After an "extremely successful" two month trial at mainline and Underground stations in London, mobile weapons scanners are to go live at main railway stations throughout the UK, Transport Secretary Alistair Darling has announced.
The nature of this 'success', the kinds of deployment that will be made, and the things the machines are really intended to detect are, however, less clear than the secretary of state would have us believe.
According to the Department for Transport (DfT), British Transport Police has been running a three month trial in London using the scanners. The DfT and Transport Police have this year made substantial investments in scanning technology, most recently in the TPXi-640 x-ray unit, which as you see is a portable lightweight scanning unit with notebook computer. Image Scan Holdings announced in January that it would be delivering unspecified quantities of these units to British Transport Police over the following three months. The TPXi is claimed "to give the operator the greatest probability of detecting potential threats from explosive, chemical or even biological sources concealed within suspect packages", and that it is described by Image Scan as "the latest tool in the fight against terrorism".
According to Image Scan, however, these are high energy units designed to check baggage, not suitable for use on people, while the devices used in the knife scan trials are conventional metal detectors.
In this "successful" trial, DfT intended to combat knife crime. Ten thousand people were scanned, 100 were arrested and 68 knives detected. As we understand it, arrests related to the knives detected were in the mid forties, but the offences for which the other arrests were made have not been specified. For a fixed scanner at an airport a hit rate of this order could be seen as a success of sorts (only of sorts, because finding that number of people trying to carry weapons on board would scare airport managers witless), but these are not fixed scanners.
As deployed, the mobile version used teams of police accompanied by sniffer dogs (trained to smell knives???), with backup officers detailed to stop and question those who appeared to be avoiding the scanner. So, even at pilot scale it's an expensive operation to mount, and it can (or at least should) only be run by operators who're properly trained, and who're able to give subjects accurate information regarding the machines being used.
Considering the likely cost of all this, 68 knives (types not specified) out of 10,000 scans doesn't look particularly cost-effective, especially if you take into account that the scanner teams will essentially have been mounting surprise operations in high-risk areas, and will have achieved higher scores simply because the targets were not aware that the equipment was waiting for them. This won't be the case once they've been in use for a little longer, their use on a widespread basis will be prohibitively expensive, and taking 68 knives out of the hands of London's teenagers over three months scarcely makes the capital a safer place. It is, effectively, psyops, as was the case with the Met's operation Blunt in 2004; it was intended to persuade youth that it should not carry weapons because with the deployment of wondrous new technology they stand a very real risk of being caught. And as far as the general public is concerned, it's another prime example of 'reassurance policing' - conveying the impression of action and effectiveness by means of symbolism.
The x-ray mobile scanners will be similarly reassuring and similarly pointless as and when used to look for bombs and drugs, natch.
Alongside the mobile trials, you'll recall we have a fixed scanner trial at Paddington Heathrow Express, this one being particularly fascinating in that, when it was rolled out, it was viewed almost universally by those involved as being wholly impractical for widespread deployment. Transport for London has in the interim ruled out fixed scanners on the grounds of practicality.
Nevertheless, the importance of symbolism to New Labour may be sufficient to drive further fixed scanner deployments. On mass transit systems, however, the proponents of detection technology are currently between several rocks and hard places. Simple metal detectors just plain won't work in permanent deployments because they'll pick up keys, coins and so on, and running them in airport style would simply paralyse transport systems.
More sophisticated x-ray or millimetre wave (the "see through clothes" scanners) are getting faster, but they're currently dependent on trained operators capable of spotting problems, so we're still talking about expensive-to-run systems with queues, and a pause as each subject/suspect is examined.
You can therefore see the point in the use of mobile scanners, despite the fact they're not going to be significantly effective. They are scanner deployments of a sort but, as their deployment is intermittent, their overall disruptive effect is limited. Don't work much, don't hurt much, you could say. Just believe we're doing something. ®
*An earlier version of this story erroneously confused the Image Scan supplied mobile baggage scanners with the mobile metal detectors that Transport Police will be using in the knife crime initiative. Our apologies to Image Scan for the confusion.