Stop at the Point of Contact
Making sites less susceptible to vehicle attacks
The vast majority of discussions involving security and parking
areas focus on protecting people and property from
vandalism, theft or violent crimes. Thus, when planning
security features for a new or existing parking lot or garage,
the first consideration must be the level of security required for that
particular facility. A parking garage for a foreign embassy or federal
courthouse will require far more serious security measures than a mall
parking lot. Other primary considerations include the frequency of vehicles
moving in and out and whether there will be vehicle inspections
performed or a fully automated system at the entrance.
Reviewing Some Basic Physics Principles
When evaluating the security risk for a car bomber or crasher for
a given facility, focus on the weights and velocities of vehicles that
could be used to attempt penetration into sensitive areas. A vehicle
moving towards a barricade has a certain kinetic energy—the major
measure of how much “hitting power” it possesses.
Mathematically, kinetic energy is derived from the vehicle velocity
and its weight (mass). On impact, some energy is converted to
heat, sound and permanent deformation of the vehicle. To stop the
vehicle, the stopping point must absorb the remainder.
The remaining energy depends primarily on the velocity of the
vehicle at the moment of impact. The amount of kinetic energy possessed
by a vehicle changes by the square of its velocity. A vehicle
moving at 50 mph has 25 times as much kinetic energy as at 10 mph.
An armored car weighing 30 times as much as a Toyota moving at 10
mph has less hitting power than the Toyota moving at 60 mph.
Because of the relationship of velocity to the total kinetic energy,
the security engineer must make every effort to force a vehicle to slow
down before it reaches the barricade.
Security Starts With an “S”
Straight lines make for faster and easier approaches for vehicles, so
it’s best to create curves on access roads to your facility as a natural
impediment to speeding cars or trucks.
The most frequently used technique is to require a sharp turn immediately
in front of the entrance. When vehicle speed is reduced
by 50 percent, “hitting power” is reduced four times. If the speed is
reduced by two-thirds, the force of impact is reduced nine times. Failing
to understand this and not using the proper equipment to counter
the threat leads to a false sense of security.
Upon designing a way to slow down vehicle approach, precautions
should also be taken so that the attacking car cannot make a
“corner cutting shot” at a barricade. Often, only a light post defines a turning point and a speeding car can take it out and not even hesitate.
Knolls and other impediments should be considered.
Where turns cannot be created, many are turning to an “Early
Warning System.” This system is best applied at locations where there
is a long and relatively straight run into the facility that would allow a
large vehicle to build up its speed. A vehicle traveling at 60 mph can
cover 88 feet per second so it is imperative that guards are alerted
Intelligent vehicle systems can check the velocity of an approaching
vehicle, or set off an alarm if a car is coming down the wrong
lane. Intelligent systems will also protect innocent drivers who might
be trapped between barricades and a speeding, approaching vehicle.
Intelligent vehicle systems also are able to tell if a vehicle is too large
to enter a parking structure, potentially saving countless dollars on
Continuous Doppler Radar picks up instantaneous changes in velocity
and addresses the threat scenario in which an inbound vehicle
approaches at normal speeds and then accelerates to commence the
attack. It will also warn if a hidden vehicle suddenly passes a larger
vehicle and attempts an attack. Once alerted, the guards can take action,
including raising the barrier systems.
Security equipment for parking facilities ranges from tire-puncturing
devices to simple swing arm gates to pop-up crash barriers built
into the roadway that will stop errant vehicles dead in their tracks.
Use the Barrier You Choose
Today’s barriers and bollards are capable of stopping and destroying
a truck weighing up to 65,000 pounds and traveling at 50 mph.
Such barricades can be raised or lowered at will to stop traffic or let it
through. In an emergency, the thick steel plates or bollards pop out of
the ground within 1.5 seconds.
With any barrier system, frequency of operation is also a key consideration.
For example, a sliding gate would not be practical for a
business that requires admitting and releasing hundreds of employee
cars per day. In reality, due to the inconvenience to the employees,
most operators would simply leave the gate open.
With vehicle barriers, the most common security breach is tailgating.
When a system suspends a tailgating car, it’s literally doing its
job—stopping an unauthorized vehicle from entering a facility. Most
vehicle barrier systems are set up to allow only one car at a time. How
do you avoid these “accidents,” yet avoid weak links? Employ loop
detectors. These little sensor subsystems determine when the first car
has passed by and automatically and immediately drop the gate or
raise the bollards.
Another common planning deficiency occurs when designers
choose non-certified barriers or barricades. No area is more critical
to the vehicle barrier selection process than testing. Without adequate
testing, there is no assurance that the barrier will resist the threat.
Certified equipment has been tested and proven to work under
extreme conditions, giving planners the confidence they rely on. Testing
is normally done by an independent testing company or government
agency, such as the U.S. Department of State (DOS) and military.
Comprehensive reports of test results are issued and are available
from the testing agency or manufacturer.
Example: Barricades Bolster Security
at Miami Federal Courthouse
To regulate traffic, provide a safe place to transfer prisoners and offer
secure underground parking for judges, the Miami Federal Courthouse
installed hydraulic barricade systems. Each 10-foot wide barricade
is a moving ramp that is surface-mounted and rises to 18 inches
In normal operation, these barricades stay up and are lowered
only to allow passage of authorized vehicles. The speed at which the
barrier deploys can be fully adjusted to the security site and facility
requirements. Security personnel at the Miami Federal Courthouse
can have different speeds on different barriers and change the speeds
as security warrants.
To ensure the units will not rise if a car is on or in the way of the
barrier, the Miami Federal Courthouse barriers use the afore-mentioned
loop detectors. The loop detector holds the barrier open until
the last part of the vehicle has passed the closing loop, located beyond
the unit. The detector then gives a pulse on departure, instructing the
barrier to rise after the vehicle has passed.
Vehicle Attacks: A Growing Threat
Although the obvious goal of such a system is to protect when assaulted,
the larger objective for the system is to deter. Barriers, bollards
and other vehicle control equipment discourage attempts to
cause harm and encourage employees and visitors to feel secure.
Whether building a new parking structure, or retrofitting an old
one, there are a myriad of ways to protect people and property by
using everything from common sense design to the latest technology
innovations. When integrated properly into a total system, including
fences, lights, alarms, gates and other security components,
well planned vehicle barrier systems are a key measure in preventing
threats to sensitive resources.
It’s critically important to consider supplemental gate and fencing
reinforcements that may be necessary to optimize vehicle barrier
effectiveness. Failing to understand this aspect, and not using the
proper equipment to counter the threat, may lead to a false sense of
This article originally appeared in the October 2019 issue of Security Today.