**Hostile Vehicle Mitigation (HVM)** systems are physical security measures designed to **prevent, stop, or mitigate hostile vehicle attacks**, including:

* **Vehicle-as-a-Weapon (VAW)** attacks

HVM systems differ fundamentally from conventional access control or traffic management barriers. They are **security-first, defence-led installations**, where **threat mitigation takes precedence over convenience, vehicle protection, or user comfort**.

As a result, HVM systems often behave in ways that appear aggressive or counter-intuitive when compared to standard parking or access bollards.

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HVM systems are commonly deployed in locations where the consequences of hostile vehicle access are high, including:

* Transport hubs and stations

* Government and local authority buildings

* Ports and maritime infrastructure

* Stadia and major event venues

* Critical National Infrastructure (CNI)

* High-footfall urban public realm locations

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HVM systems are designed to counter:

Deliberate vehicle ramming intended to cause casualties.

Use of a vehicle to deliver explosives close to a protected asset.

Closely following an authorised vehicle to breach a secure perimeter.

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* Hydraulically or electro-mechanically operated

* Crash-tested to PAS 68 or IWA 14-1

* Designed to immobilise or destroy vehicles

* Fast deployment times prioritised

These are the most common automated HVM barriers used in constrained urban environments.

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* Large steel wedges or plates that rise from the roadway

* Extremely high stopping capability

* Suitable for heavy vehicles and high-energy impacts

Often used in ports, embassies, and high-security perimeters.

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* Reinforced planters, benches, street furniture

* Structural barriers integrated into landscaping

* No moving parts or control systems

Typically used to create hostile-vehicle stand-off distances.

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* Reinforced foundations and locking points

* Designed for impact resistance, not throughput

* Usually slower and manually supervised

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HVM systems are intentionally designed around the following principles:

This philosophy directly influences how HVM systems behave in live operation.

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Many HVM installations incorporate **automated access** for authorised vehicles, typically via:

* Intercom systems

* Guard control panels

* Timed or conditional lowering of barriers

However, automation in HVM systems is **deliberately restrictive and tightly controlled**.

Unlike conventional access barriers, automation is not designed to accommodate hesitation, reversing, or abnormal vehicle manoeuvres.

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Most automated HVM systems rely on **inductive ground loop detectors**.

* A magnetic field is generated within the loop

* When a vehicle passes over, the inductance changes

* The controller interprets this change as vehicle presence

Ground loops detect **metal mass**, not:

* Vehicle intent

* Direction of travel

* Speed or driver behaviour

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A common HVM configuration uses **two ground loops**, typically positioned:

* One on the *secure side* of the barrier

* One on the *non-secure side*

The control logic is designed to:

1. Lower the barrier when authorised access is granted

2. Detect vehicle entry onto a loop

3. Monitor loop occupancy and clearance

4. **Immediately raise the barrier once a loop is cleared**, indicating the vehicle has exited the protected zone

This logic exists specifically to counter **tailgating and forced entry**.

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In HVM systems:

* The barrier may begin preparing to raise as soon as a vehicle is detected entering a loop

* Once the system believes the vehicle has cleared the detection zone, the barrier will raise **without delay**

If a vehicle:

* Hesitates

* Reverses

* Rolls forward and backward

* Stops partially over a loop

…the system may interpret this as the vehicle having exited the secure area and will deploy the barrier.

This behaviour is **intentional, compliant, and expected** in an HVM context.

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Standard access or parking bollards typically prioritise:

* Vehicle safety

* User convenience

* Obstruction detection

* Predictable driver behaviour

HVM systems do not.

In an HVM environment:

* Safety sensors that could delay deployment are often omitted

* Ambiguous vehicle movement is treated as a potential threat

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Most automated HVM systems provide a **manual control mode**, in which:

* Ground loop inputs are ignored

* The operator directly controls barrier movement

* Deployment is supervised visually

Manual operation should be used when:

* Long vehicles (e.g. lorries) are passing

* Multiple vehicles are travelling in convoy

* Vehicles may need to stop, reverse, or manoeuvre

* Escorts or abnormal movements are expected

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HVM barriers are **not primarily safety devices**.

