Heightened Senses

We turn our attention to the screening of passengers and their carry-on baggage - both of which require a considerably different approach to hold baggage screening. Take a traditional check point for example: the screening of the carry-on baggage can only ever be as good as the operator because little if any automation is currently in place to assist screening. However, because machine operation requires much concentration for long periods of time, a "half-way house" is to make the manual operation such that the operator is comfortable but does not get tired quickly. Smiths Detection, for example, working with the University of Heidelberg, conducted a study into x-ray inspection equipment operation. It was established that operator performance can be enhanced through ergonomic improvements to the equipment: such as minimising vertical head and eye movement to ward off the onset of tiredness.

Following the studies, Smiths Detection redesigned the keyboard of its ProLine x-ray inspection unit (Fig. 3), simplifying operation to just three priority and three belt control keys - thus negating the need for the operator to look down from the screen. Other improvements include an ergonomic operator support and adjustable monitor support.

A method of enhancing operator performance is so-called threat image projection (TIP), which superimposes a threat object over the image of a scanned bag to not only check the operator but also to train him/her. TIP is not new though, and the Transportation Security Administration (TSA) in the USA imposed TIP ready x-ray (TRX) back in the late 1990s. Furthermore, the success of TIP has recently resulted in requirements in Europe that 10 % of bags passing through a non-TIP capable machine be opened and inspected.
Also, customers are requiring that generated TIP data be collated and transferred to a central site for analysis and training preparation. This aspect has necessitated the networking of checkpoints within airports and the uploading of data to one site.

Next is the calling for the automatic detection of explosives in carry-on baggage: in much the same way that an Explosive Detection System (EDS) is able to automatically scan baggage for the hold. Meeting this requirement has run into a few problems though. Because of the configuration of a checkpoint (or even multiple checkpoints), operators do not have the luxury of implementing a fully automated Level 1 check, and diverting suspect baggage to a Level 2 check [see previous article]. This means that suspect baggage is flagged as such at the checkpoint.
When an EDS like Smiths Detection's HI-SCAN EDtS detects a possibly explosive material (at the Level 1 check) during hold baggage checks, the suspicious object is framed in red to assist the Level 2 check. Regulators are, understandably, of the opinion that a similar flagging of possible explosives at a carry-on checkpoint would a) distract the operator from looking for weapons etc, and b) cause undue alarm.
From a technical perspective, the majority of x-ray machines deployed at checkpoints are currently single beam and are hardly able, with any high degree of reliability, to distinguish between (say) Semtex and chocolate. Accordingly, such "semi-automatic" screening could see many false alarms - exasperating the fears of some regulators that fully automated screening of carry-on baggage could do more harm than good.

It therefore follows that to introduce any kind of automation into the screening of carry-on baggage one or more solutions need to be implemented, including: the use of automated x-ray technology, the automatic detection of weapons [considered a virtual impossibility due to the large number of components for instance a gun can be stripped down into], and other detection methods to either confirm or refute the presence of explosives.
Regarding the last point, one suggestion is to employ so-called "trace detection" which exploits the fact that most explosives exude particles or vapours that are absorbed by or cling to the surfaces of materials and fibres they come into contact with. Detection of these particles and vapours clinging to a person's carry-on baggage - or even the clothes they are wearing and their skin - can therefore be indicative of the fact that the person is either carrying or has come into contact with explosives.
At the heart of trace detection is a technology called ion mobility spectrometry (IMS), which makes use of the fact that the speed at which an ion drifts within an electromagnetic field is dependent on the ion's mass and structure. Timing the "ion drift" therefore produces a profile of the compound sampled.
IMS technology forms the basis of Smiths Detection's Ionscan (Fig. 1) drug and explosives trace detectors - thousands of which are in operation in hundreds of airports around the world. When the x-ray operator is of the opinion that a carry-on bag might contain explosives the exterior then interior of the bag are swabbed - with the swab then inserted into Ionscan for analysis.

Also employing IMS technology is Smiths Detection's Ionscan Sentinel (Fig. 2), a walk-through explosives detector. Similar in appearance to a traditional airport archway metal detector, Ionscan Sentinel uses jets of air to dislodge particles and vapours from a passenger's clothing, skin and hair.
The sampling air is pulsed to dislodge particles from the passenger's clothing and body and runs for approximately 4 seconds. The air is collected, at a rate of about 20,000 litres per minute, through vents at the base of the portal and is pre-concentrated before presentation to the IMS detector.
Current thinking is that a machine such as Ionscan Sentinel could be attached to the end of a conventional carry-on baggage x-ray inspection machine to assist in automatic identification. A longer term solution might see the integration of IMS trace detection, and possibly other technologies, into an x-ray machine to produce a combined-technology single unit.
Add to this improved object (i.e. weapons or parts thereof) identification algorithms and we would be close to automating checkpoint screening - at which point it might be possible to reduce the number of checkpoint operators and simultaneously improve passenger throughput.
However, the "checkpoint of the future" would most likely see combined screening systems working hand in hand with other security technologies and techniques, including biometrics (for example, fingerprint and/or facial recognition) and, on request, the operator having access to a great deal of information about not only the traveller but also how and when he/she purchased his/her ticket.
But the crux of the matter is this: In order for passenger and carry-on baggage screening to achieve a high operational throughput it is essential to clear, as quickly as possible, all genuine (non-suspicious) passengers - and to do that requires more than just one or two point solutions. It requires integrated systems within the airport and access to information outside of the airport.
This however raises the thorny subject of public acceptance. How will we feel about airport security equipment operators having access to (possibly) private information? If the introduction of these future security measures runs into the obstacles that previous proposals have then opinion will be divided. One camp will be of the opinion that we should not need to carry (or let others gain access to) detailed information about ourselves and have to prove, to the nth degree, that we are who we say we are. The other camp will be of the opinion that, with nothing to hide, if the new security measures help them personally to board the plane quicker then those measures are acceptable.
Perhaps the best demonstration of this issue is to consider passenger imaging systems, using either x-ray or millimetre-wave technologies. X-ray systems for screening people already exist and can, for example, be found in many of the diamond mines in South Africa. But how would air passengers feel about walking through x-ray machines.
As for millimetre-wave technology, it has already been trialled in a passive detection system with some ability of imaging plastic explosives and non-metallic weapons. The technology produces an image of the passenger and sees through a person's clothes. Trials at airports allegedly went well with the majority of passengers participating in the trials accepting "intensive" screening.
Trials and volunteers aside though, would an enforced passenger screening be considered an invasion of privacy? Once again security measures are caught between a rock and a hard place - delivering high detection rates whilst endeavouring to keep passengers and airport operators happy. One thing is certain though, today's checkpoint solutions are the best they have ever been, and there is little (technology-wise) preventing their integration into a "security net". Only regulatory and public acceptance can forestall such integration.
On a final note, today's checkpoint solutions are extremely dynamic and most have scaleable sensitivity. Any security network built from today's or tomorrow's detection units would also be dynamic and scaleable - meaning that airport security could be scaled according to risk (i.e. flight to from certain countries) or in response to a national state of alert.