In mid-August the Los Angeles County Metropolitan Transportation Authority and the Transportation Security Administration announced Metro has paid $100,000 each for several TSA-approved portable terahertz millimeter-wave screening devices. Made by the U.K.-based company ThruVision, the devices will be deployed within the city’s metro rail system to detect at a distance weapons capable of causing mass casualties.
Operators compare CCTV footage with what the scanners see – which is cold patches around the body that could mean a suicide vest or weapon. Someone suspicious will be assessed by sniffer dogs.
And the scanners have a range of 10 metres, which is handy, and works on people in motion.
But the technology seems to have some serious problems:
The device cannot see inside bodies, backpacks or shoes.
In a demonstration of the system at ThruVision’s offices, the operator immediately spotted the large bunch of keys in my back left pocket but didn’t notice the closed medium-size Swiss Army knife in my back right pocket until told it was there. He was unsurprised: the knife is about the smallest size they expect to be detectable at that distance and resolution, and it is not among the items LA Metro wants to detect.
