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. It is important to note that only passive barrier devices found in the most recent publication of the DOD Anti-Ram Vehicle Barrier List are considered compliant forms of passive barrier. Refer to the Army Corps of Engineers Digital Library here: DOD Anti-Ram Vehicle Barrier List

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. TEA 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	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	Can deploy in less than 2 seconds Significant surface for delineation	Fixed object In-ground hydraulics May require replacement if struck
Bollards	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	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
Portable Barriers	Most suited to barrier normally closed use in low volume conditions	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. TEA 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.

0-Second Full Containment Scheme: 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.

5-Second 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.

7-Second Hybrid Beacon Safety Scheme: The Hybrid Beacon Safety Scheme uses hybrid beacons for traffic control and extended vehicle detection loops to detect the presence of vehicles approaching the AVB. The safety scheme’s design provides adequate stopping sight distance for an innocent driver to stop prior to, or to clear, the AVB.

9-Second Hybrid Beacon Safety Scheme: The 9-second Hybrid Beacon Safety Scheme uses signals located with sufficient distance to provide adequate warning to drivers to stop in advance of the barriers. This system allows the free flow of vehicles, through the AVB, allowing high traffic volume requirements to be met. There are also applications for combining these schemes, where one scheme would be used inbound and another outbound. If the barriers are located at an intersection, special considerations are required. Either relocate the barriers for the outbound direction between the ID check and the intersection, or if the outbound barriers must be located at the intersection, a longer response time (12 seconds) must be used.