Provide a concrete example of an engineering control specifically applied to reduce the risk of vehicle-as-a-weapon attacks at a perimeter, beyond simple bollards.

A concrete example of an engineering control specifically applied to reduce the risk of vehicle-as-a-weapon (VAW) attacks at a perimeter, beyond simple bollards, is a Hydraulic Wedge Barrier System. An engineering control is a physical modification to a workplace or environment designed to reduce exposure to hazards by physically removing or reducing the hazard itself, or by placing a physical barrier between the hazard and the protected area. In this context, the hazard is an attacking vehicle.

This system consists of a robust steel plate or series of interconnected steel plates, typically flush-mounted within the roadway at a controlled access point. In its normal, permissive state, the wedge barrier lies flat and is level with the road surface, allowing authorized vehicle traffic to pass freely. Upon detection of an unauthorized vehicle, or in response to an operator's command during a suspected threat, a powerful hydraulic mechanism rapidly elevates the heavy steel barrier section to an upright position, typically reaching heights of 30 to 40 inches above the road surface.

The elevated wedge presents an impenetrable obstacle designed to physically stop a hostile vehicle. These systems are rigorously tested and certified to specific crash ratings, such as K-ratings or M-ratings. A K-rating (e.g., K12) or M-rating (e.g., M50) signifies the barrier's capability to halt a specific vehicle mass, like a 15,000-pound truck, traveling at a certain speed, such as 50 miles per hour, with minimal or no penetration beyond the barrier line. This certification demonstrates its immense structural integrity and ability to absorb and dissipate the kinetic energy of a high-speed, heavy vehicle impact, preventing it from breaching the protected perimeter.

Unlike simple, passive bollards, which are fixed posts that rely solely on their static strength and spacing, a hydraulic wedge barrier is an active control. Its dynamic deployment capability allows for selective access control, remaining hidden until needed, and then rapidly deploying to create an impassable barrier only when a threat is detected or anticipated. This combination of dynamic operation and superior, certified crash resistance makes it significantly more effective against a determined vehicle-as-a-weapon attack than a series of static bollards alone.