounted Rotating Plates
4.6 INNOVATIVE BARRIER SYSTEMS
4.6.1 The NOGO barrier
4.6.2 The TigerTrap
4.6.3 The Turntable Vehicle Barrier
4.7 CONCLUSION
