Vehicle Barriers

Vehicle Barriers

Full containment and control of vehicles are required at all ECFs. To contain a threat vehicle, an ECF utilizes passive and active vehicle barriers. Passive barriers direct and channelize traffic while active barriers are used only upon activation by personnel, equipment, or both. Passive and active barriers are designed based on their ability to stop threat vehicles.

Passive Barriers

Passive barriers are generally parallel to the direction of travel. They should be arranged to prevent a vehicle from circumventing the ECF. Ideally, crashworthy barriers such as guardrails, earthen berms, or high sloped face curbing should be used. Non-crashworthy barriers like reinforced walls, reinforced fences, trees, or bollards should be located outside of the clear zone.

Passive Barrier Requirements
Dense Trees

Must be large enough to stop threat vehicle, min 4-inch (100 millimeter) diameter
Aesthetically pleasing and environmentally friendly solution

Boulders

Must be designed (and approved) to stop threat vehicle
Aesthetically pleasing
May not be cost effective unless material is readily available
Army does not allow

Earthern Berms

Careful design is required to contain threat vehicle and to limit ramping
May help control ECF and limit view of ECF and installation from exterior areas

Ditches

Design must prevent vehicles from traversing
May serve dual purposes: contain threat and drainage for roadway

Bioretention Zones

Design must prevent vehicles from traversing
May serve dual purposes: contain threat and treat stormwater run-off on site

Reinforced Fencing

Must be reinforced to stop threat vehicle
Can be aesthetically pleasing

Bollard

Must be large enough to stop threat vehicle
Can be aesthetically pleasing

Jersey Barrier or High Slope-faced Curb

Can be located within clear zone consistent with AASHTO
If greater than 8 inches (200 millimeters), cannot be traditional curbing

Walls

Must be design to stop threat vehicle
Can be aesthetically pleasing

Guardrail System

Can be located in clear zone if crashworthy but should be located outside clear zone, if possible
May not prevent head-on penetration
May not immobilize larger vehicles

 

Active Barriers

Many installations use active barriers as arresting devices to stop unauthorized vehicles. Some drivers who attempt to enter the installation without authorization are lost, confused, or inattentive, but there are also those with hostile intentions. A properly designed barrier minimizes the risk to those making an honest mistake and stops those with hostile intentions. There are several different types of barriers available, some of which are better suited to different applications.

The placement of a barrier must allow for sufficient response time after the ID checkpoint area between the time that the threat vehicle is detected, the guard reacts to the threat, a signal in front of the barrier properly sequences, and the barrier activates. SDDCTEA has developed multiple barrier safety schemes, one of which must be used with any active barrier installation. The barrier safety scheme can vary depending on space available, and roadway geometry.

Type Pros Cons
Nets
Nets

Less likely to be lethal
Can deploy in less than 2 seconds
Limited hydraulics below grade
Spans multiple lanes (reduce costs)
Reusable after impact
More than one manufacturer

Limited surface area for delineation
Concerns over motorcycles when traversing in down position
Need to channel pedestrians away from roadside AVB area
Wedges
Wedge

Can deploy in less than 2 seconds
Significant surface for delineation

Fixed object
In-ground hydraulics
May require replacement if struck
Bollards
Bollard

Can deploy in less than 2 seconds
Can be used for partial closures

Vehicle intrusion on impact
Gaps greater than 3 feet are a potential vulnerability
Limited surface area for delineation
In-ground hydraulics
May require replacement if struck
Crash Beams
Beam

Most suited to barrier normally closed use in low volume conditions
Better suited for cold weather locations

Vehicle intrusion on impact
Limited surface area for delineation
In-ground hydraulics
Deployment times may exceed 2 seconds
May require replacement if struck
Spikes
Spikes

Minimal property damage
Not recommended as an AVB, best as a secondary AVB or to gauge intent

Not certified
Vehicles may continue to travel on flat tires
Limited durability if not inset
Portable Barriers
Barriers

Most suited to barrier normally closed use in low volume conditions
Not recommended as an AVB

May damage undercarriage of vehicles through normal use
May require replacement if struck


The placement of a barrier must allow for sufficient response time after the ID checkpoint area between the time that the threat vehicle is detected, the guard reacts to the threat, a signal in front of the barrier properly sequences, and the barrier activates. SDDCTEA has developed multiple barrier safety schemes, one of which must be used with any active barrier installation. The barrier safety scheme can vary depending on space available, and roadway geometry.

Signs and Signals Safety Scheme: With this, a minimum of 9 seconds of travel time must be provided before the threat vehicle reaches the barrier. This system allows the free flow of vehicles, through the AVB, allowing high traffic volume requirements to be met. Emergency Hybrid Beacons or a standard three-section red/yellow/green signal may be used.

Signs and Signals Co-Located at an Intersection Safety Scheme: This safety scheme should be considered when the barrier is located within 300 feet of an intersection, and both the inbound and outbound barriers are relocated to the intersection. With this scheme, the barrier operates similarly to the conventional scheme, but the entire intersection is signalized and the entire signal is red when the barrier is activated. The total response time is approximetely 12 seconds but will vary based on the size of the intersection. The increase time is due to the outbound traffic crossing the stop bar at the instant the signal turns red. Time has to be included to allow this vehicle to cross the intersection before the AVB is deployed.

Signs and Signals Staggered at an Intersection Safety Scheme: With this safety scheme, the inbound barriers are located at an intersection and the outbound barriers are located 300 feet from the intersection. With this configuration, 9 seconds of travel time for barrier activation must be provided, similar to the conventional system. Designers should verify that the barriers for the outbound direction can effectively stop a threat vehicle since the response zone is shorter. This could employ other strategies such as wrong-way speed detection, or alternate geometry and travel paths to limit threat vehicle speeds.

High Efficiency Presence Detection Safety Scheme: With this system, a minimum of 7 seconds must be provided. If there are no vehicles detected, the traffic arm is down and the traffic signal is red. When a vehicle approaches, it is detected, the traffic arm rises and the signal turns green allowing the vehicle to continue. If more vehicles are following, the signal remains green, the traffic arm stays up and vehicles continue on. Once the last vehicle exits and a new vehicle is not detected after a few seconds, the traffic signal turns yellow then red and the traffic arm lowers.

Stop Control Safety System: This system was initiated by the need to retrofit AVB safety at constrained locations with relatively low traffic volume; less than 800 vehicles per hour per lane. This system requires all vehicles inbound and outbound to stop at the AVB. This requirement effectively eliminates the need to transition from a green signal to a red. A minimum of 5 seconds is required for this safety scheme.

Barrier Up/Barrier Platooning Safety System: These barriers are always closed and opened for authorized vehicles. Traffic flow is considerably slower, but this safety system can be acceptable in low volume applications. No time is needed for these systems since the barriers are up.

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