Effective Perimeter Security Design Solutions
The purpose of a perimeter is to delineate a property line, or in some cases to delineate the point to which protection is desired within the property boundary. Vehicle security barriers (VSB) should be considered as the first layer in a protection-in-depth barrier configuration.
Protection in Depth
A protection-in-depth layout beginning with the access point means that a vehicle would have to overcome a series of security barriers that represent an increasing degree of resistance the further towards the target they penetrate.
If a VSB is intended to also become an effective barrier, one of the early considerations that should be addressed is what the barrier is designed to defend against. For example, a single unsophisticated intruder who is seeking to gain entry surreptitiously, or is it a group of protestors intent on destroying the barrier with a vehicle? If the latter, a standard non-tested VSB may not be adequate.
Factors Influencing HVM Protection
Vehicle barriers are used at access points and other vulnerable areas around a perimeter to protect against unauthorised vehicular access by providing a physical barrier which prevents or delays incursion through the perimeter. As such they reinforce access restrictions and can be used to enforce stand-off distance around Critical locations, as well as to ensure that speed and traffic management policies are adhered to.
In line with risk assessments and the design basis threat and protection objectives, it is important to consider the types of vehicle-related attack that could be mounted on your facility and the related methods that adversaries may use to try to overcome any vehicle barriers that aim to protect against these attacks. In this respect, there are seven main strategies that they could adopt, as outlined below:
- Parked – placing a vehicle bomb adjacent to the perimeter where there is inadequate stand-off to protect assets from an explosion.
- Encroachment – manoeuvring through gaps in existing barriers to bring a vehicle closer to the asset, or tailgating through access barriers.
- Penetrative – ramming through a barrier.
- Deception – use of a false identification to gain access.
- Proxy/Duress – a vehicle driver may have been targeted to act as a mule for an attack.
- Tampering – covert tampering of a security barrier to render it ineffective.
- Vehicle as a Weapon – using the vehicle to ram into innocent bystanders.
Vehicle Barrier Design Considerations
It is important that vehicle barriers, particularly those designed to prevent penetrative attacks, are designed correctly and in this respect assistance from external specialists is likely to be required.
For high-risk facilities, it may be necessary to carry out a vehicle dynamics assessment to identify possible attack routes, vehicle speeds and angles of attack, as well as blast assessments to determine the required amount of standoff distance to protect assets and therefore the location of vehicle barriers used to enforce this. However, many facilities will require both impact-rated and non-impact-rated barriers as part of an integrated solution and therefore some general considerations are presented below:
How many vehicles will be entering and exiting the site per hour or day and as such how many mechanical operations per day will be required of the barrier.
How will barriers be configured to support the access control function, whilst preventing tailgating and encroachment. A double barrier airlock system may be required at main entrance points, or minimum separation distances between barriers may be required.
How will the barrier be controlled – what type of integration with access control will be used, what safety features such as loops, photocells, warning lights and sensors will be required. Will mechanical operation be possible in the event of a power failure?
A survey of the site to identify any routes including angles of attack other than those leading to access points that could be used by a threat vehicle to penetrate the perimeter, specialist advice or Vehicle Dynamic Assessment may be required.
Whether space is available to accommodate the foundations for a vehicle barrier as essential services running below ground may inhibit the installation of the barrier, specialist advice may need to be sought to identify shallow or surface mounted products.
Whether the intended area of installation is adequate to accommodate the barrier.
Such as flooding, snow and ice that may affect the barrier’s operation or the traffic management.
The camber, surface, kerbs or other factors could affect any barrier installation.
Crash Test Standards
One of the most important factors to be addressed in the context of vehicle barrier design is whether barriers must be able to resist penetrative attack and this should be clear from any protection objectives established. Where this is not considered a significant risk, standard vehicle barriers can be selected in accordance with functional requirements.
A crash test is a form of destructive testing usually performed to ensure design standards for various VSB are adhered to.
However, where it is necessary to protect against penetrative attack it is important that barriers are certified to provide the required level of impact resistance. In this respect, it is recommended that products certified to International Workshop Agreement (IWA) 14.1:2013 and PAS68 be considered and that the design and installation of barrier systems also conforms to IWA 14.2:2013 and PAS69 respectively. Whilst other classification systems exist internationally, such as ASTM F2656M–15 the product requirements set out in IWA 14.1:2013 and PAS68 are currently the most rigorous available. These standards classify performance based on vehicle type, vehicle mass, vehicle speed, impact angle and penetration distance..
The design of the VSB is one of the most important aspects of providing building security. Design practice has evolved rapidly for hasty installation products, to the more considered designed systems that represent today’s best practice.
Today’s best practices often involve an 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.