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Increasingly in the west we place our reliance on technology rather than people for security and many other things.

Some new technologies happily do offer some enhancements to mass transit security.  But the best approach to securing our public transport involves people, and is discussed in the final part of this series.

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New Technologies Help Protect Mass Transit against Terrorist Attack

Some ways to 'harden' the vulnerabilities of mass transit operations

So called 'security' cameras can be found in growing numbers in many major cities.  New technologies can automatically monitor the video feeds and may detect both known terrorists and anyone else deemed to be acting suspiciously.



The huge numbers of daily commuters and extensive public transport networks make it close to impossible for traditional technologies and security procedures to detect terrorists and prevent suicide bombings.

Some new technologies promise to offer some automated help that may help detect terrorists, although whether such detection will be sufficiently timely as to assist in their apprehension prior to committing their act of terror is uncertain.

For the best approach to securing our public transport system, please read on to the final part of this series.


This is part four of a five part series on the risks in mass transit systems and how to protect against them.  If you've directly landed on this page from a search engine, you might wish to start at the beginning of the series and read forward.

New Technologies

The previous part of this series showed how traditional methods of so-called 'security' are of little or no use when attempting to protect mass transit systems against suicide bombers.

Happily, there are at least four new technologies at various stages of development and deployment that could help secure our mass transit systems.

Automatic computerized video monitoring

New programs are being developed whereby computers will automatically detect suspicious behavior via video feeds.

These programs can detect obvious threat activities such as a person leaving a bag somewhere and then going away without the bag.  They also claim to be getting better at recognizing giveaway traits on the part of passengers that indicate nervousness or evil intent.

There are problems with these types of technologies.  First, with crowds of people, the ability of cameras to track individuals is limited, because they may be obscured from the camera view by other people, making it harder for an accumulation of data.

Secondly, apart from a wait on a platform, a person is moving through a station, making it harder for a computer monitoring program to follow each individual from camera to camera, and for giveaway behavior to manifest itself.  People are more likely to act suspiciously when loitering/waiting than when focused on the task of walking in a group of people from somewhere to somewhere else.

Thirdly, if the systems are tweaked to make them reasonably sensitive to suspicious behaviors, there is likely to be a high incidence of 'false positives' where they incorrectly guess that innocent passengers may be exhibiting threatening behaviors.  This not only inconveniences/annoys the passengers, but drains personnel resources from continuing to seek out real bona fide threats.

It also means that the staff sent to investigate possibly suspicious people lose their edge.  After investigating 500 false alarms in a row, how alert will they be when approaching the 501st alarm?

Fourthly, these systems tend to instill an aura of misplaced confidence in the security people, such that they relax their guard and are not as vigilant in other parts of the detection process.

Fifthly, there's the lead time issue - by the time the computer has sounded an alarm, and by the time a real person has responded to that alarm and directed security personnel to the person of interest, it might be too late.

Lastly, and just like with behavior detection done by humans, the purposeful and brief transit through a subway station gives fewer opportunities for meaningful behavior patterns to manifest.

Facial recognition

This technique has been employed in Las Vegas casinos for some years now - computers can automatically recognize 'people of interest' when sighted through video feeds.

But this recognition process presumes that the terrorists in question are known terrorists and that good facial imagery has been fed into the monitoring computer so they can then be recognized with some degree of accuracy.  These two requirements are not things that are always present in suitably optimized form.

Even when the terrorists are known to be bad guys and their images are loaded into a facial recognition system, bad light, obscured facial images by other people in the crowd, and some types of facial disguise may all still allow a terrorist to slip by.

This type of system is of course also vulnerable to lead time issues.

Explosive scanners

A type of remote invisible explosive scanner is being trialed in the UK.  It uses a UV light source to scan people, taking a couple of seconds to detect the possible presence of any explosive residue.

It will probably be possible to do this, to some hopefully sufficient extent, as people pass through fare turnstiles.

Unfortunately, UV light can damage a person's eyesight, and also harm their skin and accelerate the possibility of skin cancer.  It is not known what intensity of UV light such new systems may have or what the accumulative effect may be on commuters being exposed to it several times a day.

This also requires the terrorists to have conveniently contaminated themselves with the explosives they are carrying.

Trusted Passenger programs

To flip things around, it may be possible to take passenger tracking systems already in place, such as London's Oyster card, and to enhance these to allow for designated trusted passengers.

Anything to reduce the number of unknowns is clearly a good thing, but a trusted passenger program would only apply when going into subway stations.  Once through the turnstiles, all passengers merge into one big mass of passengers.

But automated tracking/evaluation systems could know to ignore trusted passengers and focus more carefully on unknown passengers, and unknown passengers could receive more careful scrutiny when entering stations.

The cost of establishing and running a trusted passenger system would be great, and the returns of uncertain value, and the privacy tradeoffs - the transit authority would then get to know of all your travels - appreciable.

It may be a good enhancement, and may offer some cumulative additional security, but as a freestanding system with nothing else, it is next to useless.

So, with only one part of this article series, what should be done?  At last, the answer to that question is finally only one more click away.

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Originally published 2 Apr 2010, last update 30 May 2021

You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me as original writer.

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