The complexities of implementing hostile vehicle mitigation measures in cities

Hunter Seymour examines the complex challenges of implementing hostile vehicle mitigation measures, in an environment where protective designs in densely populated cities are in high demand as part of an effective counter-terror strategy.

IFSEC Insider long-read: Key takeaways

• Vehicle as Weapon attacks in crowded city centres are viewed as a significant threat by the NPSA due to their low complexity for terrorists
• Mitigating against attacks through hostile vehicle mitigation (HVM) measures is conversely a complex challenge – in large part due to the costs involved for city councils
• There is no ‘one size fits all’ approach to HVM, yet it is viewed as an effective measure to counteract hostile actors if appropriately planned

“We need to wake up,” warns the outgoing chairman of the Commons Defence Select Committee in his recent security analysis. “The scale in which our adversaries are learning to cause us harm is faster than we’re able to put up the barriers.” 

His specific concern for “barriers” is echoed by the cautionary guidelines issued by an authoritative source, the NPSA (National Protective Security Authority), whose counter-terrorism scenarios instruct security professionals in best practice to protect PALS (Publicly Accessible Locations) from vehicle borne threats, predominantly VAW (Vehicle As a Weapon) attacks but also VBIED (Vehicle Borne Improvised Explosive Devices).

Yet it’s a daunting challenge. The formidable range of proposed measures to mitigate critical threats of concern – including violent street crime, unpredictable crowd behaviour and terrorism – reveals significant logistical challenges to security planning.

In this brief overview, we examine the simpler of the NPSA’s solutions – particularly in the context of the proposed Protect Duty bill and its pre-legislative scrutiny, which warns of significant financial implications for cash-strapped local authorities.

Cost-effective Hostile Vehicle Mitigation (HVM) strategies

The ruthless brute force of a weaponised vehicle is defined by the NPSA in these cold-eyed observations:

“Driving a vehicle into crowds is regarded by terrorists as attractive because it is likely to cause multiple casualties, is low complexity, affordable, requires little planning and skill and is perceived as less likely to be detected in the planning phase.”

Which raises the question as to whether security practitioners can fight fire with fire with cost-effective measures of corresponding low complexity and affordability for swift solutions. Holistic design innovation is encouraged.

“There is no one size fits all response to [HVM]. Every place is unique and requires an informed and considered approach.”

For example, at the most basic provision, “Traffic calming can be used to limit vehicle approach speeds to a manageable level.” These include deflections by bends and chicanes.

“Reducing hostile vehicle speeds can reduce the requirements and associated costs of HVM measures and provide more opportunities to deploy discreetly integrated protection.”

Passive measures – streetscape features

And, similarly, at the practical level of “street furniture”, passive measures include static barriers, landform elements, watercourses, walls, fences, benches, steps, statuary, public art, embankments, raised planters, trief re-direct kerbs, and many more stratagems.

It’s somewhat thought-provoking to learn that active (operable) measures, such as remotely powered security barriers, “are vulnerable to duress and deception techniques and therefore passive measures are preferred wherever possible.”

A vital component, nevertheless, in any assessment of such lines of defence must be always consideration of controlled access for emergency services and other authorised vehicles.

Troubleshooting risk in the public realm

MI5, the UK’s Security Service, is the guiding hand behind the NPSA, whose measured views acknowledge the complexity of counter terrorism security solutions.

“Introducing Hostile Vehicle Mitigation schemes into the public realm is a significant challenge and must fulfil numerous requirements in order to integrate successfully, such as: Aesthetics, Public Access, Traffic Management, Physical Constraints, Health & Safety, Cost, and Maintenance.”

Certainly, in the public realm, when risk management assesses the HVM implications of “Health & Safety, Cost, and Maintenance” on a practical level, the decision-making process is likely to require an intricate troubleshooting flowchart to align with the demanding criteria proposed by the NPSA.

“Every Metre Counts” – Maximising lines of defence

Of particular concern is the protection of pedestrians in public locations at risk. Even the installation of bollards (whether retractable or static) should be conditioned by deep analysis of predicted flow-characteristics of crowds and the dangers of increased crowd density and congested conditions at peak times or in emergency situations.

Equality Act guidance should be factored in, too, to anticipate issues of capacity and impaired mobility. As has been said, “A fleeing crowd is a brainless monster” with an irresistible momentum all its own.

