The marking, developed by Qinetiq, is undergoing six-month trials with Cambridgeshire and Hampshire Constabularies.
The material allows the roof markings on vehicles to be read with a thermal-imaging camera. This should enable air support police co-ordinating a chase in helicopters to distinguish between the pursuer and the pursued, said Dr Andrew Loveridge, project manager for the material, called Mirage.
‘When a chase involves multiple police vehicles there is sometimes a difficulty in co-ordinating the chase, because you can’t tell which is the lead car and which is the second car without turning on the spotlights, and that blows the cover of the helicopter. Anything that means the helicopter can be used in a covert manner is of benefit,’ said Loveridge. ‘One air support manager I spoke to claimed they had in the past accidentally chased unmarked police cars, because they locked on to the wrong vehicle.’
The multi-layer substructure of the material means it functions like a mirror in the infrared. As a result, when placed on a horizontal surface such as a car roof, it reflects the sky, said Loveridge.
‘In almost all weather conditions and at any time of year, the sky will be several degrees colder than the ground and any ground-based vehicles. So it is this contrast that gives you a good marking,’ he said.
The material appears ‘cold’ to the thermal-imaging camera, while the letters are ‘warm’, providing the contrast. During the day the markings retain their high-contrast, white-on-black appearance.
As well as helping air support officers to co-ordinate chases, the material should also assist them in accurately reporting, for legal reasons, every action taken by the police during the pursuit.
The material was originally developed for military stealth applications. But following discussions with the Police Scientific Development Branch about police technology needs the company realised it could also be used to help air support officers.
‘Both stealth and conspicuity require a control of contrast, and it is exactly the same process to minimise contrast, as you would for stealth, as to maximise contrast as you wish to do in a roof marking,’ said Loveridge.
After their discussions the company supplied the PSDB with samples of the material, and the organisation issued a report revising its specifications to incorporate it as standard on all marked vehicles.
The material is production-ready, and the company hopes its first few customers will begin receiving it at the beginning of May. Feedback from officers from the two forces has so far been positive, and Loveridge said the material should become standard across the country over the next two to three years.
The company also hopes to sell the material to forces in