Danger Underground

By Tony Kingham, journalist and PR consultant


Since 1976, there have been repeated deadly terrorist attacks on metro systems around the world. Thirty-nine of those have involved an Improvised Explosive Device (IED), only two with toxic substances and one a combustible fluid. They have resulted in eight thousand, eight hundred and sixty-two injured and seven hundred and forty-three deaths.

It is easy to see why metros are such an attractive target for terrorists, particularly using IEDs.

In an open space, the energy caused by the super-heated expanding gasses of an explosion are propelled outwards and rapidly dissipated.

In the enclosed environment of a tunnel, that blast is reflected back from the walls and along the tunnel like an echo in a church or water in a bath, until the energy is finally lost. All this still only takes fractions of a second, but the destructive and damaging effects are multiplied many times.

Then you are left with flames, acrid smoke, torn and twisted metal and debris of every kind, along with the mutilated dead and injured.

And here again the enclosed nature of the tunnel with its limited exits makes evacuation difficult and access for emergency services to rescue the injured incredibly slow, dangerous, and difficult. The delay inevitably resulting in yet more casualties.

In fact, it is surprising there have not been examples of the use of secondary devices targeting first responders, because the same characteristics make metros an ideal target for this tried and tested method of attack.

And finally, metros are often the most important people movers within a city. So, if terrorists were to target strategically critical rail lines, intersections, or stations, they have the ability to paralyse movement within a city for extended periods. Thus, causing maximum disruption with all the associated publicity, two of the chief aims of any terrorist attack.

Actually, it is difficult to think of a better target for a terrorist IED in today’s world.

Obviously, people will point to 9/11 as the most devastating and deadly terrorist attack in history, but it was also highly complex. It involved infiltrating bad actors into the US, undertaking highly expensive technical flight training in plain sight, seizing multiple aircraft at once and flying them to their target. There were multiple occasions when this attack could have and should have been detected and disrupted. But in 2001, the security and law enforcement agencies were not properly integrated and sharing information effectively, not just in the US but everywhere. But the main reason it wasn’t detected is probably the sheer improbability and audacity of it. Law enforcement could not conceive of it, so they weren’t looking for it!

But much has changed in the intervening years, not only in terms of the organisation and communication of law enforcement agencies, but also in terms of the systems and technical capabilities, especially around air travel. So, it is highly improbable, though not impossible for detection of an operation of that type and on that scale to happen again.

So, as we are all painfully aware, terrorists have sought other ways and other targets.

Unlike airlines, mass transportation systems like metros and railways offer incredibly soft targets. Passengers are not recorded or checked prior to boarding, the passengers and their baggage are not usually security screened in any way, all you need is a ticket, and in the case of a terrorist, a backpack containing an IED.

London underground.

During rush hour, up to three million (UK Underground) anonymous people are unceremoniously packed onto platforms and into carriages for the forward journey to their destination, somewhere else in the intimately interconnected system.

For a metro bomber, the most difficult and risky part of the operation is planning the attack. This is when members of the terrorist plot are discussing plans, often by phone or email, researching online, reconnoitering targets, and especially when attempting to obtain the materials for the bomb. This is the period when they are most likely to be detected by the security services.

Once terrorists have their working bomb(s), then the chances of the authorities stopping them getting to the target and successfully attacking it are slim.

But some relatively new technologies and some more mature technologies are helping to redress the balance.

The most obvious and the most controversial is facial recognition.

London is said to have more CCTV cameras per capita than any other city on earth, but very little is done to make these cameras smart by connecting them to effective video analysis tools. Their benefit to law enforcement and public safety is largely limited to operators being able to spot an accident or a street fight. So, it is largely reactive and more often than not, retrospective and therefore does little to protect us from potential dangers.

With behavioural analysis software and especially facial recognition software, CCTV cameras could be a game changer in making our public spaces safer. If they are only used to positively identify ‘known threats’ matched against watch lists and ignore the rest, it is difficult to see how this is any different from asking security officers to do the same thing with the mark 1 eyeball. Except a lot more effective!

Now it’s true that accuracy rates for crowd based facial recognition are much discussed and disputed, but what is also true is that a “good chance” now, is better than “no chance.” The other point is that the earlier these systems are introduced, the sooner AI gets the opportunity to be increasingly accurate.

Other technologies that have a proven track record in this area are produced by companies like ThruVision in the UK. They use a passive terahertz wave technology which can identify the size, shape and location of hidden objects on the body and have already been TSA vetted and approved for mass transit and are currently in operation on the LA Metro system.

Another frictionless system for mass screening is produced by Evolv Technologies in the US. This system uses AI-driven, ultra-low frequency, electromagnetic fields and advanced sensors to detect concealed weapons. These systems are widely used in other public spaces where mass walk through screening is required, like stadia and at least one airport, however, as far as I’m aware, they are not yet in use in any metros or train stations.

ThreatScan®-LS1 is a lightweight, portable, battery powered x-ray scanning system.

An already established technology are flat panel x-ray detectors. With millions of people moving through metro systems every day, with most carrying some kind of bag, backpack or package, it is inevitable that some will be left, lost or discarded. Unaccompanied bags automatically create a security situation and have to be dealt with immediately, if not, they will cause disruption at best or something much worse. It is therefore essential to be able to identify the contents of a bag or package quickly, safely and accurately.

3DX-RAY LTD, CEO, Vincent Deery said: “Our ThreatScan flat panel x-ray systems are in use with bomb squads worldwide and are very much a proven technology. They consist of a high penetration x-ray generator with a flat imaging panel, able to scan most bags in situ with just one scan, without the need to open or disturb it. This means that security staff or first responders can immediately identify whether a package is a threat or not and act accordingly. We currently have systems in service on metros with the British Transport Police in UK, Brazil and many others.”

Whilst the threat of terrorism remains, mass transportation systems, like metros will be high on the terrorist hit list. It will always be true that the chances of stopping a terrorist once an operation is underway are slim, but that does not mean that we are without the tools to redress the balance! ■

Download PDF: 45-47 Tony Kingham article – 3DX-Ray – COUNTER-IED REPORT, Autumn 2023