Keeping pedestrians safe, protecting structures from accidental or intentional automobile crashes and force protection (keeping employees and visitors from harm) have always been a concern. From pedestrian-filled farmers’ markets and universities to new and used car lots, a wide variety of agencies find peace of mind through the use of barriers, bollards, barricades and crash gates for vehicle-based physical access control at the perimeter.
Risk assessment starts with Physics 101
When evaluating the security risk for a given facility, particular attention must be focused on the weights and velocities of vehicles that would be used to attempt penetration into sensitive areas.
A vehicle moving towards a barricade has a certain kinetic energy, which is 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 of this energy is converted to heat, sound and permanent deformation of the vehicle. The barricade must absorb the remainder of this energy if the vehicle is to be stopped.
The amount of remaining energy varies depending on many factors, primarily the velocity of the vehicle at the moment of impact. The amount of kinetic energy posed by a vehicle changes as the square of its velocity. For example, a vehicle moving at 80 kph has 25-times as much kinetic energy as it would at 16 kph. Thus, an armoured car weighing 30-times as much as a Toyota Corolla and moving at 16 kph would have less hitting power than the Toyota moving at 96,5 kph.
Because of the relationship of velocity to the total kinetic energy possessed by the vehicle, every effort must be made by the security engineer to force a vehicle to slow down before it reaches the barricade. The most frequently used technique is to require a sharp turn immediately in front of the barrier. When vehicle speed is reduced by 50%, the ‘hitting power’ is reduced by four times. If the speed is reduced by two-thirds, the force of impact will be reduced by nine times.
Upon designing a way to slow down vehicle approach, precautions should also be taken 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.
Failing to understand this and not using the proper equipment to counter the threat may lead to a false sense of security.
Overcoming common design deficiencies
As discussed above, linear thinking won’t get you very far when planning a vehicular perimeter security system. Straight lines make for faster and easier approaches for vehicles, so it’s best to create curves on the access roads to your facility as a natural impediment to speeding cars or trucks.
Another common planning deficiency occurs when designers choose non-certified barriers or barricades. Certified equipment has been tested and proven to work under extreme conditions, giving planners confidence.
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. Testing is normally by an independent testing company or government agency, such as the US Department of State (DOS) and military. Comprehensive reports of test results are issued and are available from the testing agency or manufacturer.
Today’s barriers and bollards are capable of stopping and destroying a truck weighing up to 29 484 kg and travelling at 80 kph. 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.
When integrated properly into a total system, including fences, lights, alarms, gates and other security components, vehicle barriers are a key measure in preventing threats to sensitive resources. It’s important to consider supplemental gate and fencing reinforcements that may also be needed to optimise vehicle barrier effectiveness.
In designing a barrier system, you must also consider whether to use a passive or active system. Normally, an active system keeps the barrier in the active or up position. It must be deactivated to permit access. Active systems are preferable to ones that must be activated to prevent access because they are more secure.
One final area that should not be overlooked is aesthetics. With today’s smart designs, it’s no longer necessary to choose between form and function. You can have them both. Designers are creating secure environments with more compatible and aesthetically pleasing architectural elements.
If you visit many implementations today, you’ll see landscaped islands at the entrance drives which regulate vehicular access. If allowed to drive into the complex, you will cross over vehicle control barriers and bollards at the entrances. Indeed, all exits at the end of all drives are controlled with barriers, which pop from the ground when needed.
You’ll see similar barriers and bollards at refineries, distribution centres and headquarters offices, literally around the world.
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