d) Deter "casual" intruders from penetrating into a secured area by presenting a
barrier that requires an overt action to penetrate;
e) Cause an intruder to make an overt action that will demonstrate intent;
f) Briefly delay penetration into a secured area or facility, thereby increasing the
possibility of detection.
In the field of security, perimeter barriers provide the first line of defense for a
facility. The true value of a perimeter security fence comes in its association with other
components of a security system. When perimeter security is required, the security fence forms
the basic building block for the rest of the system.
Location. Active vehicle barriers can be located at facility entrances, enclave entry
points (gates), or selected interior locations (e.g., entrances to restricted areas). Exact locations may
vary among installations; however, in each case, the barrier should be located as far from the critical
structure as practical to minimize damage due to possible explosion. Also, locate support
equipment (e.g., hydraulic power, generator, batteries, etc.) on the secure side and away from guard
posts to lower the threat of sabotage and injury to security personnel. Passive barriers can be used at
entry points, if traffic flow is restricted or sporadic (i.e., gates that are rarely used). Passive barriers
are normally used for perimeter protection.
Aesthetics. The overall appearance of a vehicle barrier plays an important role in its
selection and acceptance. Many barriers are now made with aesthetics in mind that will blend in
with the environment.
Safety. An active vehicle barrier system is capable of inflicting serious injury. Even
when used for its intended purpose, it can kill or seriously injure individuals when activated
inadvertently, either by operator error or equipment malfunction. Warning signs, lights, bells, and
bright colors should be used to mark the presence of a barrier and make it visible to oncoming
traffic. These safety features must always be provided to ensure personnel safety. The following
issues should be addressed to manufacturers and users to identify potential safety issues affecting
the selection of an active barrier system:
a) Backup power;
b) Emergency cutoff switch;
c) Adequate lighting;
d) Installation of safety options, such as alarms, strobes (or rotating beacons), and safety
interlock detectors to prevent the barrier from being accidentally raised in front of or under an