14 March 2005

Speed-measuring equipment used by the police isn’t accurate enough, according to a recent investigation carried out by the BBC. Tests of the laser equipment by BBC South-West programme Inside Out found that a brick wall could be timed at 58mph, and a completely stationary car could be registered at 4mph.

The BBC’s tests centred around something called ‘slip’ – a level of inaccuracy in the measuring process caused by movement while operating the handheld gun. Even the slightest shake caused large discrepancies. The discrepancies may pave the way for more cases like one heard recently in Inverness, in which a driver was measured by a handheld laser at an indicated 137mph. It was later proved his vehicle had a maximum speed of 107mph.

Meanwhile, retired electronics engineer David Edgar has been trying to prove the Gatso might not be as accurate as its maker claims. Facing a blemish on his 41-year-old spotless licence, he became concerned by the calibration of the Gatso’s twin-flash sequence. The cameras work by taking two pictures 500 milliseconds apart and measuring the distance covered in between. Edgar has developed a device that shows the flashes can be 630 milliseconds apart in some cases, giving a false reading.

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