Author’s note: “Capacity” is the maximum flow rate at which pedestrians can safely flow through a space (p/m/min) and calculated by multiplying the maximum flow rate by the usable width of the path.

Dominating these calculations, however, is the critical imperative to determine the site-specific distance from the source of a potential VBIED (Vehicle-Borne Improvised Explosive Device) to a protected space (such as a footway) when the enforced traffic-managed protective perimeter is established.

The blast stand-off distance is the most important factor in determining the extent of damage that can be caused. Maximising the blast stand-off distance will reduce damage sustained by the protected area.

Hostile incursions and counter measures

This brief outline of some of the major counter terrorism methodologies, currently conceived to thwart hostile incursions, presents just a glimpse of the diverse issues of concern.

Assessing risk and balancing competing demands will mean tough questions to evaluate risk tolerance levels. Justifiable? Achievable? Sustainable? Practical? Affordable? Reasonable?

Beyond this, the psychology of VAW assailants and their motivation are aspects of intense study by NPSA security experts. And the tactics of the assailants are astonishingly wide-ranging, from well planned conspiracies to self-initiated terrorists (lone actors):

• Trojan Vehicles – replicating legitimate vehicles
• Unknowing Mules – legitimate drivers unknowingly delivering hidden IEDs (Improvised Explosive Devices)
• Duress/Coercion – at a VACP (Vehicle Access Control Point)
• Penetration by Insiders with access rights
• Sabotage preparatory to an attack
• Forged/Stolen ID to gain admittance to a secured perimeter
• and other ruses to exploit weaknesses in operational and/or physical security measures

In fact, it can be seen at once, that to defeat these many deceptions, your design of a robust HVM strategy will demand an equally wide range of options incorporated into it.

The greatest vigilance is demanded of risk management. As the UK moves to strengthen police protection of British communities following escalations of terrorist incursions globally, acts of terrorism will increasingly influence outbreaks of incidents nearer to home.

Risk tolerance levels in practice – Case studies

As to further NPSA advice on likely actual costings for an HMV strategy, the Authority recommends, “Check additional sources for HVM funding. Are there national or local government initiatives?”

Such questions, of course, are already central to the recent pre-legislative scrutiny of the Terrorism (Protection of Premises) Bill – also known as the Protect Duty or Martyn’s Law.

Counter-terrorism security measures on London Bridge (Credit: Graham Prentice/AlamyStock)

The Local Government Association says: “We broadly support the Government’s approach to consider what more can be done to protect local places from attacks and introduce new measures that require those responsible for certain public premises and events to take proportionate steps in mitigation.

“We also recognise that the nature of the terrorism threat has changed over recent years. However, it must be accepted that it is impossible to eliminate all risks and threats entirely. The new Duty must be proportional and not unduly burdensome for those within scope.”

The realities of funding HVM

But are there, many will ask, any realistic measurements to gauge what is ‘unduly’ burdensome?

Let’s examine the recent case of the City Council of a medieval English cathedral city, characterised by the hazards of “tight foot-streets”, where we read this account of procurement of HMV by balancing the books:

The York City Executive recommends that the HVM scheme to “protect the city centre from a vehicle borne terrorist attack” is “in excess of the available budget and that an additional £1,750k be approved, to be funded by bringing forward funds from the 2026/27 Highways Maintenance capital programme… to meet the forecast for inflation and the utilities costs.”

Significantly, the recommendation is qualified by a decision to “… lobby the Home Secretary to seek financial support with the installation of HVMs and the production of a long term government plan to support councils in implementing their Protect Duty.”

Further high level deliberations on HVM costings can be found in the recent proceedings of the London Assembly where a submission to the Spending Review states that “funding from Government is urgently required to make permanent all the temporary hostile vehicle mitigation measures across the eight central bridges in London.”

These examples are cited to give a glimpse of a complex subject, which clearly in the long term is going to require a constantly developing expertise. From such expertise on the fallout from a Hostile VAW (Vehicle as Weapon) attack, we learn for example…

The Law of Unintended Consequences: The NPSA warns us, “The end of a VAW attack may look similar to a road traffic incident: the vehicle losing control and crashing into barriers, buildings, street furniture or other vehicles. Individuals may approach the vehicle to help the occupants, inadvertently becoming targets for follow-on bladed weapon or firearms attacks.”

Further reading: The impact of Martyn’s Law and UK counter-terror strategy: Moving the goalposts for the security industry?

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