Computed tomography (CT) scanners are being trialled at Heathrow airport. The result? You won't have to take liquids and electronics out of your cabin
In airports, efficiency matters. Small delays in loading baggage, cleaning planes, or restocking airplane meals can have knock-on effects that cause havoc for hundreds of passengers. For frequent flyers, the difficulty comes with baggage.
In the US, the Transport Security Administration (TSA) sees more than five million pieces of cabin baggage passing through its airports each day. Every single one of these items needs to be checked as it passes through an airport's security systems. Laptops, tablets, and liquids have to removed from hand luggage before the bags can be scanned.
But, this process may become a thing of the past – improving the speed people can travel through airport security. Heathrow airport is the latest airport – after Amsterdam's Schiphol and New York's John F. Kennedy – to trial technology that can fully image everything that's inside a piece of hand luggage.
A small number of trials lasting between six and 12 months started this Spring, a spokesperson for the Department for Transport says. It refused to give more details for security reasons but said the scanners being trialled, which are equipped with automatic explosive detection, could lead to it being mandatory for items to be removed from hand luggage.
So, how does it work? Airport scanners that provide 3D images and let security staff see completely inside baggage use a process called computed tomography (CT). Essentially, it's the same process as is involved in medical CT scans that allow doctors to see inside patients without cutting them open. CT uses x-rays to scan an area and then creates a computerised version of the results.
"Traditionally, these scanners typically provide 2D images," says Hans Joachim Schoepe, who works in CT scanning at Smiths Detection. The company says more than 2,100 of its CT machines are used in airports around the world.
CT scanners for cabin baggage work by using a spinning gantry that captures hundreds of images of an item as it passes along the conveyor belt. These are then combined with the x-ray data. "We capture one 2D image every half degree of the rotation. In total, per rotation we receive 720 2D images," Schoepe says. "It can't show these images to the operator, so what happens then is this constant data stream of 2D images goes into a reconstruction algorithm that calculates a 3D image out of the data."
The result is a 3D image. This appears on the screens of airport security staff who can rotate, turn and inspect what's in the object from multiple different angles. Being able to look at all items within a bag, from one image that can be manipulated, means that laptops and liquids don't need to be removed. Smiths' CT scanner can have 1,000 bags per hour pass through.
CT technology isn't new. Schoepe says airports have used CT machines to inspect checked baggage, which is put in a plane's hold, for around 20 years. Why hasn't it been used to speed up security for cabin bags before now? The machines were too large, slow, and the computing power to quickly process images while people wait wasn't easily available. All that has changed. "Over the last four or five years, CT technology had became realised," Schoepe says. "There are now a handful of suppliers."
But as well as problems with the tech not being good enough, regulations across Europe meant the machines couldn't be used. In 2015, the EU passed common standards called Explosive Detection Systems for Cabin Baggage (EDSCB). These set out the requirements for airport baggage scanners: a C1 machine mean elections and liquids must be removed, C2 states electronics can stay in bags but liquids must be removed and at the C3 standard, nothing has to be taken out of a bag.
As a result, it's likely more airports will start trialling CT machines in the hope that queuing times can be reduced. On July 30, the TSA announced that by the end of this year it would be trialling 40 CT machines around the US and 145 will be in airports by the end of the 2019 fiscal year. Next, baggage scans will be automated.