6.1.2 Controlled Access Zones
Access control refers to points of controlled access to the facility through the perimeter line. The controlled access check or inspection points for vehicles require architectural features or barriers to maintain the defensible perimeter. Architects and engineers can accommodate these security functions by providing adequate design for these areas, which makes it difficult for a vehicle to crash onto the site.
Deterrence and delay are major attributes of the perimeter security design that should be consistent with the landscaping objectives, such as emphasizing the open nature characterizing high-population buildings. Since it is impossible to thwart all possible threats, the objective is to make it difficult to successfully execute the easiest attack scenarios such as a car bomb detonated along the curb, or a vehicle jumping the curb and ramming into the building prior to detonation.
If space is available between the perimeter line and the building exterior, much can be done to delay an intruder. Examples include terraced landscaping, fountains, statues, staircases, circular driveways, planters, trees, high-strength cables hidden in bushes and any number of other obstacles that make it difficult to rapidly reach the building. Though individually these features may not be able to stop a vehicle, in combination, they form a daunting obstacle course. Other ideas for implementing secure landscaping features may be found in texts on Crime Prevention Through Environmental Design (CPTED). These concepts are useful for slowing down traffic, improving surveillance, and site circulation.
On the sides of the building that are close to the curb, where landscaping solutions are limited, anti-ram barriers capable of stopping a vehicle on impact are recommended for high-risk buildings. Barrier design methods are discussed in more detail below.
The location of access points should be oblique to oncoming streets so that it is difficult for a vehicle to gain enough velocity to break through these access locations. If the site provides straight-on access to the building, some mitigation options include concrete medians in the street to slow vehicles or, for high-risk buildings, use of anti-ram barriers along the curb capable of withstanding the impact of high-velocity vehicles.
Place parking as far as practical from the building. Off-site parking is recommended for high-risk facilities vulnerable to terrorist attack. If onsite surface parking or underground parking is provided, take precautions such as limiting access to these areas only to the building occupants and/or having all vehicles inspected in areas close-in to the building. If an underground area is used for a high-risk building, the garage should be placed adjacent to the building under a plaza area rather than directly underneath the building. To the extent practical, limit the size of vehicle that is able to enter the garage by imposing physical barriers on vehicle height.