Common characteristics include:

* No pressure edges

* No photocells or obstruction detection

* No automatic re-opening on contact

This is consistent with their security role and threat model.

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HVM systems are typically designed and assessed against:

* **PAS 68** - UK impact testing standard (legacy but still referenced)

* **IWA 14-1** - International vehicle impact test standard

* **ISO 22343-1** - Vehicle mitigation barriers

* **NaCTSO / CTSA guidance** - UK counter-terrorism protective security advice

Final design should always be informed by:

* Site-specific threat and risk assessments

* Police or CTSA input

* Operational requirements

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HVM systems are mechanically intensive and require:

* Regular inspection for impact damage

* Hydraulic servicing (where applicable)

* Control logic verification

* Periodic major servicing, often requiring removal from ground

Repeated low-speed impacts are common and **do not necessarily indicate failure**, but they do accelerate wear and servicing requirements.

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HVM systems are **designed to be struck by vehicles**. Even low-speed or “non-hostile” impacts can transfer significant energy into:

* Structural foundations

* Hydraulic assemblies

* Drive mechanisms and seals

* Anchor points and reinforcement cages

While many impacts may not result in immediate or visible failure, **hidden damage** can compromise performance during a genuine hostile event.

As such, **post-collision inspection should be treated as best practice**, in addition to scheduled preventative maintenance.

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A post-collision inspection should be considered following **any unplanned vehicle contact**, including:

* Vehicles mounting or striking raised bollards

* Vehicles driving over partially raised barriers

* Slow-speed manoeuvring impacts

* Reversing or turning collisions

* Repeated “nudges” or scrapes over time

Impacts do **not** need to result in visible deformation to warrant inspection.

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Following a collision or suspected impact:

1. **Record the incident**

* Time and date

* Vehicle type and direction of travel

* Barrier state at time of impact (raised / lowering / raising)

2. **Carry out a visual inspection**

* Alignment and verticality of bollards

* Signs of cracking, distortion, or abnormal movement

* Oil leaks or hydraulic residue

3. **Functional testing**

* Raise and lower cycles

* Synchronisation between multiple bollards

* Abnormal noise, vibration, or speed changes

4. **Control system checks**

* Fault logs and alarms

* Confirmation of correct detection behaviour

* Verification of manual override operation

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* **Minor impacts** may only require logging and monitoring

* **Repeated impacts** should trigger increased inspection frequency

* **Significant impacts** (including any involving heavy vehicles) should prompt:

* Temporary isolation if necessary

* Engineering inspection

* Consideration of partial or full barrier removal for assessment

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Post-collision inspections **do not replace** scheduled servicing.

They should be considered **event-driven maintenance**, complementing:

* Routine inspections

* Manufacturer-recommended service intervals

* Periodic major servicing (out-of-ground inspection)

Ignoring post-impact checks risks:

* Progressive degradation

* Hydraulic contamination

* Misaligned deployment

* Reduced stopping capability during a real hostile event

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From an operational and legal standpoint, post-collision inspections:

* Demonstrate proactive asset management

* Reduce the likelihood of undetected latent failures

* Provide defensible maintenance records

* Support incident investigations and insurance claims

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| Assumption | Reality |

| --------------------------------------- | --------------------------------- |

| “It malfunctioned because it raised” | Raising may be correct behaviour |

| “It should wait longer” | Delay increases security risk |

| “It should have safety sensors” | Sensors may compromise mitigation |

| “Automation should handle all vehicles” | Automation is limited by design |

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HVM systems must be understood, operated, and assessed **as defensive security assets**, not as convenience access equipment. Automated behaviour that appears abrupt or unsafe is often **intentional, standards-aligned, and necessary** to achieve effective hostile vehicle mitigation.